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Positive for Strongyles: What is cheaper?

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  • What wormer kill strongyles
  • Best time to dose horses for small strongyles

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    01-14-2009, 09:07 PM
I just opened a boarding facility (2.5 months ago) and 3 of the 10 horses are my own. They were wormed every 8-10 weeks with alternating wormers. Now there are 10 horses in 3 pastures ranging in (2.5-4 acres). I recently wormed them with Safeguard and then did the test 2.5 weeks later. One of the other boarder horses we tested were wormed 2 months ago and he tested the same.

I think you miss understood. I was thinking about the weekly alternating wormer for a month and then back on the regular 8-10 week schedule instead of the 5 day powerpak. I was just wondering if that would work just as well and/ or be safer and also catch any flares of encysted strongyles.
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    01-14-2009, 09:48 PM
First, take safeguard out of your deworming program. If you dewormed 2.5 weeks before the fecal and had a huge load of strongyles (and considering the 90%+ rate of resistance in studies) it's highly likely that you are dealing with resistant strongyles.

There is still simply no good reason to deworm once a week--it's just wasting your boarders' money. Deworm now with ivermectin or moxidectin and then deworm from now on based upon the egg reappearance period of the drugs (8 weeks after ivermectin, 12 weeks after moxidectin and 4 weeks after pyrantel --if you use pyrantel you should also consider running fecals occasionally 2 weeks after dosing it to watch for resistance). If you deworm like this for a year, you will significantly reduce the parasite burden on your pastures without wasting money or exposing the parasites to drugs (which allows for the development of resistance) more frequently then necessary.
    01-14-2009, 09:53 PM
Originally Posted by zanytactics    
If he's that bad wouldn't it be better to hit him with a good wormer followed by another one that covers different strands of worms 2 weeks later?
This is rather "old thinking" --a hold over from when the drugs that were used for deworming only got one species of worm or occasionally 2. Since all of the drugs on the market are broad spectrum, rotating to "get the different worms" isn't really necessary unless you are dealing with foals and have to rotate because ascarids are showing resistance to ivermectin and strongyles are showing resistance to fenbendazole and pyrantel. (Ascarids are only a worry in young horses or very old horses.)
    01-15-2009, 11:00 AM
Rotating dewormers is absolutely neccesary! Put the same thing into your horse every 8-10 weeks and they will end up with resistant worms!

Here are some different types of worms and the treatments they respond to best:
-Strongyles - The small are sometimes resistant to benzimidazole, so a combination of fenbendazole and piperazine works.

-Migrating worms/larvae - These can be treated with fenbendazole daily for 5 days, 2 doses of oxfendazole on alternate days or ivermectin.

-Bots - Treat with ivermectin a month after the first killing frost and during summer.

-Tapeworms - Double dose of pyrantel paomate in late fall and before heavy spring grazing season.

-Threadworms & Roundworms - Combine oxibendazole with piperazine.

-Eye Worms - Larvicidal doses of fenbedazole (10mg/kg for 5 days) or oxifendazole (10mg/kg, twice at a 2 day interval).

Yes, Ivermectin is good at killing strongyles, but overuse and you will have resistance. Another good stongyle dewormer is moxidectin - gets all but the S. Equinus variety. I would not hesistate to switch between these products.

Just make sure you rotate all year long between ivermectin, fenbendazole (which will kill adult strongyles) and pyrantel paomates.
    01-15-2009, 12:25 PM
My Beau, I'm sorry but your information is simply out of date.

Fenbendazole has a very wide-spread resistance problem in strongyles. You can (again) look at any number of recent studies and find this is the case. In fact, most of the benzimendazoles have resistance issues in strongyles. As far back as 2002 there are studys showing wide-spread resistance to fenbendazole by strongyles. The Horse: Dewormer Resistance in Small Strongyles If you go on pubmed you cand find lots and lots of studies about fenbendazole resistant strongyles in horses. If you have read any of the major horse magazines in the last 2 years, you will have found multiple articles on strongyle reisstance.

Evaluation of parasiticidal activity of fenbendazo...[Parasitol Res. 2008] - PubMed Result

Prevalence of anthelmintic resistant cyathostomes ...[J Am Vet Med Assoc. 2004] - PubMed Result

Prevalence and clinical implications of anthelmint...[J Am Vet Med Assoc. 2001] - PubMed Result

Cyathostome fecal egg count trends in horses treat...[Vet Parasitol. 2001] - PubMed Result

"Dr. Ray Kaplan from the University of Georgia indicates that the equine deworming programs and drugs we used 30 years ago are now ineffective at killing small strongyles, and small strongyles are the most harmful intestinal parasite to horses at this time. To prove his point, he performed a study in 2002 on over 1200 horses at 44 stables in five southern states. Fecal egg counts were used to determine the effectiveness of each dewormer. A fecal egg count is a test performed on a small amount of feces from each horse after deworming to determine the number of eggs. This tells your veterinarian how effective the dewormer was in killing the adult worms.
Surprisingly, at over 97% of the farms' worms were resistant to Safeguard or Panacur, 53% showed resistance to Anthelcide EQ, and 40% were resistant to Strongid T. "

So, using fenbendazole as a main staple in deworming adult horses (where strongyles are the primary parasite of concern) is a poor choice because it is too easy to just assume that you are doing a good job of deworming when it's very likely that it's not effective.

