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Coccidia are small protozoans (one-celled organisms) that multiply
in the intestinal tracts of dogs and cats, most commonly in puppies
and kittens less than six months of age, in adult animals whose
immune system is suppressed, or in animals who are stressed in other
ways (e.g.; change in ownership, other disease present).
In dogs and cats, most coccidia are of the genus called Isospora.
Isospora canis and I. ohioensis are the species most often encountered
in dogs. Regardless of which species is present, we generally refer
to the disease as coccidiosis. As a puppy ages, he tends to develop
a natural immunity to the effects of coccidia. As an adult, he may
carry coccidia in his intestines, and shed the cyst in the feces,
but experience no ill effects.
How are coccidia transmitted?
A puppy is not born with the coccidia organisms in his intestine.
However, once born, the puppy is frequently exposed to his mother's
feces, and if the mother is shedding the infective cysts in her
feces, then the young animals will likely ingest them and coccidia
will develop within their intestines. Since young puppies, usually
those less than six months of age, have no immunity to coccidia,
the organisms reproduce in great numbers and parasitize the young
animal's intestines. Oftentimes, this has severe effects.
From exposure to the coccidia in feces to the onset of the illness
is about 13 days. Most puppies who are ill from coccidia are, therefore,
two weeks of age and older. Although most infections are the result
of spread from the mother, this is not always the case. Any infected
puppy or kitten is contagious to other puppies or kittens. In breeding
facilities, shelters, animal hospitals, etc., it is wise to isolate
those infected from those that are not.
What are the symptoms of coccidiosis?
The primary sign of an animal suffering with coccidiosis is diarrhea.
The diarrhea may be mild to severe depending on the level of infection.
Blood and mucous may be present, especially in advanced cases. Severely
affected animals may also vomit, lose their appetite, become dehydrated,
and in some instances, die from the disease.
Most infected puppies encountered by the authors are in the four
to twelve week age group. The possibility of coccidiosis should
always be considered when a loose stool or diarrhea is encountered
in this age group. A microscopic fecal exam by a veterinarian will
detect the cysts confirming a diagnosis.
What are the risks?
Although many cases are mild, it is not uncommon to see severe,
bloody diarrhea result in dehydration and even death. This is most
common in animals who are ill or infected with other parasites,
bacteria, or viruses. Coccidiosis is very contagious, especially
among young puppies. Entire kennels may become contaminated, with
puppies of many age groups simultaneously affected.
What is the treatment of coccidiosis?
It should be mentioned that stress plays a role in the development
of coccidiosis. It is not uncommon for a seemingly healthy puppy
to arrive at his new home and develop diarrhea several days later
leading to a diagnosis of coccidia. If the puppy has been at the
new home for less than thirteen days, then he had coccidia before
he arrived. Remember, the incubation period (from exposure to illness)
is about thirteen days. If the puppy has been with his new owner
several weeks, then the exposure to coccidia most likely occurred
after the animal arrived at the new home.
Fortunately, coccidiosis is treatable. Drugs such as sulfadimethoxine
(Albon®) and trimethoprim-sulfadiazine (Tribrissen®) have
been effective in the treatment and prevention of coccidia. Because
these drugs do not kill the organisms, but rather inhibit their
reproduction capabilities, elimination of coccidia from the intestine
is not rapid. By stopping the ability of the protozoa to reproduce,
time is allowed for the puppy's own immunity to develop and remove
How is coccidiosis prevented or controlled?
Because coccidia is spread by the feces of carrier animals, it is
very important to practice strict sanitation. All fecal material
should be removed. Housing needs to be such that food and water
cannot become contaminated with feces. Clean water should be provided
at all times. Most disinfectants do not work well against coccidia;
incineration of the feces, and steam cleaning, immersion in boiling
water, or a 10% ammonia solution are the best methods to kill coccidia.
Coccidia can withstand freezing.
Cockroaches and flies can mechanically carry coccidia from one place
to another. Mice and other animals can ingest the coccidia and when
killed and eaten by a dog, for instance, can infect the dog. Therefore,
insect and rodent control is very important in preventing coccidiosis.
The coccidia species of dogs and cats do not infect humans.
Giardia are protozoa (one-celled organisms) that live in the small
intestine of dogs and cats. Giardia are found throughout the United
States and in many other parts of the world. Infection with Giardia
is called 'giardiasis.'
There are many things we do not know about this parasite. Experts
do not agree on how many species of Giardia there are and which
ones affect which animals. Veterinarians do not even agree on how
common Giardia infections are and when they should be treated. Generally,
it is believed that infection with Giardia is common but disease
is rare. There is much about the life cycle we do not know either.
How do Giardia reproduce and how are they transmitted?
Giardia multiply by dividing.
A dog becomes infected by eating the cyst form of the parasite.
In the small intestine, the cyst opens and releases an active form
called a trophozoite. These have flagella, hair-like structures
that whip back and forth allowing them to move around. They attach
to the intestinal wall and reproduce by dividing in two. After an
unknown number of divisions, at some stage, in an unknown location,
this form develops a wall around itself (encysts) and is passed
in the feces. The Giardia in the feces can contaminate the environment
and water and infect other animals and people.
What are the signs of a Giardia infection?
