Schistosomiasis mansoni in an area of low transmission. II. Risk factors for infection

Risk factors for Schistosoma mansoni infection were identified using a 1:1 matched case-control design. The work was conducted in the municipality of Pedro de Toledo, São Paulo State, Brazil, an area where the snail host is Biomphalaria tenagophila. Information on water contact patterns, knowledge, attitudes and practices (kap), socioeconomic and sanitary conditions were obtained by mean of questionnaires. The crude odds ratio estimates and the adjusted odds ratio estimates using the logistic regression model are presented. Most of the examined individuals admitted recent water contacts (90.6 of the cases). The most frequent reason for contact was swimming, playing and fishing and the preferential site of contact was the river. According to the logistic regression technique, the main risk factors for infection were: a) water contact through swimming, playing and fishing; b) fording; c) bad hygiene. We concluded that recreational activities are the main reasons for schistosomiasis transmission in Pedro de Toledo and leisure alternatives should be offered to the local population.

Controle da esquistossomose mansônica em área de baixa transmissao / Control of schistosomiasis mansoni in a low transmission area

The schistosomiasis is transmitted by Biomphalaria tenagophila in our study area (Pedro de Toledo, Sao Paulo, Brazil). From 1980 to 1990 epidemiological surveys in a population of 4.000 inhabitants, has shown that: prevalence Kato-Katz (KKT), immunofluorescence (FT) and intradermal (IDT) techniques were 22.8%, 55.5% and 51.8% respectively; intensity of infection was low, 58.5 eggs per gram of faeces (epg); there were no symptomatic cases; prevalences were higher in mates, children and rural zone; index of potential contamination was 57.5% in the age group 5 to 20 years; 2/3 of patients were autochtonous; cases were no-randomly aggregated; transmission was focal and only 0.4% of snails were infected; water contacts through recreation showed the most important odds ratio; knowledge, attitudes and practices were satisfatory. From the epidemiological control findings a control programme was carried out; yearly faeces exams, chemotherapy, molluscocide, health education and sanitation. Thus, the prevalence decreased sharply to 3.3% and intensity of infection to 30.3 epg; the incidence rates ranged between 0.4% and 2.5% annualy; the sanitation became better and the youngsters were the main target in prophylaxis. To improve control, immunodiagnosis has to be conducted and the involvment of the population should be increase. However, we cannot forget that re-infection and the involvment of the population should be increase. However, we cannot forget that re-infection, therapeutic failure, etc, could play a major role in the maintnance this residual prevalence

Competição biológica entre Biomphalaria glabrata (Say, 1818) e Biomphalaria tenagophila (D’Orbgny 1835), em criadouros naturais no Município de Ourinhos, Estado de São Paulo-Brasil / Biological competition between Biomphalaria glabrata (Say, 1818) and Biomphalaria tenagophila (D’Orbgny,1835), observed in their natural breending sites in Ourinhos, State of São Paulo-Brazil

Foram feitas observações sobre a provável competição entre Biomphalaria glabrata e Biomphalaria tenagophila, em três criadouros do tipo vala, situados no Município de Ourinhos, (SP), durante o período de 27/11/1973 a 20/02/1979. As coletas foram realizadas trimestralmente até dezembro de 1976 e semestralmente de 1977 a 1979, num total de 17 capturas. Foram coletados 5.249 exemplares de Biomphalaria tenagophila e 353 de Biomphalaria glabrata no criadouro 1; no criadouro 2 o total de exemplares foi de 1703 e 64 para Biomphalaria tenagophila e Biomphalaria glabrata, respectivamente e no criadouro 3, 1249 e 4 exemplares de Biomphalaria tenagophila e Biomphalaria glabrata respectivamente. Apenas os dados relativos ao primeiro criadouro forneceram informações relacionadas com o deslocamento de Biomphalaria glabrata e Biomphalaria tenagophila, sendo que a análise estatística sugeriu ter havido competição entre as duas espécies estudadas com tendência à exclusão de Biomphalaria glabrata. A substituição parece ter ocorrido num período de pelo menos cinco anos. Apesar de terem sido observadas evidências de deslocamento competitivo entre as duas espécies, não foi possível detectar o mecanismo do fenômeno.