And I would not say that the treatments you listed are the ones that the parasites "respond best to".

Migrating larva can be more easily treated and as effectively with a single dose of ivermectin or moxidectin. In fact, using power pac dosing has adverse affects that weren't recognized until 2006 so it's risk vs benefit profile changed making it a less desirable choice for treating parasites with. (It causes severe GI inflammation and even can cause ulceration after power pac dosing due to the way it kills encysted strongyles.)

Tapeworms are as effectively killed by a product containing praziquantel as by a double dose of pyrantel.

Threadworms are as easily treated with ivermectin or moxidectin without having to combine different products.

Roundworms are as effectively treated with fenbendazole or pyrantel without having to combine different products.

Bots should be treated for after the first frost and again in the early spring. Besides ivermectin, moxidectin I also effective against these.

I would highly recommend that any horse owner who hasn't already should read the 12 part series on parasites and deworming in horses that was published by The Horse magazine. It's free for download from their site. The Horse: Downloadable Parasite Series

And also view the webinar on strategic deworming that they offer (also free).

There is lots of old information out there on deworming and it can lead to wasting money on ineffective treatments and allowing for horses to become heavily parasitized due to assuming that products are still as effective as they used to be.
    01-15-2009, 05:28 PM
Holy cow. There is just too much!!

Your answers are not clear enough....

I was looking for "This is what I would do:
Worm your horse with .............. right now. Then ........ weeks later do ..........

And this is why: ................... "
    01-15-2009, 08:45 PM
If they were my horses I would deworm now with moxidectin and then 2 weeks later deworm with ivermectin. Run fecals. And if needed deworm with ivermectin again 2 weeks after that.

Ryle - Do you rotate dewormers?
    01-15-2009, 09:23 PM
Beau that answer makes me most sense to me....
    01-16-2009, 01:26 PM
Yes, I rotate so long as I find no resistance by doing fecals regularly on my horses.

The recommendation to deworm with moxidectin and then 2 weeks later with ivermectin is again a bit of a waste of money but not nearly so as the initial recommendation. Moxidectin is highly effective at removing parasites, including some of the encysted strongyles so you will not have further pasture contamination for 12-13 weeks after using it. Treating with ivermectin in 2 weeks will kill whatever new migrating larva so will actually do something for the parasite load in your horses so it's a better choice then the fenbendazole or the pyrantel, neither of which treat migrating larva (fenbendazole will at power pac dosing but not as a single oral dose). There is no reason at all to use either pyrantel or fenbendazole for a full 12 weeks after treating with moxidectin. However, again just to minimize pasture recontamination you would do just as well by just waiting 12 weeks and deworming again.

Sorry, I was very under the weather yesterday.

To give you the base answer: I would treat now with moxidectin and then retreat again in 12 weeks with either ivermectin or moxidectin, because there is very little resistance to ivermectin in strongyles and none currently to moxidectin and you know that you have a strongyle problem in your pastures.

This is why: moxidectin is still highly effective at removing strongyles and even will remove some of the encysted strongyles that your horses may have. Due to the fact that it does kill so many of the different life stages of strongyles, you will not see much if any egg shedding for that full 12 weeks after dosing so you don't need to deworm again for that long in order to keep your pastures from getting recontaminated.

By deworming at appropriate intervals with ivermectin, moxidectin and pyrantel, you can deworm less often while still minimizing recontamination of your pastures thus minimizing the number of parasites that horses will pick up in your pastures so that next season you won't have nearly the strongyle problem that you do this year. That means deworming again 8 weeks after using ivermectin or 12 weeks after using moxidectin. And if you can be sure that you don't have strongyles that are resistant to pyrantel (you can find out by using it and then doing a fecal egg count in 10-14 days) you can add it in and you would deworm again 4 weeks after using it. By deworming in this fashion, you stop the horses from shedding strongyle eggs for a while (called the egg reappearance period) and then deworm again at the time when they will have adult parasites but still not be shedding copious amounts of eggs in your pasture. Basically you time it so that you deworm often enough to keep the pasture cleaner without deworming so often that you miss the window when the drugs will be most useful. And it's necessary to do it this way for several months because you already have alot of parasite ova and larva on your pastures so you have to keep from having lots more shed there by the horses during the several months (until our really really hot weather is going on at least) that our weather is conducive to them surviving in the pastures.

I would NOT use fenbendazole in your deworming program anymore because we know that it is most likely not effective at killing strongyles on farms in the southern US or even most places in world based upon studies in the last 10 years.
    01-17-2009, 04:07 PM
I talked with my vet today and he recommended doing a Panacur Powerpak. He said Ivermectin is still the most effective wormer in general but he advises the PowerPak for the high strogyl load. He said he has heard of a horse being colicky from all the encysted worms but has never seen it and has never seen any signs of GI inflammation.

I guess that's what I'm going to go with.

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