In this series on fall deworming we look at several topics that you should review in your horse’s health program. Environmental control and understanding how the differences in geography and climate affect parasite burdens in horses is part of that review.

Environmental Control

Removal of manure at least twice a week in paddocks and pastures helps to cut down on the number of infective parasite larvae a horse might ingest while grazing. You also can help cut down on pasture parasite passage by rotating fields and avoiding overstocking pastures with too many horses.

When possible, harrow and drag pastures during hot, dry weather to allow sunlight to kill infective larvae. Keep horses out of those pastures for a couple of months to maximize how well the pasture is decontaminated.

Difference in Geographical Areas

In the northern latitudes, it is possible for internal parasite larvae to survive over the winter with the potential to infect a horse year-round. Deworming helps to reduce the numbers of eggs and infective larvae shed into the pasture environment.

If a horse is confined to a dry lot or stall, which are routinely cleaned of manure, then once the horse is dewormed in the fall, there is no need to deworm again until spring pasture turnout.

In southern temperate regions, summer tends to suppress development of infective larvae passed in feces due to high ambient temperatures. However, as temperatures cool in autumn months, there is a greater risk of infective larvae on pastures so this is an optimal time to deworm.