The Hidden Parasite Every Dog Owner Should Watch For

Giardia is one of the most common and most frustrating parasites affecting dogs worldwide. Whether you’re caring for rescued street dogs, puppies, or your own beloved pet, understanding how giardia spreads, how to spot it, and how to treat it effectively is essential.

Below is a clear, practical guide you can share with adopters, volunteers, supporters, or your general audience.

What Is Giardia?

Giardia is a microscopic parasite that infects the intestines of dogs (and many other species, including humans). It attaches to the intestinal wall, interfering with nutrient absorption and causing gastrointestinal problems.

There are two stages:

• Trophozoites – the active, feeding form living in the intestines

• Cysts – the hard-shelled, infective form shed in faeces

Dogs become infected when they ingest these cysts from contaminated soil, water, bowls, or surfaces.

Giardia spreads via the faecal–oral route. Common sources include:

• Drinking contaminated water (puddles, streams, shared bowls)

• Licking contaminated fur or paws

• Eating faeces or sniffing areas where infected dogs have defecated

• Kennels, rescue centres, and foster homes with multiple dogs

• Poor sanitation or crowded conditions

Giardia is especially common in:

• Puppies

• Stray or free-roaming dogs

• Immunocompromised dogs

• Shelters and rescue environments

Symptoms of Giardia in Dogs

Not all infected dogs show symptoms, but those who do may present with:

• Soft, greasy diarrhoea

• Mucus in the stool

• Foul-smelling bowel movements

• Intermittent diarrhoea (comes and goes)

• Weight loss despite a good appetite

• Gas or bloating

• Dehydration in severe cases

In puppies, giardia can be particularly dangerous due to dehydration and malnutrition.

How Giardia Is Diagnosed

A single stool sample can miss the infection because dogs do not shed cysts continuously. Vets may use:

• Microscopic stool analysis

• Giardia antigen tests (snap tests)

• PCR testing for stubborn or unclear cases

For accuracy, sometimes multiple samples over several days are recommended.

Preventing Re-Infection (The Most Important Step!)

Giardia is notorious for recurring. Prevention focuses on hygiene and environmental control:

Cleaning & Disinfecting

• Use boiling water or steam to disinfect surfaces.

• Wash bedding, bowls, toys, and cloth items with hot water and detergent.

Hygiene Practices

• Pick up faeces immediately.

• Prevent dogs from drinking from puddles or shared outdoor bowls.

• Bathe the dog during treatment to remove cysts.

• In foster/rescue settings: implement strict cleaning protocols and separate infected dogs when possible.

Environmental Considerations

Giardia cysts can survive for weeks to months in damp, cool environments. Drying out the environment is key sunlight helps.

When to Seek Veterinary Help

Contact a vet right away if your dog has:

• Diarrhoea lasting more than 48 hours

• Blood or severe mucus in the stool

• Vomiting and lethargy

• Signs of dehydration

• Weight loss or poor appetite

Puppies or sick dogs should be seen immediately.

Final Thoughts

Giardia is incredibly common, especially among rescued dogs and those from challenging environments. The good news is that with proper treatment, hygiene, and environmental care, most dogs recover fully.