Final answer:
Host factors that influence susceptibility to cold weather injuries include preexisting conditions, environmental factors like secondhand smoke, genetic immune factors, and stress levels. Ectoparasite survival and the abiotic environment, such as severity of the winter, also play a role in host susceptibility to cold weather injuries.
Step-by-step explanation:
There are several host (individual) factors that influence susceptibility to cold weather injuries. Preexisting conditions and environmental factors play a significant role in determining an individual's vulnerability. For instance, exposure to secondhand smoke can weaken immune defenses, and certain genetic factors may determine the effectiveness of an individual's immune response to pathogens. Stress has also been shown to increase susceptibility to infections like the common cold, potentially due to the adverse effects it has on the immune system.
Additionally, the interactions between a host's life-history traits and the external environment can affect the probability of ectoparasite survival and transmission, which in turn influences the likelihood of cold weather injuries. For example, in colder climates, a prolonged developmental period due to low temperatures may reduce the chances of ectoparasites encountering a host, resulting in a decreased risk of infection for the host.
Ectoparasites' ability to survive and spread is highly dependent on the abiotic environmental conditions, such as severity of the winter, which affects their off-host survival rates, and in turn, affects the host's risk of infection or infestation. Hosts living in areas with harsh frosts are also at a higher risk for injuries related to extreme cold weather conditions, which can affect their overall health and vulnerability to infections.