strategic parasite management

Our goal is to ensure that your horse(s) receives the parasite control that is required for optimum health during the grazing season. Below is an excerpt from an article on why we feel a good parasite management plan is important and recommended for your horse(s).

For approximately the last 30 years, horses have traditionally been dewormed at regular intervals throughout the year, typically every 6 to 8 weeks. In foals, such regimens have been used to control Parascaris equorum (roundworms). In older animals, interval treatment regimens were primarily designed to control Strongylus vulgaris. However, subsequent to the introduction of ivermectin in the 1980s, S. vulgaris has become an uncommon infection of horses. This is largely because ivermectin, unlike earlier dewormer, eliminated both adult and immature stages of S. vulgaris. In contrast to S. vulgaris, small strongyles (cyathostomes) have become increasingly important as a cause of sickness and death in horses, and today are considered the primary reason for deworming animals that spend time at pasture.  Horses become infected with cyathostomes by ingesting infective third-stage larvae present in pasture. The parasites then invade the wall of the large intestine and undergo a period of arrested development that lasts weeks to months. Eventually, due to stimuli that are poorly understood, the parasites begin to develop, increase in size, and eventually break out into the lumen of the large intestine where they mature and produce strongyle eggs. The increasing importance of cyathostomes over the last 20 years is thought to have occurred because none of the currently licensed anthelmintics, except moxidectin (Quest), have activity at standard dosages against immature stages encysted in the wall of the large intestine. In addition, cyathostomes have been particularly adept at developing dewormer resistance. Because this resistance appears to have arisen in association with excessive and inappropriate use of dewormers, there is a need for veterinarians to critically examine the deworming programs used by clients so that problems with dewormer resistance do not worsen.

Since it is unlikely that new classes of deworming drugs will be introduced in the near future, it is increasingly important to use parasite control programs that decrease the rate of selection of dewormer resistance. The most important risk factor for development of anthelmintic resistance appears to be the frequency of deworming treatments. The primary objectives for a sound parasite control program should therefore be to minimize the number of deworming treatments AND to minimize environmental contamination with parasites.

Based on these guidelines, parasite management plans must be individually developed for each farm, and sometimes for each horse, following a thorough assessment of all lifestyle factors.  Routine fecal testing is a vital part of this assessment and must be done routinely on all animals in order to continually evaluate changing environmental and lifestyle factors. 

Ideally a fecal parasite test should be performed in early spring, prior to turnout on fresh pasture.  Another check in late August or September is also recommended as this is generally the peak of parasite season in our area.  Additional fecal testing may be recommended based on your farm’s unique risk factors.

Deworming products should only be given following a recommendation by your regular veterinarian.  This will ensure the appropriate product is being used for each animal and will help ensure resistance issues do not develop.

(RSLVS 2017)