Anopheles darlingi Loreto Peru biting behavior 2016-17 nextRADseq

Background: In Loreto Department, Peru, a successful 2005-2010 malaria control program (known as PAMAFRO) included massive distribution of long-lasting insecticidal nets (LLINs) and indoor residual spray (IRS). A 2011-2012 study of the primary regional malaria vector An. darlingi detected a trend of increased exophagy compared with pre-PAMAFRO behaviour. We tested the hypothesis that since the end of the lifetime of LLINs and IRS (~late 2012), An. darlingi has reverted to pre-intervention biting behavior by studying biting behaviour in the villages of Lupuna and Cahuide, and in Santa Emilia, a village excluded from PAMAFRO. In addition, we used nextRAD genotyping-by-sequencing to test for genetic differentiation between exophagic and endophagic An. darlingi biting at different times.Methods: In 2013-2015 we collected An. darlingi by human landing catch during the rainy and dry seasons, and tested specimens for Plasmodium. To evaluate population structure in Lupuna and Cahuide, we analyzed 1,021 genome-wide single nucleotide polymorphisms from 162 An. darlingi using model-based and non-model-based methods.Results: Exophagic and endophagic An. darlingi were collected in all villages. In the two PAMAFRO villages, the abundance of An. darlingi varied substantially across years, villages, and time periods, and there was a two-fold decrease in the ratio of exophagic:endophagic An. darlingi over the study period. Unexpectedly, we found evidence of a rainy season population decline in An. darlingi. Plasmodium-infected An. darlingi were detected indoors and outdoors throughout the night, and the monthly An. darlingi human biting rate was correlated with the number of malaria cases in Lupuna and Cahuide. All genotyped An. darlingi belonged to a homogeneous population, with no evidence for genetic differentiation by biting location or time.Conclusions: We identified a decreasing proportion of exophagic An. darlingi in Lupuna and Cahuide after the end of the lifetime of LLINs and cessation of IRS. As we found no evidence for genetic differentiation between endophagic and exophagic An. darlingi, this shift in biting behaviour may be the result of behavioural plasticity. This study highlights the need to target vector control interventions to the biting behaviour of local vectors, which, like malaria risk, shows high temporal and spatial heterogeneity.