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

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.

Diversity and larval habitats of mosquitoes (Diptera: Culicidae) in urban areas in Ha Noi, Vietnam

“…Knowledge of larval habitat characteristics in an area and its impacts on mosquito diversity, abundance, and distribution is critical for developing integrated vector control strategies and mitigating future outbreaks of mosquito-borne diseases. The current study has reported a higher number of mosquito species than previous studies in Ha Noi (Pham, 2015;Nguyen et al, 2021). Moreover, it is worth noting that there were five new records for urban areas of Ha Noi city including An.…”

“…Particularly, a study investigated insect fauna in residential areas in Ha Noi has reported only a few mosquito species, including Culex quinquefasciatus, Culex tritaenyorhynchus, Aedes aegypti, Aedes albopictus, and Anopheles sinensis (Pham, 2015). The study by Nguyen et al (2021) aimed to assess the effects of livestock on the abundance of mosquitoes in urban households in Ha Noi has reported 10 species including Ae. aegypti, Ae.…”

Envisioning urban environments resilient to vector-borne diseases: a protocol to study dengue in Vietnam

“…The etiological agent of one of the most problematic mosquito-borne diseases of humans, dengue virus (DENV) causes around 100 million symptomatic cases each year worldwide, approximately 70% of which occur in Asia [11]. In 2013, the global economic burden of dengue was estimated at US $8.9 billion [12], a figure which will have grown considerably in the intervening decade. In tropical and subtropical countries, dengue is increasingly prevalent in cities and suburbs [11,13], compared to rural areas, as the predominant Aedes aegypti (Ae.…”

Study on the temporal and spatial distribution of Culex mosquitoes in Hanoi, Vietnam

“…Mosquitoes are key players in the spread of vector-borne diseases, such as Japanese encephalitis and West Nile fever, representing a significant global health concern. Vector-borne viruses collectively account for close to 700,000 deaths each year and are rapidly emerging as prominent threats to local populations 1 , 2 . Factors that may change vector dynamics and can alter vector abundance, such as urbanization, changes in land-use, deforestation, and climate change contribute to the escalating prevalence of mosquito-borne illness worldwide 3 .Understandng the abundance and dynamics of mosquito vectors is crucial for assessing the risks of arboviral diseases and anticipating future outbreaks 4 – 6 , and to enable timely implementation of control measures to mitigate the risk of human infection 4 .…”

“…Mosquito-borne diseases are highly prevalent in South-East Asia, including Vietnam 3 , and Japanese Encephalitis virus (JEV), dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) are examples of viruses endemic in Vietnam 2 , 3 .JEV is a highly pathogenic mosquito-borne flavivirus, that causes encephalitis in humans and horses in tropical and temperate regions of Asia 7 , 8 . Pigs act as amplifying hosts and can be affected by the virus, mainly resulting in abortions and neonatal deaths 7 , 8 .…”