A short period of diarrhoea following foreign travel from which one recovers reasonably quickly, is often dismissed as “something I ate”. However, some infections are waterborne diseases and can require hospitalisation or may prove fatal in the immunocompromised. Here, Michelle Holland looks at Giardia and Cryptosporidium.
Giardia lamblia is the most frequently identified protozoan parasite in stool specimens submitted to US public health laboratories.1 First identified in the 17th century, it was not until the 19th century that Giardia was first found in human faeces, when it was thought to be a commensal organism. In the 1970s, Giardia came to be considered as one of the world's most common causes of diarrhoeal illness.
The parasite, which grows in the intestine of infected humans or animals, can be transmitted by consumption of water, beverages or food that have been contaminated by faeces of infected humans or animals, or by direct contact. Infection may also be caused by swallowing water contaminated by sewage in swimming pools, whirlpool baths, rivers, ponds and lakes.
After the parasite has left the body, it forms a hard, protective shell that protects it from the environment – known as Giardia cysts – and they can survive outside the body for several months or sometimes several years.2
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