Most infections with Giardia are asymptomatic. In the rare cases
in which disease occurs, younger animals are usually affected, and
the usual sign is diarrhea. The diarrhea may be acute, intermittent,
or chronic. Usually the infected animals will not lose their appetite,
but they may lose weight. The feces are often abnormal, being pale,
having a bad odor, and appearing greasy. In the intestine, Giardia
prevents proper absorption of nutrients, damages the delicate intestinal
lining, and interferes with digestion.
Can Giardia of dogs infect people?
This is another unknown. There are many species of Giardia, and
experts do not know if these species infect only specific hosts.
Sources of some human infections have possibly been linked to beavers,
other wild animals, and domestic animals. Until we know otherwise,
it would be wise to consider infected animals capable of transmitting
Giardia to humans.
You may have heard about Giardia outbreaks occurring in humans due
to drinking contaminated water. Contamination of urban water supplies
with Giardia is usually attributed to (human) sewage effluents.
In rural settings, beavers most often get the blame for contaminating
lakes and streams. Giardia outbreaks have also occurred in day care
centers fueled by the less than optimal hygienic practices of children.
How do we diagnose giardiasis?
Giardiasis is very difficult to diagnose because the protozoa are
so small and are not passed with every stool. Tests on serial stool
samples (one stool sample every day for three days) are often required
to find the organism. Special diagnostic procedures, beyond a routine
fecal examination, are necessary to identify Giardia. The procedures
we use to identify roundworms and hookworms kill the active form
of Giardia and concentrate the cyst form.
To see the active form, a small amount of stool may be mixed with
water on a microscope slide and examined under high magnification.
Because these forms have flagella, you can see them move around
on the slide. The active forms are more commonly found in loose
stools. If you ever have the opportunity to see the active form
of Giardia under the microscope, take it! It is an interesting-looking
creature. It is pear-shaped and its anatomy makes it look like a
cartoon face, with eyes (which often look crossed), nose, and mouth.
Once you see it, you will not forget it.
Cysts are more commonly found in firm stools. Special solutions
are used to separate the cysts from the rest of the stool. The portion
of the solution that would contain the cysts is then examined microscopically.
In spring, 2004, a diagnostic test using ELISA technology became
available. This test uses a very small fecal sample, and can be
performed in 8 minutes in a veterinarian's office. It is much more
accurate than a fecal examination.
We have done the tests, now what?
Now we come to how to interpret the test results. It can be a dilemma
for your veterinarian. What you see (or do not see) is not always
a correct indication of what you have. A negative test may mean
the animal is not infected. However, few, if any, laboratory tests
are 100% accurate. Negative test results can also occur in some
infected animals. If a negative test occurs, your veterinarian will
often suggest repeating the test.
What about a positive test? That should not be hard to interpret,
right? Wrong. Giardia can be found in many dogs with and without
diarrhea. If we find Giardia, is it the cause of the diarrhea or
is it just coincidence we found it? The animal could actually have
diarrhea caused by a bacterial infection, and we just happened to
find the Giardia. Test results always need to be interpreted in
light of the signs, symptoms, and medical history.
If we find Giardia, how do we treat it?
Here we go again; treatment is controversial too. There is a question
about when to treat. If Giardia is found in a dog without symptoms
should we treat the animal? Since we should not know if G. canis
can infect man, we often err on the side of caution and treat an
asymptomatic infected animal to prevent possible transmission to
If we highly suspect infection with Giardia, but can not find the
organism, should we treat anyway? This is often done. Because it
is often difficult to detect Giardia in the feces of dogs with diarrhea,
if there are no other obvious causes of diarrhea (e.g.; the dog
did not get into the garbage several nights ago) we often treat
the animal for giardiasis.
There are several treatments for giardiasis; some of them have not
been FDA approved to treat giardiasis in dogs. Metronidazole is
one of these, but is the old standby. The nice thing about this
drug is that it also kills some types of bacteria that could cause
diarrhea. So if the diarrhea was caused by bacteria, and not Giardia,
we still kill the cause of the diarrhea and eliminate the symptoms.
Makes us look pretty sharp! Unfortunately, metronidazole has some
drawbacks. It has been found to be only 60-70% effective in eliminating
Giardia from infected dogs. In some dogs, it can cause vomiting,
anorexia, and some neurological signs. It also can be toxic to the
liver in some animals. It is suspected of being a teratogen (an
agent that causes physical defects in the developing embryo), so
it should not be used in pregnant animals. Finally, it has a very
bitter taste and many animals resent taking it.
Quinacrine hydrochloride has been used in the past, but is not very
effective and can cause side effects such as lethargy, vomiting,
anorexia, and fever.
A newer drug, albendazole, has been shown to be 50 times more effective
than metronidazole and 10-40 times more effective than quinacrine
hydrochloride in killing Giardia in the laboratory. It has not been
approved for use in dogs. Some serious side effects of albendazole
have been noted, including injury to the bone marrow. Since it may
also cause birth defects, it should not be used in pregnant animals.
In a recent small study, fenbendazole, which has been approved for
treatment of roundworm, hookworm, and whipworm infections in dogs,
has been shown to be effective in treating giardiasis in dogs. It
is safe to use in puppies.
Most recently, a combination of praziquantel, pyrantel pamoate,
and febantel has been shown to decrease cyst excretion in infected