Frederico Simões Barbosa

Esquistossomose: reprodução e expansão da endemia no Estado de Pernambuco no Brasil

Schistosomiasis mansoni can be considered an important public health problem in Northeastern Brazil, in spite of the reduction in the prevalence of the hepatosplenic clinical forms which have been attributed to the large scale use of chemotherapy in this country. However, the rise in the prevalence rates and the spread of this endemic disease to new areas show that schistosomiasis is assuming its must cruel expression: less lethal but more greatly incapacitating in terms of irreversible physical and moral damage to human beings. The state of Pernambuco presents growing rates for schistosomiasis infection in humans. The epidemiological profile of this disease displays high and consistent prevalence rates (up to 80%) in rural areas, and new cases of acute infection on the coast, where schistosomiasis has recently been introduced. The reproduction and expansion of this endemic disease can be better understood on the basic of a conception of structural and historical causation. The disease construction process should be reconstructed in the light of biological as well as the social, political and cultural factors which are jointly responsible for the present endemic situation. Within that frame work, the historical and socioeconomic features that interact with the parasite and give rise to the present proportions of the schistosomiasis epidemic in Pernambuco are discussed. The mode of occupation and use of the land, unemployment, under-nutrition, migration, etc., raise the question of the growing difficulties confronting the control of the disease, both in rural areas where populations are extremely mobile as well as in the poorly organized urban population. Epidemiological investigation is fulfilling its role in its attempts to understand the complex relationships of an intrinsecally social nature of the health/disease process between health problems and the quality of life for the purpose of producing consistent disease control models.A esquistossomose continua a ser um problema de saude publica no Nordeste do Brasil embora o emprego, em larga escala, da quimioterapia venha sendo apontado como um dos fatores responsaveis pela reducao das formas graves. O Estado de Pernambuco vem apresentando taxas crescentes de infeccao humana para esquistossomose com perfil epidemiologico de prevalencias cronicas (ate 80%) na regiao rural e casos recentes de infeccao aguda no litoral. Discute-se a reproducao e expansao da esquistossomose a partir de uma concepcao estrutural e historica de causas, onde se inserem fatores nao so de ordem biologica mas tambem sociais, politicos e culturais que vem contribuindo para a formacao dos quadros endemicos: a forma de ocupacao e do uso da terra, desemprego, desnutricao, migracao e outros. Questionam-se as crescentes dificuldades para o controle da doenca e o papel da investigacao epidemiologica na compreensao da essencia social do processo saude/doenca.

Control of schistosomiasis mansoni in a small north east Brazilian community.

Abstract A seven-year project for the control of schistosomiasis due to S. mansoni was launched in November 1960 in the small village of Pontezinha, county of Cabo, state of Pernambuco. Control measures were limited to environmental sanitation and a community health education programme. Human infection rates were progressively reduced in the project area. Surveys made in 1967 and 1968 show that a successful degree of control of schistosomiasis has been achieved in the project area. Studies on snail population dynamics and on natural infection of small mammals captured in the area were made. The average monthly cost of the project was US

Padrão epidemiológico da esquistossomose em comunidade de pequenos produtores rurais de Pernambuco, Brasil

1,402·00, or an equivalent of US

Urban schistosomiasis in Itamaracá Island, Pernambuco, Brazil: epidemiological factors involved in the recent endemic process

0·98 per month per protected person.

Alternative approaches in schistosomiasis control

This article is part of a larger study in which epidemiological and anthropological methods were used to help understand the production and maintenance of schistosomiasis in a small endemic area in Pernambuco State. A cross-sectional study identified several local risk factors for schistosomiasis, quantifying socioeconomic, sanitary, and behavioral variables and then relating them to the prevalence and intensity of schistosomiasis infection. Using univariate analysis, three variables (age group, schooling, and human/water contact) showed significant association with S. mansoni infection. Causal factors and confounding variables were identified through multivariate analysis. Quantitative epidemiological analysis is critically discussed regarding a qualitative ethnographic study in relation to environmental risk situations (contamination and transmission) as well as risk practices (economic and behavioral).

