Gabriel Mbugua

Comparison of different chemotherapy strategies against Schistosoma mansoni in Machakos District, Kenya : effects on human infection and morbidity

A comparison was made of the long-term impact of different methods of administration of chemotherapy (oxamniquine, 30 mg/kg in divided doses; or praziquantel, 40 mg/kg) on prevalence and intensity of Schistosoma mansoni infection in four areas in Kangundo Location, Machakos District, Kenya. In Area A, treatment was offered in October 1983 and again in April 1985 to all infected individuals. In Area H, treatment was offered in April 1985 to individuals excreting greater than or equal to 100 eggs per gram (epg) of faeces. In Area S, treatment was offered in April 1985 to all infected school children, within the framework of the primary schools. In the witness area, Area W, treatment was given in April 1985, for ethical reasons, to a small number of individuals excreting greater than or equal to 800 epg. Prevalence and intensities of infection were subsequently monitored at yearly intervals for three complete post-treatment years. In the Area S schools, clinical examination was also carried out at yearly intervals. Treatment of all infected individuals on two occasions (Area A) was the most effective and long-lasting way of reducing prevalence and intensity of infection. In this area, however, some earlier interventions had been carried out and pre-treatment intensities were lower than in the other areas. Treatment only of infected schoolchildren (Area S) also had a marked and prolonged effect, comparable to or better than treatment of individuals with heavy infections (Area H). Treatment of infected schoolchildren also caused a persistent reduction in the prevalence of hepatomegaly, and there was suggestive evidence from intensities of infection in community stool surveys (but not from incidence rates) of an effect on transmission. In all study areas, reinfection was most rapid and most intense among children. These findings are discussed in the light of theoretical considerations and of results from other studies, both on schistosomiasis and on intestinal helminths. We conclude that, in areas of low morbidity such as Kangundo, chemotherapy of schoolchildren only, at intervals of up to 3 years, is a satisfactory way of producing a long-term reduction in both intensity of infection and morbidity.

Differences in the rate of hepatosplenomegaly due to Schistosoma mansoni infection between two areas in machakos district. Kenya

The relationship between intensity of Schistosoma mansoni infection and the degree of related morbidity was suspected to differ locally within the Machakos district of Kenya. To test this possibility, prevalences of hepatomegaly and splenomegaly among 1483 school children were compared between 2 areas, Kangundo and Kambu, within this district. These areas, which were similar in many geographical and economic respects and populated by the same tribe (Akamba), had comparable levels of S. mansoni infection and no S. haematobium infection. A relationship was observed between the prevalence of hepatomegaly and intensity of S. mansoni infection, which showed no consistent difference between the 2 areas. In contrast, a relationship between the prevalence of splenomegaly and intensity of S. mansoni infection was observed only in the Kambu schools, and not in the Kangundo schools where the overall prevalence of splenomegaly was much lower. It was possible that part of the splenomegaly observed in Kambu was due to malaria. However, the observation that malaria and schistosomiasis in 2 Kambu schools were not positively correlated allowed approximations to be made of the relative contributions of each to the prevalence of splenomegaly. It was concluded that, in a school close to the river that formed the main transmission site of S. mansoni, schistosomiasis-related hepatosplenomegaly was present in at least 17% of children. The reason for the high prevalence in Kambu of hepatosplenic schistosomiasis remains uncertain, but it could include a synergistic interaction of schistosome infection with malaria.

Schistosomiasis mansoni in Kenya: relationship between infection and anaemia in schoolchildren at the community level

Haematological surveys were carried out in 3 schools in 2 areas where Schistosoma mansoni is endemic in Machakos District, Kenya, before and after a treatment campaign using praziquantel. Earlier clinical impressions of differences in the levels of anaemia between the 2 areas were not confirmed. Although individual haemoglobin levels and haematocrits often fell below international norms, significant anaemia with abnormal red blood cell morphology was rare (< 5%), but varied between schools. Altitude could have accounted for some of these differences, but other factors, including diet and parasitism, were involved. Anaemia was associated with splenomegaly and, to a lesser extent, hepatosplenomegaly. Epidemic malaria (mainly Plasmodium falciparum) appeared to be the main cause of parasite-induced anaemia. There was no significant association with the scarce hookworm infections (mainly Necator americanus); nor did the much commoner S. mansoni cause severe anaemia at the community level, but haemoglobin levels dropped as its intensity increased. Treatment with praziquantel eliminated this trend except in a few subjects with splenomegaly alone (probably due to malaria) or with schistosomal hepatosplenic disease. Possible pathogenic mechanisms are reviewed, including the consumption of red blood cells by adult schistosomes as a possible cause of anaemia.

Prevalence and Familial Aggregation of Schistosomal Liver Morbidity in Kenya: Evaluation by New Ultrasound Criteria

Severe periportal fibrosis is not an inevitable consequence of infection with Schistosoma mansoni. Genetic predisposition may be a deciding factor in the development of disease. To assess the contribution of genetic factors in the severity of hepatic fibrosis, the degree of familial aggregation was determined in a Kenyan population. Schistosomal fibrosis was identified with hepatic ultrasound and newly proposed World Health Organization criteria, which include both qualitative and quantitative observations. These 2 aspects of the criteria correlated well with one another. The peak prevalence of ultrasound proven fibrosis trailed 5-10 years behind peak prevalence of infection and declined sharply after age 50 years. This pattern was consistent with either resolution of severe fibrosis over 10-20 years or early death of those severely affected. Genetic predisposition appears to be a weak factor in the development of severe disease in this population, since no household or familial aggregation could be identified.

