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.
Typically 7 - 10 days, but may range from 3 – 25 days.
Voluntary laboratory reports and surveillance of general outbreaks of infectious