A long-term schistosomiasis control project with molluscicide in a rural area of Brazil

Schistosomiasis has been considered as a rural endemic disease. In the State of Pernambuco, migratory human movements from endemic areas to urban ones with precarious sanitary and environmental conditions, is being pointed out as responsible for expansion and transmission of schistosomiasis (CS Barbosa et al. 1996 Rev Saude Publica 14: 693-700). The possibility that schistosomiasis mansoni could reach urban populations of high socio/economic background levels have been negleg. In 1991, four autochthonous cases from accidental exposure were detected near the Fort Orange beach, in Itamaraca Island, Pernambuco (JF Goncalves et al. 1992 Cad Saude Publica 7: 424-425). All cases occured in individuals from medium/high classes, that were in vacation in the island. After the detection of these accidental cases our major objective was to search for factors involved in schistosomiasis transmission in this area: a condominium composed by 560 houses of vacationists or tourists, built upon a destroyed mangrove ecosystem. An epidemiological quantitative study was conducted through demographic, sanitary, parasitological, social/economic and malacological surveys. Information about previous morbidity were also provided by the individuals that were temporary visitors in the area. The malacology survey identified 19 breading sites of Biomphalaria glabrata and 27 capture stations were set up. Snails were collected and examined each month during a year. The results show sazonal variation in mollusc populational density, associated with infection rates. The concentration of snails in water collections during the period from September to December 1997 were the highest observed, with infection rates of 18.2% (CS Barbosa et al. 1998 unpublished data). So, it is possible to imagine the potencial environmental risk of infection for human population in summer vacation on this beach. In the coproscopical survey, fecal samples of 349 vacationists and 91 local inhabitants were collected. Among vacationists, 10 cases of Schistosoma mansoni infection were detected (Table I). Moreover, 12 additional confirmed and autochthonous cases of schistosomiasis, in the last three years, were detected by refered morbidity survey (Table II). The prevalence of infection among local residents (fisherman and civil construction laborers) was 41.8%. Either, vacationist and local residents showed very few eggs of S. mansoni, indicating low levels of exposure. However, vacationists showed clinical acute forms, with characteristic exacerbated symptoms. The autochthony of cases was confirmed by personal interviews. We can conclude that the urban transmission of schistosomiasis in Itamaraca Island have dis-

The bioecology of snail vectors for schitosomiasis in Brazil

Measures for the control of schistosomiasis were implemented in Egypt beginning 1922. This shows that developing endemic countries are facing this problem for near 70 years. However, results in the control of this infection have not been satisfactorily obtained in spite of the technologies and strategies recently developed. The idea that social and economic components are relevant in the control of schistosomiasis is not new although its extension and profundity have not usually been well understood. More recently, most of the workers have recognized that the focal distribution of the prevalence rates of schistosomiasis should not be neglected in the control of the infection. At present, field work projects on the control of schistosomiasis are being developed in rural areas of two Brazilian studies (Espírito Santo and Pernambuco). The adopted strategy aims to interfere in the complex relationships between man and his bio-social-cultural environment, without forgetting that the unequal distribution of the space is a consequence of the political and economic organization of the Society.

Competitive displacement of Biomphalaria glabrata by B. straminea

A long-term controlled field experiment is described from northeastern Brazil, in which the molluscicide Bayluscide was used as the sole means of control against Schistosoma mansoni infection.Bayluscide was effective in the reduction of all of the parameters used for evaluation of the disease: incidence, prevalence, intensity of the infection (egg counts) in man, snail population (dynamics and natural infection rate) and the infectivity of natural water bodies (as measured through the exposure of sentinel mice). A less pronounced reduction of the same parameters was seen in the untreated area.Comments are made on the use of molluscicides and on the present situation in schistosomiasis control in the social and economic context of northeastern Braeil.

Cross-sectional studies on Schistosoma mansoni infection in northeast Brazil.

This paper describes the ecology of two species of Biomphalaria: B. glabrata and B. straminea. These species have been intensively studied in Brazil and in other countries since the 1950s. The literature in this area can be broadly subdivided into three categories, linked to three distinct historical periods: 1) an accumulated store of early studies carried out in the laboratory and in the field; 2) the development of quantitative ecological models; and 3) the development of an alternative methodology for breeding snails under seminatural conditions.

Dynamics of snail populations of Biomphalaria glabrata and B. straminea under semi-natural conditions

Data on the interaction between populations of closely related species of Biomphalaria, B. glabrata and B. straminea, are presented in the current paper. Laboratory and field observations and experiments have shown that B. straminea has competitive advantages over B. glabrata.