# heart worms and Ivermectin



## Gerald Dunn (Sep 24, 2011)

have any of you used Ivermectin for treating heart worms or for prevention? this articular is two years old but I just moved back to Texas and the vet here will not give me the median unless SHE runs new test on my dogs for over $200 even with the records from the old vet showing there clean:-({|=yes I know so I did it to myself.

found this articular and web sight 
a once-every-three-months dose of Ivermectin will give your dog 100% protection.

http://terriermandotcom.blogspot.com/2008/05/billion-dollar-heartworm-scam.html


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## Brett Bowen (May 2, 2011)

Gerald Dunn said:


> have any of you used Ivermectin for treating heart worms or for prevention? this articular is two years old but I just moved back to Texas and the vet here will not give me the median unless SHE runs new test on my dogs for over $200 even with the records from the old vet showing there clean:-({|=yes I know so I did it to myself.
> 
> found this articular and web sight
> a once-every-three-months dose of Ivermectin will give your dog 100% protection.
> ...


I live here in TX too. I know my vet has told me before that every 6 weeks and they are fine, but 6 weeks is too hard to remember so once a month is what they recommend.....and it helps everyone make more money. She also the type that doesn't freak if they have a positive test. She'll put them back on hwp and if they start having symptoms that's when they'll do the heavy duty treatment, so take it for what it's worth.


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## Connie Sutherland (Mar 27, 2006)

Both Ivermectin and Ivomec as your search terms will call up* many *threads on the topic, too.


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## julie allen (Dec 24, 2010)

Word of caution, heartgard, triheart, and interceptor have been failing in the south, especially the Mississippi valley area. Haven't heard much yet around Texas, but you may want to research it.


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## Nancy Jocoy (Apr 19, 2006)

I asked my vet about that and she said that was not the case (ivermectin failing). Do you have any references on that because all they want to sell anymore is some combo .... and now no interceptor but trifexis or revolution etc. I just want to prevent heartworms, eh?

I was planning on just buying ivomec.


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## Karen M Wood (Jun 23, 2012)

http://www.revivalanimal.com/SNAP-H...Tag&gdftrk=gdfV2457_a_7c543_a_7c2273_a_7c8885
For $200 you can buy your own snap test and some needles. You only need like 3 drops of blood to run the test. As a former vet office employee, I've seen this done dozens of times a day. I've held the dog so the blood could be drawn. Really not difficult of even takes that long. Matter of minutes you cna know if your dogs are clear or have picked up HW. Now what i'm not sure of is if they sell the test to non-vets. But i'm not digging in that far right now.
Word of caution with Ivermec, do not think that a little more is better because i've seen people make their dogs go blind. Abort litters of puppies, and suffer other overdose issues. Get them weighed and use exacting dose. 
HW suck hope your dogs never get even one.
K


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## Gina Pasieka (Apr 25, 2010)

Using injectable Ivermectin orally is a fine way to prevent HW disease as long as everyone is careful about the calculated dose. Please request that your primary care veterinarian calculate it for you based on your dogs current weight. Being off by a decimal place could result in serious signs including death. Please do not believe that crazy blog regarding treating heart worm, especially since you live in Texas which means your dog is exposed to HW year round because of the weather. Here is a link to the Heartworm Society's webpage for the most up to date information. PS the slow kill method is not recommended...so a dog that has adult heart worms should receive the injectable treatment.

http://www.heartwormsociety.org/pet-owner-resources/canine-heartworm.html


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## Nancy Jocoy (Apr 19, 2006)

When I did my own calculation using the same mg/lb as on the Heartguard Circular compared to the 1% ivomec (which is 10mg/mL) I came out with a LOT lower volume than the one commonly quoted. I realize there is a tremendous tolerance for the drug but to me significantly more than is necessary is not good either.

Having a couple of college degrees in chemistry and having taught high school and college basic level chemistry courses I figure I got it right.


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## Scott Schroeder (Dec 8, 2010)

I having been using Ivermectin for over 15 year with all clean heart worm tests. My Vet formulates the calculations for me and we mark it on the calender


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## Ang Cangiano (Mar 2, 2007)

Nancy, the higher dosage you're probably seeing will also take care of some intestinal worms (won't touch tape though). The lower dosage will only take care of heart worm.

