Gastrointestinal & Zoonoses

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Gastrointestinal & Zoonoses



Giardiasis is a disease caused by intestinal infection with the protozoan parasite Giardia lamblia. Human infection occurs through ingestion of environmentally resistant Giardia cysts in food or water. Although humans appear to be the main reservoir of infection, animals, including dogs, cats, rodents and domesticated ruminants can also be affected, but their role in transmission to humans is not clear. In developed countries, illness is usually associated with water-borne outbreaks or travel abroad. In Britain, there area approximately 3,500 cases per year, most commonly affecting children less than 5 years of age, with a peak seasonal incidence between July and October.

Main clinical features

Diarrhoea, which may be prolonged with associated weight loss, accompanied in some cases by malaise, flatulence, cramps, bloating, nausea and inappetance. Approximately 25% of infections are asymptomatic.

Incubation period

Typically 7 - 10 days, but may range from 3 – 25 days.


Voluntary laboratory reports and surveillance of general outbreaks of infectious intestinal disease.

Surveillance Tables