Giardia is by far the most commonly diagnosed parasite in New Mexico. It is diagnosed in both cats and dogs and it can also infect people.
In contrast to most intestinal parasites (roundworms, tapeworms) Giardia is not visible to the naked eye. Pets usually acquire Giardia by ingesting the cysts from contaminated water. Clinical signs range from significant diarrhea to no signs at all. The life cycle of Giardia includes two stages. Usually a dog will ingest cysts in contaminated water or directly from the feces of another animal. Once the cysts are ingested and reach the intestines they transform into a fragile swimming form called a trophozoite which attaches to the lining of the intestines to feed. If enough trophozoites attach to the lining diarrhea develops (severity often correlates with the number of organisms present). As part of their life cycle the trophozoites produce very resistant cysts which pass through the GI tract and exit the body in the animal’s feces. Once the cysts are in the environment the cycle begins anew once they are ingested.
Treatment is usually straightforward, but some pets require multiple rounds of treatment to clear the infestation. Fenbendazole (Panacur), metronidazole (Flagyl) or a combination of both are usually effective. Because cysts are very resistant bathing of the patient on the second and fifth day of treatment is recommended to decrease the incidence of reinfestation. In some instances with heavy soiling disinfection of the premises is required, but in most situation prompt removal of feces is all that is required for the management of the environment. Because there is a small possibility of human infection, proper hand washing is emphasized and any Gastrointestinal problems in people in contact with the dog should be brought to the attention of their physician. People who are immunosuppressed are at higher risk of infection and should practice meticulous hand hygiene when dealing with infected dogs.
At Aztec Animal Clinic we recommend fecal exams to check for parasites (including Giardia) for all puppies and kittens, all new adoptions, and ideally once per year in at risk pets. At risk pets include indoor/outdoor cats, dogs who spend time outdoors, and pets who eat raw food or hunt. We consider this disease to be endemic in Albuquerque and in many parts of NM. Being able to enjoy the many outdoor activities that NM has to offer is one of the reasons a lot of us live here, but it does require some vigilance to keep our pets healthy.