International Journal of Molecular Veterinary Research, 2024, Vol.14, No.6, 244-253 http://animalscipublisher.com/index.php/ijmvr 248 4.3 Genetic bottlenecks and consequences for disease susceptibility The domestication of dogs has involved significant genetic bottlenecks and selective sweeps, which have increased the prevalence of deleterious genetic variants. These bottlenecks have led to a higher genetic load in domestic dogs compared to wild wolves, with dogs exhibiting 2-3% higher genetic load on average (Marsden et al., 2015). This increased genetic load is associated with a higher incidence of breed-specific diseases and reduced overall fitness. For example, the lack of protective alleles in the TLR5 gene in domestic dogs, which are present in some wild canids, suggests a higher predisposition to inflammatory diseases such as inflammatory bowel disease (IBD) (Henson et al., 2017). Additionally, the enrichment of copy number variations (CNVs) in genes related to immune response in domestic dogs further underscores the impact of domestication on disease susceptibility (Serres-Armero et al., 2017; Kessler et al., 2020). These genetic changes highlight the trade-offs associated with domestication, where artificial selection for specific traits has inadvertently increased the risk of certain diseases in domestic dogs. The immune system differences between wild wolves and domestic dogs are marked by significant genetic variations in both innate and adaptive immunity. Wild canids exhibit greater genetic diversity in immune-related genes, which likely contributes to their robust immune responses. In contrast, domestic dogs have experienced genetic bottlenecks and selective breeding, leading to reduced genetic diversity and increased susceptibility to certain diseases. These findings underscore the complex interplay between domestication, genetic variation, and disease resistance in canids. 5 Environmental and Behavioral Influences on Disease Resistance 5.1 Influence of habitat and lifestyle on disease exposure The habitat and lifestyle of canids significantly influence their exposure to diseases. Wild wolves, for instance, inhabit diverse and often harsh environments that expose them to a wide range of pathogens. This constant exposure can lead to a more robust immune system due to natural selection favoring individuals with better disease resistance. In contrast, domestic dogs often live in more controlled environments with less pathogen exposure, which can result in a less diverse immune response (Figure 3) (Marsden et al., 2015; Pilot et al., 2021). Domestication has also led to population bottlenecks and selective breeding, which have increased the genetic load of deleterious variants in domestic dogs compared to wild wolves. This increased genetic load can make domestic dogs more susceptible to certain diseases (Marsden et al., 2015). Additionally, the shift in diet and lifestyle during domestication has led to structural variations in the genome of domestic dogs, which are associated with changes in immune system function and disease susceptibility (Wang et al, 2018). 5.2 Interaction between behavior and immune responses Behavioral factors play a crucial role in the immune responses of canids. For example, the social structure and pack behavior of wild wolves can influence disease transmission and immune system development. Wolves living in packs may have a higher exposure to pathogens due to close contact with other pack members, which can lead to a more robust immune response (DeCandia et al., 2020). In domestic dogs, selective breeding for specific behaviors and traits has also impacted their immune responses. For instance, certain breeds have been found to have higher incidences of specific diseases due to the genetic bottlenecks and inbreeding associated with breed formation. Moreover, the interaction between behavior and immune response is evident in the case of inflammatory bowel disease (IBD) in canids. Studies have shown that domestic dogs have developed protective alleles against IBD, which are not present in wild canids like the red wolf and maned wolf, suggesting that these protective alleles may have developed post-domestication due to changes in behavior and lifestyle (Henson et al., 2017). In summary, the environmental and behavioral factors significantly influence disease resistance in canids. Wild wolves, with their diverse habitats and social behaviors, tend to have more robust immune systems compared to domestic dogs, which have undergone genetic changes due to domestication and selective breeding. These
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