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Culex pipiens pallens is the most abundant Culex mosquito species in northern China and is an important vector of bancroftian filariasis and West Nile virus. Deltamethrin is an insecticide that is widely used for mosquito control, however resistance to this and other insecticides has become a major challenge in the control of vector-borne diseases that appear to be inherited quantitatively. Furthermore, the genetic basis of insecticide resistance remains poorly understood. In this study, quantitative trait loci (QTL) mapping of resistance to deltamethrin was conducted in F2 intercross segregation populations using bulked segregation analysis (BSA) and amplified fragment length polymorphism markers (AFLP) in Culex pipiens pallens. A genetic linkage map covering 381 cM was constructed and a total of seven QTL responsible for resistance to deltamethrin were detected by composite interval mapping (CIM), which explained 95% of the phenotypic variance. The major QTL in linkage group 2 accounted for 62% of the variance and is worthy of further study. 12 AFLP markers in the map were cloned and the genomic locations of these marker sequences were determined by applying the Basic Local Alignment Search Tool (BLAST) tool to the genome sequence of the closely related Culex quinquefasciatus. Our results suggest that resistance to deltamethrin is a quantitative trait under the control of a major QTL in Culex pipiens pallens. Cloning of related AFLP markers confirm the potential utility for anchoring the genetic map to the physical map. The results provide insight into the genetic architecture of the trait.

Dust events in northern China, particularly in the springtime, affect millions of people in the source and downwind regions. We investigate the population affected by various dust levels in China in the springtime from 2003 to 2020 using satellite retrievals of dust optical depth (DOD). We select three DOD thresholds, namely DOD > 0.2, DOD > 0.3, and DOD > 0.4, to estimate the population affected and find that each year the population affected can differ by one order of magnitude. The population exposed to DOD > 0.2 ranged from 16 million (2019) to over 200 million (2006). The population exposed to DOD > 0.3 ranged from 10 million (2015) to 70 million (2006). The population exposed to DOD > 0.4 ranged from 4 million (2017) to 36 million (2006). In years when dust events are frequent, people in the source and downwind regions are both affected, whereas, in years when dust events are less frequent, people affected are mainly in the source regions. Furthermore, we use the relative index of inequality to assess whether dust hazards impose unequal pollution burdens on different socioeconomic groups. We find that low-income communities have been more likely affected by dust pollution since 2013. [ABSTRACT FROM AUTHOR]