Prevalence and spatial distribution of intestinal parasitic infections in a rural Amazonian settlement, Acre State, Brazil / Prevalência e distribuição espacial de parasitoses intestinais em assentamento agrícola na Amazônia rural, Acre, Brasil

A population-based survey of the prevalence and spatial distribution of intestinal parasitism was carried out in an agricultural settlement in the Amazon Basin of Brazil (Granada, Acre State). More than half (53.4 percent) of the 429 stool specimens from subjects in all age groups, living in 113 households, had cysts, ova, or larvae of intestinal parasites. The most prevalent parasites were Giardia duodenalis (19.6 percent) and soil-transmitted helminths (12.7 percent); 105 (24.5 percent) subjects were infected with more than one species of parasite. Significant age-related differences in prevalence were only found for G. duodenalis (children < 1 year and adults > 30 years were less affected). Six households (5.3 percent), situated within a radius of 690m, comprised 48.1 percent of all subjects harboring soil-transmitted helminths in our study area. Households within this cluster were poorer and more crowded than those outside the cluster. The observed spatial clustering of infections with soil-transmitted helminths provides valuable information for the spatial targeting of sanitary interventions in this area.

Estudo de base populacional sobre a prevalência e distribuição de parasitoses intestinais foi realizado em assentamento agrícola na Amazônia Brasileira (Granada, Acre). Mais da metade (53,4 por cento) das 429 amostras analisadas de indivíduos de todas as idades, moradores de 113 domicílios, continha cistos, ovos ou larvas de parasitas intestinais. Os parasitas intestinais de maior prevalência foram Giardia duodenalis (19,6 por cento) e os geo-helmintos (12,7 por cento); 105 (24,5 por cento) indivíduos apresentavam co-infecção por mais de uma espécie de parasita. Houve diferença significativa em relação à idade na prevalência somente de G. duodenalis (crianças < 1 ano e adultos > 30 anos foram menos afetados). Seis domicílios (5,3 por cento), localizados num raio de 690m, concentraram 48,1 por cento de todos os indivíduos infectados por geo-helmintos na área de estudo. Domicílios incluídos nesse agregado (cluster) eram mais pobres e com maior número de habitantes do que os domicílios localizados fora do agregado. A distribuição espacial dos agregados de casos de infecção por geo-helmintos fornece informações valiosas para intervenções sanitárias na comunidade da área de estudo.

The Acre Project: the epidemiology of malaria and arthropod-borne virus infections in a rural Amazonian population

The authors describe the baseline malaria prevalence and arbovirus seroprevalence among 467 subjects in an ongoing cohort study in rural Amazonia. Most subjects (72.2 percent) reported one or more previous episodes of malaria, and 15.6 percent had been hospitalized for malaria, but only 3.6 percent of individuals five years or older had malaria parasites detected by microscopy (10 with Plasmodium vivax and 4 with P. falciparum). Antibodies to Alphavirus, Orthobunyavirus, and/or Flavivirus were detected by hemagglutination inhibition (HI) in 42.6 percent of subjects aged five years or older, with a higher seropositivity rate among males (49.2 percent) than females (36.2 percent). Since 98.9 percent of subjects had been immunized for yellow fever, the presence of cross-reactive antibodies to dengue and other Flaviviruses cannot be ruled out, but at least 12 subjects (3.3 percent) with IgM antibodies to dengue virus detected by ELISA had a putative recent exposure to this virus.