Thursday, May 06, 2010

The Billion Dollar Heartworm Scam

This is a repost from this blog on this day in 2008.


Almost everything you have been told and taught about heartworm is probably an exaggeration or an outright lie, and this misinformation is probably costing you more money than it needs to.

Here's the truth:
  • Heartworm is not a canine pandemic.
  • In fact, heartworm is pretty rare in much of the country, and in very cold areas of the country a veterinarian may go his or her entire career without seeing a single case. Look at the map, above, put out by a major vendor of heartworm tests (Idexx) who has every reason in the world to overstate (rather than to understate) the problem. You will notice how low the baseline state numbers are -- 500 cases is the top of the color scale -- and that this map covers seven years of data collecting. You will also note that this map does not show adult heartworm infestation in dogs, but simply the number of dogs that tested positive for heartworm. More on that important distinction in a minute.
    . . . . Data on heartworm incidence rates at the local level reinforces how rare heart worm really is. For example, on the map above, California is coded red-hot with 500 cases. And yet, when a total of 4,350 dogs in 103 Los Angeles County cities coming from 21 participating animal hospitals were tested, only 18 heartworm-positive tests turned up. And yet, veterinarians are training their staffs not to talk about heartworm tests and medications as an option, but as a need, and for this "needs to be given" message to be bombarded on the customer 3-5 times per office visit.
  • Heartworm infection is NOT rapid and will not kill your dog overnight.
  • It takes about three months for microfilaria (baby worms) to grow inside your dog to a larval stage, and even longer for these larva to mature into adult heartworms. If your dog is dosed with a simple Ivermectin treatment at any time during this period before adult worms are present (a period that lasts about three months long), the larvae will never develop into adult worms, and will die. Read that statement again: a single dose of Ivermectin will stop heartworm dead up to 3 months after your dog is first infected.
  • In most of the country, only seasonal heatworm "prevention" is needed.
  • The short story here is that heartworm is a kind of nematode (dirofilaria immitis) spread by mosquitoes (and only by mosquitoes). The lifecycle of the nematode involves six stages, and a dog can get infected with heartworm only if two of these stages are fully completed inside the body of the mosquito, and those stages can only be completed inside the body of the mosquito if the temperature stays above 57 degrees for at least 45 days straight, both day and night. If the temperature drops below 57 degrees even once during that 45-day period, the lifecycle of the nematode is broken, and heartworm cannot be transmitted to your dog. What this means, in simple terms, is that a year-round program of Heartgard (sometimes spelled 'Heartguard") or some other "preventative" medicine is NOT needed in most of the country outside of Florida, the Rio Grande Valley of Texas.
    . . . . . Look carefully at the maps below (click to enlarge). These maps come from “Seasonal Timing of Heartworm Chemoprophylaxis in the United States” by Dr. David Knight and James Lok of the American Heartworm Society. Find your area on the map, and begin heartworm treatment on the first day of the month noted in Map A, and end treatment on the first day of the month noted in Map B. In short, if you are living in Virginia, you would begin treating your dog June 1st (top map) and end treatment on December 1st (bottom map).
    . . . . . This is a very aggressive treatment schedule -- more active than is really needed. After all, if heartworm larvae gets into your dog on June 1st, they will have NO IMPACT on your dog for months and months. In fact, if you are in Virginia simply treating your dog with Ivermectin (Heartgard) on September 1st and again on December 1st will give 100 percent heartworm protection for your dog. Even in areas where heartworm is a year-round vexation (Florida and the Rio Grande Valley of Texas), a once-every-three-months dose of Ivermectin will give your dog 100% protection.

(click on maps to enlarge)

  • There is no "preventive" medicine for Heartworm.
  • Despite what your veterinarian may have told you, there is NO "prevention" for heartworm infection; there is only heartworm treatment. ALL heartworm medicines work the same way -- they kill heartworm microfilaria present in the body of the dog.
  • Heartworm "prevention" medicines are actually toxins.
  • The drugs used to kill heartworm microfilaria are Ivermectin (Heartgard, Heartgard Plus, Iverhart, Merial and Verbac) or Milbemycin (Interceptor, Safeheart, Sentinal and Norvartis). Both drugs are nematode poisons, and in both cases a single dose will kill all microfilarial infection that occurred up to 90 days earlier (i.e. all Stage 3, 4 and young Stage 5 heartworm infections).
  • Humans cannot get heartworm.
  • Heartworm cannot be passed on to humans -- we are the wrong host animal. Very rarely a heartworm-positive mosquito will bite a human and a small benign cyst may develop in the lung of a human, but this is NOT heartworm, and can be best thought of as a tiny scar showing where a bit of microfilaria attached to the lung wall where it was killed off by the human body.
  • Some breeds are more sensitive to Ivermectin.
  • Some lines of collies and collie-crosses have sometimes fatal reactions to ivermectin, the most common heartworm preventative medicine. Though this is not common, and is even rarer today with low-dose Ivermectin such as Heartgard, and seems to only hold true for collies, serious thought needed to be given to dosing any collie, collie-cross, or herding dog with white feet. For these dogs, the safest heartworm medicine is Interceptor, though in fact the Heartgard box features a Border Collie on it face, and many working Border Collie folks dose their own dogs with a low dose of sheep drench 0.08% Ivermectin.
  • What about that wormy heart-in-a-jar at my vets office?
  • Most veterinarians have a "fear bottle" in their office which shows a canine heart riddled with spaghetti-like heartworms. Nothing generates cash like a heartworm fear bottle -- a veterinarian will often place one prominently in his or her office as a kind of cash-generating machine since one look will sell a heartworm test and year's worth of Heartgard, no questions asked. So where do these fear bottles come from? I've been told by a pharmaceutical sales representative that most of these wormy hearts in these jars come from stray animals killed in Mexico, and that the heart specimens themselves (often decades old) were given out by pharmaceutical company representatives when they first began selling Heartgard back in 1986. One thing for sure: today, you can got to Maine and find a wormy heart in a jar even though the local veterinarian has never even seen a dog with this problem in the last 20 years.
  • Do I have to go a veterinarian to get Ivermectin?
  • No. More on that in a second. Suffice it to say that it's not necessarily a bad thing to go to a vet for a prescription for Heartgard, especially if you are going to see your vet on another matter anyway. I would not buy Heartgard from the vet, however, without first checking prices online. Most vets price-gouge their customers by 100 percent or more for medicines sold in their offices, and in most states a veterinarian cannot charge you more for writing a prescription for a medically necessary medicine as part of an incidental visit.  In addition, be aware that former executives from Merial, the maker of Heartgard, are now making a generic version of this product, PetTrust, that is considerably cheaper.
    . . . . . Another cash-saving tip is to get a prescription for Heartgard for a dog twice the size of your dog, and then split the tablets in half. This trick results in considerable savings because the marginal cost between one Heartgard weight category and the next is often very slight despite the fact that one pill contains twice as much active ingredient as the next.
    . . . . .
    Finally, remember that, depending on outside temperature, you do not have to dose your dog all year long in large parts of the U.S.
    . . .Of course, if you want to dose your dog every month and do so cheaply and without going to a veterinarian for a prescription, there's a trick here too. Here it is:  Order Ivermectin in a pre-mixed solution from J.R. Enterprises. The cost is $25 for a 65-cc bottle of .05% Ivermectin, which is enough to treat five 20-pound dogs for 26 months. J.R. Enterprises even throws in a measuring spoon! Since this Ivomec and polypropelene gylcol solution is not FDA-approved for dogs, they sell it for experimental purposes only. That said, it works fine, and this is exactly the kind of heartworm preventative medicine used on all dogs all across this country prior to the advent of Heartgard and "the billion-dollar heartworm scam" in 1986.
    . . . . .
    .Finally, and if for no other reason that to explain how J.R. Enterprises does it, here's how you can treat a huge number of dogs with non-prescription Ivermectin for a dirt-cheap price. Whether this is cost-effective or not (and whether it is worth the trouble or not) really depends on how many dogs you have. In case you run a shelter, here's the scoop 1) Buy a 0.08 percent sheep drench online or at a feed store. Sheep drench is sold in various sized containers, but the smallest on Amazon is about $30 for 8 oz.  This will be high-grade Ivermectin made by Merial, an established veterinary pharmaceutical company. You will be giving only a very small dose of this sheep drench to your dog.  You dose by weight, and if you want to be very sure you have dosed enough, you can double the dose and the dog will be fine (but see the Collie warning at point #7).

    * up to 14 pounds: 1 drop (0.05 cc)
    * 15 to 29 pounds: 0.1 cc
    * 30 to 58 pounds: 0.2 cc
    * 59 to 88 pounds: 0.3 cc
    * 89 to 117 pounds: 0.4 cc
    * 118 to 147 pounds: 0.5 cc
    • Do I need to have my dog tested for heartworm before starting Ivermectin?
    • Generally, no. Unless your dog is an older dog loaded with years of untreated heartworm (which you will know from the dog's long-term lethargy and chronic coughing), a dose of Ivermectin will not do your dog harm. A puppy, under six months of age, of course, will always test negative for heartworm because the microfilaria have not yet had a chance to develop and circulate. Testing a dog under age 6 months for heartworm is a common veterinary scam; do not fall for it!
    • Is curing heartworm expensive and difficult?
    • No it is not. Any veterinarian who tells you otherwise is not keeping up with the literature. It turns out that even if your dog has adult heartworms, if the dog otherwise appears healthy (i.e. it is active, not lethargic, and does not have a chronic cough), a monthly dosing of Ivermectin at a dosage normally used to kill roundworms (a dosage that is 3 times higher than that used to simply prevent heartworm), plus a once-a-month 5-day dosing of Doxycycline (sold as Bird Biotic, and the same antibiotic used to treat Lyme disease) will kill all the adult heartworms if it is sustained for a period of 18 months. This treatment works better than previous Ivermectin-only treatments because the Doxycline wipes out the Wolbachia microbe that grow in the gut of the adult heartworm, essentially sterilizing all of the female heartworms. A round-worm strength dosing of monthly Ivermectin will not only prevent new heartworm microfilaria from taking hold in your dog, it will also work to dramatically shorten the life of any existing adult worms in your dog. Bottom line: after 18 months of treatment, your dog will be heartworm-free at very little cost compared to other remedies.
      . . . . . A repeated caution, however: if you have border collies or herding dogs with white feet that also appear to have full-blown heartworm, consult a veterinarian, as some lines of collies are very susceptible to Ivermectin toxicity. This is very rare, and the cause is unknown, but it is an area of concern among collies and collie-crosses.

