Screening of the deltamethrin-resistant strain of Aedes albopictus (Diptera: Culicidae) and its susceptibility to dengue virus
JIA Zhi-Rong1, LIU Zhuan-Zhuan1,2, WANG Xiao-Ming1, Tricia WILLIAMS1, LIU Pei-Wen1, LI Xiao-Cong1, YAN Gui-Yun1, CHEN Xiao-Guang1,*
(1. Key Laboratory of Tropical Disease Research of Guangdong Province, Department of Pathogen Biology, School of Public Health, Southern Medical University, Guangzhou 510515, China; 2. Laboratory of Infection and Immunity, Department of Pathogenic Biology and Immunology, Xuzhou Medical University,Xuzhou, Anhui 221004, China)
Abstract 【Aims】 To establish a strain of the Asian tiger mosquito, Aedes albopictus,resistant to deltamethrin, and to compare the susceptibilities of the susceptible and
resistant strains of Ae. Albopictus to dengue virus. 【Methods】 The lethal concentrationrequired to kill half of the sample (LC50 value) of deltamethrin against Ae. albopictus larvae was determined by impregnation method. Then, Ae. albopictus mosquitoes were selected at LC50 of deltamethrin for 11 generations. Deltamethrin resistance of each screened generation was tested by WHO tube assay. Female adults of the susceptible strain and the obtained resistant strain of Ae. albopictus were fed with defibrinated sheep blood mixed with dengue virus-2 (DENV-2). The midguts, ovaries and salivary glands from female adults of the two strains were dissected at 0, 4, 7 and 10 d post infection, and the infection rates and titers of DENV-2 in these tissues were detected by RT-PCR and RTqPCR, respectively. 【Results】 The resistance of Ae. albopictus to deltamethrin tended to be stable after selection for 9 generations. The LC50 value of deltamethrin against the 9th generation of this mosquito was 0.053 mg/L, the resistance ratio was 10.58, and the mortality rate of adults was 80%, showing that moderate resistance to deltamethrin was reached. DENV-2 was positive in all mosquitoes 0 d after infection and the virus titer in the resistant strain was higher than that in the susceptible strain. The infection rate in midguts of the susceptible and resistant strains by DENV-2 maintained between 92.75% and 97.18% at all the tested time points, without significant difference between both (P>0.05). The dissemination of DENV-2 in the ovaries started from 4 d. The infection rates in ovaries of the susceptible and resistant strains at 7 d and 10 d after infection by DENV-2 were significantly higher than those at 4 d (P<0.05). However, no significant difference existed between the two strains at the two time points of 7 and 10 d post infection (P>0.05). The average virus titer was higher in the resistant strain than in the susceptible strain at 4, 7 and 10 d post infection. The first positive detection of DENV-2 in salivary glands began at 7 d, and the infection rate showed no obvious increase at 10 d. Neither the infection rate nor the virus titer of salivary glands showed significant difference between the two strains (P>0.05). 【Conclusion】 The sequential administration of deltamethrin results in a gradual increase of the resistance level of Ae. albopictus larvae and adults. A laboratory strain of Ae. albopictus resistant to deltamethrin has been established. The susceptible and resistant strains infected with DENV-2 present similar infection rates but different virus titers, suggesting that the susceptibility of Ae. albopictus with moderate resistance to deltamethrin to dengue virus changes somewhat as compared to that of the susceptible strain.
JIA Zhi-Rong,LIU Zhuan-Zhuan,WANG Xiao-Ming et al. Screening of the deltamethrin-resistant strain of Aedes albopictus (Diptera: Culicidae) and its susceptibility to dengue virus[J]. ACTA ENTOMOLOGICA SINICA, 2018, 61(1): 11-17.