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

Abstract

Two contiguous villages in Tracunhaém county (State of Pernambuco), endemic for schistosomiasis, were studied: Itapinassu (138 inhabitants) and São Joaquim (91 inhabitants). Agriculture predominates in the former region while ceramics is the main activity in the latter. Although no statistical difference was found regarding prevalence, severe infection (> 400 epg) predominated in Itapinassu, probably related to the kind of occupation. No association was found between parasite burden and severity of disease, in spite of the high infection rates for Schistosoma mansoni in both communities (approx. 60%). Typical epidemiological features of schistosomiasis such as age-related prevalences and intensities of infection (high in children, low in adults) were also mutual characteristics. Nutritional status determined through anthropometric evaluation was carried out by measuring specific anthropometric indicators. A deficit of energy intake, as well as vitamin A and riboflavin deficiencies were detected. The prevalence of moderate or severe undernutrition in patients under 18 years old was 21.9% in Itapinassu and 24.1% in São Joaquim. In this group an association was found between prevalence of schistosomiasis and chronic undernutrition. Similarly, for patients over 18 year old the prevalence of undernutrition was higher than 20%. However, in this case no association between nutritional status and either prevalence of schistosomiasis or parasite burden could be detected. The two communities had not been treated for eight years.

PIP: Patterns of schistosomiasis infection were compared in two contiguous endemic villages in Northeast Brazil's Tracunhaem County (Pernambuco State): Itapinassu (138 inhabitants) and Sao Joaquim (91 inhabitants). The overall prevalence of schistosomiasis in Tracunhaem State was 58.7%; this rate was 61.6% in Itapinassu and 54.2% in Sao Joaquim. Severe infection (400 epg) was more prevalent in Itapinassu (35.1%) than Sao Joaquim (13.3%) and ultrasound revealed more severe pathologic changes (e.g., periportal fibrosis, right liver lobe shrinkage, left lobe and spleen enlargement) in the former village. The higher prevalence of severe infection in Itapinassu is likely related to the predominance of agricultural occupations; in Sao Joaquim, most residents are engaged in ceramics. Schistosomiasis prevalence was significantly positively associated with increasing age, male sex, residence in the village for more than 5 years, daily water contact, fishing, laundering, less than a 10 m distance from an infected stream, lack of cesspools, and chronic undernutrition. A deficit of energy intake, as well as vitamin A and riboflavin deficiencies, was detected in both villages. The role of each of these factors (especially nutritional status) will be analyzed further in order to develop an integrated model for local control of the disease.