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  Discussion on Anything new about praziquantel in mares?
Author Message
Member:
lindas

Posted on Wednesday, Dec 24, 2008 - 12:54 pm:

Hi Dr. O.
I have been reading your articles about the safety of Zimectrin gold in pregnant mares. I last used this product in my horses early last April, then bred the mare at the end of the month. Have followed a regular deworming and fecal program since. I would like to worm for tapes again, and bought Zimectrin gold for everybody, but would like to be certain about the pregnancy issue before giving it. You only quote the one study, have there been others done? Was it a large sample population in the study? Is there anything new about praziquantel or is it still considered safe for 7 1/2 months of pregnancy?
Thanks,
Linda
Member:
scooter

Posted on Thursday, Dec 25, 2008 - 9:32 am:

Hi Linda, not Dr.O.! but according to his article it is safe, one of my horses(not PG) seems to have a reaction to it so I use a double dose of strongid on her. If the praziquantel makes you nervous, maybe that would be an option?
Member:
ekaufman

Posted on Thursday, Dec 25, 2008 - 10:56 am:

Hi Linda,

Also not DrO, but I'm certain that the other brand name praziquantel/ivermectin dewormer is labeled as safe for pregnant mares, though I can't lay my hand on the box to remind myself of the name. That suggests to me that the other vendor has done its own study, but not the manufacturer of ZGold. I have used praziquantel safely in my own broodmares.
Member:
gsmangus

Posted on Thursday, Dec 25, 2008 - 11:24 am:

Hi Linda, also not Dr. O - but in the fall of 2004 we wormed our entire barn with a praziquantal wormer. The stallion and young stock took it like a sugar pill but ALL of my brood mares reacted so badly I thought they would all abort. I called the company and talked with their company vet who told me that the reaction was due to a heavy parasite load - that was NOT the case as we worm regularly and had just that previous spring wormed with a 2x dose of pyrantel wormer for tapeworms. Maybe they have improved or changed the product but I will never use it on bred mares again!!
Member:
ekaufman

Posted on Thursday, Dec 25, 2008 - 11:31 am:

Hi Susan,

That's scary to hear-- can you describe the reaction that you saw? Had you done fecals prior to worming?
Member:
gsmangus

Posted on Thursday, Dec 25, 2008 - 1:27 pm:

Hi ELK, no at that time we had not done fecals - just a regular year round worming rotation. Here are the mare reactions as I wrote in my records at the time (2004) - all the mares quit eating completely for at least 2 or more days (including one mare that I swear would go thru fire for her feed), all were extremely lethargic and "depressed" in attitude, 2 had warm hooves but not bad enough to say laminitis, all mares laid down more than normal and when turned out just stood in one spot with their heads hanging. We took temps but nothing elevated enough to call a vet. Gum color seemed to me to be less pink than normal but my husband wasn't sure on that. Manure was loose but not diarrhea. Water intake reduced too. The reactions started within 12-24 hours of giving the praziquantal wormer and it was about 5-7 days before all the mares were 100% back to "normal" in appetite and behavior. And remember we had done a 2x dose of pyrantel for tapeworms just 6 months previous on that rotation.
You can see why we were concerned enough to call the company, and this effected FOUR mares, not just one. I really thought they would all abort - they did not but we sweated bullets until they foaled... wondering too if the wormer would have some sort of teratogenic effect on the foals (it did not). I know the "label" says it is OK, but I refuse to use this wormer with pregnant mares again... too many other wormers out there that we have used with no reactions. We recently did do fecal counts (which we do about once a year or so) and all our horses (except one weanling) came back "zero" so our program does seem to work. Remember too this was in 2004 and maybe they have since changed the formula so pregnant mares can handle it better ?? I still won't use it tho.
Moderator:
DrO

Posted on Friday, Dec 26, 2008 - 8:31 am:

Hello DrS,
For the latest information on this product check out Treatments and Medications for Horses » Dewormers (Anthelminics) » Praziquantel. There you will find a very informative description of safety studies in pregnant mares done in 2003. I find no new information on this since then.

Susan once you read this article you may wonder whether it was the praziquantel or some other factor causing your mares problems as the mares in the study cited received much larger doses over a much longer time than your horses did with no problems. Also included in the study is the the possible effects on the foals born to these overdosed mares. We should note there have been no changes in formulation. So how do we explain all 4 horses having remarkable reactions twice in a row? Right now we don't, but there appears to be some "unique" event that all the horses were exposed to when compared to the population of horses as a whole. There have been such odd events reported with other dewormers, for instance the three horses that developed ivermectin toxicity reported at the AAEP this year (To toot our own horn, we reported it when it happened several years in our ivermectin article). Currently the best thoughts on the subject is that ingestion of a toxic weed opened up the blood brain barrier to the drug allowing toxic amounts of drug into the brain. I would also note that Susan's symptoms are consistent with either praziquantel (in other species since there are no reported cases in horses) or ivermectin toxicity.
DrO
Member:
lindas

Posted on Saturday, Dec 27, 2008 - 12:08 am:

Thanks Dr. O,
Yes I read that study, I just wanted to know if there is anything "new". Thanks for your response. Guess I'll go ahead and worm everybody, though since I'm going out of town for a few days I'll wait until I get back to do the broodmare.

Susan, I think that Dr. O. will agree that we should not depend on fecals for tapeworm diagnosis. Typically you do not always see tapeworm eggs on fecals and they can be loaded with them! I see it in dogs and cats every day, and I believe the same thing is true in horses. The rest of the worms are in a different "family" of worms, and are typically easier to find. However fecals do not always tell the whole story. Remember that we are using a very small sample (1 gram, ideally) And the worms are living creatures that do not always lay their eggs consistantly. That is why the parasitologists recommend that we back up with an anthelmintic (dewormer) even with negative fecals. As for your mares' toxicity, I'm not sure I can comment on that. Did they get the shakes or act uncoordinated? Neurologic toxicity is a sign of possible ivermectin toxicity, which I have frequently seen in dogs. I don't think I have ever seen a case of praziquantel toxicity.

Dr. O, do you know of any particular breeds or bloodlines of horses that are hypersensitive to ivermectin like herding breeds in dogs?
Linda
Moderator:
DrO

Posted on Saturday, Dec 27, 2008 - 8:41 am:

There are some mini-horse breeders who believe that mini's are hypersensitive to moxidectin. I suspect strongly the smaller degree of safety has resulted in over dosages particularly in foals. Otherwise no we are not aware of any unusual breed based sensitivities.
DrO
Member:
lindas

Posted on Saturday, Dec 27, 2008 - 11:33 am:

Yes, I've heard that about minis. I think it is probably because they are so small it is very easy to overdose. My horse vet is comfortable with moxidectin in minis and foals as long as you know the exact weight and measure very carefully, with a small syringe, to get the correct amount. More is not better!
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