Journal of Mosquito Research, 2024, Vol.14, No.5, 247-255 http://emtoscipublisher.com/index.php/jmr 249 3 Environmental Factors Affecting Transmission 3.1 Climate and weather patterns (temperature, rainfall, humidity) Climate and weather patterns significantly influence the transmission dynamics of Japanese Encephalitis (JE). Temperature, rainfall, and humidity are critical factors that affect the development and survival of mosquito vectors, as well as the replication of the JE virus. Studies have shown that JE incidence is positively associated with higher temperatures and increased rainfall. For instance, a study in Southwestern China found that JE cases increased with daily average temperatures above 20°C and with higher daily rainfall, with a 25-day and 30-day lag, respectively. Similarly, research in Eastern Uttar Pradesh, India, indicated that increases in mean temperature, minimum temperature, rainfall, and relative humidity were associated with higher JE admissions and mortality. These findings underscore the importance of considering meteorological factors in JE prevention and control strategies, particularly in warm and rainy conditions (Yi et al., 2019; Liu et al., 2020; Singh et al., 2020). 3.2 Landscape and land use changes (agricultural practices, urbanization) Landscape and land use changes, including agricultural practices and urbanization, play a crucial role in JE transmission. The presence of wetlands, rain-fed agriculture, and the density of domestic pigs and chickens are significant risk factors for JE outbreaks. A study in India highlighted that JE outbreak risk was strongly associated with landscapes that support wild ardeid birds and domestic pigs, particularly in fragmented rain-fed agricultural areas and wetlands. Additionally, urbanization has been found to inversely correlate with JE incidence, suggesting that rural areas with extensive agricultural activities are more prone to JE outbreaks. These findings emphasize the need for targeted public health interventions in high-risk landscapes to mitigate JE transmission (Zhang et al., 2018; Walsh et al., 2022). 3.3 Water bodies and irrigation practices Water bodies and irrigation practices are critical environmental factors influencing JE transmission. Mosquito vectors, particularly Culex species, thrive in water-rich environments, which provide breeding grounds for their larvae. The presence of paddy fields, irrigated lands, and other water bodies has been identified as a significant risk factor for JE occurrence. Research in China demonstrated that JE cases were concentrated in areas with broad-leaved evergreen forests, shrubs, paddy fields, and irrigated lands, highlighting the role of these environments in supporting mosquito populations. Effective management of water bodies and irrigation practices is essential to reduce mosquito breeding sites and control JE transmission (Huang et al., 2018). 3.4 Seasonality and mosquito population dynamics Seasonality and mosquito population dynamics are pivotal in the epidemiology of JE. The seasonal distribution of JE cases is closely linked to the population dynamics of mosquito vectors, which are influenced by climatic conditions. Studies have shown that JE incidence peaks during the monsoon season when temperature, rainfall, and humidity are optimal for mosquito breeding and virus transmission. For example, in Gorakhpur, India, temperature was significantly associated with JE during pre-monsoon and post-monsoon periods, while rainfall, relative humidity, solar radiation, and wind speed were associated with JE during the monsoon season (Singh et al., 2020). Additionally, the density of mosquito populations in livestock sheds has been found to affect JE outbreak risk, further illustrating the importance of understanding mosquito population dynamics in relation to seasonal changes (Tu et al., 2021). These insights are crucial for developing timely and effective JE control measures. 4 Ecological Factors Influencing JE Transmission 4.1 Host-vector interactions (humans, animals, and mosquitoes) Japanese Encephalitis Virus (JEV) transmission is heavily influenced by interactions between hosts and vectors. The primary vectors of JEV are mosquitoes, particularly those in the Culex genus, such as Culex tritaeniorhynchus and Culex annulirostris, which are known for their high vector competence and capacity (Auerswald et al., 2021; Eynde et al., 2022). These mosquitoes feed on both pigs and birds, which are key amplifying hosts, thereby facilitating the virus's zoonotic cycle (Oliveira et al., 2018; Pearce et al., 2018; Hurk et al., 2022). Human infections occur when these mosquitoes feed on humans, who are considered dead-end hosts as they do not contribute to further transmission of the virus (Mulvey et al., 2021).
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