What Is Canine Giardiasis?
Giardia duodenalis is a flagellate protozoan that colonises the small intestine. Dogs become infected by ingesting cysts in water, soil or the faeces of infected animals. Cysts are resistant to chlorine at standard disinfection concentrations and can survive months in the environment. It is very common in puppies and in high-density animal settings (kennels, shelters).
Symptoms
- Diarrhoea β soft, mucoid, greasy or frothy β the most common sign. Rarely bloody.
- May be continuous or intermittent (alternating with normal stools).
- Weight loss and poor body condition.
- Dull, flat coat.
- In puppies: growth retardation, abdominal distension.
- Many adult dogs are asymptomatic carriers.
Diagnosis
- Faecal ELISA antigen test: the method of choice in practice. High sensitivity. In-clinic rapid kits are very reliable.
- Zinc sulphate flotation: allows microscopic cyst detection. 3 samples on alternate days improves sensitivity (cysts are shed intermittently).
- Faecal PCR: most sensitive and specific; allows assemblage typing.
Treatment
- Metronidazole: 25-50 mg/kg/24h for 5-7 days. Most commonly used β reduces cyst shedding.
- Fenbendazole: 50 mg/kg/24h for 5 days. Effective and well tolerated.
- Combination: metronidazole + fenbendazole in resistant cases.
Environmental Control Measures
- Clean and disinfect areas where the dog defecates with quaternary ammonium compounds (chlorine does not kill cysts).
- Bathe the dog at the end of treatment to remove perianal cysts from the coat.
- Avoid areas with stagnant water.
- Wash hands with soap and water after contact with faeces.
- In multi-pet households: treat all animals simultaneously.