Socioeconomic vulnerability associated to schistosomiasis in indigenous communities of southern Brazil

Schistosomiasis, a snail-borne Neglected Tropical Disease (NTD), has been caused by trematode blood flukes of genus Schistosoma . Besides the presence of gastropod snail intermediate hosts, disease spreading has been associated with poor sanitation and low human development index, particularly in communities living in deprived areas. Although present in 19/27 (70.4%) Brazilian States, schistosomiasis in vulnerable communities of non-endemic areas, particularly in southern and southeastern regions, remains to be fully established. Accordingly, the present study aimed to evaluate the seroprevalence of anti-S. mansoni antibodies based on ELISA-IgM and ELISA-IgG tests and associated risk factors to seropositivity in 713 individuals living in six indigenous communities of southern (n = 412) and four in southeastern (n = 301) Brazil. Overall seropositivity (IgM and/or IgG) was 5.3% (38/713; 95% CI: 3.9–7.2%), with 5.8% (24/412; 95% CI: 4.0-8.5%) in the southern and 4.7% (14/301; 95% CI: 2.8–7.7%) in the southeastern region; no statistical difference was observed between regions. Surprisingly, seropositive individuals presented more IgM (33/38; 86.8%) than IgG (10/38; 26.3%) reaction, suggesting recent infection. Univariate analysis indicated higher chances (OR > 4.5) for seropositivity in indigenous persons drinking water from the river, and feces disposal in open pits. In addition, the final logistic regression revealed that indigenous individuals living in peri-urban villages were more likely (OR = 3.60) seropositive than those living in rural areas. The results herein have shown the importance of schistosomiasis surveillance in low-endemic areas, which should be primarily directed to indigenous communities and other vulnerable populations.