    PLEASE BE ADVISED THAT I WILL NOT ANSWER QUESTIONS ABOUT DOSING YOUR DOG.   If you are too lazy to read this post or too confused and wrapped around your own axle to follow simple directions, I cannot help you.  Please go to a veterinarian.


Anonymous said...

For more info on ivermectin sensitivity in the collie breeds, see
From reading australian shepherd lists for a number of years, the ivermectin sensitivity issue is real in Aussies. Ivermectin is the tip of the iceberg for drugs that affect the MDR1 (multi-drug-reactive) mutants. I know my Aussie is very sensitive to Ace, used as a pre-anesthetic. The reaction seemed to get worse over time, even when years went by between reasons for anesthesia.

It is kind of fun to be able to call her a mutant, though, and know I'm right.

PBurns said...

The notion that collies are extremely susceptivble to Ivermectin toxicosis is VERY overstated, and is based on HUGE Ivermectin doses being given to collies -- doese you will NOT find in Heartgard when taken as prescribed. For the record, the dose of Ivermectin in Heartgard is 6 - 12 micrograms per kg of body weight while the toxicity studies dosed the dogs with 50 micrograms per kg. See >> where they note that "Two clinical studies showed that 200 micrograms per kg of ivermectin dosages resulted in 50% of the collies displaying severe toxic signs, and NO signs of toxicity when the dosage was below 100 micrograms per kg. Because the 100 microgram per kg dose is nearly 16 times higher than the manufacturers recommended minimum effective dose for the prevention of heartworm (ie. 6 micrograms/kg), it appears that treatment with ivermectin for the prevention of heartworm disease would be safe in even the most ivermectin-sensitive dogs."

That said, I like to err on the side of caution, and Interceptor can be gotten by collie owner easy enough.


an American in Copenhagen said...

For 70 dollars there is a genetic test available from Washington State University (Go Cougs!) to see if your collie or collie cross carries the gene that results in ivermectin sensitivity.

As it turns out Ivermectin does not kill dogs with this mutation. Rather, when dosed with too much Ivermectin it causes them to fall into a coma which they eventually come out of given enough time.

Pai said...

So are pretty much the majority of dog illnesses being exaggerated as scams to boost vet pharmaceutical profits? It's outrageous -- and you never hear a dissenting opinion from the majority of pet people or pet sites...

PBurns said...

Well, a LOT of things are bunk, yes. Bunk is the bread and butter of veterinary. That said, when on those rare occassions you NEED a vet, you REALLY NEED a vet. How often is this? Most folks will go an entire life with a dog and never need anything nor more than a put-to-sleep, take his nutts off, or spay. I am not anti-vet; I am pro-integrity. There are vets with integrity, but they are getting to be bit like free-range tigers (a rare thing more often hear about than seen).


Anonymous said...

Hi Terrierman, What a great article, thank you. I have had personal experience with collie ivermectin sensitivity--my collie got demodectic mange and her parents had tested free of the MDR1 mutation, so we treated her with one low dose of ivermectin, and she went into a coma that lasted a week. It took her over two weeks to recover fully. It turns out the test results had been falsified by the breeder, we think, and our dog had two copies of the mutant gene, making her VERY sensitive to ivermectin. Anyway thanks for another great article!

Tommy and Teaghan said...

Thanks for this information. This has to be one of the most informative posts I've read in a while. Besides a vet trying to push the food that they sell or vaccines that animals don't need here's yet another thing to watch out for.

Cassandra Was Right said...

Thanks, Terrier Guy. We (my dogs and I) knew you'd come through with some unbiased, commonsense information and advice on heartworm, which is being pushed here in No. Va. rightly - since it is an actual problem - but wrongly when all the info hangs on incredibly expensive testing and medication. My vet, an otherwise great guy and highly recommended in the area, insisted that my two dogs who had never set foot in the US but had been born in and just arrived from a heartworm-free country be tested. What a surprise that they turned out negative, at $40 per useless test.

YesBiscuit! said...

By my math, using the 6mcg/kg formula (2.72mcg per pound), the .05% diluted Ivermectin solution contains 500mcg per ml. Giving 1 ml to a 40 pound dog is more than necessary. 1 ml would be the right dose for a 185 pound dog, not a 40 pound dog.

PBurns said...

The Ivermectin formula/recipe I give is better than fine and very safe too.

That said, the explanation here is interesting and since we are dealing with a toxin (albeit a very weak toxin for mammals) let me explain.

The Heartgard Plus dose for Ivermectin is 2.72 mcg per pound which is a VERY MINIMUM DOSE because Merial (the company that makes both Heartgard Plus and 1 percent Ivomec for cattle) wants to get Ivermectin-sensitive Border Collie/Collie/Sheedog owners to use their Heartgard Plus product.

As unbelievable as it sounds, Merial even puts a picture of a Border Collie on their product label of Heartgard Plus ivermectin tablets. See >>

Now my position here (call me too cautious) is that regardless of Heatgard's packaging I do NOT recommend folks use Ivermectin on their Border Collies as another product is available. Why take chances?

That said, it IS true that low doses of Ivermectin are not as dangerous to collies as generally said. Even in Ivermectin sensitive collies, the magic dose threshold seems to be around 120 micrograms per kilo which is far more Ivermectin than you would use for heartworm (though it is about half the dose of Ivermectin you would use to treat a dog for mange).

Why use more than 2.72 micrograms of Ivermectin to dose your dog for heartworm? The short answer is that a 2.72 mcg dose is a very, low dose and pretty marginal in terms of effectiveness, and since the dose here is liquid being mixed in with food (not in a chewable tablet form as with Heartgard) you want to make sure it gets in the dog and is not left on the plate.

Don't worry about the dose I have given here being "too much Ivermctin." Ivermectin at this very low dose rate is not doing ANY harm and IS doing the job in terms of heartworm prevention and microfilarie eradication.

Ivermectin has a very low toxicity (Category IV on the EPA scale, which is their lowest level of toxicity). As the Merck Vet Manual notes (see >> ): "At least 10 times the normal dose of Ivermectin is needed for toxic reactions [in border collies] ... The critical point [in collies] seems to be 120-150 micrograms per kilo, at which transient, nonfatal clinical signs (mydriasis, ataxia, tremors) are seen."

The dose given in the mixture I detail in this post is for 500 micrograms for a 40 pound dog (18 kilos), or less than a 1/4 of what will get you into trouble if you have a very Ivermectin-sensitive collie.

In short, it is pretty darn safe!And it is effective. Which brings me back to the Heargard dose.

Is Heartgard's dose of 2.72 micrograms per kilo of dog too low? The short answer is " Maybe". The Heartgard package insert itself says (see >> ): "While some microfilariae may be killed by the ivermectin in HEARTGARD Plus at the recommended dose level, HEARTGARD Plus is not effective for microfilariae clearance."

Huh? What's that mean?

The short answer is that it means they are running too low a dose of Ivermectin solely to sell their product to border collie owners.

The Ivermectin dosage in Heartgard is so low that it prevents the microfilarie (larval worms) from moving to the next stage of their life cycle, but it does not necessarily kill them outright. A higher dosage of Ivermectin is safe and WILL kill them outright, however, and it will also give you a bit of margin should a little Ivermectin be left on the plate when given in a liquid oral form. In short, there is a reason for a slightly stronger formula than Heartgard uses: we are sriving for "Safe AND Effective," and we are not trying to sell this product to folks who own Ivermectin-sensitive border collies.

Hope that explains all.


YesBiscuit! said...

I understand and appreciate your explanation Patrick. Thank you for always giving me more food for thought!

Anonymous said...

Great post, one all dog owners should read. I find your explanation of Heartgard's dosing to be pretty scary, actually. This was on one of the blogs I read pretty regularly:

Interesting, and food for thought.

Penny said...

Forgive me but I need to ask for assistance in my situation as I am startled by the information you've provided and not sure I've digested it all. We recently rescued from the streets a young dog (approx 2 years old or younger) in North Carolina. She just tested positive for heartworms and I was shocked to find out that it will cost us approximately 700 dollars to treat. She is very very healthy, huge appetite and exhibits no coughing or lethargy. She was roaming our neighborhood for a year (apparently someone feed her but never put tags on her or kept her contained) before we adopted her and moved to KY. We couldn't take her in while we lived there (lease issues), but she would visit and play with our dog daily. Without knowing much about the risks, about 9 months ago, I once applied a dose of Revolution to her to keep the fleas off, concerned for her comfort and maybe to prevent fleas getting on me or the house. I didn't know it had heartworm medication in it. She never had a reaction to it.

