In what circumstance can animals be more susceptible to infections?

Animals can be more susceptible to infections when they are closely kept with other animals due to the increased potential for disease transmission. When animals are in close proximity to one another, they are more likely to share pathogens, whether through direct contact, respiratory droplets, or contact with contaminated surfaces. This situation can lead to higher exposure rates to infectious agents, as well as stress-related factors that may weaken their immune systems, making them more vulnerable to diseases.

In contrast, while aging, individual housing, or being stray can also contribute to susceptibility in different ways, the direct contact and interaction found when animals are closely kept together actively facilitate the spread of infections. Thus, this environment poses a significant risk for outbreaks of illnesses within groups of animals.