Our lab has been on it since he was 6 months old. Taken his chewable on the 25th of the month…EVERY month. Never were we even a day late giving him his meds. Well, his yearly heartworm test was positive. Vet switching him over to Heartgard (Ivermectin). He’ll be on this and get re-tested. Good thing is that we will not have to pay a dime if he has to have the expensive treatments. Oh BTW, the vet confirmed that Ivermectin will treat Covid and treat it well. Said he took it when he had Covid and was better in 24 hours.

Jonathan Bradshaw a vet in Arkansas who prefers to work with sporting dogs posted on social media a while back that heartworms are becoming immune to Ivermectin in many instances. I know that Sentinel is not Ivermectin based but he said in his opinion the best thing for heartworms are any medicine that is Moxidectin based such as ProHeart. I have been using the ProHeart 6 month shot on my dogs since it came back on the market and have been please with it.

Not directed at you Mully, just my thought out loud: How the heck are heartworms becoming immune to Ivermectin ... are the jumping from host to host? Crazy

Yes...that's how infectious stuff works.

Ivermectin is basically alcohol or sugar to any singular cell organism there is. Thats why it works, it disinfects. It kills the common cold.Ivermectin is natures extra bleach.

If I recall I believe he actually said the heartworms are gaining resistance to the ivermectin compound and that parasites in general have a way of becoming resistant to certain meds.

True

Arkansas is where the resistance started with Heartgard brand. Basically pet owners didn’t give dosages every month as required thereby allowing resistance to the med being built up by the heart worm. One must follow the directions otherwise resistance occurs. Pet owner were forgoing treatment in winter months or forgot a month happening. It was planned for that meds lasted longer than 30 days but not long enough for 60 days.

The same way that weeds become resistant to Roundup. It’s natural selection. The resistant ones live and spread their genes.

I was always under the impression that if you gave a dog Ivermectin that had heart worms it would kill the worms. Then the worms would stop up the heart like blood clots and in part killing the dog. Is that a myth?

Ivermectin resistance is a known thing. It was first reported in New Orleans before Katrina hit. These worms exhibited a change in gene sequence that altered a P glycoprotein that triggered a resistance to macrocylic lactones. Then Katrina hit and these dogs were displaced to all over the country. These worms were able to pass on these genes to other worms. Still don't know exactly how prevalent it is, as most failures of prevention are due to poor compliance (ie giving correct dose every month). Ivermectin does not kill the adult worm in preventative doses. Adult worms are given a different drug to kill them. Preventives kill the microfilaria (larval hearworms) before they are able to mature into adults. The concern with preventatives and concurrent heartworm disease is high levels of microfilaria dying off and causing severe reactions.

That is true for compliance issues, but doesn't lead to resistance being passed on as it's been identified as a genetic mutation. Heartworm transmission has to occur throught a mosquito. In some northern states, some practitioners will forgo treatment during winter months due to no mosquitos being present to vector transmission. Probably not the best idea, but their choice. In Alabama, we have mosquitos year round, so year round preventative is needed. I had a case not long ago where a client brings in a dog I suspected of severe end stage heartworm disease, though they insisted they had been on Heartgard every month. Hot positive for heartworms, and subsequently died due to liver and renal failure. In discussing the possibility of resistance, I asked where they had been getting the medicine. Their response was from an online pharmacy, and that the pharmacy never asked for a prescription from a veterinarian. Which is a huge red flag that it may have been dispensing counterfeit medications. I unfortunately have seen it before. A prescription is required before dispensing medication because we need to asses current heartworm status before we initiate preventative, due to the risk of a mass microfilaria die off causing reactions.

Pretty good study done by some of my professors at Auburn. This study was done with heartworms that were not resistant, and had some pretty shocking efficacy data. The only drug with 100% efficacy was moxidectin (Advantage Multi, ProHeart). https://www.sciencedirect.com/science/article/pii/S0304401711000185?casa_token=fIjMxxY3IwAAAAAA:tOkGxyyEsMNiHSBfRhh2KqYMHrEkxu5XOnF_8Kh-Tbj0GoI3E6VbyRr-CzNyjzwnf6ZpcKxrtw

Thanks for posting
I'll read link when I get more time.
Post more, I like info like this

If I read that correctly only one group remained free of heart worms and it wasn’t the ivermectin group.

I’m good friends with two vets and know several others. I get to listen to tales in the duck pit or traveling to and from camp. I’ve learned a lot of things LOL. My best friend gets all into exotics and graduated from Auburn. The other guy is younger and does dogs and cats but large animal too. His wife is into high dollar show horses.

We met him at his house one time after having to pull a dead (for a long time) calf out of a cow. Damn he stunk!!!!!

They always mentioned Arkansas as being where things seemed to have gone wrong for the meds. Different type mosquitoes maybe? I don’t recall all of that conversation.

Thanks for the info, had to put my buddy down a few weeks back due to cancer but my daughter still has her dog and I need to ask her what she’s been giving her.

Carter, the only group that had 0% infection was moxidectin. Ivermectin and the other all had 7/8 dogs test positive, and have worms on necropsy. Now that being said, they injected 100 larvae and in each positive case, there were few worms per case. As such, the efficacy percentage is still high.

The resistance issue isn’t with the mosquito, it’s the actual heartworm that’s resistant. The mosquito is just the vector by which heart worms are spread. If I remember correctly, there was a pocket around the delta that exhibited resistance. But without genetic testing of worms, we don’t know exactly how prevalent it is, as most is lack of preventative compliance

That’s why I mentioned I wasn’t sure of the conversation, I just listened to them talk shop but they mentioned Arkansas and I’m pretty sure the Delta which I probably rolled right into AR. Shan sold a ton of Heartgard plus and we had our dogs on that until he said switch because of the failures in some dogs. I’m not sure what we’re giving now. The wife handles that but I’ll mention this study so we may be switching again.

My Boston I found on the side of the road. She was heart worm positive, pretty bad case and had Ehrlichiosis. She had to be crated and careful to not get too active. She did have damage from the heart worms.


I appreciate the link

Wasn’t Heartgard sued?

Ivermectin based products have been useless since Hurricane Katrina. Bradshaw is late to the party