Decreasing proportion of Anopheles darlingi biting outdoors between long-lasting insecticidal net distributions in peri-Iquitos, Amazonian Peru

Abstract

BackgroundIn Loreto Department, Peru, a successful 2005–2010 malaria control programme (known as PAMAFRO) included massive distribution of long-lasting insecticidal nets (LLINs). Additional local distribution of LLINs occurred in individual villages, but not between 2012 and 2015. A 2011–2012 study of the primary regional malaria vector Anopheles darlingi detected a trend of increased exophagy compared with pre-PAMAFRO behaviour. For the present study, An. darlingi were collected in three villages in Loreto in 2013–2015 to test two hypotheses: (1) that between LLIN distributions, An. darlingi reverted to pre-intervention biting behaviour; and, (2) that there are separate sub-populations of An. darlingi in Loreto with distinct biting behaviour.ResultsIn 2013–2015 An. darlingi were collected by human landing catch during the rainy and dry seasons in the villages of Lupuna and Cahuide. The abundance of An. darlingi varied substantially across years, villages and time periods, and there was a twofold decrease in the ratio of exophagic:endophagic An. darlingi over the study period. Unexpectedly, there was 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. Using nextRAD genotyping-by-sequencing, 162 exophagic and endophagic An. darlingi collected at different times during the night were genotyped at 1021 loci. Based on model-based and non-model-based analyses, all genotyped An. darlingi belonged to a homogeneous population, with no evidence for genetic differentiation by biting location or time.ConclusionsThis study identified a decreasing proportion of exophagic An. darlingi in two villages in the years between LLIN distributions. As there was no evidence for genetic differentiation between endophagic and exophagic An. darlingi, this shift in biting behaviour may be the result of behavioural plasticity in An. darlingi, which shifted towards increased exophagy due to repellence by insecticides used to impregnate LLINs and subsequently reverted to increased endophagy as the nets aged. 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.Electronic supplementary materialThe online version of this article (10.1186/s12936-018-2234-4) contains supplementary material, which is available to authorized users.

Genetic heterogeneity in Anopheles darlingi related to biting behavior in western Amazon

“…In the Peruvian Amazon, there was no evidence of genetic differentiation between exophagic and endophagic An. darlingi [29]. Hence, this is the first study to report a genetic component related to An.…”

“…darlingi biting throughout the night with two peaks, one in the dusk and another in the dawn (data not published, supplementary). Prussing and collaborators [29] found no evidence of genetic differentiation between An. darlingi biting times during the night in Iquitos, Peru.…”

“…The drivers of behavioral shifting have been difficult to isolate and pinpoint in anophelines, although a general consensus is that the responses are mainly due to the distribution of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) [27][28][29]. Vector behavioral heterogeneity could be resulted of genetically differentiated subpopulations or behavioral plasticity i.e.…”

Evidence for family-level variation of phenotypic traits in response to temperature of Brazilian Nyssorhynchus darlingi

“…darlingi were used to create a catalog using STACKS cstacks, permitting 4 mismatches between stacks and enabling gapped alignments. In order to generalize the catalog to be useful across projects, samples used in this catalog were from previous publications [37,41,42]; similar sequencing methods were employed. This catalog consisted of 13 individuals from this study (the life history localities) and additional Ny.…”

Natural Malaria Infection in Anopheline Vectors and Their Incrimination in Local Malaria Transmission in Darién, Panama

“…pseudopunctipennis in three communities (Bajo Chiquito, Alto Playona y Morti). These differences in the frequency and distribution of mosquito species could be related to human social and cultural activities (host exposure and density), that allow a greater contact with the vector, giving rise to a higher rate of infected anophelines [63]. However, other factors could also be implicated such as: climatic conditions, housing types, presence of other animals in the peridomestic area and the e ciency of control measures.…”