Giardia in Pets: A Common Cause of Persistent Diarrhea
Giardia is a microscopic parasite that causes stubborn diarrhea in dogs and cats. Learn how it spreads and how to eliminate it.
Giardia is a microscopic protozoan parasite that infects the small intestine, causing persistent diarrhea. It's one of the most common intestinal parasites in pets and is particularly stubborn to eliminate. Giardia is also zoonotic — it can spread to humans, making good hygiene especially important.
Key Points
- Giardia is a microscopic parasite — you can't see it without a microscope
- It causes persistent, often foul-smelling diarrhea
- Transmission is through contaminated water or feces
- Treatment requires specific anti-parasitic medication
- Environmental decontamination is essential to prevent reinfection
- Giardia can spread to humans (practice good hygiene)
How Giardia Spreads
Giardia cysts are shed in the feces of infected animals and can survive in the environment for months, especially in moist conditions. Pets become infected by drinking contaminated water (puddles, streams, communal water bowls), grooming contaminated fur, or coming into contact with contaminated soil. Dog parks, boarding facilities, and shelters are common sources.
Signs of Giardia
The hallmark sign is persistent, soft, pale, foul-smelling diarrhea that may come and go. Some pets have mucus in their stool. Weight loss, poor coat quality, and lethargy can occur with chronic infection. Some pets carry Giardia without showing any signs — they can still shed cysts and infect other animals.
Diagnosis and Treatment
Giardia is diagnosed through fecal testing (antigen test or zinc sulfate flotation). Standard fecal flotations alone may miss it. Treatment typically involves fenbendazole for 5-7 days, sometimes combined with metronidazole. A second course may be needed. Bathing your pet on the last day of treatment removes cysts from the fur and prevents reinfection.
Environmental Control
Giardia cysts are resistant to many disinfectants. Clean contaminated areas with bleach solution (1:32 dilution) or quaternary ammonium products. Wash bedding in hot water. Remove feces from the yard promptly. Avoid letting your pet drink from puddles or communal water bowls. After treatment, retest to confirm the infection is cleared.
When to See a Vet Immediately
- Persistent soft stools or diarrhea
- Foul-smelling stool with mucus
- Weight loss despite eating normally
- Diarrhea that keeps coming back
- You've been told your pet was exposed to Giardia
- Diarrhea in a puppy or kitten
How RVC Can Help
RVC offers Giardia-specific testing and treatment protocols. We can test, treat, and help you decontaminate the environment to prevent reinfection. Call +853 6677 6611.
This article is for educational purposes only and does not replace professional veterinary advice. If your pet is showing any symptoms, please contact Royal Veterinary Center immediately at +853 6677 6611.