Giardia and Cryptosporidium infection in Finland: a registry-based study of their demographic determinants.

Giardia and Cryptosporidium are protozoan parasites that can cause prolonged gastrointestinal infection especially in immunocompromised individuals. We studied the characteristics of giardiasis and cryptosporidiosis cases notified to the Finnish Infectious Disease Registry (FIDR) during 1995-2006, and of persons tested for these parasites in the clinical laboratory of the healthcare district of Helsinki and Uusimaa during 2004-2006. According to reporting, the incidence of both infections was higher in persons residing in the Helsinki area than in other parts of Finland. Persons born abroad were more often tested than were persons born in Finland, and the proportion of the Giardia infected among those tested was very high (14%) in children under the age of five born abroad. Giardia was tested for over 70 times as often as Cryptosporidium, which thus appears to be heavily under tested and therefore underdetected.