Treatment and Control of Equine Strongyle Infections

Control of small strongyle infections with anthelmintics

The table, below, shows a sampling of the drugs used in practice against the small strongyles. There are, in fact, many more drugs that are approved for use against the small strongyles in the United States but the marketplace of horse-owners and veterinarians has selected those in the table as the most widely accepted drugs for use in parasite control programs. As a result, some manufacturers have withdrawn a number of other drugs from the market even though they remain on the approved list by the Food and Drug Administration (FDA)


Drug Dose EL3s
LL3s Mucosal L4s Lumen L4s Adults
Oxibendazole oral
10 mg/kg
----- ----- ----- ----- ++++
Fenbendazole oral
10 mg/kg
daily for 5 days


++++ ++++ ++++ ++*
Oxfendazole oral
10 mg/kg
----- ----- ----- ----- ++*
Febantel oral
6 mg/kg
----- ----- ----- ----- ++*
Pyrantel pamoate oral
6.6 mg/kg
----- ----- ----- ++++ ++++
Pyrantel tartrate oral
continuous feeding
@14.4 mg/kg
----- ----- ++++ ++++ ++++
Ivermectin oral
----- ----- ----- ++++ ++++
Moxidectin oral
0.3 mg/kg
----- ++++ ++++ ++++ ++++
* Benzimidazole resistance, ++ = partial activity, ++++ = highly effective, ---- = minimal activity


Fenbendazole given orally at a dose of 10mg/kg daily for five days has the broadest spectrum of activity against parasitic stages of the small strongyles. It is generally recommended that larvicidal doses of Fenbendazole should be incorporated into parasite control programs at least once and possibly twice during the calendar year. The single yearly treatment is usually given in November or December and the twice yearly treatments are recommended for April and October. The problem of anthelmintic resistance among the   small strongyles is particularly prevalent in the benzimidazoles. Oxibendazole and larvicidal doses of Fenbendazole are effective against adult small strongyles but veterinarians and horse-owners should be particularly vigilant for the emergence of anthelmintic resistance to these two drugs. The use of larvicidal doses of Fenbendazole is becoming popular and this increased use could hasten the emergence of drug resistance.




Parasites and Parasitic Diseases of Domestic Animals
Dr. Colin Johnstone (principal author)
Copyright 1998 University of Pennsylvania
This page was last modified on January 24, 2000