Ang


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## rick smith (Dec 31, 2010)

re: "PS the slow kill method is not recommended...so a dog that has adult heart worms should receive the injectable treatment."

imo this blanket statement is too genera,l and as with most med treatments there are often no absolutes 

depending on well thorough the diagnosis was, and a few different factors the slow kill method (if by that you mean the preventative dose) can work just fine until the adult worms are shed individually and eliminates any of the reactions that CAN occur with the injections or blockage from mass shedding
- been proven effective for going on about 20 years here

the only way i would agree on the injections is when a dog is severely infested with adults that will NOT affect the major organs if shed in mass, and in some cases surgical removal may be even safer.....again, all cases are different

multiple ways to treat .... ymmv ... to each his own, and no i'm not a vet, just dealt with MANY HW cases over the years treated by both stateside (mwd/Army) vets and Ja vets 

prevention of course is the only true "gold standard"...treatment should only occur with a rescue and should probably never have to happen for a dog raised as a pup


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## julie allen (Dec 24, 2010)

Three of mine tested positive. Two are old dogs, raised from pups never missed a dose. 
One was a year old, adopted, tested negative, given prevention, retested when I adopted her, negative, on prevention for four months, tested positive.
Not sure if anything is proven yet. Vets here first thought it was missed doses. Then saw a huge amount of dogs positive. Then they thought ivermectin resistance. Then saw failure with interceptor.
Their not sure why the failure. The prevention was purchased from the clinic, never online. I believe auburn is doing a study on it now. I have also heard they are considering the slow kill method partly to blame, but I don't buy that either.

One of mine has been through the immiticide treatment. One on the doxycycline and advantage multi or gold (cant remember?) For three rounds (slow kill) for two years. His last test is still positive. The third was given higher doses of the liquid ivomec, and tested negative three months later.
I have switched to the liquid. The dose is higher than heartgard. I have had no issues. I also use comfortis, which you have to be careful as a drug reaction between the two can result. I stagger them two weeks apart. Everyone has since been negative, with the exception of the old mal, who has cardiac and respiratory issues from the HWs.

Most here are switching to trifexis, but with seven dogs, its much more cost effective to use the liquid ivomec. Plus I don't think its a drug resistance, since other drugs are failing. It's more prevalent with heartgard/triheart, but probably 80% of dogs on prevention here use that.


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## julie allen (Dec 24, 2010)

Nancy I don't have any links sorry. Google heartworm resistance, mp3 hw strain, or heartworm prevention failure. It will all take you to recent cases. Louisiana, Mississippi, Tennessee, Missouri, are all affected.


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## Nancy Jocoy (Apr 19, 2006)

I will do that. Good to know. We are not in that basin but it is not all that far-My last dose of interceptor is October 1! Trifexis is so darned expensive on top of the other drugs.


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## Amber Scott Dyer (Oct 30, 2006)

Trifexis is just generic Interceptor and Comfortis. resistance to Interceptor would also mean resistance to Trifexis.


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## Nancy Jocoy (Apr 19, 2006)

Amber Scott said:


> Trifexis is just generic Interceptor and Comfortis. resistance to Interceptor would also mean resistance to Trifexis.


Interceptor unavailable.
Trifexis expensive plus I am not sure I want to give oral flea control.
Spinosad + Ivermectin has known interactions.


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## Maureen A Osborn (Feb 12, 2010)

Unless you have bigger dogs, using ivermectin is difficult. The dosage of the 1% injectable for swine is 0.0015-0.003 ml/lb. My dog weighing 100lbs gets 0.3 ml.Unless you get yourself a TB syringe, you can't get these small doses.


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## Nancy Jocoy (Apr 19, 2006)

Your calcs match mine.....eppendorfs..micropipettes....i have a 100 ul gc syringe somwhere.....


