Giardia cysts survive in the environment for weeks and are ingested when pets drink from puddles, streams, or contaminated bowls. The parasite attaches to the intestinal lining and interferes with nutrient absorption, producing foul-smelling, greasy diarrhea. Diagnosis requires a fecal antigen test since cysts are shed intermittently and may not appear on a standard fecal float. Treatment typically involves fenbendazole or metronidazole, combined with thorough environmental cleaning. Bathing the pet on the last day of treatment removes cysts from the coat. Some infected animals show no symptoms but still shed cysts, posing a risk to housemates.