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J Ouma

Publications and source records attributed to J Ouma.

23 records · Page 2Linked to original sources
PubMed1981

Distribution in Kenya of intermediate hosts of Schistosoma.

A major factor in the geographical distribution of endemic schistosomiasis in Kenya is the discontinuous distribution of intermediate hosts. Biomphalaria pfeifferi is the main transmitter of S. mansoni and is found in the altitude zone 300-2,300 m; its absence from the costal region results in the absence of endemic schistosomiasis mansoni amongst the large human population in the coastal region. Snails belonging to the Bulinus africanus group appear to be responsible for all transmission of S. haematobium; they occur from near sea-level to an altitude of about 1,800 but are discontinuously distributed. There appears to be considerable potential for increase in the areas in which each form of schistosomiasis is endemic, taking into account existing patterns of snail distribution and likely developments in irrigation and water conservation. New localities reported here considerably extend the known distribution in western Kenya of B. truncatus, which could serve as an effective intermediate host for S. haematobium if a suitable strain were to become established in Kenya.

Animals↗
PubMed1979

Schistosome infection rates in field snails: Schistosoma mansoni in Biomphalaria pfeifferi from Kenya.

Six collections of Biomphalaria pfeifferi were made in the Nairobi and Machakos areas of Kenya. Individual cercarial shedding (Method A) showed that 6.9% (65/938) of the snails had mature 'patent' Schistosoma mansoni infections (range 3.1--34% in the six collections). Crushing (Method B) about one-third of the remaining snails detected no additional mature infections but yielded 1.4% (four snails from one collection) with secondary sporocysts from immature 'prepatent' infections. Weekly shedding observations for five weeks (Method C) on the remainder of the snails showed that 6.9% (40 snails from four collections--range 1.5--30%) shed cercariae maturing from infections immature at the time of collection. As Method B detected no cercariae, Method A apparently detected all 'patent' infections reliably, despite the stress suffered by the snails before examination. Method C was simpler and more efficient than Method B in the detection of infections which were immature at the time of collection. Judging from the rate at which infections matured in Method C, field snails in heavily endemic areas are subjected to pulses of infection rather than to a continuous flow of miracidia. The 'patent' infection rate was not correlated to the 'prepatent' infection rate. Some of the implications of these findings to mathematical models of schistosome transmission are discussed.

Animals↗
PubMedDate not supplied

A malariometric survey in Turkana District, Kenya: chemosensitivity in vivo of Plasmodium falciparum infections and identity of the vector.

We have carried out a limited survey in vivo of the efficacy of chloroquine (n = 39) and pyrimethamine-sulfadoxine (n = 29) as treatments for falciparum malaria in Kaling, Turkana District, northern Kenya. Both treatments were effective, achieving clinical cure (> 75% reduction in parasitaemia on day 2 with clinical improvement, and negative blood slide on day 7) in both children and adults. A limited entomological survey suggested that the main malaria vector in this area was Anopheles arabiensis.

Adolescent↗
PubMedDate not supplied

Models to predict the intensity of Plasmodium falciparum transmission: applications to the burden of disease in Kenya.

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 and this is particularly important in the Horn of Africa and parts of East Africa. We have used a fuzzy logic climate suitability model to define areas of Kenya unsuitable for stable transmission. Kenya's unstable transmission areas can be divided into areas where transmission potential is limited by low rainfall or low temperature and, combined, encompass over 8 million people. Among areas of stable transmission we have used empirical data on P. falciparum infection rates among 124 childhood populations in Kenya to develop a climate-based statistical model of transmission intensity. This model correctly identified 75% (95% confidence interval CI 70-85) of 3 endemicity classes (low, < 20%; high, > or = 70%; and intermediate parasite prevalences). The model was applied to meteorological and remote sensed data using a geographical information system to provide estimates of endemicity for all of the 1080 populated fourth level administrative regions in Kenya. National census data for 1989 on the childhood populations within each administrative region were projected to provide 1997 estimates. Endemicity-specific estimates of morbidity and mortality were derived from published and unpublished sources and applied to their corresponding exposed-to-risk childhood populations. This combined transmission, population and disease-risk model suggested that every day in Kenya approximately 72 and 400 children below the age of 5 years either die or develop clinical malaria warranting in-patient care, respectively. Despite several limitations, such an approach goes beyond 'best guesses' to provide informed estimates of the geographical burden of malaria and its fatal consequences in Kenya.

Child, Preschool↗