Does it seem reasonable that she would be a good candidate to treat her heartworms with the Ivermectin solution you outlined above? Also, if the vets are all for the expensive treatment, how would I convince them to prescribe her the antibiotic to add in the heartworm treatment? Wouldn't they turn me away? I have a feeling they don't want to lose out on 700 bucks.

PBurns said...

Yes, treat the dog with Ivermectin ordered from the link suggested -- J.R. Enterprises -- and order your doxycline (no prescription needed) from any online veterinay supply ( or for example). The doxycline will be labeled for birds or fish, but it's perfect for dogs and is the exact same thing as you get at the pharmacy. Dose by weight as directed in this post.


Hillsidefarm said...
This comment has been removed by the author.
PBurns said...

See a vet. A bitch that is in ill health should not be having pups, and an abortion is probably in order. If this dog was intentionally bred while she was in ill health, then the pups will only be born into misery anyway. If the mating is unintentional, then an abortion is simply putting back right what was started out wrong.


Pai said...

After getting into a huge fight over this exact issue on another board, I found these interesting tidbits:

DHHS Warning to Merial over their claims that Heartguard offers 100% protection

...and then I read this (still haven't been able to find the study quoted there online): A 1988 study that found waiting up to 4 months between heartworm doses offered 95% protection

Put 2 and 2 together... monthly doses do not give 100% protection... 4 months between doses gives 95% protection... could it be that those 4-month doses actually were actually giving the SAME amount of protection that you get from a monthly dose? Seems pretty obvious. So there's another source that supports your premise, and one that's pretty old at that.

Also consider that the Vice President of the AHS is in the employ of Merial, and things become quite a bit more clear as to why both those studies seem to have been largely ignored by the industry, and why the wording about Heartworm risk on the AHS site is vague and fear-inducing rather than honest about what the science has shown.

PBurns said...

Pretty amaazing isn't it? More amazing still is that you can break HHS / FDA rules and even get warning letters from them, but the companies just igmore the warning letters and nothing happens. Nothing!

As for conflict, lies, etc. it's not just in veterinary medicine

See "Harvard as Big Pharma" at >>


Anonymous said...

Now, that's really informative. Those maps explain why some dog owners I know never treat their dogs for heartworm, and their dogs NEVER get it when tested for it.

I read somewhere that the red wolf is somewhat resistant to the heartworm nematode. And I've also heard the same thing about the Dixie pariah dog or Carolina dog.

Unknown said...

I have a question about using the Ivermectin recipe you describe. When I went to the J R Enterprises website it says they have 05% Ivermectin (Our special blend). It doesn't mention mixing it with anything. Should this still be mixed with Porpylene glycol...if so how much?

PBurns said...

Please read the post CAREFULLY as it is self-explanatory. The stuff from JE Enterprises is ALREADY TO USE AS IS. No mixing is needed; simply follow dosage directions on the bottle.


HurricaneDeck said...

I don't mix my Ivermectin. I just use .1cc per 10 pounds of dog, dump it in something yummy, and have them eat it that way. I usually start treatment in the spring and end when the first good snow hits. And really, I only do it because I travel to mosquito infested areas often.

Laura L. said...

Patrick, this is exactly the kind of stuff that drives my sister nuts. :) She works at a vet's office (a pretty pricey one too) and she's horrified that I worm my dogs myself and give ivermectin for heartworm preventitive too.

Thank you for the work you put into your blog.

Viatecio said...

Laura L - No worries, and your sister is probably a bit brainwashed (no offense). I'm a vet tech in training, and am hoping to find somewhere with integrity to work once I'm out of school. Plus, I'll be such a BAD client: I'll do my own physicals, fecals (when/if necessary), vaccines (puppy series then DONE, rabies only because legal requirement), worming, medicating, and whatever else there is. Oh, and I'm planning on NOT neutering and NOT breeding. So, only using a vet when necessary.

BAA-A-A-A-D client. I either better find a good place to work, or I should just get on blood pressure medication now to counteract the frustration I feel when I'm forced to push high-priced food, expensive meds, yearly dentals and boosters, etc. It'll probably be a combination of both.

Anonymous said...

I'm glad to see that other other people diluting Ivomec for canine heartworm prevention. The Plumb's formulary book that I used to look up the dosages listed that ivermectin could also be mixed with vegetable oil, and that's exactly what I did for my pups. My local Tractor Supply had Ivomec on the shelf for ~$35. This is going to end up being a HUGE savings for me, since I have 5 dogs, with one in each weight range. I was terrified of overdosing my jack and initially diluted the solution even further to where my dog's resulting dose was larger in volume. Won't do that again - one of the larger dogs had diarrhea later that night!
And even though I do work in a vet's office and can get preventatives at hospital cost, it's still WAAAY cheaper to go this route for dogs. I also have horses and w/ their dosage, it comes out a hair more expensive to worm this way.

Anonymous said...

Viatecio - try to work for either an emergency or specialty vet. No food, heartworm preventative, flea product sales - or anything else that a "regular" vet does.

Vicki said...

Are you confident JR Enterprises sends exactly what they promise?
I worry that the product that JR Enterprises makes isn't accurate or exact. What do you think?

I have adopted some rescues and also am a foster so have many dogs to treat. HW and flea/tick gets expensive. I'm also a believer is less is more when it comes to my health and the health of my dogs.
I don't like compromising our immune systems with drugs.

PBurns said...

I give it to my dogs, and I am as confident of this company as I am of any company who makes anything. Let me ask you this: who made the medicine you give now and where were they made? Who made the coffee you drink in the morning and where? Are you sure poison is not in any of it and that it is exactly as it seems? How about the brake lines in your car? You have no idea, and that is true for 99 perent of everything, from the person driving the train in the morning, to the company that makes your dog food and bakes your bread. JR Enterprises has been around for a number of years, their core products are bought directly from Merial (and you can buy them from Merial too as I note) and mixing this stuff up is not rocket science. Use it if you want, don't if you don't. But I work in the arena of health care fraud (Google me) and I know what most people salute in health care is nonsense. Not all that glitters is gold, and not all that is gold glistens. But of course, a lot of people think otherwise, which is how Bernie Madoff got rich.


Choons said...

I have spent the whole evening doing my own number crunching on ivermectin meds for dogs and then found this great article. I noticed that microgram quantities of ivermectin are used for our dog meds which got me thinking what it really costs to make the stuff. Apparently a helluva lot more for dogs than livestock! As mentioned, 50 ml 1% ivermectin solutions are readily available for about $30. That works out to $60/gram for ivermectin if we are talkin horses, cattle, or pigs. BUT start talkin dogs? - 6 month supply HeartGard for 50 lb dog is $35 for 6 tablets that each contain 137 mcg ivermectin. That works out to 4.25 cents per mcg or a SHOCKING RIPOFF of $42,500+ per gram for ivermectin in our dog meds- an astounding 70,900% markup over the already retail-priced livestock products. NEVER AGAIN! Thanks for the article!

bdalzell said...

Now that ivermectin is off patent it is much cheaper. As long as your dog does NOT have two doses of the MDR1 gene (most commonly seen in collie related breeds, Silken Windhounds and Irish Setters) you can safely dose 1% ivermectin at 1 cc per 130 lbs orally (not injected) as the "worming dose" which will take care of almost all nematodes (hooks, rounds, whips, and some exotics) and in our experience it also helps keep fleas at bay.

The last bottle of Durvet Ivermectin I purchased without prescription at a farm supply store (such as Central Tractor) was $42 for 200ml. That is 400 doses for 60 lb dogs. We use it year round because of the anti-flea effect. Be sure to get the cattle drug where the only active ingredient is ivermectin. We measure it in a syringe to get the 1/2 cc dose and then just squirt it into the mouth against the inside of the cheek.

I have been using it on my Borzois since the mid 1980s with no indications of ill effects.

However the MDR1 gene is a real danger and if in doubt you should test your dog for the MDR1 gene. Dogs homozygous for that gene really will seizure with high doses of ivermectin (they need 1/100th of the "worming dose").

Here is a site that discusses the various drugs that dogs homozygous for MDR1 are sensitive to:

Ivermectin is used in humans in tropical countries to treat a variety of nasty human parasitic diseases (including a human specific species of heartworm).

However occasional instances of canine heartworm in humans have occured in tropical climates (Florida). These heartworms can reach full size in humans but do not make microfilaria.

Adam said...

We live in Minnesota and our rescye dog came from the Kentucky area. He's tested negative for heartworm since he came home in October '09 and was treated for the 2010 season with vet prescribed preventative. When he came home, his health fell apart for about 8 months. He's been doing great now, with just the occasional dip in his health, but we're concerned that the heartworm medication is really hard on his body. We gave him his first dose of the season yesterday and noticed a marked change in his energy level and "brightness" today.

He weights in at 27.5 pounds and is currently on the Interceptor dose for 26 - 50lb dogs. From what we've been reading here, it seems that the Interceptor is the better choice, rather than Ivermectin—his breed mix is unconfirmed, but if it's helpful to know, we think he might be a Carolina dog/Boston Terrier cross. He is primarily a red roan color with the white feet of a herding dog. Since he falls at the low end of the recommended weight range, we're wondering about giving him a smaller dose of the Interceptor (next weight category down) and possibly less frequently. We would welcome any advice or other avenues for reading. Although our vet practices some alternative and eastern medicine methods, they tend to run the "party line" when it comes to drug use so we don't feel confident that they're the best resource to ask about lower dose/less often.

