Dengue epidemiology and molecular characterization of vector mosquitoes; Aedes aegypti and Aedes albopictus in Mizoram, Northeast India

Background Dengue is the most important arboviral disease, and Aedes aegypti and Aedes albopictus are the major vectors. It is one of the most recent emerging diseases in Mizoram state with a fast-growing burden over the years. The present study aimed to explore the epidemiological patterns of dengue in Mizoram, and to identify vector mosquito species. Methods In the present study, two years secondary data of dengue disease in Mizoram was studied. Dengue vector mosquitoes and dengue virus serotypes circulating in vector mosquitoes in Aizawl City were identified by sequence analysis of COX1 and C-prM genes respectively. Results In Mizoram State, the annual case prevalence of dengue was found to be 300.45 per 100,000 persons. Seasonality of the disease was also noted, with the peak season occurring from July to December. There is a significant positive relationship between age and the disease prevalence (p < 0.05, r = 0.909). DENV was detected in 10 pools of Ae. aegypti with a minimum infection rate (MIR) of 18.05, and 8 pools of Ae. albopictus with a minimum infection rate of 16.03. The viral isolates were found to correspond to serotypes 2 (DENV2) and 3 (DENV3). A total of 6 pools of Aedes aegypti and 4 pools of Aedes albopictus tested positive with DENV2 serotype, while 4 pools of Aedes aegypti and 3 pools of Aedes albopictus tested positive with DENV3 serotype. DENV2 serotype was more common, and multiple serotypes (DENV2 and DENV3) were also detected in two pools from one locality. Conclusions There is an increasing trend in dengue infection in Mizoram, and seasonality of the disease was observed with the peak season during July to December. The higher incidence rate among the adults indicated that outdoor activities may be related to the high risk of the infection. However, lack of immunity among the older people may also be a possible reason of higher disease incidence rather than the activity pattern. Early identification and frequent monitoring of infected vector mosquitoes will yield an early warning indicator for forecasting dengue epidemics in the future.