John Henry Ouma

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Schistosoma mansoni infection is highly endemic in parts of Uganda, and periportal fibrosis is common in communities along the shore of Lake Albert. In this study, we have identified cellular immune responses associated with fibrosis. A cohort of 199 individuals aged 6-50, resident in the village for at least 10 years or since birth, were examined for(More)
Previous studies in school children have demonstrated the slow development with age of resistance to reinfection after chemotherapy of Schistosoma mansoni infections, and have indicated that inappropriate ("blocking") antibody responses prevent the expression of immunity in young children. The present study was designed to investigate further the nature of(More)
Persons employed as vehicle washers in the town of Kisumu, Kenya are exposed for several hours each day to water in Lake Victoria that contains Schistosoma mansoni-infected Biomphalaria pherifferi snails. This results in a focus of high endemicity for schistosomiasis and these persons have very high concentrations of eggs in their feces (mean +/- SD = 1,469(More)
There is an increasing need to provide spatial distribution maps of the clinical burden of Plasmodium falciparum malaria in Africa. Recent evidence suggests that risk groups and the clinical spectrum of severe malaria are related to the intensity of P. falciparum transmission. Climate operates to affect the vectorial capacity of P. falciparum transmission(More)
Urinary schistosomiasis remains a significant burden for Africa and the Middle East. Success of regional control strategies will depend, in part, on what influence local environmental and behavioral factors have on individual risk for primary infection and/or reinfection. Based on experience in a multi-year (1984-1992), school-based Schistosoma haematobium(More)
Levels of prepatent Schistosoma haematobium infection were monitored in intermediate host snails (Bulinus nasutus) collected from transmission sites in coastal Kenya, using a polymerase chain reaction (PCR) assay amplifying the Dra I repeated sequence of S. haematobium. The timing and number of prepatent and patent infections were determined for each site(More)
Anopheline mosquitoes were sampled inside houses, where residents slept under untreated bednets, by CDC light traps and human-biting catches to evaluate light traps as a means for determining human exposure to malaria vectors in Kilifi District, Kenya. Mosquitoes were sampled during 2 all-night collections by light traps and one all-night biting catch in a(More)
Infants and children are routinely vaccinated with bacillus Calmette-Guérin (BCG) in areas of the world where worm infections are common. Because maternal helminth infection during pregnancy can sensitize the developing fetus, we studied whether this prenatal immunity persists in childhood and modifies the immune response to BCG. Children and newborns(More)
Neonates exposed to parasite antigens (Ags) in utero may develop altered fetal immunity that could affect subsequent responses to infection. We hypothesized that cord blood lymphocytes (CBL) from offspring of mothers residing in an area highly endemic for schistosomiasis, filariasis, and tuberculosis in Kenya would either fail to respond or generate a(More)
Urinary schistosomiasis remains a major contributor to the disease burden along the southern coast of Kenya. Selective identification of transmission hot spots offers the potential for more effective, highly-focal snail control and human chemotherapy to reduce Schistosoma haematobium transmission. In the present study, a geographic information system was(More)