Bummer that our vet system is set up to profit from use and overuse of drugs. It makes it hard to trust that we're doing the right thing by our animals. Thanks in advance for your replies.

PBurns said...

Adam, look at the map and you will see that there's only a 4-month period for even a POTENTIAL heartworm problem in Minnesota)July-Aug-Sept-October.

As I note, "It takes about three months for microfilaria (baby worms) to grow inside your dog to a larval stage, and even longer for these larva to mature into adult heartworms. If your dog is dosed with a simple Ivermectin treatment at any time during this period before adult worms are present (a period that lasts about three months long), the larvae will never develop into adult worms, and will die. Read that statement again: a single dose of Ivermectin will stop heartworm dead up to 3 months after your dog is first infected."

Bottom line: dose once in August and again in October, and you will be fine.

Your dog is a mix breed -- almost zero chance it is a Carolina Dog.

No reason to use Interceptor, especially if your dog is not tolerating it well (most do). Go with a low dose Ivermectin and you will be fine -- Ivermectin even works with Border Collies at the very low (proper) dose.


onlnguitar said...

I love this site! Amazing information.

My wife and I are very much into being as natural as possible with ourselves and our dogs. We have known our our vet for years, even before we had pets. I know he doesn't intentionally push things on us, but it seems he has succumbed to alot of the marketing out there.

Just had our 3 dogs there for 3 year rabies and heartworm test. We had not administered heartworm preventative for about 10 months or so. Glad I came across this site before I made a large purchase of medicine. Also, he definitely made sure I understood they recommend more vaccinations than just the rabies. Glad I've done my research. Just a little bit of thinking and 5 minutes of googling to realize dog vaccines are no different than human vaccines. We have slowly taken our dogs off of everything. We have a local holistic feed and seed that I am sure sells the ivermectin.

Again, thanks for this site and helping us loving pet owners educate ourselves.

cherae said...

Thanks for all this information. I have been baffled by the idea that heartworms are such a "horrible killer" and that my dog MUST go through the $700 regimen with no guarantees of success and possibly death... and was also told NOT to give a dog Heartgard once it had tested positive for heartworms. It certainly seems ridiculous that something so "prevalent" and "rampant" would have no over the counter remedies with easier access to the many dog owners who only want to take care of their pets.
I have a dog which tested positive for heartworms several months ago and I have been in turmoil about what to do til I read this article and called some friends who have cows and many dogs and was told similar instructions as you give here. I am currently searching for
doxycycline online without a Rx but can only find oxytetracycline at Tractor Supply.
Will this work as well or must it be doxycycline?

PBurns said...

Use Doxycycline and Ivermectin together, in proper dosage and after reading ALL of the above post carefully, to treat for hearworm.

Bird Doxycycline (exactly the same as ALL doxycycline) is available from Amazon without a prescription in 100 mg capsules. Dose as noted.

Ivermectin can be diluted as noted above, but can also be purchased as sheep drench in an 0.08% solution. Again, available through Amazon and other farm and vet suppliers.


cherae said...

Thank you for answering my questions and please forgive my ignorance about dosages etc but I want to make sure I understand and measure correctly as I am working with a 1% solution and a mL syringe.

Is it necessary to dilute the 1% solution? Would it be ok, for example, to give an 80 lb dog (with heartworms) .2cc of undiluted 1% ivermectin? and would this be given weekly or monthly?
Also, what is the correct dosage for doxycycline?

I have found a variety of instructions regarding this. One recommends the following: a protocol of ivermectin (Heartgard) given weekly at the normal monthly heartworm preventative dose (6 mcg/kg), combined with doxycycline at the rate of 10 mg/kg/day for weeks 1-6, 10-11, 16-17, 22-25, and 28-33

This seems a huge amount of doxy at approx total of 511 100mg pills being given over a 36 week period pulsed at above schedule.
Have you heard of this? And I am wondering if the 5 day a month dosage would be just as well? I can't imagine shoving 3.5 pills down my dog every day for 6 weeks straight. I think she would begin to avoid me within a few days of this routine.

PBurns said...

I have said this before, but let me say it again: If you cannot do measurements and if you will not follow dosing directions, please GO TO A VET and pay the money. At least your dog is not likely to be killed.

My advice is not for people who cannot do measurements or follow directions. Dosages matter A LOT. Too little and they not only do not work, they increase the immunity of the pathogen. Too high, and you may overdose your dog and kill it. Go to a vet and ask them to put your dog on an ivermectin and doxycline protocol if you are confused, and tell them you have the doxy and the ivermectin (they will often sell it to you at cost if they know you know the true cost and have an alternate source).


Carla said...

PBurns, I thank you for finally putting it out there that not everything vets suggest is necessary and that with a little research, there are alternatives.

I have a question though before I start ordering.
I have 4 90-100lb rottweilers.
Buying from JR Enterprises the 60ml .05% Invermectin, yields 7 months worth of 2ml/cc doses for 4 dogs.
Cost $25

Buying from KVsupply the 50ml of 1% Invermectin and the gallon of Propylene Glycol, yields 9 years worth of 2.25ml/cc doses
Cost $55
Plus 90 capsules of Doxycycline Hyclate (enough for 18 months) for 1 of my dogs which tested positive
Cost $14 from

Total $70

That's 9 years! Does the product remain effective that long? What's the shelf life in a cool dry place?
I'm hoping I didn't do my math wrong but I don't think so

Can you help?
Thank you
Carla and her beasts ;o)

Deb said...

Excellent article! I have used the cattle Ivomec for years and never had a positive HW test on my dogs. I start it in June until November so pretty close to what the maps say for my state. My vet knows I am using this med and no longer bothers lecturing me about it. As an NICU RN I no longer dilute the med as I am used to miniscule dosing and just give .05 to .1 ml depending on the size of the dog I am treating. I paid $36 today at Farm & Fleet for a 50 ml bottle that doesn't expire until 4/15. With 8 dogs being dosed from this bottle I am in good shape for 4 to 5 years now.

PBurns said...

Doxycyline is good for several years past the expiration as research done by the U.S. military's Shelf Life Extention Program has shown.

Ivermectin is good for two years according to its expiration date and probably longer than that.

Be fare, figure two years, and share with friends.


Natasha said...

Does Interceptor provide three months of protection? I just happen to have a years worth and would rather use it then buy new meds. Up until this point I was testing my dogs every two-three months, I guess this is an easier way!

PBurns said...

Interceptor is an insecticide and it is designed to kill the larval heartworm, same as Ivermectin. The only difference is that Interceptor (generc is Milbemycin Oxime -- look it up) is a little LESS effective than Ivermectin and requires more expense and a prescription. If you already have it, great, but I would not use Interceptor unless I had a collie or collie cross.


Natasha said...

Thanks so much, great article.

One more question, will the twice a year dosing schedule also provide necessary protection against hookworms and roundworms or should I regularly run fecal tests to check?

I was actually bringing my dog in for blood work every two months in the summer prior to reading this rather than give him heartworm meds, this article made my life A LOT easier.


PBurns said...


Nowhere do I say dose twice a year. I have NO idea where you are, etc.

For information on dosing for intestinal worms, please see the posts on that >>


Unknown said...

Thank you for your information. I've been reading your blog for years with interest, as I'd been running with some houndsmen. I finally bit the bullet and got dogs myself this year. I'm quite capable of medicating and treating them myself (except for rabies vaccinations!) but it's nice to have dosages and alternatives all laid out in one place like this. I can't imagine running to the vet every time one gets a little laceration when I can glue it closed myself (or even suture it if needed.)

Melissa said...

I was wondering how much doxocyclin I would need to order for a 50 pound dog? I understood the part on dosage for heartworm meds, but wasn't sure about the other. Could you please help?

PBurns said...

5 mg per pound of dog per day. Doxy is NOT a sensitive dose drug, however, so if you give 300 mg (three 100 mg capsules of doxy) to a 50-60 pound dog, you are fine.


PBurns said...

5 mg per pound of dog per day. Doxy is NOT a sensitive dose drug, however, so if you give 300 mg (three 100 mg capsules of doxy) to a 50-60 pound dog, you are fine.


Lysakila said...

I love this article so much.

At first, with your first few paragraphs, it bothered me a little bit, because I have a dog with adult heartworms in her heart and lungs. If you had been telling people that heartworm preventive medication unnecessary, that would have been wrong.

But instead you tell people to do what I've just done for my heartworm-positive dog: buy cheap ivermectin online ;) That's the best thing to do, and it avoids all the veterinary bills. I do think that for any dog that hasn't been tested or on heartworm preventative, and has been exposed to mosquitos, its good to test. (if they're older than 6 months) If I hadn't tested my dog, I might not realize how important the hw-preventative was, and I definitely would not know to give her doxycycline, which is super important if you are doing the slow-kill method.

Also I don't know how important this is, but I think it's also good to give dogs anti-inflammatory--my vets gave me one to give to my dog along with the doxycycline.

Thanks so much for the verrry informative article :)

FromHangTown said...

Four years now using JR Enterprises.

Very easy to use.

Viatecio said...

Figured you might enjoy this.

The clinic where I work had a positive heartworm test on a dog. It was confirmed by the presence of large numbers of microfilariae on a filter test. The dog was put on Doxy, given a dose of Heargard and will have to go through the whole rigamarole of melarsomine after a battery of tests "to make sure he's healthy enough to go through with the treatment" (at over $100 per Immiticide injection).

I can just hear now that the money-maker for the clinic will be that "We recently had a dog with a positive heartworm test, we need to test your dog and you need to buy more Heartgard to dose your dogs through the coming winter months." Or some similar sales pitch.

The kicker?

