The Distribution and Composition of Vector Abundance in Hanoi City, Vietnam: Association with Livestock Keeping and Flavivirus Detection.

Lieu Thi Vu,Jiaxin Ling,Tung Duy Dao,Åke Lundkvist,Ulf Magnusson,Duoc Trong Vu,Long Pham-Thanh,Phong Vu Tran,Johanna Frida Lindahl,Vuong Nghia Bui,Thang Nguyen-Tien,Anh Ngoc Bui,Thuy Thi Hoang,Son Tran-Hai,Hung Nguyen-Viet

doi:10.3390/v13112291

Abstract

Background: Dengue virus and Japanese encephalitis virus are two common flaviviruses that are spread widely by Aedes and Culex mosquitoes. Livestock keeping is vital for cities; however, it can pose the risk of increasing the mosquito population. Our study explored how livestock keeping in and around a large city is associated with the presence of mosquitoes and the risk of them spreading flaviviruses. Methods: An entomological study was conducted in 6 districts with 233 households with livestock, and 280 households without livestock, in Hanoi city. BG-Sentinel traps and CDC light traps were used to collect mosquitoes close to animal farms and human habitats. Adult mosquitoes were counted, identified to species level, and grouped into 385 pools, which were screened for flaviviruses using a pan-flavivirus qPCR protocol and sequencing. Results: A total of 12,861 adult mosquitoes were collected at the 513 households, with 5 different genera collected, of which the Culex genus was the most abundant. Our study found that there was a positive association between livestock keeping and the size of the mosquito population—most predominantly between pig rearing and Culex species (p < 0.001). One pool of Cx. tritaeniorhynchus, collected in a peri-urban district, was found to be positive for Japanese encephalitis virus. Conclusions: The risk of flavivirus transmission in urban areas of Hanoi city due to the spread of Culex and Aedes mosquitoes could be facilitated by livestock keeping.

Highlights

The paired-end sequencing read 1 (R1) and read 2 (R2) were combined, and the reads were mapped to the database (NCBI non-redundant nucleotide and protein database)
The paired-end sequencing read 1 (R1) and were combined, and the reads were mapped to the database (NCBI non nucleotide and protein database)
Our study indicated that the district lived in, pig keeping, and preventive practices of people were associated with the abundance of mosquito populations—especially Culex mosquitoes

Summary

Introduction

Mosquitoes are considered the deadliest animal in the world, since they are vectors for many important human pathogens, causing a large number of human deaths per year. One group of such pathogens are viruses within the genus flavivirus (Flaviviridae family), and include some significant human pathogens such as dengue virus (DENV) and Japanese encephalitis virus (JEV), spread by the bites of mosquitoes in the genera Aedes and Culex [1,2]. JEV is transmitted by Culex species—primarily Cx. tritaeniorhynchus—and its transmission cycle involves water birds and pigs as maintenance and amplification hosts, respectively, while humans are dead-end hosts [3] This virus is the leading cause of viral encephalitis in Asia, estimated to cause nearly 68,000 cases and more than 13,000 deaths annually [4]. In complement to vector control, vaccination has contributed to decreasing the risk of infection in endemic areas and is part of routine immunization programs in several Asian countries [1], including Vietnam

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