Select topics written by the veterinarians from Kuenzi Family Pet Hospital

CANINE GIARDIASIS

By Rodney S. Kuenzi, D.V.M.

Giardiasis is an intestinal disease that can affect most warm-blooded creatures. It is caused by a microorganism called Giardia. Animals and people can be infected by consuming food or water that is contaminated with Giardia cysts. Once in the gastrointestinal tract, the cysts transform into highly motile protozoa and divide rapidly. They then attach to cells of the upper small intestine in massive numbers, where they produce disease by blocking absorption, competing for nutrients, and producing toxic substances. Giardia can severely damage the cellular lining of the small intestine to the point of producing permanent scarring.

The most common sign of Giardiasis in dogs is diarrhea, which can be acute, chronic, or intermittent. Frequently, afflicted animals lose weight, become listless, and have profuse watery stools that may or may not contain mucus or blood. This disease, in its acute form, can cause severe abdominal cramping and life threatening dehydration from fluid loss into the stool. Animals usually survive the initial episodes and the diarrhea commonly becomes chronic or intermittent. Loose, mucousy stools and diarrhea may last for weeks or months. Even after signs have dissipated, there is some debate as to whether certain individuals can become silent carriers. These individuals could act as reservoirs by occasionally shedding Giardia cysts. Because of the chronicity of this disease, and the nature of the stools, Giardia can easily be mistaken for pancreatic insufficiency and malabsorption syndromes.

No one single sign is diagnostic of Giardiasis. Definitive diagnosis can only be reached by demonstration of the organism in the stool. Diagnosis of Giardia can be extremely difficult because the organism is often excreted intermittently. Furthermore, fecal floatations, which are routinely performed in veterinary offices for worms rarely demonstrate Giardia. Direct smears of fecal swabs and centrifuge concentration techniques, which are stained with iodine based stains, are the only consistent way to diagnose Giardia. Unfortunately, even these procedures are only about 50-75% effective in most studies. Frequently, it is necessary to perform repetivitive fecal checks to diagnose this problem. Occasionally, endoscopic intestinal biopsy is necessary to diagnose this disease. Currently, fecal and serum antibody tests are under development for detection of Giardiasis.

Metronidazole (Flagyl^Ò) is the most frequently used drug in veterinary medicine for treatment of Giardia. Animals undergoing treatment with this drug require close observation, because of the possibility of neurologic side effects.

Individuals that have had Giardia once can get it again. Therefore, it is essential to eliminate the source of reinfection. In a kennel situation, this can be extremely difficult. Drinking water should be tested by local health authorities. Low spots that stay moist for long periods need to be graded to improve draining and prevent puddle formation. Concrete surfaces should be cleaned thoroughly, dried, and re-sealed. Gravel should be replaced and all kennel feeding equipment should be disinfected with 1% bleach solution.

Eliminating Giardia from a premises is so difficult because the cysts are very hardy. They survive standard chlorination protocols for drinking water. They survive freezing down to –13^oC and can withstand desiccation in drying fecal material for long periods of time.

Remember, Giardiasis is a zoonotic disease (that is, it can be transmitted from animals to man). As a matter of fact, it is the most frequently diagnosed intestinal parasite of humans in the U.S. For this reason it is necessary to be exceptionally hygienic when cleaning up after infected individuals. Dog owners with positive animals should consider having their own water tested.