This dog was found as a stray in MICHIGAN and brought back to central Ohio by his well-meaning rescuer.

The infection did NOT originate here, and the cold weather we've had probably means that mosquitoes are not active, and the L1-L2 stages within them are not maturing, as per the Knight/Lok paper. And since the dog was brought home recently, it's unlikely (but not impossible) that a mosquito could have fed from the dog and shared the wealth.

But keep on pushing those yearly heartworm tests (by the way, the paper--written back in 1998--advocates for testing ever 2-3 years...interesting to see how economic advantage has presided over sanity!), "prescription HW preventatives," and year-round dosing!

And yes, the "fear jar" does do its part!

Unknown said...

$700 to treat heartworms is now a bargain. I'm guessing our bill will be $1300. Our 4 yr old German Shep who is a foster, is between a Stage 2B & a Stage 3. Because of the large level of infestation, I lean towards the aggressive, offensive Immiticide method. I don't know if this sweet boy will make it 18 months. I wonder of if he will make it thru 3 arsenic injections.

Your Blog is excellent!

PBurns said...

I have deleted the section on diluting cattle ivermectin to dog forumula, because it's simply cheaper and easier (and therefore safer) to use sheep drench at the correct dosage.

Since this post was written four year ago, a new generic version of Heartgard has come out, and I have added information on that as well.

Folks who tell you it is dangerous to split Heartgard tablets have no idea how pills are made, and are simply lying or are misinformed.

Tiffany Hartman said...
This comment has been removed by the author.
herbluvver said...

Mr. Burns, thank you for this article. I appreciate your "cut to the chase" attitude about heartworm treatment. My previously heartworm-positive dog recently tested negative for microfilariae after I administered the roundworm dose of ivermectin for three years. Did the research myself about this. The doc wanted to use strychnine -- "it's the only sure way to kill them." Ha. I probably gave the increased dose too long, but anyway, it killed them. Thanks to your article, I will back off and give my dog a heartworm treatment every three months now, using the dosing in your article.

Unknown said...

My vet is telling me that I must get xrays of my dog prior to any treatment of heartworms. Are these just ways to pad the bill? They're saying xrays first, then blood work. I just ran across your very informative page last night and don't want to get caught up in tje hype. My 4 year old lab exhibits no symptoms and was tested as a positive for heartworm in July in Michigan, and I've been giving him a heartguard tablet every 2 Weeks since. Any additional advice is greatly appreciated.

PBurns said...

Yes, a complete scam. Dose with Ivermectin and Doxy as detailed. Please read the COMPLETE post and follow the links as well. Maintain the regime, and with some portion of the money this will save you, make a donation to a local rescue.

Patton Brand Strategy said...

Finally, an explanation that makes sense. Thank you for taking so much time to explain this issue. I grew up on a farm and know how treat most animals for basic health care needs. Our farm vet was an "Integrity" vet with a lot of common sense and great dedication. But now days, small animal vet clinics are as much into sales as they are animal care. Unfortunate for a number of reasons, not least because they are losing consumer trust.

HLM said...

So happy to have read this article. I am currently treating my Lab for heartworms. We live in NC and my particular neighborhood is SO infested with mosquitos, due to the ponds all around us I'm sure.

I'm not sure if there are adult worms present or not. We were just told he tested positive. He's not lethargic and doesn't have a cough. The only sign is his face is turning white. He's only 4 yrs old and I was told he shouldn't look aged just yet. :( Poor guy..I feel horrible. This is how the vet has us treating him.

2 100mg Doxycycline tablets twice a day for 30 days.

He told us to give him 1 1/2
20mg Prednisone tablets 1 hour before giving him heartgaurd. Then another 1 1/2 Prednisone tablets 6 hours after the heartgaurd. The prednisone is for his first "treatment" of heartgaurd only. Then after this he said to give him just the heartgaurd monthy, then bring him back in 3 months to check his progress.
I gave him the prednisone this morning and am due to give him the other dose this afternoon. I am concerned that the amount of Ivermectin in the heartgaurd is not enough to get rid of the worms.

I would like to change him to the treatment that you described for prevention after I get him free of the heartworms he has now...that being said..
He's 65 on a normal basis I would give him 0.3cc of Ivermectin for "prevention" between the months of June and December. Just so I'm clear, I can give that amount every 3 months, right?

Right now though for the treatment of heartworms, I would give him 3 times the amount I normally that 0.9cc per month or is that on an every 3 month treatment as well? ... Along with 2 100mg of Doxycycline tablets twice a day for 5 days per month for 18 months then have him retested?

Thank you for all the that I found your blog!! :)

Unknown said...

Great article. I am always double and triple checking what any vet says. Let me tell you about an experience we had with our Dingo. Shortly after moving to California out dog came running in the door one after noon yelping and trying to rip her face off. We looked at her face and her eye appeared to be bulging out of its socket. We rushed to the emergency vet (assuming snake bite or similar) and after a very expensive once over the e.r vet told us that our dog had a retro-bulbar tumor (not sure of the spelling but a tumor behind her eye) which was likely inoperable and they suggested that we put our dog to sleep. The told us that IF it could be treated it would be very very expensive. I found it hard to believe that the dog was fine when she went outside and 2 hours later had developed cancer to the point that her eye was bulging out. We took our dog home, made phone calls to other vets to be told the same thing (they were of course assuming the dog had a tumor since they did not see her) and finally ended up talking to a cancer specialist. We drove 3 hours to get to this specialist who kept our dog for testing. 3 days later we were told ever test possible had been run and there was no sign that this was cancer. They thought maybe a dental infection. So they called in a doggie dental specialist who did extensive exams to find nothing wrong there either. The doggie dentist was not satisfied and we sure the teeth were somehow the cause of this so they put my dog under so they could get a more in depth look. They found the problem. Our dog had one of those sharp little stickers (the kind with 5 or 6 little arms on it) that had worked its way under her gums back behind her molars (in the area of the eye socket) and it was infected and causing sever swelling behind the eye (the bulging eyeball). They did minor surgery to remove it, cleaned out the area well and gave her antibiotics. The cost of all of this? $1200 at the E.R. (the one who wanted to kill my dog over a sticker) and nearly $6000 at the cancer treatment center for all the testing, the hospitalization and the solution. I learned a valuable (expensive) lesson and that was always to do my own research and check things out and never ever take a vet's word as gospel. Even the ones with the best intentions and with no desire to rip you off.....are after all...only human and capable of mistakes.

Renea said...

I'm about 3 yrs late but so glad i found your article. Still relavant! Thanks for the info PBurns! I always thought there was something odd about the HW meds & tests being pushed constantly. I caught this post just in time as my vet has been pushing me to get my dog tested TOMORROW! As for some people on here, they really need to REALLY read your article above before posting. Geez!

Devon said...

Everyone above has already said it, but I'll say it again: Excellent post, and much appreciated!!!

Anne said...

Thanks for this. I found it while looking for a more economical way to treat my dog. I just adopted her from a local shelter, and she tested positive, but asymptomatic. I will have her tested again at the local non profit vet to confirm her status - we are in FL, so I expect that she is indeed infected. And then I will start her on this regimen. Thank you again for giving such detailed & helpful information.

jess said...

I have read this post a few times! Thank you for this valuable information! I can only find the drench (topical) or injectable ivermectin, not the oral. Can these be given orally? I've been searching through southern states and tractor supply. I have a 29-lb dog and a 70-lb dog. Thanks!

PBurns said...

The sentence reads: "...many working Border Collie folks dose their own dogs with a low dose of sheep drench 0.08% Ivermectin.: Yes, it is given orally at proper dosage for weight.

Barbara said...

Hello and thank you for your expertise. I am curious about a new strain of heart worms as a result of Katrinia (or so they say) and that Advantage Multi is the only "Heart worm Preventative" that was 100% effective, whereas Heartguard failed miserably. I live in Memphis, on the Mississippi river which is reported to be a danger zone for this type of heart worm. Can you please give your advice?

PBurns said...

It's all marketing. Ignore the nonsense.

There is no substantive research that shows Heartguard is not working, and there is no medicine anywhere that can ever claim a medicine is always 100% effective. Both sides here are selling nonsense.

The simple truth is that Ivermectin is very cheap and very effective and that if you properly dose your dog with this cheap low-cost medication, almosty ANYTHING is more likely to kill your dog than heartworm, including you falling on the dog, accidental ingestion of a human medicine that slips off the counter, car accident, choking, torsion, poison, stray bullet, lightning strike, poisoned by commercial dog food, poisoned by non-commercial dog good, eating a tic-tac, and death by rat bite.

Relax and use cheap, old, and proven-effective Ivermectin. Katrina did not create a new species of anything; but greedy liars and flim-flam scare-mongers have always been with us.

PBurns said...

The folks who sell stuff are leanign pretty heavily on this paper >> but they are generally not reading it veruy closely.

The paper says:

"Macrocyclic Lactone (Macrolide) Antibiotics. The introduction of the macrocyclic lactone endectocides (macrolides), ivermectin (Heartgard®, Iverhart ®, TriHeart®), ivermectin with pyrantel pamoate (Heartgard® Plus, Iverhart Plus®, TriHeart® Plus), ivermectin with pyranel pamoate and praziquantel (Iverhart Max®), milbemycin oxime (Interceptor®), milbemycin with lufenuron (Sentinal®) and with spinosad (Trifexis® ), selamectin (Revolution™), and moxidectin (ProHeart®, ProHeart® 6), and moxidectin with imidicoprid (Advantage/MultiTM)
has provided the veterinary profession with highly effective, incredibly safe heartworm preventatives in a variety of formulations and with a variety of spectra (see Table 1). These agents, because they interrupt larval development (L3 and L4) during the first 2 months after infection, have a large temporal window of efficacy and are administered monthly. These products have enjoyed great efficacy, virtually 100%, when used as directed. Recently, a single isolate (MP3) from north-eastern Georgia has shown restistance/tolerance to some macrocyclic lactones, when administered once 30 days after heavy experimental challenge. (emphasis in original)

"All are safe in collies when used as directed at preventive dosages…..

