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Name Giardia, Canine
Short Description
Giardia
Affected Animals: Dogs and many other animals.
Overview:Found worldwide, Giardia is caused by a
protozoan parasite affecting the intestines of both humans and most
types of domesticated animals. While dogs have a high rate of
Giardia infection, few will develop symptoms. Giardia usually causes
clinical signs only in dogs that have weakened immune systems, in
dogs that have been exposed to an abnormally large number of the
parasites, and in young puppies.
Giardia is transmitted by cysts containing Giardia trophozoites,
which are singled-celled organisms shaped like teardrops. Infected
dogs pass these parasites into the environment via their feces. Dogs
that ingest infected fecal material may contract the disease, the
primary symptom of which is diarrhea.
Most dogs treated for Giardia will recover quickly. With proper
preventive measures, few dogs will have a recurrence. A recently
introduced vaccine is available that may aid in the prevention of
Giardia infection.
Clinical Signs: The primary sign is diarrhea that is usually
pale, malodorous, and steatorrheic, or containing fat. Most puppies
and adult dogs infected with Giardia suffer no loss of appetite but
may lose weight with continued diarrhea.
Symptoms: Typically, an owner will bring a dog or puppy to
the veterinarian because it is having diarrhea. The diarrhea may be
pale in color, have an unpleasant smell, and contain fat. Most dogs
will continue to eat, but they may lose weight with continued
diarrhea.
Description: Giardia is a protozoan organism that can cause
infection in dogs, cats, and humans. The organisms may be found
either as trophozoites that swim freely in the intestines or as
trophozoites housed in cysts that protect them from the environment
and thereby facilitate their transmission. Animals usually contract
Giardia by coming into contact with the cyst form in the external
environment; the feces of infected animals periodically contain
these cysts. Animals that ingest the infected feces will take these
cysts into their small intestines, where the trophozoites will
excyst, or come out of their protective housing, and infect the
animal by multiplying within the intestines. Afterwards, many
trophozoites will encyst, or revert to cyst form, before returning
to the external environment within the feces. The cysts may survive
in the environment and infect other animals for a period of weeks;
conversely, trophozoites that have passed into the feces without
encysting will die quickly and cannot transmit the disease.
Giardia is commonly found either in dogs that have poorly
functioning immune systems or in dogs that have been grouped
together in close quarters and hence have been exposed to an
unusually large number of the parasites. Consequently, young
puppies, older dogs that are sick and debilitated, and dogs that are
kept in kennels are susceptible to Giardia.
Diagnosis: Giardia is frequently diagnosed by means of a
zinc sulfate fecal flotation examination, in which Giardia cysts and
trophozoites may be identified under a microscope. If trophozoites
are seen moving around on a slide smeared with a mixture of fecal
material and saline solution, the canine will test positive for
Giardia. However, because Giardia cysts and trophozoites are not
always passed into the feces, a negative result for this examination
does not rule out the possibility of Giardia. Consequently, for the
diagnosis to be definitive, it is necessary for the veterinarian to
periodically examine fresh fecal samples from the animal over the
course of a few days.
There are other tests for the detection of Giardia although these
are generally less expeditious and more expensive than a fecal
flotation examination. An enzyme-linked immuno-absorbent assay, or
ELISA test, may be used to detect Giardia antigens in a fecal sample
but is available only in certain veterinary hospitals and
specialized laboratories. A direct immunofluorescent test may be
used to detect the presence of Giardia cysts in feces but also
requires that a veterinarian send samples to an off-premises
laboratory and await the results
Prognosis: Giardia is a very treatable condition. Most dogs
recover quickly and do not have additional problems. However, if
proper preventive steps are not taken, it is common for dogs with a
previous history of Giardia to become re-infected.
Transmission or Cause: Dogs contract Giardia by swallowing Giardia cysts
found in the feces of an infected animal. Free-swimming trophozoites
cannot infect an animal with Giardia.
Treatment: Treatment of Giardia often involves the use of
medications such as fenbendazole or metronidazole. Fenbendazole in
particular has been shown to be very effective in the treatment of
Giardia infections. Neither of these medications is suitable for
pregnant dogs; there are a number of suitable alternative treatments
available, however, for dogs that are pregnant.
Prevention: Giardia may be prevented by the strict sanitation
of animal living environments using cleaning agents approved for the
elimination of the parasite. In kennels and other places that house
animals in larger numbers, routine disinfection of the entire
facility is critical. Dogs should be bathed in order to eliminate
any Giardia cysts they may be carrying in their coats. The periodic
use of de-worming medications such as fenbendazole may also be
effective in preventing the recurrence of Giardia infection.
A new vaccine was introduced recently that is reported to aid in the
prevention of Giardia lamblia infection. The vaccine may be given to
healthy dogs as young as eight weeks old. A booster shot is usually
given two to three weeks after the initial vaccination and then
yearly thereafter.
The vaccine prevents or lessens the signs of infection and the
amount of cyst shedding. However, some cyst shedding may occur in
vaccinated dogs, so the preventive measures discussed above should
be observed.
