Elsevier

Acta Tropica

Volume 99, Issues 2–3, October 2006, Pages 260-271
Acta Tropica

Socioeconomic determinants of schistosomiasis in a poor rural area in Brazil

https://doi.org/10.1016/j.actatropica.2006.09.001Get rights and content

Abstract

The objective of this paper is to identify and quantify socioeconomic determinants of Schistosoma mansoni infection in the rural area of Virgem das Graças in Minas Gerais State of Brazil. A cross-sectional study was carried out to examine the prevalence and intensity of schistosomiasis in relation to socioeconomic characteristics of the households. Log-binomial regression analysis was used to examine the data on both the household and individual levels, analyzing the prevalence ratios for the association of schistosomiasis and socioeconomic variables related to the head of the household. Multiple comparisons through mixed effect modeling were used to examine the relationship between intensity of infection (geometric mean egg counts) and different levels of socioeconomic variables, respectively. In the univariate analysis, place of residence, number of persons per room, and lack of motorized transport were associated with schistosomiasis at the household level and age and unsafe water contact at the individual level. Age, unsafe water contact, number of persons per room, household possessions and lack of education of head of household remained significant predictors of schistosomiasis in the multivariable analysis. Only age was significantly associated with intensity of infection of individuals. It is concluded that widespread poverty, the rural environment, and weak socioeconomic differentiation that result in intense contact with infective water appear to minimize the protective effect of piped water supply and other socioeconomic parameters on schistosomiasis found in other studies. The potential role of socioeconomic development in conjunction with schistosomiasis control is described and areas for further studies are identified.

Introduction

There is considerable evidence that socioeconomic conditions are often strongly associated with schistosomiasis occurrence. This relationship was first described in detail by Farooq et al. (1966) in Egypt and since then by studies in different endemic areas (Rosenfield, 1990, Yi-Xin and Manderson, 2005). In Brazil, the role of socioeconomic factors in Schistosoma mansoni transmission has been examined by studies in rural areas (Coura-Filho et al., 1994, Lima e Costa et al., 1991, Silva et al., 1997) and urban (Barreto, 1991, Kloetzel, 1989, Lima e Costa et al., 1987, Ximenes et al., 2003). However, only Ximenes et al. (2003) studied the relationship between socioeconomic determinants and schistosomiasis distribution in depth, using non-causal determinism, which posits that socioeconomic conditions determine and operate through various conditioning factors, or intermediate mechanisms, not necessarily in a causal manner. They found a strong relationship between socioeconomic variables and schistosomiasis in a town in northeast Brazil, but their findings are not applicable to rural areas, where the generally weaker socioeconomic differentiation and more widespread schistosomiasis risk present a different epidemiological setting. Socioeconomic studies are still called for as Brazil is still in need of an adaptable national schistosomiasis control methodology that considers local differences in disease ecology (WHO, 2001).

The study area, Virgem das Graças, is located in the S. mansoni-endemic area of northern Minas Gerais State and shares many physical and socioeconomic environmental features with the larger endemic region of northeastern Brazil, of which the study area forms part of the southern fringe. They include a semiarid climate with unreliable rainfall, marginalized subsistence farming, widespread poverty, high rates of rural–urban migration, and many communities with hyperendemic schistosomiasis. Partly due to its isolation, the Virgem das Graças population had never been treated for schistosomiasis by the government program. The hypothesis of this study is that the distribution of schistosomiasis in the Virgem das Graças population is determined by socioeconomic factors rather than occurring at random. Due to the high degree of household aggregation of schistosomiasis reported by Bethony et al. (2001) from a nearby rural study area and by Ximenes et al. (2003) in a town in northeastern Brazil, the role the household as a social organization and in economic decision making (Berman et al., 1994, Kroeger, 1985), particular emphasis in this study was given to the household level.

This study constitutes part of a broader epidemiological and immunological project. Malacological surveys revealed the high transmission potential of the 11 types of natural and manmade snail habitats studied by Kloos et al. (2004). Concomitant water contact studies carried out in three representative localities in the study area that used multiple methodologies indicate high exposure risk levels for the study population (Kloos et al., 2006).

Section snippets

Study area, economy and population

Virgem das Graças is a 60 km2 large rural area of Ponto dos Volantes Municipality, located in the Jequitinhonha Valley in northern Minas Gerais State, 120 km north of the town of Teófilo Otoni. According to our census survey in 2001, 589 people (48.2% males and 51.8% females) lived in the study area in 141 households. More than one-third of both the male and female population were 14 years old and younger (Table 1), indicating a high dependency ratio. Sixty-two percent of the population had been

Results

Of the 559 study subjects in the 136 households, 47.2% were males and 52.8% females. The population age ranged from 2 to 95 years (mean 30.9, S.D. 22.4, and median 24.0 years). The extreme age groups, <14 years and >65 years, represent 32.6% and 8.1% of the entire population, respectively. No significant differences were found between the responses of male and female heads.

The overall geometric mean egg count was 52.3 eggs per gram of feces, while the overall prevalence of infection was 58.7%.

Discussion

This study in an impoverished rural area within the region of high endemicity for schistosomiasis in Brazil shows a weak to moderate relationship between most socioeconomic indicators and infection. Education of head of household, household possessions, and number of persons per room were the major socioeconomic predictors of schistosomiasis occurrence and occupation of head of household became marginally significant in the multivariable model when included with education. The association of

Acknowledgements

This study received financial support from a Fogarty International Center Training Grant (1D43TW006580), Conselho de Desenvolvimento Tecnológico e Científico/CNPQ, Fundação de Amparo a Pesquisa do Estado de Minas Gerais/FAPEMIG, and the National Institutes of Health (NIH-ICIDR Grant A145451). Sara Crawford's research was supported in part by an appointment to the Research Participation Program at the Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division

References (37)

  • P. Coura-Filho et al.

    Control of schistosomiasis mansoni in Ravena (Sabará, State of Minas Gerais, Brazil) through water supply and quadrennial treatments

    Memórias Instit. Oswaldo Cruz

    (1996)
  • E.M. Coutinho et al.

    Factors involved in Schistosoma mansoni infection in rural areas of northeast Brazil

    Memórias Instit. Oswaldo Cruz

    (1997)
  • S.A. Esrey et al.

    Effects of improved water supply and sanitation on ascariasis, diarrhea, dracunculiasis, hookworm infection, schistosomiasis, and trachoma

    Bull. WHO

    (1991)
  • M. Farooq et al.

    The epidemiology of Schistosoma haematobium and S. mansoni infections in the Egypt-49 Project Area. 2. Prevalence of bilharziasis in relation to personal attributes and habits

    Bull. WHO

    (1966)
  • A. Gazzinelli et al.

    Domestic water use in a rural village in Minas Gerais, Brazil, with an emphasis on spatial patterns, sharing of water, and factors in water use

    Cadernos Saúde Públ.

    (1998)
  • A. Gazzinelli et al.

    Exposure to Schistosoma mansoni infection in a rural area of Brazil. I. Water contact

    Trop. Med. Int. Health

    (2001)
  • P. Jordan et al.

    Value of individual household water supplies in the maintenance phase of schistosomiasis in Saint Lucia, after chemotherapy

    Bull. WHO

    (1982)
  • P. Jordan et al.

    Human Schistosomiasis

    (1993)
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