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## Betsie Janson (Jan 2, 2012)

A couple of inaccurate accounts on the terrierman's page from recent data and research:

Ivermectin and others can kill ONLY microfilaria in L4 life stage or earlier; which is a window of 40-55 days once infected from a mosquito bite. Past this stage, and maintenance dosage will not touch the lifestage population. This gives a false sense of safety to the owner. 
Seasonal treatment is ok, but also, research has shown that heartworm larvae are intermittent developers, which can suspend development in colder temperatures, and continue again once optimal temperatures are reached. Unusual weather patterns versus HW+ cases in more northern areas have supported these findings. 

Also, Collie ivermectin reactions studied are based on high dosage, not preventative dosage found in monthly medications, which accounts for his border collie and working herder discrepancies. 

I have explained the "doxy" treatment and other treatment options below.

Here is a summary:

The lifecycle:
Heartworm starts its life as microfilariae (L1), circulating in the blood and tissues of a host canid (usually). We have found that these microfilariae are usually crepuscular (active in the dawn and dusk) and only tend to circulate in the blood intermittently. This makes the usage of these buggers as a diagnosis tool difficult and not totally reliable. You could do 20 blood draws on the same infected dog, yet get different results for each sample. 
Once a mosquito bites the host, it takes in the microfilariae. These guys then develop for 14-22 days within the mosquito hosts. The larvae needs 57 F to develop. Interestingly enough, we have recently found out that they are intermittent developers. It was once thought that the larvae needs 14-22 consecutive days of optimum or higher temperature to develop. This has been proven false. The larvae can in fact suspend their development, which can prove to offer faster infective stages during early season. 
The infective larvae (now called L3) live in the mosquito saliva, therefore bite induces infection. Mosquitoes begin to salivate before biting, therefore it has been shown that infected mosquitoes offer immediate exposure. 
Once bitten, the L3 larvae migrate through tissues and circulation. In 3-5 days, they develop to stage L4. Within 40-50 days of infection, the L4 larvae reach a sub adult stage and begin to migrate towards the heart and pulmonary vessels. By 6 months, the worms are seated in the pulmonary vessels and reproducing; and spreading microfilariae throughout the vasculature and tissues; ready for a mosquito to come have a meal. 

Diagnosis:
Microfilaria in blood smear or Knott's test:
This test is to detect the presence of the first stage larvae, which indicates a mature and breeding infection in the animal. As I explained earlier, this not a definitive form of testing, and should be used as a supplemental tool, not solely relied upon. 
ELISA Driochek or Idex snap or Heska cartridge:
This is the gold standard. This tests for heartworm antigen, which is based upon secretions from the female worm's uterus. The best of the tests above is the Dirochek. It is a more complex test. The simpler tests, which are one step tests are not as sensitive, but just as specific. The Dirochek will detect 2 adult female worms. The other two need 3-7 females for a positive result. 
However, even these tests have limitations. First, they only react to females; only potentially half of the population. They only test for mature breeding worms, which means you can have an immature infection, but it goes undetected. 

Preventative:
All of the drugs used as preventative are of the same family (macrocytic lactones). These include avermectins and milbemycins. These preventatives only kill the L3 stage and part of the L4 stage. This means that unless the worms are killed before they reach ~40-55 days post infection, they are immune to ANY treatment or preventative. If the larvae are not removed at this stage, there is no current drug or treatment that can remove them until they are sexually mature adults. 
Infective treatment:
Immiticide is the most effective and current "gold standard" for the removal of adult infections. This can be done in 2-3 injections, and 3-4 months of observation and supplemental treatment. However, this drug is in short supply, and very difficult to get. Many Vets can not obtain the required amounts. This drug however, is ineffective on the immature worms, which is why the preferred treatment is to follow up with another shot 2-3 months after the fact. 
Arsenic is the "old school" drug used, but the side effect are extremely dangerous and costly. 
Ivermectin is another method often resorted to by shelters and those who can not obtain immiticide. This however is an extremely slow method. Treatments can resume for 30+ months, and strict cage rest. The drug does not kill the adults, it shortens their life and sterilizes them. This treatment type does increase the risk of complication; embolism, anaphalaxis, etc. It does however assist in the prevention of repeat infections. 
We have also discovered a rickettsial organsim (wolbachia) that lives commensally with the heartworm. It seems to be integral in the reproductive and immunity properties the adults possess. Many Vets are treating dogs with a round of doxycycline previous to treating the adults. This seems to improve effectiveness and decrease durations of treatments. There are studies being done with tetracycline to see if it is as effective against wolbachia. 



