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Coccidiosis:
Understanding the Drugs Available for Control
by N. Galen Walters, DVM
Most Pygmy goat owners are
aware that coccidiosis is a lurking condition always awaiting
the opportunity to become a full-blown disease in their herds.
Many understand that “treatment” is a matter of controlling
rather than eradicating the condition, but few realize that
several treatment choices are available, each appropriate to
specific stages in the life cycle of the organism. This becomes
useful information when owners are faced with attempting to
treat an outbreak of disease or trying to prevent one. The
following schematic life cycle of coccidia will help clarify
where the various drugs available for treatment have their
effect.
STEPS OF DEVELOPMENT OF
COCCIDIA
-
1 - Oocyst (egg) contaminates
the environment via feces from an infected animal.
-
2 - After the oocyst matures
in the soil (1-7 days) to become an infective sporocyst
stage, a susceptible Pygmy ingests it.
-
3 - Sporocyst bursts open
inside the internal lumen and releases sporozoites.
-
4 - Sporozoites enter internal
cells and multiply, producing thousands of merozoites.
-
5 - Merozoites rupture from
intestinal cell walls and enter more intestinal cells.
-
6 - Merozoites unite to
eventually form an oocyst which will be released from the
intestinal cell wall and be passed out via feces.
-
7 - Oocysts rupturing from
intestinal wall and passed via the feces.
The three most commonly
available drugs (coccidiostats) for use in goats are Sulfa
drugs, Amprolium (Corid®), and Decoquinate (Deccox®).
Sulfa drugs are the only drugs actually labeled for use in
goats.
IMPORTANT POINTS TO KEEP
IN MIND
-
All drugs available are
only effective in reducing numbers produced; they do not
directly kill the organism.
-
Clinical disease occurs as
a direct result of intestinal cell wall damage and most
during the merozoite stage, 14-20 days after initial
ingestion.
-
Goats have the ability to
develop an active immunity against coccidia which generally
requires ten days to develop. Medication helps slow down the
organisms’ multiplication long enough for the animal to
develop this immunity.
-
Immunity may be overridden
by massive exposure to oocysts.
-
Epidemics occur when:
-
Resistance is decreased
due to stress (feed changes, crowding)
-
There is an increased
exposure to oocysts, massive contamination, poor
cleanliness, accumulation of feces, crowding.
-
Susceptible (young)
animal is introduced to a contaminated area – too young to
have developed an immunity.
-
Coccidiosis is a
self-limiting infection provided the animal is not reinfected,
i.e., once the organism completes its life cycle, it is shed.
-
Control of the infective
cycle is the key in prevention (oocysts in feces and in
environment for greater than 7 days).
-
Environmental factors in
control:
-
Complete dryness or
exposure to direct sunlight is lethal to oocysts.
-
Infection stage takes
1-7 days to develop from time oocysts pass in feces.
-
Optimum temperature for
the development of oocysts is 68-73°F. Few develop below
32-40°F, but oocysts can survive for up to 8 months as low
as 6°F.
SULFA DRUGS
-
Mode of action: Reduces
numbers of organisms at the end of the life cycle, steps
5-6, the merozoite stage.
-
Effective time to use:
When you actually see clinical outbreaks of disease.
-
Disadvantages: Because
effect is late in the cycle, intestinal damage may already be
extensive. Can be toxic at wrong dosage.
-
Advantages: Helps prevent
secondary bacterial infections.
-
Treatment: Sulfamethazine
(poultry prep) added to water or milk at 60 mg/lb per day.
Treat kids at 3-4 weeks of age for 7 days and repeat in 3
weeks. May have to treat at 21-day cycles through 3 weeks
post-weaning.
AMPROLIUM (Corid®)
-
Mode of action: Acts early
in the life cycle, steps 4-5.
-
Effective time to use: The
choice to use when you are already in a known contaminated
area and/or just beginning to see clinical disease.
-
Disadvantages: Interferes
with thiamine utilization in the coccidia organism, hence
retards their growth and multiplication. Thought to make the
host thiamine deficient as well. May need to supplement with
thiamine.
-
Treatment: Have to start
kids at 2 weeks old. 25-30 mg/lb for 10 days or 15-30 mg/lb
for 21 days. Repeat in 3 weeks.
DECOQUINATE (Deccox®)
-
Mode of action: Effective
in reducing numbers very early in the life cycle, steps 3-5,
the sporozoite stage.
-
Effective time to use:
Best used any time you move susceptible animals into an
infected area. First day they enter then area, put in the
ration.
-
Advantages: Works well as
a preventative and treatment before marked intestinal wall
destruction takes place.
-
Treatment: Start at 2
weeks old and use for 28 continuous days. ¼ mg/lb. In older
kids and adults, offer free choice in granulated salt, mixed
at the rate of 2 lbs. of 6% Deccox premix in 50 lbs. of salt.
Excerpts from:
Kinne, Maxine, ed.
Pygmy Goats: Best of Memo
2
(1982-1987)
National Pygmy Goat Association: pp 118-119
This document is for
informational purposes only and is in no way intended to be a
substitute for medical consultation with a qualified veterinary
professional. The information provided through this document is
not meant to be used in the diagnosis or treatment of a health
problem or disease, nor should it be construed as such.
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