Horses and Worms - Strongyle Egg Shedding

Horses grazing in field.
Horses grazing in field. Shutterstock

Newsdate: May 22, 2018, 10:30 am
Location: MAHOMET, Illinois

At Horsemen’s Laboratory we have reviewed the results of over 70,000 samples that we have examined over the 25 years that we have been helping horse owners evaluate their horse’s worm control program. We compiled the information into a two-part article along with graphs, so our clients and anyone interested can evaluate the data.

Pasture source of horse parasites.

Pasture source of horse parasites

To follow the new worm control program in horses, the first step is to start doing fecal egg counts.
© 2014 by Smerikal New window.

We have found that the overall average is 35% positive and 65% negative.  Over 95% of the positive samples are due to strongyle eggs.  We are unable to determine whether these are eggs from large strongyles or small strongyles because their eggs all look the same. 

However, since the introduction of ivermectin dewormer in 1981, most large strongyles have been killed off, therefore through research it has been determined that over 90% of strongyle eggs passed by horses are from small strongyles. Therefore, all of the data we reference refers to small strongyles.

Visit our website at: to read the complete article and to view the informational graphs.

To follow the new worm control program in horses, the first step is to start doing fecal egg counts on the horses periodically. Horsemen’s Laboratory has been performing fecal egg counts through the mail for over 25 years.  Most of our clients have expressed a deep appreciation for how convenient our service is and the peace of mind that knowing their horses’ worm control program is effective. 

If your horse has not been dewormed for 3 months or more now is the time to order our postage paid sample containers and have a fecal egg count done.  Order now at or call (800) 544-0599.

About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.