We get a lot of questions about deworming, and often hear horse owners confused by myths and rumors. So we’re clearing the air and demystifying deworming!
Myth #1
“I don’t need to deworm my horse because his fecal always comes back 0/negative.”
Busted! You’re doing a great thing by performing regular fecals on your horse, but it’s critical to realize that a negative fecal egg count test does not mean your horse is parasite-free. Believe it or not, there is little correlation between fecal egg count results and a horse’s parasite load. That means that your horse with a negative fecal still almost assuredly has intestinal parasites—those parasites simply are not actively shedding eggs.
Failing to deworm based on a negative fecal could have serious health consequences. The American Association of Equine Practitioners (AAEP) recommends that even horses with a negative fecal, or those categorized as low shedders, be dewormed 1-2 times annually.
Myth #2
“My horse never leaves the barn, so I don’t need to deworm him.”
Danger! While horses do technically get “infected” with parasites, it doesn’t happen exactly like getting infected with a contagious disease like influenza or rhino (Equine Herpes Virus). With parasites, a horse can re-infect himself with his own intestinal worms (yuck!). So even if you have just one horse that never goes off-site, he could still have quite a parasite load just from the eggs he himself passes and re-ingests.
Myth #3
“Targeted deworming is a ton of work (and expensive!).”
No way! Targeted deworming is actually lesswork and less expensive and more effective!
Step one is having a fecal performed on your horse. If it comes back less than about 200 eggs per gram (of feces), then your horse is likely a low egg-shedder and only needs to be dewormed twice a year. If the results show more than 500 eggs per gram, then your horse is likely a high egg-shedder and needs to be dewormed more often, maybe four to six times during the grazing season in your area. It’s as simple as that!
Myth #4
“Rotating dewormers every two months prevents resistance and is still the best way to protect against parasites.”
Nope! Of the three chemical classes that horse owners were advised 30 to 40 years ago to rotate between, parasites have become widely resistant to one of them (benzimidazoles), somewhat resistant to another (pyrantel), and are showing emerging resistance to the third (macrocyclic lactones like ivermectin and moxidectin). So when you give a benzimidazole, few if any worms may be killed—you might as well be giving water! Do your horse a favor by only using dewormers that are effective against parasites.
Myth #5
“Horses should be dewormed regularly year-round.”
False!
An expert in parasitology once compared deworming horses to mowing your lawn. In the North, you wouldn’t mow your lawn in January, as the grass doesn’t grow then (plus it’s cold, brr!). And in the South, you wouldn’t cut grass in August because, again, it’s probably not actively growing then. So if you’re in a more northern climate, you may be able to refrain from giving dewormers when parasites aren’t active (winter, your non-grazing season) and vice versa for those in southern climates.
Remember that your veterinarian is your best resource when it comes to making the final call on when it’s best to deworm your horse based on factors like your location, your horse’s shedding status, and others.
Very helpful. My horses get fecals every year and follow a schedule recomended by my vet.
Hi there ladies,
You are telling me these dewormers don’t work anymore! So could you please tell me which ones do. Please!
Thank you, Kelle Thorne
I think what they are saying is… that because resistantance has built up in general. SOME horses may be very resistant to a particular dewormer. So it is now necessary to do the fecals and based upon the results determine A, the number of times to give per year. And B, if the wormer is actually working. So I am guessing again here. But the if that wormer is working your fecal count should go down and other clinical signs improve. Like sheding, coat condition, weight, energy… I believe… They are cautioning against roating because you could be hitting duds in the cycle. And against deworm and done thinking, because that may not be the case. I am glad to learn that sheding does not equal worm load.
Would someone confirm I have this understood properly please?
Thanks for your question, Kelle. Resistance can vary depending on the area of the country you live in, and even from barn to barn. That’s why it’s so important to work closely with your veterinarian to determine the best parasite control program for your horse(s) individually. They’ll likely recommend performing fecal tests. Not only can fecal tests be useful for measuring what type of shedder each horse is (low, medium, or high), but they may also help you and your vet determine resistance at your farm. For more information about parasite control, please see the blog below:
http://blog.smartpakequine.com/2013/03/deworming-q-a/
– SmartPaker Carolyn
What wormer should I use if benzimidazoles, pyrantel, and now ivermectin are now resistant. I do regular fecal tests 4 times per year.
Thank you for your question, Elle. That’s great that you’re performing fecal tests on your horse, but remember that fecal testing is really only accurate during the worm transmission season (so not during the winter in the north and not during the summer in the south). So you might be able to cut out a few of the fecal tests. Also, fecals don’t tell you if any how many worms your horse has at the time and whether you need to deworm, fecals identify the shedding status of horses as low, medium, high and then you work with your veterinarian to develop an appropriate parasite management program based on this extremely helpful info. While you’re correct that the ingredients you mentioned are showing varying levels of resistance, resistance can differ depending on where you live, and even from farm to farm, which is why it’s important to review the fecal test results with your veterinarian to help develop a parasite control program for your individual barn and horse(s).
– SmartPaker Carolyn