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Coccidiosis in Dogs
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Coccidia
Coccidia
There are many different species
of coccidia for dogs and cats, but the most common infections are with coccidia
of the genus Isospora.
The information presented here pertains to Isospora species
What on Earth are Coccidia?
Coccidia are single celled organisms that infect the intestine. They
are microscopic parasites detectable on routine fecal tests in the same
way that worms are but coccidia are not worms and they are not visible to
the naked eye. Coccidia infection causes a watery diarrhea which is sometimes
bloody and can even be a life-threatening problem to an especially young
or small pet.
Where do Coccidia Come From?
Oocysts (pronounced o'o-sists), like those shown above, are passed in
stool. In the outside world, the oocysts begin to mature or “sporulate.”
After they have adequately matured, they become infective to any host (dog
or cat) that accidentally swallows them.
To be more precise, coccidia come from fecal-contaminated ground. They
are swallowed when a pet grooms/licks the dirt off itself. In some cases,
sporulated oocysts are swallowed by mice and the host is infected when it
eats the mouse. Coccidia infection is especially common in young animals
housed in groups (in shelters, rescue areas, kennels, etc.) This is a common
parasite and is not necessarily a sign of poor husbandry.
What Happens Inside the Host?
The sporulated oocyst breaks open and releases eight sporozoites. These
sporozoites each finds an intestinal cell and begins to reproduce inside
it. Ultimately, the cell is so full of what are called “merozoites” that
it bursts releasing the merozoites which seek out their own intestinal cells
and the process begins again. It is important to note how thousands of intestinal
cells can become infected and destroyed as a result of accidentally swallowing
a single oocyst.
As the intestinal cells are destroyed in larger and larger numbers,
intestinal function is disrupted and a bloody, watery diarrhea results.
The fluid loss can be dangerously dehydrating to a very young or small
pet.
How Are Coccidia Detected?
A routine fecal test is a good idea for any new puppy or kitten whether
there are signs of diarrhea or not as youngsters are commonly parasitized.
This sort of test is also a good idea for any patient with diarrhea. The
above illustration demonstrates coccidia oocysts seen under the microscope
in a fecal sample. Coccidia are microscopic and a test such as this is necessary
to rule them in. It should be noted that small numbers of coccidia can be
hard to detect so just because a fecal sample tests negative, this does
not mean that the pet is not infected. Sometimes several fecal tests are
performed, especially in a young pet with a refractory diarrhea; parasites
may not be evident until later in the course of the condition.
How is Coccidiosis Treated?
We do not have any medicine that will kill coccidia; only the patient’s
immune system can do that. But we can give medicines called “coccidiostats”
which can inhibit coccidial reproduction. Once the numbers stop expanding,
it is easier for the patient’s immune system to “catch up” and wipe the
infection out. This also means, though, that the time it takes to clear
the infection depends on how many coccidia organisms there are to start
with and how strong the patient’s immune system is. A typical treatment
course lasts about a week or two but it is important to realize that the
medication should be given until the diarrhea resolves plus an extra couple
of days. Medication should be given for at least five days total. Sometimes
courses as long as a month are needed.
The use of sulfa drugs in pregnancy can cause birth defects. Sulfa drug
use can also lead to false positive test results for urine glucose.
Can People or Other Pets Become Infected?
While there are species of coccidia that can infect people (Toxoplasma
and Cryptosporidium, for example), the Isospora species of dogs and cats
are not infective to people. Other pets may become infected from exposure
to infected fecal matter but it is important to note that this is usually
an infection of the young (i.e. the immature immune system tends to let the
coccidia infection reach large numbers where the mature immune system probably
will not.) In most cases, the infected new puppy or kitten does not infect
the resident adult animal.
Copyright
1991 - 2007, Veterinary Information Network, Inc.
This work was originally published by Veterinary Information
Network, Inc. (VIN)
and is republished with VIN's permission.
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The above information is simply informational.
It's intent is not to replace the advice of a veterinarian nor to assist
you in making a diagnosis of your pet. Please consult with your own veterinarian
for confirmation of any diagnosis. Your pets life may depend on it.