The list of differentials for diarrhoea in companion animals is long. It can be broadly describes as infectious or non infectious in origin. Infectious causes of diarrhoea can include infections with protozoa, bacteria and viruses. Non infectious causes may include food intolerances, pancreatitis, irritable bowel disease, hormonal imbalances (Addison’s), neoplasia, congenital abnormalities, organ dysfunction, toxin ingestion and so on. The initial work up is usually based on history, duration, clinical presentation, blood tests, faecal test and diagnostic imaging such as abdominal ultrasound. Some infectious causes of bacterial in out companion animals can also be transmitted to us. This is known as zoonosis. A common zoonotic protozoa that affects companion animals is giardia. Giardia is estimated to affect around 5-15% of cats and dogs. There is a number of different species but the most common in companion animals is Giardia dupdenalis, which can also infect people.
The protozoa is found in water, food and soil with contaminated with affected faeces. Young or immunocompromised animals are more likely to be affected. The most common clinical signs is diarrhea. It may be waxing or waning or continuous. Some animals will be asymptomatic carriers. Typically animas begin to shed the protozoa within 5-16 days of infection.
Cysts can be identified by performing a faecal float, however, as they are spread intermittently, a negative faecal float does not rule out infection and ideally screening should be carried out at least 3 times over 5 days. A faecal PCR is more accurate than a faecal float and can be used to test for other potential infectious causes of diarrhoea at the same time. Treatment can be challenging but is based around antibiotics and immune support.
If your pet suffers from gastrointestinal signs like diarrhoea, contact your local veterinarian.