A regular parasite control program is critical to your horse’s
health. Infestations of internal parasites can cause your
horse to feel ill all of the time, become colicky, and can
even cause death. Parasites can cause damage to a horse's
internal organs. Signs of parasite infestation include overall
poor condition, dry and dull coat, diarrhea, bloating, and
an itchy tail. Deworming your horse regularly is necessary
because he can be continually re-infected from parasite eggs
in pastures or from bot flies. A haphazard deworming program
is hard on your horse’s system; Getting rid of internal parasites
and keeping them away is the best procedure for your horse’s
In some cases where a horse is confined, as with stallions,
or he is very young, old or not thriving, a modified worming
program may be advisable. Consult your veterinarian to determine
whether an individualized program is recommended.
Parasite Life Cycle
Most internal parasites are ingested as larvae, where they
migrate to your horse’s digestive system and live in the intestines.
There, they mature and lay eggs which are passed out in manure.
The eggs hatch into larvae and spread into the environment.
Your horse, or another horse, ingests the larvae, and the
Deworming your horse with a paste dewormer purges the adults
already in his system before they lay eggs. It breaks the
cycle by stopping any more eggs from being passed. The problem
lies with the fact that if he shares a grazing area with other
horses or if manure is allowed to lie in his pasture, he can
be immediately reinfected; The smaller the area, the bigger
the potential problem. Horses normally will not graze near
manure, but if the grazing area is not large enough to sustain
the number of horses, or your pastures are not properly rotated,
the desire for grass may over ride his natural tendencies.
Deworming with a paste dewormer requires all of the horses
that share grazing space to be treated at the same time, thereby
killing all of the adult parasites before eggs are laid. It
is also good practice to remove manure from any grazing area.
If you choose a paste dewormer, it is important to give your
horse the proper dose. Be certain to read the dosage information
on the packaging and to adjust dose according to each horse’s
age and weight. Rotate between wormers that have different
types of chemical bases. This will not only kill a broader
spectrum of parasites, it helps prevent parasite immunity
to one chemical.
A sample rotation schedule might be:
1. Spring (March) An Ivermectin based product controls
large strongyles, small strongyles, pinworms, ascarids, hairworms,
large-mouth stomach worms, bots, lungworms, and intestinal
2. Late Spring (May) A fenbendazole-based product
(Safe Guard) controls large strongyles, encysted early- and
late-third-stage and fourth-stage cyathostome larvae, small
strongyles, pinworms, and ascarids.
3. Summer (July) A pyrantel pamoate based product
(Strongid) control large strongyles, small strongyles, pinworms,
ascarids, and tapeworms when double-dosed.
4. Fall (September) A moxidectin based product (Quest)
controls large strongyles, small strongyles, pinworms, ascarids,
encysted cyanthostomes, hairworms, large-mouth stomach worms,
5. Late Fall (November) An oxibendazole based product
(Anthelcide) large strongyles small strongyles, large roundworms,
and pinworms, including various larval stages and threadworms
Another option is to use a daily dewormer. It is recommended
to first use a larvacidal dewormer such as ivermectin or moxidectin
before beginning a daily treatment plan. This will help destroy
existing larvae and adult parasites. Pyrantel Tartrate is
the chemical ingredient in daily wormers. It controls large
strongyles, small strongyles, pinworms, ascarids, and tapeworms.
If you choose a daily wormer, your horse should also receive
ivermectin or moxidectin in early Spring and late Fall to
control bots AND praziquantel in early Spring to control tapeworms.
Timing is Critical
For daily programs, be certain that your horse gets his daily
dose every day, as missed doses will decrease the levels of
dewormer in his system, rendering it less effective.
For purge programs, timing is essential. If you treat too
early, targeted worms will be too immature to be affected
by the dewormer. If you treat too late, adult worms will have
the opportunity to produce eggs, infesting your horse's environment
and raising his (and other horses) risk of exposure.
How to Stay on Schedule
· Post a calendar in your barn. Clearly mark the day for
· Purchase the entire year’s worth of dewormer at one time.
Write the horse’s name and the date to be given with an indelible
pen on the tube.
· Put the wormer out where it can be seen the day before
you will administer it.
· Keep wormer out of the reach of children and pets.
Following a regular deworming schedule is critical to keeping
your horse healthy.
About the Author
Ron Petracek was raised in southern Idaho with horses and
the great outdoors. With this continued passion He now shares
through a a vast equine network. Learn more by clicking the
Amazing Equine Network System