Abstract
Vector control largely relies on neurotoxic chemicals, and insecticide resistance (IR) directly threatens their effectiveness. In some cases, specific alleles cause IR, and knowledge of the genetic diversity and gene flow among mosquito populations is crucial to track their arrival, rise, and spread. Here we evaluated Aedes aegypti populations’ susceptibility status, collected in 2016 from six different municipalities of Rio de Janeiro state (RJ), to temephos, pyriproxyfen, malathion, and deltamethrin. We collected eggs of Ae. aegypti in Campos dos Goytacazes (Cgy), Itaperuna (Ipn), Iguaba Grande (Igg), Itaboraí (Ibr), Mangaratiba (Mgr), and Vassouras (Vsr). We followed the World Health Organization (WHO) guidelines and investigated the degree of susceptibility/resistance of mosquitoes to these insecticides. We used the Rockefeller strain as a susceptible positive control. We genotyped the V1016I and F1534C knockdown resistance (kdr) alleles using qPCR TaqMan SNP genotyping assay. Besides, with the use of Ae. aegypti SNP-chip, we performed genomic population analyses by genotyping more than 15,000 biallelic SNPs in mosquitoes from each population. We added previous data from populations from other countries to evaluate the ancestry of RJ populations.All RJ Ae. aegypti populations were susceptible to pyriproxyfen and malathion and highly resistant to deltamethrin. The resistance ratios for temephos was below 3,0 in Cgy, Ibr, and Igg populations, representing the lowest rates since IR monitoring started in this Brazilian region. We found the kdr alleles in high frequencies in all populations, partially justifying the observed resistance to pyrethroid. Population genetics analysis showed that Ae. aegypti revealed potential higher migration among some RJ localities and low genetic structure for most of them. Future population genetic studies, together with IR data in Ae aegypti on a broader scale, can help us predict the gene flow within and among the Brazilian States, allowing us to track the dynamics of arrival and changes in the frequency of IR alleles, and providing critical information to improving vector control program.
Highlights
In 2016, Brazil’s number of dengue cases was near 1.5 million, representing 69% of the dengue cases in South, Central, and North America combined
We chose representative municipalities of the principal geographic/administrative regions of the Rio de Janeiro State (RJ) state to explore the insecticide effectiveness in Ae. aegypti, their genetic structure and gene flow among them (Fig 1): Campos dos Goytacazes (Cgy) in the North, Itaperuna (Ipn) in Northwest, Iguaba Grande (Igg) in the Coastal Lowland (Região dos Lagos), Itaboraı (Ibr) in the Metropolitan Region II, Mangaratiba (Mgr) around the Ilha Grande bay and Vassouras (Vsr) in the Center-South region (Fig 1)
The highest average dengue incidence for this period occurred in Ipn (17.6%), 6.5 greater than the RJ average (2.7%)
Summary
In 2016, Brazil’s number of dengue cases was near 1.5 million, representing 69% of the dengue cases in South, Central, and North America combined. Within the Southeast region of Brazil, Rio de Janeiro State (RJ) is a crucial hub for the import and export of goods and a tourist attraction and port of entry. In 2016, RJ registered high dengue, chikungunya, and Zika, with 443.7, 108.1, and 414.2 cases per 100,000 inhabitants, respectively [1]. The State capital Rio de Janeiro City (Rio) and the Região dos Lagos are the leading destinations for domestic and foreign visitors. The region plays a significant role in introducing mosquitoes, mostly in eggs attached to goods that travel by road, air, sea, and arboviruses affecting humans. Historical records show most of the dengue virus emergencies from Brazil in RJ [2,3,4,5]
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