Questions (and Answers) About Horse Worms with Dr. Dan
Equine Wellness "Fecal Test Article" with Dr. Dan


What process does a fecal test typically follow?

Personally we do a fecal floatation test which concentrates any eggs present.


How should one go about collecting a fecal from their horse?

It is as simple as picking up a small amount of fecal material and putting it into a sealed baggy. Ziplock type baggies work great and if turned inside out when picking up the sample, it even works as a glove. Of course, proper labeling of the baggy with horses name, date collected, owners name, address etc. is needed too.


Is it better to have a veterinarian do it during a routine visit?

Many veterinarians will not even do fecal's on horses. Unfortunately such have bought into the misunderstanding that all horses have worms all the time. They frequently will tell there clients that tests are not effective and it is best just to routinely deworm on a calendar basis.


Unfortunately this practice has led to a resistance issue and have created what I have called "super worms". FORTUNATELY this practice is changing and the need and suggestion to do fecal's instead, is "trickling down" from parasitologist s to vet schools and is finally reaching veterinarians in the field.

At our lab we actually have a veterinary microbiologist reviewing the samples. It is important to have someone who frequently does fecal exams to do the testing.


There is no doubt that equine samples are much more difficult to read than pet fecal's. If one collects a sample from their horse, how soon must it be delivered to their veterinarian for testing?

The sooner the better, however, we frequently have samples mailed from as far away as Hawaii. These may take a week or more by first class mail. As long as the sample has been sealed properly and not actually dried out, we get great results. Our lab has actually become quite adept at identifying larvae as well.. Larvae would be present if eggs hatched in transit.


How often should riders consider having a fecal test done on their healthy horse?

It really depends on the age, prior fecal results and condition. Older horses generally have fewer issues from natural resistance that has developed. Young horses, especially those under three years of age, need more frequent testing. Horses that appear wormy with poor hair coat, pot bellies and especially if they are under three, we often will deworm even if no parasites are seen on the fecal exam.

Please understand that No test is 100% accurate and common sense should be used. Veterinarians and horse owners in general have gotten into the habit of just deworming because the calender says it is time to so without considering negative consequences. Resistant "super worms" are being created by such practices.

The immune system and general health of the horse may be potentially threatened by such as well. All one has to do is listen to an advertisement on TV these days to remember that ALL drugs have some consequence. This common sense just seems to have been forgotten when it comes to traditional deworming recommendations.

As a rule of thumb, we would suggest fecal's a minimum of 4 times per year for adult horses. If they are under three years of age, every other month is best. This schedule should be followed until there are no parasites or until very low numbers are seen on a few consecutive samples….. then and only then, can the frequency between sampling be lengthened.

Of course, it is not uncommon even in a "herd situation" to find many horses that are always negative or at least "almost always" negative. Such horses have either developed resistant immunity or are just no longer being exposed. If no or very low numbers are consistently seen on fecal's increase the length between testing. If you consistently find positive results on a horse then test more often AND consider boosting the immune system.

Also look at other factors that might be stressing the horse. It is really very simple and more economical AND MOST OF ALL, at least in my humble opinion, much healthier for the horse. Of course, if new horses are introduced into the head then check them all and start over with the testing frequency.


If they have an unhealthy horse (ie rescue case) should tests be done more frequently?

Yes, see above.


What about foals or elderly equines?

The above applies as well.


What worms can the test look for? What worms, if any, are not visible in a fecal?

Tapes, bots and of course parasites that are migrating through tissue (encysted larvae) may not show up. But when testing is done as suggested above, then you certainly have a much more healthier approach than just "calendar drugging". Sorry.. I couldn't resist!


How accurate are fecal's?

I don’t think there are any studies that actually have been done especially since such studies would require many many necropsies, ie dead horses, to be used as research to tell. As far as comparing to just "calendar deworming" I think one would have to consider the big picture of potential negative health issues to really say which is best. This of course would be "subjective" and science in general does not like such. A quick look at other species will give the answers however.

Hardly anything is working for goats and sheep today. "Super worms" that are resistant have been created form over use of chemicals. A simple analogy would be MRSA Staph infections from overuse of antibiotics.

What worm counts are considered normal or average for each worm type? At what point do the worm counts indicate some type of action needs to be taken (chemical or natural dewormer)?
Generally if we find more than 2 or 3 eggs per slide we suggest deworming. of course, we suggest a more natural approach than drugs.


If a worm overload is discovered, and the horse is dewormed, should the horse have another fecal test done after deworming? If so, how soon after?

We suggest a follow up to positive results in 3-4 weeks.


The most negative impact would be a dried out sample. If such are received at our lab we ask for new samples to be sent. Improper labeling is also an issue. Occasionally we will receive a "group sample" where multiple horses in the same herd were mixed together to have tested as a group. These we refuse to test. Just because there are worms present in some horses do not mean all the horses in the herd are positive.

Such thinking completely disregards "individual immunity and resistance".

For the most part, all horses are exposed on a regular basis to parasites anyway but that does not mean they should be dewormed "just because" any more than we all should be treated with antibiotics every time we are "just exposed" to the flu.


Are there any factors that can affect a fecal tests accuracy?

The most negative impact would be a dried out sample. If such are received at our lab we ask for new samples to be sent. Improper labeling is also an issue. Occasionally we will receive a "group sample" where multiple horses in the same herd were mixed together to have tested as a group. These we refuse to test. Just because there are worms present in some horses do not mean all the horses in the herd are positive. Such thinking completely disregards "individual immunity and resistance". For the most part, all horses are exposed on a regular basis to parasites anyway but that does not mean they should be dewormed "just because" any more than we all should be treated with antibiotics every time we are "just exposed" to the flu.