Protozoal gastrointestinal infections

Human intestinal protozoal infections are found worldwide, in both developing and industrialized countries. Protozoa produce diarrhoeal disease by infecting the small or large intestine, or both. Amoebiasis is an important cause of dysentery and liver abscess worldwide. Giardiasis and cryptosporidiosis are important causes of diarrhoea in children; the latter is particularly associated with growth failure and malnutrition. They also cause water-borne and food-borne outbreaks. Food-borne outbreaks may also be caused by Cyclospora cayetanensis. The importance of intestinal protozoa has increased with the HIV/AIDS pandemic, which has led to the recognition of new protozoal pathogens (e.g. microsporidia, Cyclospora). Intestinal protozoa are difficult to identify, and diagnostic laboratories may have to perform additional procedures to identify specific infections. Many protozoa respond readily to well-established antibiotics, but some (particularly cryptosporidiosis) can be difficult to treat, especially in immunocompromised patients. Recently, molecular biological work has helped clarify the classification of these parasites and more importantly is beginning to unlock features of their biology which may help in prevention.