Horse deworming schedule planner

Why the old rotation schedule changed

For decades horses were dewormed every 6 to 8 weeks, rotating products. That bred parasites resistant to nearly every dewormer class. The American Association of Equine Practitioners (AAEP) now recommends strategic deworming: every adult treated once or twice a year, and extra treatments only for horses that shed a lot of eggs.

How shedding works

In most herds, a small share of horses sheds most of the eggs. A fecal egg count sorts them: under 200 eggs per gram is low, 200–500 moderate, over 500 high. The shedder level stays fairly consistent for each horse, so testing a couple of times a year is enough to set the schedule.

Timing by climate

Parasite eggs develop on pasture when it's warm but not scorching. In cold-winter areas that's spring through fall, so treatments go in spring and fall. In the hot South, summer heat kills larvae and transmission happens fall through spring, so treatments shift to fall and winter. Every horse needs one treatment a year that covers tapeworms (praziquantel), usually the last one of the season.

Foals and young horses

Foals face roundworms (ascarids) first, then strongyles, and need about four treatments in their first year starting at 2 to 3 months. Young horses up to about 3 years get more frequent treatment than adults.

This planner follows the AAEP Internal Parasite Control Guidelines. It isn't a prescription: your vet knows your farm's parasite resistance and will choose products and doses. Pair it with the horse weight calculator, since dewormers are dosed by weight.