"This failure of complete rapid microfilarial clearing, coupled with concern in the Mississippi River delta region (areas of LA, AR, MS, TN), has caused concern that resistance to this class of drugs may be developing.

"The proof of this is small, but taken together, the data argue that a small percentage of microfilariae, isolated from dogs in this region have characteristics suggesting tolerance to the drug group. A joint consensus of the AHS and CAPC stated the following (excerpts). 'There is evidence in some HW populations for genetic variations that are associated with decreased in vitro susceptibility to the macrocyclic lactones. Whether the observed genetic variations constitute heritable resistance is being investigated. Most credible reports of LOE that are not attributable to compliance failure are geographically limited at this time. The extent of the problem is obscured by demonstrated lack of owner and DVM compliance, possible changes in environmental/vector factors, and more effective antigen testing. The potential for resistance is not a reason to abandon use of approved preventive products.'

In short, folks are LOOKING for resistance (they have been for 30 years) but so far they have not found it and what very few problems they have seen are, most likely, due to failure to administer Ivermectin.

Barbara said...

Thank you, thank you, thank you...... I appreciate your candor, humor and intelligence!

Unknown said...

I'm sure you've heard this a thousand times but I will say it anyway. Thank you so very, very much for this information. This is what i remember from my childhood on a ranch in west Texas. We recently rescued 10 dogs and several have tested positive for heartworms and the cost of trying to treat even a portion of them would be astronomical. Here in San Antonio the prices are over $1000 for a small dog and some of these rescues are not small.
You are a life savor, literally. Some of these dogs would probably have had to be put down as no one would adopt them with the prospect of the expensive vet treatment to be right off the top.
Once more thank you so much.
Scott Rhamey
Our Little Friends, small animal rescue
San Antonio, Tx

Taz Tech said...

I have recently rescued a boxer/pit mix. Took him to the vet and found that he has intestinal worms and heartworms. I paid the $170 for the visit tests and treatment of the intestinal worms. I am supposed to take the dog back in three weeks to start the treatment for heartworms to the tune of $700. (Which I can't afford) After doing some research I found your site. But I have two questions. Do you treat with the Ivermectin then start the 5 days of Doxycline, or is it better to finish the five days of Doxycline then give the Ivermectin? Also if I am reading this right this treatment would take care of both the intestinal round worms and the heartworms both. The vet was having me treat them separately.

Peg said...

Brilliant article. Thank you!

Unknown said...

Thank you so much for this!!

Unknown said...

Thank you so very, very much for this great information. I had never heard any of this before so I tried to fact check before taking it as gospel, and was thrilled to find it so easy to confirm. I've been worried about where to find the cash to medicate my 7 dogs this summer and this is a complete life saver! Thank you, thank you, thank you for the great information!

Bebe Russell said...

I live near frozen Chicago, Illinois. The people at the vet's office look at me with confusion when I say I only treat for heartworm for six months. It's just common sense that if there are no mosquitoes, there is no way for it to be transmitted. When these medications first came out, we only treated for six months. When and why did it morph into 12 months? Then I tell them I want Heartgard not Heartgard Plus, which has a wormer. Last year all they had were the Sentinel and Revolution type of medications, which treat worms, fleas and even ear mites. Why would I treat my JRT every month for worms, fleas and ear mites when she doesn't have worms, fleas and ear mites? It's just common sense. I end up having to get a prescription for Heartgard, which I give every 6 weeks. I am also the client who declines the yearly vaccinations and asks for a vaccine titer instead, but that's another subject.

Unknown said...

I grew up on a farm and worked for a Vet my senior year in high school. We have always used Ivomec on all the sheep and the dogs (though were VERY careful treating them as we had Collies). I have used Ivomec as a shot for my dogs (since moving out on my own) for years, any kind of pest will vacate the animal within a couple of days after treating them.
I try to tell people not to buy that expensive crap from the vet or even online. Its a waste of money. I have a 14 year old Blue Heeler, 11 Year old Lab/Collie mix, 7 year old Australian Shepherd/Great Pyrenees mix, all of which baffle every vet they've been too in the last couple of years. Aside from their Rabies Vaccinations, the vets never have to do anything else as far as maintenance for their health goes. All of them are outside much of the time and get plenty of exposure to all kinds of pests. And considering their age, there's usually SOMETHING the vet can pick on...
I have tried for years to tell/train all my friends some listen...others don't. I love this article though...It will be shared on facebook...I LOVE being able to tell people "I TOLD YOU SO"!

jude said...

Thank you for the thoroughness of your information.

Unknown said...

Very interesting post. I've been doing a lot of reading this weekend as my 5 year old perfectly healthy male lab was diagonosed with heartworms. He has absolutely NO signs of heartworms. He has been on monthly Heartgard plus since he was 8 weeks old. The dr started him on a 14 day dose of Minocycline and wants to do immiticide injections following the Minocycline. After reading this and other articles I am very confused. First I can't believe he has HWs, secondly he has not been retested. We give the HG plus every month year round. I think im going to get him retested before the injections because Ive got to believe after reading this it may have been a false positive test. But what if not? We live in Greenville NC near the river so there are Mosquitos but he stays inside most of the time. I would have been equally surprised if they told me he was pregnant. What do I do?

Puddin said...

In the article, you mentioned testing positive and you wrote "more on that important distinction" but then I didn't see more.

Can you talk about that?

Here is the quote
"You will also note that this map does not show adult heartworm infestation in dogs, but simply the number of dogs that tested positive for heartworm. More on that important distinction in a minute."


PBurns said...

The test is positive if microfilariae are there (very tiny larva) which can be wiped out with a simple dose of Ivermectin. Heart WORM is a worm as distinct from "heat worm positive" which can mean EITHER the worm or just the microfillariae. There is a big difference in treatment and concern here, but the confusion also means big bucks for veterinarians.

j-schrec said...

We hit some hard times this year and my husband has been out of work. We were out of heartguard, and I was very upset and absolutely panicked that we could not afford to shell out a few hundred for our dogs one year supply of heart-worm meds (we have two, 70ish pound rescues). A simple google search for, "how to save money on heart-worm meds" led me hear and I am so glad and grateful! Thank you for spreading the word on this!!!

concretenprimroses said...

I had read this post some time ago and forgotten some important details when I went to the vet. I was told there by a tech that heart worm was also carried by ticks! Since ticks were out tho not mosquitos when I started dosing again, I got the test. Arrgh. I am going to write a complaining letter to the vet/owner.

Hcross said...

I live in South Carolina and did not have my dogs on preventative because they were almost always indoors. Sadly, one dog died of heartworms and the other had to be treated. The treatment was expensive and very painful for our other dog. I made a terrible mistake and regret not keeping my dogs on preventative.

Al Magaw said...

a list of dogs with % potential for the MDR1 mutation -------

Roslyn said...

A great big thank you for your myth busting article. We live in AZ, and I have been dosing our little Aussie Terrier only half the year and unfortunately I just had her tested & replenished the 6 month supply of Heatguard!
I am also a believer in minimal vaccination & Button has always been on a 3 yr. routine. Now at age 9 our breeder recommends no further Vacc. at all other than mandatory Rabies which I understand is ALSO a myth! I was horrified to discover that in Mexico dogs must have rabies vacc every 6 months.
Thanks again

Unknown said...

I can see two testimonials that the stuff from JR Edwards works - you use it, and FromHangTown. Why aren't more people chiming in and saying that this works?

Vicki said...

I have purchased from JR Edwards several times, Brooke R. Since I have so many dogs, I prefer to prepare the mixture as it is cheaper for me. I've used the above HW prevention for many years. Also, I've cured eight dogs who were HW+ using the slow treatment. I live in a rural area and both my vets do to_they treat their animals as Paul recommends.
Additionally, if I treat dogs per pound, they do not have fleas or parasites. Easy.

PBurns said...

And sheep drench ivermectin (available online from Amazon or your local feed store) is all over >

Lillaby said...

Hi, GREAT article! Thanks so much.
Just to be clear I'm understanding.
If we get the generic heartguard or large-dog pills and cut them in half, that dosage is once/3 mo. according to our area.
But the sheep drench and the JR Enterprises ivermectin should be administered monthly? or can we do per 3/mos. there, too?

PBurns said...

Who makes it does not change dosage. Dosage by WEIGHT of the dog. You can dose every month if you want to, but it's not required as noted. Dosing in cold weather makes no sense at all as noted.

Unknown said...

I'm currently treating one of my dogs with the slow kill method. I was wondering if moderate exercise is ok while he is being being treated?

PBurns said...

Since I have no idea how bad off your dog was, or what you mean by moderate exercise, I could not tell you. If the dog was not wheezing and coughing before treatment, and if by "moderate exerise" you mean running around in the back yard a little, I doubt there is a serious worry. If, however, you mean two mile runs on a wheezing dog, then NO. If in doubt, consult a vet.

Unknown said...

