Insecticide resistance and genetic structure of Aedes aegypti populations from Rio de Janeiro State, Brazil

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, providing critical information to improving vector control program.

First national-scale evaluation of temephos resistance in Aedes aegypti in Peru

“…Similarly, in Brazil (Juazeiro do Norte) [ 74 ], a decrease in resistance to temephos was observed, from a RR of 10.4 to a RR of 7.2, 7 years after this larvicide was replaced by Bacillus thuringiensis israelensis (Bti). Also in Brazil, Rahman et al [ 75 ] observed a reduction in the level of resistance to temephos in Rio de Janeiro, in the municipality of Campos dos Goytacazes, 15 years after discontinuationof its use, from a RR of 7.8 in 2001 to a RR of 2.6 in 2016. These authors also detected a significant decrease in the levels of resistance to temephos in the municipality of Itaperona, from a RR of 25.6 in 2011 to a RR of 7.3 in 2016, after this larvicide was substituted by IGR [ 75 ].…”

“…Also in Brazil, Rahman et al [ 75 ] observed a reduction in the level of resistance to temephos in Rio de Janeiro, in the municipality of Campos dos Goytacazes, 15 years after discontinuationof its use, from a RR of 7.8 in 2001 to a RR of 2.6 in 2016. These authors also detected a significant decrease in the levels of resistance to temephos in the municipality of Itaperona, from a RR of 25.6 in 2011 to a RR of 7.3 in 2016, after this larvicide was substituted by IGR [ 75 ]. Consequently, rotating to a new insecticide with a different mode of action could be advantageous in terms of temephos resistance management.…”

First National-Scale Evaluation of Temephos Resistance in Aedes Aegypti in Peru.

“…Similarly, Conde et al [56] observed in Colombia (Caldas) the reduction of temephos resistance from RRs of 13.27 and 11.48 in 2007 to 4.75 and 5.61 in 2011 after discontinuation of its use for four years. Similarly, Brazil (Juazeiro do Norte) [70] observed a decrease in resistance to temephos from a RR of 10.4 to 7.2 after 7 years when this larvicide was replaced by Bacillus thuringiensis israelensis (Bti) and Rahman et al [71] observed in Rio de Janeiro in the municipality of Campos dos Goytacazes the reduction of temephos resistance from a RR of 7.8 in 2001 to 2.6 in 2016 after discontinuation of its use for 15 years and detected signi cant decrease in the levels of resistance to temephos in the municipality of Itaperona from a RR of 25.6 in 2011 to 7.3 in 2016 after this larvicide was substituted by IGR. Consequently, rotating to a new insecticide with a different mode of action could be advantageous for temephos resistance management.…”

City puzzles: Does urban land scape affect genetic population structure in Aedes aegypti?

“…Previous studies analyzed Ae . aegypti population genetic structure within cities using nuclear markers such as microsatellites [ 14 – 21 ] or SNPs [ 20 , 22 – 25 ]. While most of these works did not focus on the effect of urban heterogeneity on vector’s genomics, those that did showed a clear effect of urban landscape on genetic structure and vector dispersal [ 18 , 24 ].…”

“…aegypti is key to improve any control strategy. Fine-scale genetic structure can provide critical information about the potential dissemination of alleles associated to insecticide resistance, particularly those of the kdr gene [ 35 , 36 ], and vector competence for different arboviruses [ 7 ]. It also conditions the potential success of vector control programs based on the release of Wolbachia -carrying or genetically modified mosquitoesto limit arboviral transmission [ 37 ].…”