Abstract
BackgroundPlasmodium vivax and Plasmodium falciparum cause a significant illness burden in Peru. Anopheline indices for populated communities in the peri-Iquitos region of Loreto have been reported to be remarkably low, with entomological inoculation rates (EIR) estimated at one to 30 infective bites per year based on a few studies in close proximity to the urban centre of Iquitos and surrounding deforested areas. Local reports suggest that a large number of the reported cases are contracted outside of populated communities in undeveloped riverine areas frequented by loggers and fishermen.MethodsTo better understand vectorial capacity in suspected high malaria transmission zones in a rural district near Iquitos, Peru, mosquito collections were conducted at different points in the seasonality of malaria transmission in 21 sites frequented by occupational labourers. Prevalence of Plasmodium spp in vectors was determined by circumsporozoite protein ELISA on individual mosquitoes. Slide surveillance was performed for humans encountered in the zone.ResultsIn total, of 8,365 adult female mosquitoes examined, 98.5% were identified as Anopheles darlingi and 117 (1.4%) tested positive for sporozoites (P. falciparum, P. vivax VK210 or P. vivax VK247). Measured human biting rates at these sites ranged from 0.102 to 41.13 bites per person per hour, with EIR values as high as 5.3 infective bites per person per night. Six percent of the 284 blood films were positive for P. vivax or P. falciparum; however, 88% of the individuals found to be positive were asymptomatic at the time of sampling.ConclusionsThe results of this study provide key missing indices of prominent spatial and temporal heterogeneity of vectorial capacity in the Amazon Basin of Peru. The identification of a target human subpopulation as a principal reservoir and dispersion source of Plasmodium species has important implications for vaccine development and the delivery of effective targeted malaria control strategies.
Highlights
Plasmodium vivax and Plasmodium falciparum cause a significant illness burden in Peru
Plasmodium vivax remains more prevalent than P. falciparum, accounting for 27,523 of the malaria cases reported in 2012, approximately seven times the number of P. falciparum cases reported during the same period [6]
Mosquito analysis From July 2008 to April 2009, a total of 8,364 adult female mosquitoes were captured over 1,324 total personhours, of which 8,347 (99.8%) anopheline mosquitoes were available for morphological species identification and analysis by enzyme-linked immunosorbant assay (ELISA) for the presence of P. vivax VK210, P. vivax VK247, and P. falciparum sporozoites
Summary
Plasmodium vivax and Plasmodium falciparum cause a significant illness burden in Peru. Local reports suggest that a large number of the reported cases are contracted outside of populated communities in undeveloped riverine areas frequented by loggers and fishermen. Plasmodium vivax remains more prevalent than P. falciparum, accounting for 27,523 of the malaria cases reported in 2012 (up to epidemiological week 52), approximately seven times the number of P. falciparum cases reported during the same period [6]. Accounting for approximately one-quarter of the geographical size of Peru, the Department of Loreto was reported to have a population of 942,457 inhabitants in 2007 and represents a large portion of the malaria case burden within Peru [7]. Up to the 52nd epidemiological week of 2012, Loreto reported 3,935 cases of P. falciparum and 21,048 cases of P. vivax, representing over 79% of all of the malaria cases reported in Peru during this time period [6]. Because the major industries in the region include agriculture, fishing, logging and petroleum [1], a large portion of the population work as labourers that move between populated cities and large villages and rural areas with high malaria transmission to extract natural resources
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