*Giardiasis is a protozoal intestinal infection of humans and many domestic and other animals which occurs worldwide.
Clinical Features - Infections in adult cats are usually subclinical but clinical disease is also seen. The subclinical carrier rate varies from about 2 - 10 %. Acute and chronic diarrhea occurs mainly in kittens. This parasite when present in tissue in sufficient numbers interferes with digestion and assimilation. Signs include soft to diarrheic stools, poor hair coat, stomach flatulence and loss of or failure to gain weight.
The flagellated trophozoites can sometimes be seen in saline fecal wet mounts; they are shed intermittently. Detection of cysts in feces is more effective if the zinc sulfate fecal floatation procedure is used. Staining cysts with iodine aids identification. An ELISA and an indirect immunofluorescence assay are used to detect antigen in feces but they do not appear to be more accurate than zinc sulfate floatation.
The infection may be self-limiting and not need treatment. Albendazole (25 mg/kg, 12 - 24 hour interval, 2 - 5 days) is preferred for cats. Metronidazole (cat: 10 - 20 mg/kg, 12 - 24 hour interval) and tinidazole (cat:15 mg/kg, 24 hour interval) are also effective. Treatment is usually for 3 - 5 days, followed if necessary by a 5 day course. Immunosupression due to FeLV or FIV can make treatment less effective.
Vaccines for cats, consisting of killed G. duodenalis are available as an aid to prevent infection and cyst shedding. Keep litter box clean. Keeping cats indoors reduces the chances of infection.
Public Health Significance - It is widely claimed that humans can be infected from ingestion of organisms from the feces of infected dogs and cats although it has not been proved. It should be kept in mind that many humans are subclinical carriers. The clinical disease in humans resembles that seen in dogs and cats.