The Gold Standard for worming has changed. It is now suggested that worm control starts with using worm counts and tests, only treating for worms as they are needed.
Horse worms have become increasingly resistant to some worming medication. This means that we can no longer rely on keeping horses worm free purely by giving them wormers.
It is far more effective to test before drenching to determine the animal that is a high shedder to minimize the use of treatment.
Using worm treatments occasionally should also mean that they stay effective for those times when horses really need them.
If a horse pasture management system is in place this will help to reduce the reliance on chemicals to control your horse’s worm burden. To keep horses healthy it is suggested that:
Keep the number of horses per acre to a minimum to prevent overgrazing and reduce pasture contamination with parasite eggs and larvae.
Pick up and dispose of manure regularly (at least twice a week, even in dirt or sand yards).
Spreading manure on fields that animal graze is not recommended; instead, compost it in a pile away from the pasture.
The worm count result will be reported as a number of eggs per gram (EPG). It is quite common for there to be no worm eggs seen in a sample and this will be reported as <50 EPG (less then 50EPG).
A count of less than 200 EPG is regarded as a LOW count, which shows that your worm management program is working. In most situations you won’t need to worm at this level.
A count between 200 EPG and 500 EPG it is a MEDIUM count and the horse might need worming. If the count is over >500 EPG (greater than 500EPG) it is a HIGH count, the horse needs worming and the worm management program needs to be revised as resistance may be apparent.
The aim is not to eradicate all parasites, but rather to keep them at an acceptable level for the good health of your horse.
If you see Bot Fly eggs remove them immediately from the horses coat (flea combs work well in some instances).
Mow pastures periodically to break up manure piles and expose parasite larvae to the elements. Larvae can survive freezing, but they cannot tolerate extreme heat and drying for very long.
Consider rotating pastures by allowing sheep or cattle to graze them, thereby interrupting the lifecycles of equine parasites.
Keep foals and weanlings separate from yearlings and older horses to minimize the foals’ exposure to ascarids and other parasites.
Use a feeder for hay and grain rather than feeding on the ground.