Journal of Mosquito Research, 2024, Vol.14, No.5, 256-263 http://emtoscipublisher.com/index.php/jmr 258 face immune responses like the activation of the mosquito's RNA interference (RNAi) pathways and innate immunity. In Aedes aegypti, certain arboviruses can escape these defenses, allowing them to spread from the midgut to other tissues, including the salivary glands, which are essential for transmission to humans during a blood meal (Figure 1) (Alonso-Palomares et al., 2019). Furthermore, the mosquito microbiota also influences pathogen interactions by either enhancing or suppressing the replication of viruses and parasites (Bhowmik et al., 2023). Figure 1 Transmission of different arbovirus by mosquitoes (Adopted from Alonso-Palomares et al., 2019) 4.2 Barriers to pathogen transmission in mosquitoes Several anatomical and physiological barriers in mosquitoes prevent or reduce pathogen transmission. These include the midgut infection barrier, midgut escape barrier, and salivary gland infection barrier. For instance, some mosquito species, such as Culex tarsalis, exhibit a midgut escape barrier that prevents the virus from disseminating beyond the gut. The ability of a pathogen to overcome these barriers often dictates the mosquito’s vector competence. For arboviruses like chikungunya, selective pressures favor viruses with traits that enhance their ability to bypass these barriers, such as faster replication rates, which allow them to cross the midgut barrier and invade the salivary glands more efficiently (Merwaiss et al., 2020). 4.3 Factors influencing transmission efficiency Several factors influence the efficiency of pathogen transmission by mosquitoes, including environmental conditions, mosquito genetics, and pathogen characteristics. Temperature plays a crucial role in modulating the transmission of viruses like Zika, with cooler temperatures reducing the replication rate of the virus in the mosquito midgut, thus limiting transmission efficiency (Ferreira et al., 2020). The presence of specific microbiota in the mosquito gut can also affect transmission efficiency. For example, certain bacterial species enhance or inhibit the ability of pathogens like Plasmodium or dengue virus to establish infections within the mosquito (Heu and Gendrin, 2018). 5 Environmental and Genetic Factors Influencing Transmission 5.1 Impact of climate and environmental changes Climate and environmental changes significantly influence the distribution and transmission dynamics of mosquito-borne diseases. Factors such as rising temperatures and altered precipitation patterns can expand the geographical range of mosquito vectors, leading to increased risks of outbreaks in previously unaffected regions. For example, warming temperatures favor the survival and reproductive rates of mosquitoes like Aedes aegypti and Culex species, which transmit diseases such as dengue, Zika, and West Nile virus (Yeh et al., 2020; Couper et al., 2021). Climate variability, particularly extreme weather events, also influences mosquito breeding habitats, creating favorable conditions for pathogen transmission in new regions (Elbers et al., 2015).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==