International Journal of Molecular Zoology 2024, Vol.14, No.4, 233-243 http://animalscipublisher.com/index.php/ijmz 236 3.3 Environmental stressors and immunosuppression Environmental stressors, such as food limitation, pollution, and habitat loss, can lead to immunosuppression in wildlife, increasing their susceptibility to infections. Food stress, for instance, has been shown to elevate virus titres and prolong infectious periods in hosts, thereby enhancing transmission dynamics (Figure 2) (Owen et al., 2021). Similarly, pollution and other abiotic stressors can decrease host survivorship and increase pathogen intensity, further complicating disease management efforts (Vicente-Santos et al., 2023). The physiological stress response induced by these environmental factors can compromise immune function, making wildlife more vulnerable to diseases and potentially exacerbating the impact of emerging infectious diseases on species at risk of extinction (Hing et al., 2016). Understanding the interplay between stressors and disease dynamics is critical for predicting and mitigating zoonotic disease outbreaks (Norte et al., 2021). Figure 2 (a) WNV titres (log PFU/0.1 ml blood) for experimentally infected American robins fed normally (red circles; n=11) and robins food-deprived for 48 h prior to inoculation (green down triangles; n=10). (b) Average (±1 s.e.) virus titre per log PFU/0.1 ml blood for normal (red circles) and food-restricted (green down triangles) robins. Virus titres below 0.7 log pfu/0.1 ml are undetectable (grey squares) via Vero cell plaque assay. (c) Mean (±1 s.d.) infectious (i.e. capable of infecting a biting mosquito) index for the two groups (Adopted from Owen et al., 2021) The study of Owen et al. (2021) illustrates the effect of food restriction on West Nile virus (WNV) infection in American robins. It shows that robins subjected to a 48-hour food deprivation prior to inoculation had higher WNV titres in their blood compared to those fed normally. This suggests that food restriction might increase the susceptibility or enhance the replication of the virus in these birds, making them more infectious. The data underscores the importance of nutritional status in modulating host-pathogen interactions, potentially affecting the spread of vector-borne diseases like WNV. By integrating insights from various studies, it becomes evident that environmental factors, including habitat quality, climate change, and stressors, play a pivotal role in shaping the susceptibility and resistance of wildlife to infections. Addressing these factors through conservation and management strategies is essential for mitigating disease risks and preserving biodiversity.
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