Common Signs of
Parasite Infestation
Some horses can have dangerous parasite levels and appear to
be perfectly healthy. From the outside they may be fat, sleek, and shiny, while
on the inside worms are doing irreparable damage. But in other horses,
especially young ones, parasites can leave some pretty substantial visible
signs.
Signs of infestation could include:
Dull or rough hair coat
lethargy or decreased stamina
weight loss
coughing and/or nasal discharge
tail rubbing and hair loss
resistance to the bit due to mouth lesions
colic
depression
loss of appetite
unthriftiness or loss of condition
diarrhea
Fecal Examinations
One of the most underutilized and cheapest tools in an
effective parasite control program is the fecal examination, which merely
involves taking two to three fresh fecal balls to your veterinarian for
laboratory analysis. This simple process can identify the specific parasites
infecting a horse. Rarely are the worms themselves visible in the manure. But
by counting the types and numbers of parasite eggs present in the fecal sample,
your veterinarian can recommend the right deworming agents to do the job.
Counts of fecal eggs per gram counts also tell an owner about the degree of
parasite infestation on a farm or within a herd. The fecal exam is a
cost-effective follow-up to deworming to determine whether the dewormer has
worked. It is good practice to do a fecal EPG count within two weeks after
deworming.
Management
Management programs that interrupt the life cycle of the
parasite before infestation occurs are the keys to successful control. Clean
and sanitary stall areas are essential. Manure should be removed and placed in
a compost pile or spread on cropland or pastures not being grazed by horses.
The larvae in composted manure will be destroyed if sufficient heat is built
up. Spreading manure by dragging pastures will decrease incidence of infective
larvae if the climate allows for drying of manure.
Alternative grazing with ruminants (cattle or sheep) and
pasture rotation schemes will aid in disrupting the parasite life cycle.
Grazing ruminants in rotation with horses will reduce parasite infestation,
because most internal parasites are host specific. Pasture rotation may also
help by decreasing incidence of overgrazing, thus decreasing ingestion of
parasites.
Grouping horses in pastures according to age will help
minimize young horses coming in contact with heavy larval infestations. For
example, pasture mares and foals away from other horses less than 2 years of
age. Yearling horses often need a different control program than a broodmare.
It can be more difficult to control parasites in a herd if all ages and classes
of horses are in a pasture together. Be sure to isolate and deworm all new
arrivals to the farm. When feeding horses, always provide hay mangers and feed
bunks. Feeding horses on the ground and not out of containers increases the
risk of parasite infestation. All feeders, buckets, and water troughs should be
routinely cleaned to help prevent fecal contamination of feed or water.
Control
Various types of chemicals called anthelmintics, or
antiparasitics, have been developed to aid in the control of parasites. These
chemicals work in a number of ways. Some paralyze the parasite, thus allowing
the host to expel them. Other chemicals prevent nutrient utilization or limit
reproductive capabilities in the parasites, thus killing them or stopping the
life cycle. A large number of commercial antiparasitic compounds are currently
on the market to remove internal parasites from horses. These antiparasitics
are separated into six major classes. The more common classes are
avermictins/milbimycins, benzimidazoles, and pyrimides. These anthelmintics are
available in different physical forms (paste, feed additives, gel, drench) and
are sold under several trade names.
Knowledge of antiparasitics is important because these
chemicals vary in their ability to remove specific species and types of parasites.
For example, a compound may be effective at controlling strongyles and
ascarids, but not bots or tapeworms, whereas another chemical is effective in
controlling ascarids, strongyles, and tapeworms, but not bots. In addition,
some anthelmintics are not safe for certain classes or ages of horses. It is
very important that you speak with your veterinarian before starting a
anthelmintic protocol and the best way to rotate between anthelmintic classes
for maximum efficiency.
Below is a list of some management practices that can be
considered to aid in the control of parasites:
Deworm all foals at 4 to 8 weeks of age. Speak with your
veterinarian first to choose the best type of anthelmintic for your situation.
Regularly rotate pastures.
Small pastures from one to 10 acres can be divided into
smaller areas so horses can be rotated. This will help lower the worm burden as
well as give forage a chance to recover.
If possible, pasture cattle, sheep, or goats behind the
horse(s). These species consume the infective larvae of the horses’ parasites,
and the larvae will be inactivated.
Clean stalls on a regular basis and compost manure or spread
thinly over pasture not being grazed by horses. Stalled horses become
reinfested from larvae crawling up the walls and being licked off by the
horses.
Mowing and harrowing pastures to break up fecal piles during
the hottest and driest season of the year will decrease numbers of infective
larvae.
Feed horses grain and hay from some type of rack or trough.
This includes pastured horses.
A yearly fecal examination by a veterinarian will help you
evaluate how well the program is working.
Avoid overstocking a pasture, as this will increase the risk
of exposure to infective larvae or eggs.
Remove bot eggs quickly and regularly from the horse's hair
coat to prevent ingestion.
Alternate anthelmintic classes to decrease possible parasite
resistance to an anthelmintics class and administer anthelmintic to all horses
at the same time when they are kept together.
Always read and follow the label instructions of an
anthelmintic when administering.
For the full article and more information please visit: http://www.extension.org/pages/10317/management-and-control-of-internal-parasites-in-horses#.VZpz7vlViko