We just came home from taking our 3 month old puppy to the vet for a checkup. They pushed and pushed for the heartworm testing and Heartgard medication. I very emphatically told them NO every time. I have owned dogs for 50 years and have never had a problem with heartworm and I don't believe the problem is as widespread and serious as they make it sound. And I know that it is transmitted by mosquitoes. We live in WI where we have them for only 3-4 months. So why do we need to dose all year? We don't. Thank you for this article that just confirms my beliefs.

sarahmae said...

I wanted to get some Revolution for my dog's flea problem. I don't know if it is the same everywhere but here in California my vet is saying that I would first have to bring my dog in for heartworm testing and provided the test is negative, they will prescribe Revolution. On a site made for vets prescribing various heartworm preventatives it states that Revolution is safe to give heartworm positive dogs. Now, I certainly don't want my dog to drop dead while attempting to treat his fleas but SERIOUSLY? I used to be ablet to get Revolution without all that nonsense. Why aren't thousands of dogs suddenly dying in places like Australia where you don't need a prescription for Revolution? If they did wouldn't the pharmaceutical companies be exploiting those facts for their gain? It's ridiculous that you have to take your dog in for testing just to get a flea medication.....aren't fleas a disease spreading problem for all animals? My guess is that it's not quite the money making scam as heartworm prevention is.

Regret A Vet said...
This comment has been removed by the author.
Stacie said...

I have a rescue dog with heart worms. She runs, plays and doesn't have a cough. Her vet said if I used the heart worm pill we use monthly (Iverhart) every month for 12-18 months it will rid her of them. Would this be the same as using the .05% solution from JR Enterprises? Or would I have to use the dose of Doxycycline also? I ask because we have 10 dogs and are looking for a cheaper way to protect them. She is the only one with heart worms.

Jay said...

Thanks for saving me nearly a thousand dollars over the last few years. My dog thanks you too...every dollar not spent on overpriced meds is another to spend on expensive balls.

Unknown said...

Thanks for the article, you may help save my Pit. I found him starving and wounded and I said "I can't let this happen." So, he's my bro now. But he has adult heartworms. My question is about the 18 months - do they still have to limit all physical activity? He's a pup(2yrs) with insane energy levels. It will be alot of work to keep him calm.

PBurns said...

I cannot and will not advise on a dog I have not seen. Talk to a vet about the low-cost kill regime. You can afford this. Not clear if the dog can without inspection.

Aafke said...

Thank you for this very clear article. I moved to Texas two years ago and heard so much panicky stuff about heart worms, we adopted a puppy (heart worm free at 3 months!) and were given a course of Trifexis which made him very sick for two days and I started to look for alternatives. I was also freaked out by the vets here and all the ''compulsory'' testing, vaccinations, etc. I am used to far more down-to-earth/no-nonsense vets. I got the sheepdip, been using it for a year (in the hot months) now. No problems. Your article and the links make dosing clear and simple.

AbokehNfocus said...

I too love the information on this site as it validates the treatment choice for my 12 year old beagle for slow kill heart worm. My vet was very communicative with me and gave me the options available. I chose the slow kill with ivermectin and the antibiotic. after just 3 months of the treatment it was like he was a puppy again! he lost the fluid build up and the cough ceased. His energy level went through the roof! and I have had no problem what so ever with any of the meds given him. I am still amazed at how much he has improved. I also have a shit zu with major skin problems, red mange especially and flea allergies. The vet also recommended the oral ivermectin for him and he has amazingly recovered! His hair has grown back and his skin is perfect and normal. No more scaly red patches and no more problems with any allergies...and all within 3 to 4 months of using the ivermectin. I also have started using grain free foods for him with Omega3 fish such as mackeral to maintain his vitality since taking him off the Ivermectin and his immune system seems well enough to handle all of his issues...I consider the ivermectin a wonder drug for what I have experienced and am so grateful my vet suggested the alternatives that were out there. I hope this will help dispel others doubts about the potential for trying the ivermectin for numerous problems in their dogs. Thanks so much for giving us the knowledge to have choices and the faith to try them on our own. Thanks so much!

Homer10 said...

OK, I'm getting hit with a demand from our vet, that we have to test out dogs for Heartworm EVERY 2 YEARS! Let's see, if I have given our dogs the medicine for 6 months, and now it's time to get a new 6 month supply, they want a Heartworm test which costs an additional $29.00. Why should I have to test these dogs again, and again, and again. They have been taking the Heartworm all their lives. Yet the Vet insists that in order to get a perscription, we have to have them tested again! This is smelling a lot like a big pharma scam to put a little more icing on their extortion cake. What are your feelings on having the dog tested EVERY TWO YEARS for heartworm.

PBurns said...

I have never tested a dog for heartworm. Not once, ever. I dose the dogs myself, as described, and I do not go to a vet for heartworm meds or "well dog" checkups. It is as you suspect.

frabjousfrank said...

This is an excellent article, and the overwhelming posts seem to support its credibility. I have decided to to a preventative treatment of my 7.5 year old English Springer Spaniel with a Heartgard generic Tri-Heart Plus.

She doesn't exhibit any symptoms of heartworms but I take her to SW Louisiana several times a year where the mosquitoes are quite prolific, hungry and the area is known to have more than its share of heartworm incidence.

I have had 4 English Springer Spaniels over the years and I've never wormed any of them. I stay away from vaccinations other than those that are absolutely necessary for licensing and/or boarding purposes. All of my Springers have enjoyed healthy lives with minimal trips to the vet and they have all lived past the average life span for the breed.

Thanks again for the excellent article and to all of you who posted your experiences with heartworm treatment and prevention.

Unknown said...

Because a lot of 'pet' sites belong to those who push pills, vaccines and poison pet food. It keeps an already overloaded veterinarian population in business.

Unknown said...

Thank you for sharing such important information!
You are appreciated and my GSD thanks you too!

Unknown said...

One error... if the heartworm's development in the mosquito is interrupted by one or more cooler days, as soon as the temperature reaches 57 degrees it will *resume* its maturation process where it left off. The 45 days of 57 degrees need not be sequential.

PBurns said...

The lifespan of a female mosquito (the one that counts) is very short -- 30 days in the wild. Laboratory studies show that for the heartworm microfilarie to development to the L3 stage requires a 24-hour temperature in excess of 64°F for about a month. If it's a steady 57 degrees, the mosquito will probably be dead before the microfilarie mature, which is why heartworm is a warm weather disease. Even a short and intermittent drop in temperature to 57°F, or just below, will retard the maturation of the microfilarie and the mosquito will almost certainly die before transmission, except in those case where it is very warm (over 75 degrees) for the rest of the time in its lifecycle. The point is that mosquitos are a life-clock that runs out after 30 days or so. The actual equation for the speed of heartworm development factors in temperature and time. The bottom line is that for heartworm to be transmittable you need to hit a total of "heartworm development units" (HDUs) within 30 days, and the only way to do that is for the temperature to be pretty hot during the day in order to offset nightime cooling. The map (done by scientists whose research was paid by Merial), reflects this, as it defines "seasonal transmission" as the first and last calendar days on which 234 HDUswill have been accumulated during the preceding 29 days (assuming a 30-day lifespan of a wild mosquito).

Unknown said...

Are German Shepherds included in the herding group as far as the MDR1 gene?

Unknown said...

Thank you for this article. I'm sick of vets looking down their nose at me for doing things in my own for my dogs. My question is, where to German Shepherd dogs fall into the MDR1 Gene discussion? I would like to use the ivermectin on my two as well as our pointer.

Unknown said...

Thank you. Your website encompasses everything I believe about veterinary marketing and the pharmaceutical companies in our country. Keep on terrierman keep on. Peace and love from NY state.

Btw I had the human version of Babesia (inregard to your Lyme post) and it SUCKS, but doxy and artemisinin knocked it out for good no money lost on my part!

Theresa said...

Hi Patrick, I can't say enough good about your site. I've learned so much. Thank you. I buy Ivermectin at a Feed store, will now buy online. The equine Ivermectin gel is 1.87% ! I wanted to be sure I mentioned that since the percentage is much higher than the ones I read about. All of tubes state how many pounds each tube treats but everyone will have to do their own math:) I've also been giving Pyrantel paste but it must taste nasty because my Bull Terrier, 13 in Nov. pulls his head away as I try to plop the stuff at the back of his tongue. Any input on the pyrantel is appreciated too! Used it because back in the day when I did buy HG it said the ingredients were Ivermectin & Pyrantel. I really enjoy the insight you provide on shining the light on how we get wrangled into being the "best" pet parent we can be per the vets. I missed several doses of his prevention and I did see worms and hard rice-like pieces so aggressively got to deworming my dog. He was getting pale and winded but no cough. Maybe hook and tape worms. He eats droppings of any critter that leaves some in the yard. I still intend to use the Doxycycline as it cannot hurt at this point. He has no cough but does get winded. I'm getting older & broken down and let things slide. Not intending to harm my dog. He is always in the house & more so in the heat. I've been getting out to the backyard with him a little more lately. I know he is older but I don't give up easily, especially on my pets. Thanks for everything you share to help us get wiser. Sincerely, Theresa

Theresa said...

Hi Patrick, just waiting to see if I somehow lost my long note to you as I was getting squared away with email & name. It was about Durvet equine Ivermectin 1.87% & Pyrantel that I have been using. Love your site. So glad I found you and grateful for the knowledge you share to enlighten those of us that have been wrangled into the "ideal" vet approved pet parent;) Im new to this but not for long! I'm heading to your directions for affordable Doxycycline. Thanks again, Theresa and Eddie the Bull Terrier almost 13🐾

Unknown said...

