Correlations of class A and class B intestinal infectious diseases with flies and their insecticide resistance in Putian, China

Objective To analyze the correlations between flies and class A and class B intestinal infectious diseases in Putian, China, and to investigate their insecticide resistance and the frequency of resistance alleles.

Methods The density of flies in Putian from 2019 to 2022 was monitored by the cage trapping method. Data of class A and class B intestinal infectious diseases were extracted from the Disease Monitoring System of Chinese Center for Disease Control and Prevention. The correlations between fly density and intestinal infectious diseases were investigated. Insecticide resistance level and related genotypes were identified by droplet method, sequencing and PCR-RFLP (restriction fragment length polymorphism polymerase chain reaction).

Results A positive correlation was found between the incidence of intestinal infectious diseases and fly density. Houseflies were susceptible to chlorpyrifos but resistant to permethrin, with resistance ratios of 1.438 and 8.489, respectively. No mutation of voltage-gated sodium channel (Vssc) gene was detected, and the frequency of CYP6D1v1 (cytochrome P450) resistance gene was 18.57%.

Conclusion The incidence of class A and class B intestinal infectious diseases is partly related to fly density, indicating that reduction of fly density is helpful to prevent such diseases. The houseflies from Putian are sensitive to chlorpyrifos but have developed resistance to permethrin.