Epidemiological and ecological aspects related to malaria in the area of influence of the lake at Porto Primavera dam, in western São Paulo State, Brazil

Abstract

SUMMARYA study was carried out in the area of influence of the Porto Primavera Hydroelectric Power Station, in western São Paulo State, to investigate ecological and epidemiological aspects of malaria in the area and monitor the profile of the anopheline populations following the environmental changes brought about by the construction of the lake. Mosquitoes captured were analyzed by standardized indicator species analysis (ISA) before and during different flooding phases (253 m and 257 m elevations). The local human population was studied by means of parasitological (thin/thick blood smears), molecular (PCR) and serological tests. Serological tests consisted of Enzyme Linked Immunosorbent Assay (ELISA) with synthetic peptides of the circumsporozoite protein (CSP) from classic Plasmodium vivax, P. vivax variants (VK247 and "vivax-like"), P. malariae and P. falciparum and Indirect Immunofluorescence Assay (IFA) with asexual forms of P. vivax, P. malariae and P. falciparum. The results of the entomological survey indicated that, although the Anopheles darlingi population increased after the flooding, the population density remained very low. No malaria, parasite infection or DNA was detected in the inhabitants of the study area. However, there was a low frequency of antibodies against asexual forms and a significant prevalence of antibodies against P. vivax, P. vivax variants, P. falciparum and P. malariae; the presence of these antibodies may result from recent or less recent contact with human or simian Plasmodium (a parallel study in the same area revealed the existence of a sylvatic cycle). Nevertheless, these results suggest that, as in other places where malaria is present and potential vectors circulate, the local epidemiological conditions observed could potentially support the transmission of malaria in Porto Primavera Lake if infected individuals are introduced in sufficient numbers. Further studies are required to elucidate the phenomena described in this paper.

Effects of flooding of the River Paraná on the temporal activity of Anopheles (Nyssorhynchus) darlingi Root (Diptera: Culicidae), at the border state of Mato Grosso do Sul and São Paulo, Brazil

“…For this study, three areas were chosen: location A, situated in the town of Bataguassu in the State of Mato Grosso do Sul, with no direct connection with the flooding; location B, which suffered two successive floods; and location C, which suffered only one, both located in the town of Presidente Epitácio in the State of São Paulo 9,10 . This last location has no direct connection to the dam, since it is formed by a dam on the River Peixe, a tributary of the River Paraná 9 .…”

“…This last location has no direct connection to the dam, since it is formed by a dam on the River Peixe, a tributary of the River Paraná 9 . During the course of the dam project, from construction to the formation of the lake, entomological investigations consisted of three stages: stage 1, the pre-flooding period at a surface water elevation (SWE) of 247m; stage 2, initial flooding reaching at SWE of 253m and stage 3, at a SWE of 257m.…”

“…This technique consists of two people waiting for mosquitoes to land on their outfit. The second technique used was the Shannon trap (ST), which has multiple attractive stimulations 9,10 . In stage 1, captures in location A using HAT were conducted for the period from February 1998 to January 1999; captures using ST, in dawn twilight (dST), were conducted from January to November 1998; at location B, HAT was used from July 1997 to 1998.…”

Energy and Human Health

“…Some studies have shown no impact of hydroelectric dam construction on nearby malaria (68), but most show an increase in risk (112,122,234 Policy on dams needs to balance the considerable health benefits of available energy and water management with local adverse health and social impacts (127,131,230). For this purpose, guidelines have been issued for equitable, atraumatic resettlement (229).…”

Impact of dams and irrigation schemes in Anopheline (Diptera: Culicidae) bionomics and malaria epidemiology

“…Still in Brazil, An. darlingi was also found to be the predominant species in the influence area of the Porteira and Porto Primavera dams and in the area where the future Madeira dam will be constructed 7,17,34,88 .…”