Schistosomiasis in the Republic of São Tomé and Principe: human studies

Abstract

The only schistosome species found in stool specimens in the local population of the republic of São Tomé is Schistosoma intercalatum. An initial survey of schoolchildren showed an overall prevalence of 10.9%, with some schools reaching 29%. No S. haematobium egg was found in 782 urine specimens from the local population, although some were seen in the urine of Angolan soldiers stationed near the capital city. One village in the endemic area, San Marçal, had an S. intercalatum prevalence of 43%, with 14 persons > 40 years of age harbouring severe infections. The transmission area is restricted to the north-east of the main island, where 5 foci apparently account for most of the infections. Seven cases recorded from Principe may be explained by the fact that the children were attending school at São Tomé. Women carrying out domestic activities are more at risk of contracting the infection because of longer periods of water contact than men. The morbidity produced by the infection is restricted to splenomegaly and blood in the stools. High prevalences have been found of Ascaris lumbricoides and Trichuris trichiura, and hookworm and Stronglyloides stercoralis were also observed. Praziquantel was well tolerated and appears to be a good tool for control purposes, although reinfection in the transmission area apparently occurs rapidly. Control strategies based on chemotherapy should take into account an older age group as well as the schoolchildren. Focal mollusciciding and the introduction of washing facilities may also have a role to play in control. The possible recent introduction of the infection to the island is discussed.