Journal of Mosquito Research 2024, Vol.14, No.3, 135-146 http://emtoscipublisher.com/index.php/jmr 139 production of antimicrobial peptides (AMPs) and the activation of signaling pathways such as the Toll, IMD, and JAK-STAT pathways, which regulate the expression of immune-related genes (Baxter et al., 2017; Pan et al., 2017; Wang et al., 2022). These mechanisms are crucial for limiting pathogen proliferation and ensuring the mosquito's survival. 4.2 Antimicrobial peptides and their role Antimicrobial peptides (AMPs) are a key component of the mosquito's humoral immune response. These small, potent molecules are produced in response to pathogen invasion and can directly kill bacteria, fungi, and even some viruses. In Anopheles gambiae, for example, the production of AMPs such as defensin and cecropin is upregulated following infection with bacteria or malaria parasites (Kumar et al., 2018; Yu et al., 2022; Mahanta et al., 2023). The expression of these peptides is tightly regulated by the Toll and IMD pathways, which are activated upon recognition of pathogen-associated molecular patterns (PAMPs) (Baxter et al., 2017; Pan et al., 2017). AMPs play a critical role in controlling infections and preventing the establishment of pathogens within the mosquito host. 4.3 Immune modulation by pathogens Pathogens have evolved various strategies to evade or modulate the mosquito immune response. For instance, the fungus Beauveria bassiana can inhibit the mosquito's antifungal immune response by producing a deubiquitinase, OTU7B, which prevents the activation of the Toll pathway by removing polyubiquitin chains from the adaptor protein TRAF4 (Wang et al., 2022). Similarly, the bacteriumWolbachia can manipulate the mosquito's immune system to establish a symbiotic relationship, enhancing the mosquito's resistance to other pathogens such as dengue and Zika viruses (Pan et al., 2017). These interactions highlight the dynamic co-evolution between mosquitoes and their pathogens, where both parties continuously adapt to each other's strategies. 5 Transmission Dynamics of Pathogens 5.1 Pathogen dissemination within mosquito The dissemination of pathogens within mosquito vectors is a multifaceted process influenced by various biological and environmental factors. Upon ingestion of an infectious blood meal, pathogens such as viruses and parasites must navigate through several barriers within the mosquito to establish infection. For instance, the mosquito's immune response and the genetic interplay between the mosquito and the pathogen play crucial roles in determining the success of pathogen dissemination (Kramer and Ciota, 2015). The microbiota within the mosquito gut also significantly impacts the infection process, either by enhancing or inhibiting pathogen development (Mitchell and Catteruccia, 2017; Romoli and Gendrin, 2018). Studies have shown that the efficiency of pathogen dissemination can vary greatly depending on the mosquito species and the specific pathogen involved, highlighting the complexity of these interactions (Simões et al., 2018). 5.2 Factors influencing transmission efficiency Transmission efficiency of mosquito-borne pathogens is influenced by a combination of intrinsic and extrinsic factors. Intrinsic factors include the genetic makeup of both the mosquito vector and the pathogen, vector competence, and the mosquito's life-history traits such as survival and reproductive success (Ciota and Kramer, 2013; Thongsripong et al., 2017). Extrinsic factors encompass environmental conditions like temperature, rainfall, and habitat type, which can affect mosquito biology and pathogen activity (Thongsripong et al., 2017). The microbiota associated with mosquitoes also plays a pivotal role in modulating transmission efficiency by affecting mosquito immunity and pathogen development (Gabrieli et al., 2021). Additionally, larval environmental conditions have been shown to impact adult mosquito traits, thereby influencing their vectorial capacity and transmission potential (Moller-Jacobs et al., 2014). 5.3 Impact on vectorial capacity Vectorial capacity is a measure of the potential of mosquito populations to transmit pathogens and is determined by several factors including mosquito survival, population density, feeding behavior, and vector competence (Kramer and Ciota, 2015; Thongsripong et al., 2017). The reproductive biology of mosquitoes, particularly the
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