The impact of schistosomiasis among rural populations in Liberia.

Human infection with Schistosoma haematobium and/or Schistosoma mansoni is known to be widespread in central Liberia, but no information is available about its clinical manifestations or its significance for public health. Details of a cross-sectional morbidity study are reported. A sample from hospital out-patients and samples from 3 villages situated in areas with different transmission patterns (lack of transmission, transmission of only S. haematobium and transmission of both S. haematobium and S. mansoni) were examined. All 184 individuals were examined by standardized case history, clinical and parasitological investigations, including a skin snip for onchocerciasis and a count of schistosomal and other intestinal worm eggs from stool and urine. A complete blood count, urine analysis, urine cultures, hepatitis-B surface antigen determination and abdominal X-rays were also carried out. Schistosomal egg counts ranged from 1 to 6200/10 ml urine for S. haematobium and from 1 to 228/g stool for S. mansoni. Difficulties for the definition of accurate morbidity indices are discussed. Except for haematuria and dysuria, the overall morbidity in the study area was not striking, neither for S. haematobium nor for S. mansoni infection. No cumulative pathology was observed in patients with mixed infection. The frequency of hypertension, hepato- and splenomegaly, ascites and bacteriuria was low and no relationship to schistosomiasis could be established. Bladder calcifications were found in 10% of people living in an area of transmission of S. haematobium. Although the intensity of infection is low for both S. haematobium and S. mansoni, long-term follow-up studies are essential for a more accurate assessment of the public health importance of these parasites.