Cryptosporidiosis--oocyst shedding and infection in household contacts.

The incidence of cryptosporidiosis in children with acute diarrhoea when compared with age-matched controls was 6.1% in a paediatric unit. Studies were made on eight immunocompetent children with cryptosporidiosis to determine the period of oocyst shedding after cessation of diarrhoea. The majority (75%) shed oocysts for less than ten days after cessation of diarrhoea. There was considerable variation among patients, some eliminating oocysts more quickly than others. This was not related to the severity or duration of diarrhoea. The sucrose floatation technique was found to be more sensitive than direct smear for detecting small numbers of oocysts present at the end of the shedding period. Studies on household contacts showed infection in 43%, which suggests a subclinical infection or a transient carrier state, and confirms the occurrence of person to person transmission.