Parasites and De-worming Programs

Internal parasites are silent killers. There are over 100 types of  parasites that can affect horses. They can cause extensive internal damage, and you may not even realize your horses are heavily infected.  At the very least, parasites can lower resistance, rob the horse of valuable nutrients, and cause gastrointestinal irritation and unthriftiness.  At their worst, they can lead to colic, intestinal ruptures, and death.

             Using de-worming agents on a regular schedule in combination with good management procedures is critical to relieving your horse of most parasites. Since parasites are primarily transferred through manure, good management is key.  In terms of management priorities, establishing a parasite control program is probably second only to supplying the horse with clean, plentiful water and high quality feed.

With the many safe, convenient products available today, establishing an effective de-worming program is easy.  A good parasite control program will go a long way toward maximizing your horse’s appearance, performance and comfort. 

There are a few strategies for ensuring decreased parasite loads in your horses. Whichever program fits your barn and horses, keeping the pastures free of manure and keeping horses less densely stocked in pastures will improve your likelihood of success.

Rotational De-worming

     This program utilizes a regular rotation of different anthelmintic classes. Typically, horses are  de-wormed every 8 weeks and monitored with fecal exams at least bi-annually. The number of eggs per gram (EPG) give us insight as to the worm burden. However, fecal exams may not show larval infections and will not show encysted parasites, therefore the results must be evaluated with the clinical signs of the horse. Additional de-worming for encysted parasites should be worked into this program.

Daily De-worming

     This program involves feeding the horse a product on a daily basis. It is helpful for horses that will not tolerate paste de-worming or who are in an environment where it's pasture mates have unreliable deworming schedules. It utilizes a single anthelminthic class of de-wormer (pyrantel tartrate) fed daily to prevent maturation of larval stages of parasites and migration of large strongyles. It does not control tapeworms Twice annual targeted de-worming for tapeworms should be utilized with this program. As with Rotational de-wormin, twice annual fecal exams are recommended to rule out development of resistance to this drug class and to monitor the programs effectiveness in a given horse.

Fecal Exams and Targeted de-worming

     With emerging anthelminthic resistance in farm animals and on some horse farms in the south, there has been a push to utilize targeted de-worming practices on farms. The basic premise is that horses are dewormed when they are infected with worms, not on a random schedule. In this program, fecal samples of all horses on a farm are evaluated for fecal egg counts on a regular schedule throughout the year (typically 3 times (spring, mid summer and late fall)). Horses with rising fecal egg counts or counts higher than 250 are de-wormed with an appropriate anthelminthic. These horses would then be rechecked at an appropriate time after the deworming to be sure the worm infection has been cleared. The result is you are deworming your horse less and having a piece of mind that he/she is clear of infection. The bigger side benefit is that we reduce the amount of anthelminthic that the worm population is seeing which slows down (or even prevents) the development of worms who are resistant to the medications we have available. On this program horses are dewormed only twice a year, unless they show an infection.