:: WAGING
WAR ON EQUINE PARASITES
Internal
parasites are silent killers. They can cause extensive
internal damage, and you may not even realize Your
animals are heavily infected. At the very least,
parasites can lower resistance, rob the horse of
valuable nutrients, and cause gastrointestinal
irritation and unthriftiness. At their worst, they can
lead to colic, intestinal ruptures, and death. In terms
of management priorities, establishing an effective
parasite control program is probably second only to
supplying the horse with clean, plentiful water and high
quality feed. It's that important!
IDENTIFYING
THE ENEMY
There are more than 150
internal parasites that afflict horses, including
several major species. Among the most common and
troublesome are:
- Large strongyles
(bloodworms)
- Small strongyles
- Ascarids (roundworms)
- Pinworms
- Bots
- Tapeworms
- Threadworms
- Lungworms
Any or all of these
parasites can be present in the horse at one time, but
they may be at different stages in their life cycles.
This will influence the deworming program needed to
combat them. Also, keep in mind that some species can
lay more than 200,000 eggs a day, so parasite loads can
escalate quickly.
PARASITE
DAMAGE
Different parasites harm
the horse in different ways. They can damage tissues and
vital organs, including the major blood vessels to the
intestines, lungs, liver, stomach, and intestines, as
they migrate through the horse's system to complete
their life cycles. They can cause obstructions and
ulcerations within the horse's digestive tract, and they
can also cause intense irritation as they lay eggs, such
as pinworms do.
SIGNS
OF PARASITISM
Contrary to popular
belief, many horses that have dangerous parasite levels
appear to be perfectly healthy. From the outside they
may be fat, sleek and shiny, while on the inside the
worms are doing irreparable damage. But in other horses,
especially young horses, parasites can take a visible
toll. Signs of infestation might include:
- Dull, rough haircoat
- Lethargy or decreased
stamina
- Weightless
- Coughing and /or
nasal discharge
- Tail rubbing and hair
loss
- Resistance to the bit
due to mouth lesions
- Colic
- Summer sores
- Depression
- Loss of appetite
- Unthriftiness or loss
of condition
- Diarrhea
FECAL
EXAMINATIONS
One of the most
under-utilized 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. Fecal eggs per gram
counts (EPG) 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's good practice to
do a fecal EPG count within two weeks after deworming
THE
IMPORTANCE OF ROTATING DEWORMING AGENTS
Parasites can develop
resistance to many of the chemicals used to kill them.
After a period, the deworming agents may therefore
simply become ineffective. To prevent this, it's
important to rotate classes of drugs used in your
program, Be sure that you don't simply change brand
names, however, since many products contain the same
drugs but under different labels. Although some
manufacturers claim that certain products do not require
rotation, a good safeguard is to do it anyway. That way,
there's no question about resistance developing.
With opinions varying as
to how often dewormers should be rotated, it is
recommended to consult your veterinarian for guidance.
By utilizing broad-spectrum deworming agents and
rotating them as recommended by your veterinarian, you
should be able to rid your horse of most worms.
METHODS
OF ADMINISTRATION
There are three primary
ways of administering dewormers. They are:
- Oral paste syringe
- Nasogastric tube
(tubing)
- Feed additive
All three methods
are effective. The key is that the deworming product
must be given in the proper dose at the proper time,
and that it is fully consumed and retained by the
animal. Deworming pastes and feed formulations have
come into widespread use because of convenience and
ease of administration. They are a good choice as
long as the horse ingests the entire dose. (The dose
must be calculated based on the horse's weight.) The
problem is that some horses may find them
unpalatable and spit them out.
Tube deworming, once
the method of choice, is still a highly effective
means of controlling parasites. The advantage of
administering dewormers via a nasogastric tube is
that the veterinarian can ensure the proper dose is
delivered directly to the horse's stomach. The
disadvantage is that it causes the animal temporary
discomfort when it is passed through the nostrils
and down the esophagus into the stomach. Because of
the skill required to safely insert the tube, this
method of deworming should be performed only by a
veterinarian.
DEWORMING
SCHEDULES
The best way to set
up a deworming schedule is to consult your
veterinarian. Horses at different ages and stages
have varying needs concerning parasite control. For
example, young foals are especially susceptible to
ascarid roundworm) infestation, and may require
deworming at thirty day intervals until they build
some natural resistance. Older horses turned out on
a large acreage might do well on a semiannual
schedule.
And some owners may
prefer to have their horses on a continuous control
program whereby the horse is given a daily dose of
dewormer through a feed additive.
Climatic conditions
and season of year can also influence parasite
levels. Your veterinarian may recommend that you
concentrate deworming efforts when your horse's
exposure to Parasites is at its peak. Other
veterinarians may prefer that you deworm at regular
intervals, such as every sixty to ninety days. Still
others may recommend that you prevent parasitism
with a daily dewormer. In any case, the goal is to
keep parasite loads to a minimum.
A
COMPLETE MANAGEMENT PROGRAM
Importantly,
chemical control is just one Part of a total
parasite control plan. Since parasites are primarily
transferred through manure, good management is also
key. You should:
- Pick up and
dispose of manure droppings on a regular basis
(at least twice weekly)
- Mow and harrow
pastures regularly to break up manure piles and
expose parasite eggs and larvae to the elements
- Rotate pastures
by allowing other livestock, such as sheep or
cattle, to graze them, thereby interrupting the
life cycles of equine parasites
- Group horses by
age to reduce exposure to certain parasites and
maximize the deworming program geared to that
group
- Keep the number
of horses per acre to a minimum to prevent
overgrazing and reduce the fecal contamination
per acre
- Use a feeder for
hay and grain rather than feeding on the ground
- Remove bot eggs
quickly and regularly from the horse's haircoat
to prevent ingestion
- Rotate deworming
agents, not just brand names, to prevent
chemical resistance
- Consult your
veterinarian to set up an effective and regular
deworming schedule
SUMMARY
With the many safe,
convenient products available today, establishing an
effective deworming program is easy. Discuss a plan
with your veterinarian and implement it without
delay. A good parasite control program will go a
long way toward maximizing your horse's appearance,
performance and comfort. The net result will be an
animal that's as healthy on the inside as it appears
on the outside.
This
brochure was developed by the American Association of
Equine Practiitioners through a grant from Bayer
Corporation.
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