Also, considerable pulmonary and cardiovascular damage occurs once adults are present and will cause life long scarring and changes in the host. Yes, it takes a while for an infection to reach crisis, yes it can be treated, but the damage is permanent. Many owners notice life long decreases in heat and exercise tolerance, and some dogs succumb to HW+ cardiovascular/pulmonic complications even years down the road. There have been several long term studies of lasting HW+ effects on treated and "recovered" dogs as well as necropsy evidence of the extensive damage. 

In Michigan, since we often are one of the few places with more adequate and consistent Imiticide supplies; we see many HW+ dogs. Most are strays, shelter and outdoor dogs not on preventative. We have had a slew of them lately, some quite developed infections.
Exposure rate is a variable and can be addressed, but know that if a dog is exposed, very near 100% are susceptible. So, consider it a risk based venture. If you have high mosquito or unprotected dog populations, there is a likelihood of an increased risk of exposure.


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## Gerald Dunn (Sep 24, 2011)

so what is a person to do? right here next to Houston there is a problem all year long. pay the big $$$$$ and play there game or try the Ivermectin and get the dose wrong and kill your dog?????


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## julie allen (Dec 24, 2010)

Thank you for the info! Do you have any reasoning as to why so many are testing positive while being on prevention?

The dose of liquid ivomec is much higher than what is posted here. Reason being, since the lower dose in heartgard is not working.

Mine stay on prevention year round. Even in January, if we get a warm day, you will see mosquitoes out.


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## Nancy Jocoy (Apr 19, 2006)

In regards to the what is a person to do question.

Mainly the dogs who have died on Ivermectin overdose have been collies with the MDR1 mutant gene. Some other herding breeds can have it but I gather it is less common.

The drug trials started to show issues at 16 times the package insert dose. Beagles OTOH have been shown no ill effects at 400 times the package insert dose.

From what I understand all of the collies who had issues were dosed with liquid Ivomec presumably at the 0.1mL/10lbs dose that is listed everywhere. That is, I believe, about 37 times higher than the dose on the package insert.


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## julie allen (Dec 24, 2010)

Nancy Jocoy said:


> In regards to the what is a person to do question.
> 
> Mainly the dogs who have died on Ivermectin overdose have been collies with the MDR1 mutant gene. Some other herding breeds can have it but I gather it is less common.
> 
> ...


That's the dosage I use.


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## Betsie Janson (Jan 2, 2012)

julie allen said:


> Thank you for the info! Do you have any reasoning as to why so many are testing positive while being on prevention?
> 
> The dose of liquid ivomec is much higher than what is posted here. Reason being, since the lower dose in heartgard is not working.
> 
> Mine stay on prevention year round. Even in January, if we get a warm day, you will see mosquitoes out.



The LOE (lack of efficacy) is in question, Merial did have a stink about it. The problem is, that it is difficult to assess the proper usage of the product through anecdotal evidence, as there is a lot of variability in owner compliance, D. Immitis genetic diversity, etc. There was discrepancy found in the laboratory colony populations (which were isolated for 20 years or so) and current D. Immitus populations. This has been rectified, as well as the "Mississippi Delta" populations were identified, which were not resistant, but needed higher doses (calling it "reduced sensitivity"). Here is some info about recent research to test this efficacy or lack there of.

http://www.parasitesandvectors.com/content/5/1/138

http://www.ncbi.nlm.nih.gov/pubmed/16198824

You can read about ivermectin doses, and lethal dose research in dogs on the drug inserts. 

http://heartgard.us.merial.com/pdf/Dog_information.pdf


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## julie allen (Dec 24, 2010)

Betsie Janson said:


> The LOE (lack of efficacy) is in question, Merial did have a stink about it. The problem is, that it is difficult to assess the proper usage of the product through anecdotal evidence, as there is a lot of variability in owner compliance, D. Immitis genetic diversity, etc. There was discrepancy found in the laboratory colony populations (which were isolated for 20 years or so) and current D. Immitus populations. This has been rectified, as well as the "Mississippi Delta" populations were identified, which were not resistant, but needed higher doses (calling it "reduced sensitivity"). Here is some info about recent research to test this efficacy or lack there of.
> 
> http://www.parasitesandvectors.com/content/5/1/138
> 
> ...