A survey for Schistosoma mansoni induced kidney disease in children in an endemic area of Machakos District, Kenya

The association between Schistosoma mansoni infection and kidney lesions was investigated in school children selected from three primary schools in Machakos District, Kenya, namely Miu (n = 159), Kitengei (n = 160) and Misuuni (n = 99) schools. The children were examined parasitologically for S. mansoni infection, clinically for enlargement of the liver and spleen, and biochemically for proteinuria and serum and urine creatinine. High prevalences of S. mansoni infection, ranging from 84-96%, were seen in all the schools, but the geometric mean intensity of egg excretion varied, being relatively low in Misuuni (31 eggs/g), medium in Miu (182 eggs/g) and high in Kitengei (413 eggs/g). The prevalence of pathological proteinuria (> or = 200 mg/l) in the schools ranged from 10.1% in Miu to 28.8% in Kitengei. No difference in the levels of proteinuria was noted between age or sex groups. No association between intensity of infection and pathological proteinuria was observed in any of the schools, nor was any correlation between organomegaly and proteinuria observed. However, significant correlations between malaria and organomegaly (p < 0.001) and between malaria and proteinuria (p < 0.05) were observed when pooling data from all schools. These findings suggest that S. mansoni induced nephrotic syndromes are not common in children from this highly endemic area of Kenya.

Questionnaire Survey on the Occurrence of Risk factors for Toxoplasma gondii infection amongst Farmers in Thika District, Kenya

A survey was conducted to determine the occurrence of risk factors for Toxoplasma gondii infection amongst farmers in Thika District, Kenya. Interviews were conducted in a total of 385 households using a structured questionnaire. The water consumed at household level originated from taps (74.3%), rivers or streams (15.1%), wells (5.4%) and boreholes (5.2%). A number of households (46.8%) consumed water without boiling or applying any form of treatment. All respondents washed vegetables before cooking, whilst 99.0% washed fruits before eating. Boiled milk was preferred by 99.5% of the farmers. The majority (85.2%) consumed beef more often, whilst 1.6% consumed pork. The majority (98.7%) consumed thoroughly cooked meat. Meat was preserved by 17% of farmers. Only four farmers (1.2%) who practised mixed farming used gloves when handling livestock manure. Five farmers (1.6%) reported the occurrence of abortion in ruminants and pigs on their farms within the last two years before the study. Almost half (44.9%) of the households owned cats, which were kept mainly as pets (79.8%) and for deterring rodents (20.2%). The majority of households (91.3%) fed the cats on leftovers, whilst 8.1% fed cats with raw offal. Sixteen households (9.2%) provided housing for cats. Only five households (2.8%) had litter boxes, but none of the households with litter boxes used gloves when cleaning them out. Disposal of cat faeces was done mainly by women (55.5%). Only one farmer (0.3%) had some knowledge about toxoplasmosis, but was not aware of the transmission mechanism. The study highlights the need for public health education to raise awareness of risk factors for toxoplasmosis.

Development and delivery of evidence-based messages to reduce the risk of zoonoses in Nairobi, Kenya

This paper describes a trans-disciplinary process of co-generating and disseminating evidence-based messages for reducing the risk from cryptosporidiosis and other zoonoses in an urban community in Nairobi. Research findings about disease prevalence, risk factors and observed risky and risk-mitigating practices were analysed by a team comprising researchers, community members and local policy- and decision-makers. Using participatory planning, multiple strategies were developed for disseminating key information. We identified five vulnerable groups at higher risk of exposure to cryptosporidiosis and other cattle zoonoses with similar transmission pathways (women, children, elderly people, immunosuppressed people and male farm workers). For each group, targeted messages were developed. Good practices already in use, as were also practices as practices to improve environmental conditions. These messages were disseminated through printed material, in a workshop, through community campaigners and also an edutainment soap opera episode broadcast on Kenyan television. In conclusion, a participatory and trans-disciplinary process can help transform the findings of research into messages that are targeted, attractive and understandable.

Outcome mapping for fostering and measuring change in risk management behaviour among urban dairy farmers in Nairobi, Kenya

A study was undertaken to investigate and mitigate the risk from zoonotic Cryptosporidium associated with dairy farming in Dagoretti division, Nairobi, Kenya. Outcome mapping (OM), a relatively new tool for planning and evaluation, was used to foster and then monitor changes in farmer management of health risks. Elements of the OM framework, including the vision, mission and expected progress markers, were developed in participatory sessions and a set of progress markers was used for monitoring behaviour change in farmers participating in the project (the boundary partners). Behaviour change (the outcome challenge) was supported by a range of awareness and educational campaigns, working with strategic partners (extension agents and administrative leaders). The farmers the project worked with made considerable progress according to the markers; they demonstrated an understanding of cryptosporidiosis, established or maintained clean and well drained cattle sheds, and took conscious effort to reduce possible infection. Farmers who did not participate in the project (non-contact farmers) were found to be less advanced on the progress marker indicators. Non-contact farmers who carried out risk-reducing practices had done so independently of the project team. The administration leaders, as strategic partners, had a positive attitude towards the project and confidence in their ability to support project objectives. The study demonstrates the utility of OM in helping to identify and support behavioural change.