Yes! I am a professional AKC dachshund breeder. I have been doing this for 20 yrs here in the South at the recommendation of my vet. I use the 1% injectable given orally at the same one drop/10 lb. dose. However, i have read several articles by Vets stating that, like most other canine parasites, some degree of resistance by the parasite has been developed. Those Vets have recommended 2-3 times the stated dose as safe and effective as Ivermectin is given at much higher doses safely to treat other conditions.
Thanks again for your continued outstanding contributions to the knowledge base of canine husbandry.

traveling tipton said...

I read this article and the article from Dr. Atkins about heart worms b/c a German Shepherd that I had rescued from starvation and rehomed had to be returned to me b/c she had contracted heart worms. I followed these directions and the information that was posted by Dr. Atkins. It has taken 3 - 30 day doses of the Doxycycline to get her heart clean - but I hope this is the last dose she has to take. I took her back during the 1st dosing cycle then I had her tested, then started the 2nd dosing cycle. I thought she was done but she got an ear infection so while i was at the vets I just thought it wise to retest her. Although the test was much, much less than the first test I had done on her - the vet said i should go ahead and treat her again, which I am doing now. We will be done this week. I will wait a month and have her tested again. My brother had a dog that he had treated with the shots. It killed the dog. This treatment is much, much safer for the animal.

love tigers said...

We rescued a HW+ dog 2 years ago. With no job and 3 other dogs we opted for the slow kill method. After a year of inconsistent ivermectin she was still hw+. After that we became so much more regimented and gave her 10 cc every Sunday without fail plus the fish antibiotic once a month for over a year. Got the notice last week that she's NEGATIVE! After my 2 sshih tzus just dying in February this was fabulous news. She's healthy about 5 and never coughs and runs like the wind.

Petej076 said...

I am an Uber driver and 3 weeks ago while out driving I was stopped in the street by 2 crying little girls. They had been out all day trying to find someone to take their dog as the dad said not to come back home with it because he'd be putting it to sleep. I took the dog, fleas and all, hoping I could find a good home for him. He's a great dog but was chewed to pieces by fleas and himself so after cleaning him up and giving him flea treatment I brought him to the vet. They found him to be microchipped and he was tested positive for heartworm while at a shelter 5-6m ago. He was adopted out the next month with agreement to new owners that they would bring him back for treatments but they never did. I live on my own and already care for 2 dogs and 3 cats and just knew I couldn't afford the $1500+ treatment plan the vet was now saying I needed. As you can imagine I am so thrilled to find your article during my research into hopefully finding an affordable way to help this animal. I know he is 56lbs. My question is on the doxycycline. Does he need just one packet of the bird biotic 5d in a row? And do you start that 5day cycle the day you give him the ivermectin? Any and all info you have for me I would be so greatful. He is not coughing. He does sneeze quite a bit. The vet said his heart and lungs sound great.

traveling tipton said...

I want to report a CLEAN AND HEALTHY German Shepherd after 3 cycles of the doxycycline and MANY doses of the ivermectin. She now weighs 95.8 pounds and is GORGEOUS!! Spoiled rotten - but hey - you can't have everything. I want to thank you from the bottom of our hearts - we could not have done it without your help. My total cost was probably in the $500 - $600 range - and some of that was paid by the veteran that had her tested for heart worms. I got the doxycycline off shore and it was less than $70 for each treatment. The JR people are dirt cheap on the ivermectin. The blood tests were the most expensive part of the whole deal. THANK YOU SINCERELY!! Lee & Maggie Tipton, Stockton, CA

reskew said...

Fantastic article and thank you for the great information.
I noticed the link in the second paragraph for "4,350 dogs in 103 Los Angeles County" is broken. I think it should be pointed to instead.

Rolland/Michele said...

Thank you for the Great Article. Appreciate the dosage information regarding Ivermectin. Have been told that not only as a Heartworm prevention, Ivermectin will also kill other worms such as Whip and Hook worms that our dogs may be exposed to. Would greatly appreciate any and all information information in regards to that. Thank You Again Very Much.

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Unknown said...

Thanks for making this artile, I didnt know we could do our own prevention. Love it.

I am a bad client, vets literally sass me and argue with me, ive had a vet clinic rid of me.

I cant wait until my vet hears about MY own heartworm prevention.

Unknown said...

I have had a German Shepherd Rescue for 20+ years, I am sitting today with tears of frustration and $200.00 less in our Rescue check book. We took in 3 lovely mixed breed dogs, I took two to our vet yesterday for HW test, rabies, and neuters. They both came back HW positive..My vet that I started with is semi retired and so I had had the pleasure of dealing with new graduates that have ALL the answers and think I am tottering old bag for doing my own stool checks, vaccinations and use Ivermectin for preventative.. He insisted I needed 3 different blood tests ( YES THREE ) !! on the two dogs. Insisted that Imiticide treatment is the only REAL treatment that is acceptable.. I left, with a BIG bill, only leaving with rabies shots done and went home in tears and to my computer.. THANK YOU so much for your wisdom and blog.. It gave me hope that I am not crazy.. NOW to find a new vet I can work with :( We have saved over 800 dogs, only a fraction of that would have been possible if we had not medicated through wisdom and knowledge available. God Bless !!

MissFluffyBottoms said...

Thank you for this info! I have a staffy who is prone to staph infections on her skin, so the ability to keep fish antibiotics on hand has been a great relief.

I have a Border Collie, and he has been tested for the MDR1 mutation and he is negative, so I have not had any issues giving him ivermectin, but I will definitely be modifying how often my dogs get it from now on!

Unknown said...

it has been over 3 years now that I searched for an economical way to treat a rescued German Shepherd with heart worms. She had to be treated two times - but with the help from this website, the info from Dr. Atkins of Penn State and the grace of God, my rescued dog made a complete recovery. The info on the ivermectin has kept her from getting them again and also my little grand dog that now lives with us too. There are not enough words to tell you how generous and kind you are. Thank you from the bottom of my heart. Lee & Maggie Tipton, Stockton, CA

Samsara said...

My Border Collie died from what I suspect was the Ivermectin. Our vet never said a word about an issue, but when she developed a mucocele in her gallbladder I went online and made some deductions.

Anyway, we have another rescue, now; a HW+ 5 yr old Black Lab at 78lbs and asymptomatic. He also just tested + for Lyme.

SO...we're doing the doxycycline route after having him on Heartgard (our RIP Border Collie's leftover)for a year. I know we have stopped the L2-L4s but he's still (a year later) tested positive. Hopefully the 30 day doxy course will expedite death for the L5 Adults and - as we continue the monthly HeartGard he'll test negative this time next year.

I appreciate truthful articles like this and especially in the face of a young unseasoned Vet leading with, "You may have read about the Slow Kill method on the internet and if you have, it's not a cure."

Obviously she's not reading the same studies I am reading. I cannot wait to go back to her to have my dog testing negative so I can say, "Glad we insisted on 'Slow Kill' and that we didn't have to come up with $1100 to risk my healthy HW+ dog's life."

Yeah and our Sheep Drench will be here tomorrow. So thanks.

asweetwaterfarm said...

Go to work for a large animal clinic. They are used to using off label meds. I can call in a request for just about anything I need for cows and, because they know I'm somewhat intelligent, they trust me. They also know I'm much more homeopathic and respect me for it. Small animal vets and vet techs are in for the money. Large animal vets don't make a fancy living but they love what they do.

Unknown said...

I just wanted to say thank you! This treatment was very effective for my Chihuahua. She tested positive at 14 years old; 16 months later she is negative for heartworms. She is 16 years old and has the spring back in her step! Thank you!

1Seeker said...

Hey Folks, I found this post researching Heartworm Treatment, I am a RN so I don't trust Allopathic physicians much less a Vet. Bunch of flim flam artists. Anyway, I have looked at the post on the Billion dollar Heartworm scam and do appreciate it, the only thing I didn't get was the dosage for the Monthly 5 day doxycycline regimen... I read a bunch of various online postings for treatment schedules...many want the ivermectin week....doesn't match the life cycle and The dosage for Doxy is 5 mg per lb of body weight per day.
Example: A 100 lb dog would receive 500 mgs of doxycycline daily for 4 weeks and redosed again 3 months and then six months later, I just don't buy needing the med for a solid month !! could you folks with a little more experience ...throw a dog a bone...Thanks !!!!

Anth0yo_o said...

Where can I find doxycline without a prescription? Every site I visit, including the ones you provide, require a prescription.

Anth0yo_o said...

Where can doxycline be found without a prescription? Every site I visit, including the ones given by you, require a prescription.

Unknown said...

I found MilbeGuard is a generic for Interceptor. I have a white pawed collie mix 6 month old rescue I dosed once with Heartgard a few weeks ago. I haven't had a dog in 9 years and one wasn't in my plan, but he's mine and I want to do right by this pup that was once tethered and left emaciated in the coldest part of our winter. I'm researching literally everything for him. Thanks for all of the great info

Unknown said...

Buy doxycycline here, no script needed.

Unknown said...

I don't understand the whole "45 days above 54F" part. I thought the parasite only needed to mature for 15 days in the mosquito. Where does the 45 days come into play? A mosquito would obviously not live that long. Does the parasite still need that temperature threshold as it is maturing in your dog?

PBurns said...

Mature female mosquitoes need to grow up first -- they have a lifespan of at least 30 days. The parasite then has to be sucked up by a mature female mosquito which has to grows out the parasite inside it (10-30 days) and transfers it to its mouthpiece for transmission. Then that mature female mosquito has to bite an infected dog, A cold snap during any part of that daisy-chain of transmission kills the microfilariae and/or the mosquito.