So this explains why the liquid at higher doses is working for me, where the heartgard failed. Thank you!


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## Gina Pasieka (Apr 25, 2010)

The 0.1 ml/10# actually works to be twice what I would consider giving...and actually 4x the dose in Heartgard (50 ug/kg). It would likely be ok for most dogs (ie. no MDR1 defect)...as it is a dose we will use to treat mange. 
PS the slow kill method requires 2 years to kill the adult works rather than their normal 5 year life expectancy in dogs. So that is 2 years that the worms will continue to do lung damage. If you have an old dog, or a dog with liver/kidney failure I could understand, otherwise the Immiticide is the recommended treatment. The reaction to the worms is partially based upon a dogs immune response...so some dogs will not get the same damage, but why would anyone risk this in a young, otherwise healthy dog?


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## Nancy Jocoy (Apr 19, 2006)

The dose in the heartgard chewable is 6ug/kg, not 50ug/kg..so .1ml/10lbs is closer to 40 times the PI dose unless there is some flaw in my math (which I have done several times over)


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## julie allen (Dec 24, 2010)

The dog I had treated with the slow kill method was 12 when we started, and not in well enough shape to withstand immiticide.


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## Gina Pasieka (Apr 25, 2010)

Yes....but the dose that also takes care of hookworms and is the microfilaricdal dose ia 50 ug/kg...so I used that dose as a easy safe reference.


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## Nancy Jocoy (Apr 19, 2006)

Ahhhhh, I was not aware of THAT dosing. Good to know. We are on track for that too with my 10fold dose which would be 60ug/kg.

Thanks mods for letting us discuss this.....getting more and more frustrated with vets who will not write scripts and try to force a cocktail if flea + tick + HW meds into our dogs. I realize this is peer information, not "official" and you travel at your own risk on this kind of thing.


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## Gerald Dunn (Sep 24, 2011)

but do you not travel at your own risk even with the vet and there meds?????



Nancy Jocoy said:


> Thanks mods for letting us discuss this.....getting more and more frustrated with vets who will not write scripts and try to force a cocktail if flea + tick + HW meds into our dogs. I realize this is peer information, not "official" and you travel at your own risk on this kind of thing.


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## Nancy Jocoy (Apr 19, 2006)

Gerald Dunn said:


> but do you not travel at your own risk even with the vet and there meds?????


Most of the manufacturers will guarantee their heartworm product (and cover the cost of treatment) IF you give year round AND your product is prescribed by a veterinarian and I assume they would want to see documentation of your dosing. Ivomec is off label so you are "on your own"

That said - Merial did, in fact, recieve a warning letter from the FDA for its claim of 100% effectiveness for HW. Apparently they are all around 95% effective at the prescribed dose.

The only dog I have had who developed HW did so due to a summer only dosing schedule (we had just moved to SC, whoops) and might have gotten them during a winter warm spell. That was in the days of arsenic treatment. He survived and lived to be 15 which is pretty good for a GSD. They were caught on routine vet check.


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## Connie Sutherland (Mar 27, 2006)

Nancy Jocoy said:


> Ahhhhh, I was not aware of THAT dosing. Good to know. We are on track for that too with my 10fold dose which would be 60ug/kg.
> 
> Thanks mods for letting us discuss this.....getting more and more frustrated with vets who will not write scripts and try to force a cocktail if flea + tick + HW meds into our dogs. I realize this is peer information, not "official" and you travel at your own risk on this kind of thing.


I just want to mention again that I've seen terribly wrong dosing info online (on this board too), and by "terribly wrong," I mean the decimal point in the wrong place. :-o REALLY wrong. 

I still feel very strongly that the vet should explain and demonstrate the right dosage before the owner starts with off-label use.

But all JMO.


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