RESUMEN
BACKGROUND: Aedes albopictus is an important vector of chikungunya, dengue, yellow fever and Zika viruses. Insecticides are often the most effective tools for rapidly decreasing the density of vector populations, especially during arbovirus disease outbreaks. However, the intense use of insecticides, particularly pyrethroids, has led to the selection of resistant mosquito populations worldwide. Mutations in the voltage-gated sodium channel (VGSC) gene are one of the main drivers of insecticide resistance in Ae. albopictus and are also known as "knockdown resistance" (kdr) mutations. Knowledge about genetic mutations associated with insecticide resistance is a prerequisite for developing techniques for rapid resistance diagnosis. Here, we report studies on the origin and dispersion of kdr haplotypes in samples of Ae. albopictus from the Yangtze River Basin, China; METHODS: Here, we report the results of PCR genotyping of kdr mutations in 541 Ae. albopictus specimens from 22 sampling sites in 7 provinces and municipalities in the Yangtze River Basin. Partial DNA sequences of domain II and domain III of the VGSC gene were amplified. These DNA fragments were subsequently sequenced to discover the possible genetic mutations mediating knockdown resistance (kdr) to pyrethroids. The frequency and distribution of kdr mutations were assessed in 22 Ae. albopictus populations. Phylogenetic relationships among the haplotypes were used to infer whether the kdr mutations had a single or multiple origins; RESULTS: The kdr mutation at the 1016 locus had 2 alleles with 3 genotypes: V/V (73.38%), V/G (26.43%) and G/G (0.18%). The 1016G homozygous mutation was found in only one case in the CQSL strain in Chongqing, and no 1016G mutations were detected in the SHJD (Shanghai), NJDX (Jiangsu) or HBQN (Hubei) strains. A total of 1532 locus had two alleles and three genotypes, I/I (88.35%), I/T (8.50%) and T/T (3.14%). A total of 1534 locus had four alleles and six genotypes: F/F (49.35%), F/S (19.96%), F/C (1.48%) and F/L (0.18%); S/S (23.66%); and C/C (5.36%). Haplotypes with the F1534C mutation were found only in Ae. albopictus populations in Chongqing and Hubei, and C1534C was found only in three geographic strains in Chongqing. Haplotypes with the 1534S mutation were found only in Ae. albopictus populations in Sichuan and Shanghai. F1534L was found only in HBYC. The Ae. albopictus populations in Shanghai were more genetically differentiated from those in the other regions (except Sichuan), and the genetic differentiation between the populations in Chongqing and those in the middle-lower reaches of the Yangtze River (Huber, Jiangsu, Jiangxi, and Anhui) was lower. Shanghai and Sichuan displayed low haplotype diversity and low nucleotide diversity. Phylogenetic analysis and sequence comparison revealed that the 1016 locus was divided into three branches, with the Clade A and Clade B branches bearing the 1016 mutation occurring mostly in Jiangsu and the Clade C branch bearing the 1016 mutation occurring mostly in Chongqing, suggesting at least two origins for 1016G. IIIS6 phylogenetic analysis and sequence comparison revealed that F1534S, F1534C and I1532T can be divided into two branches, indicating that IIIS6 has two origins; CONCLUSIONS: Combined with the distribution of kdr mutations and the analysis of population genetics, we infer that besides the local selection of pyrethroid resistance mutations, dispersal and colonization of Ae. albopictus from other regions may explain why kdr mutations are present in some Ae. albopictus populations in the Yangtze River Basin.
RESUMEN
BACKGROUND: Anopheles stephensi is native to Southeast Asia and the Arabian Peninsula and has emerged as an effective and invasive malaria vector. Since invasion was reported in Djibouti in 2012, the global invasion range of An. stephensi has been expanding, and its high adaptability to the environment and the ongoing development of drug resistance have created new challenges for malaria control. Climate change is an important factor affecting the distribution and transfer of species, and understanding the distribution of An. stephensi is an important part of malaria control measures, including vector control. METHODS: In this study, we collected existing distribution data for An. stephensi, and based on the SSP1-2.6 future climate data, we used the Biomod2 package in R Studio through the use of multiple different model methods such as maximum entropy models (MAXENT) and random forest (RF) in this study to map the predicted global An. stephensi climatically suitable areas. RESULTS: According to the predictions of this study, some areas where there are no current records of An. stephensi, showed significant areas of climatically suitable for An. stephensi. In addition, the global climatically suitability areas for An. stephensi are expanding with global climate change, with some areas changing from unsuitable to suitable, suggesting a greater risk of invasion of An. stephensi in these areas, with the attendant possibility of a resurgence of malaria, as has been the case in Djibouti. CONCLUSIONS: This study provides evidence for the possible invasion and expansion of An. stephensi and serves as a reference for the optimization of targeted monitoring and control strategies for this malaria vector in potential invasion risk areas.