D405 - Giardia spp.

Description:

Giardia is a protozoan parasite found in the intestinal tract of human beings and most domestic animals throughout the world. It has two morphologic forms; the trophozoite form, which is motile and dwells in the intestinal lumen; the cyst form, which contains two incompletely separated but formed trophozoites, and is responsible for transmission and environmental survival. The life cycle of Giardia is direct. After ingestion, cysts (trophozoites are noninfective) excyst in the duodenum, following exposure to gastric acids and pancreatic enzymes, and the two released trophozoites separate, mature, and attach to the brush border of the villous epithelium. In dogs, the organism seems to prefer the duodenum and jejunum but has been isolated from the ileum to the duodenum. In cats, trophozoites have been found throughout the intestinal tract. Trophozoites may be passed in diarrheic stools, but cysts are more routinely shed. The cysts can survive for days or weeks in cool, moist conditions while trophozoites cannot survive long outside the host. The prepatent period of Giardia infection ranges from 5 to 12 days in dogs and from 5 to 16 days in cats. The onset of disease, when it occurs, may precede cyst shedding by 1 to 2 days. Putative differences in virulence of Giardia strains, as well as host genetics and immune status, usually determine the outcome of an infection. Most infections (where cysts are being passed in the feces) are nonsymptomatic. Acute diarrhea tends to occur in very young puppies and kittens shortly after infection. In older cats and dogs, diarrhea may be acute and short lived, intermittent, or chronic. Feces are often malodorous, pale, and steatorrheic. Affected animals may experience weight loss secondary to diarrhea, but rarely will they become inappetent. Studies have shown that birds are also susceptible to Giardia infection. Infected birds shed cysts and noninfective trophozoites in feces. Birds with clinical signs including chronic to intermittent diarrhea with loose, malodorous, mucoid stools; lethargy; anorexia; dry skin; and feather plucking should be screened for Giardia infection.

Diagnosis:

Often, Giardia infection goes undetected, even when the presence of Giardia is high in the animal. Reasons for this occurrence may include failure to consider it in the differential diagnosis, failure to recognize the organisms, use of inappropriate methods for fecal analysis, and intermittent excretion of organisms in feces of infected individuals. Commercial ELISA kits to detect fecal Giardia antigens in humans are available, but these kits have shown reduced sensitivity and specificity for detection of Giardia in dogs. Also, ELISA kits are somewhat difficult to perform and fairly expensive. A PCR-based assay is now available for the detection of Giardia in a fecal sample. This assay allows for high specificity and sensitivity of detection. Since PCR detects the presence of Giardia’s genetic material, only a few organisms need to be present in a sample, making detection very accurate and definitive.

Treatment:

No drug to treat giardiasis in small animals has been officially approved. Fenbendazole (Panacur graniles 22.2%, Hoechst-Roussel Agri-Vet Co, Somerville, NJ) at the dose approved for dogs (50 mg/kg) for the control and removal of roundworms, hookworms, and whipworms, and the tapeworm Taenia pisiformis, has been shown effective in removing Giardia cysts from the feces of dogs. The medication should be administered over 3 days at 24 intervals (Greene C. – Infectious diseases of the dog and cat. 1998).

Sample:

1. Feces in a sterile container

Special Handling:

Store sample at 4°C until pick up or shipment.

Test Code:

D405