Final answer:
The population of dogs and cats most susceptible to infectious diseases includes young animals, those with weakened immune systems, and animals in overcrowded or unsanitary environments. Additionally, certain breeds or species may be more prone to specific diseases.
Step-by-step explanation:
The population of dogs and cats that is most susceptible to infectious diseases varies depending on the specific disease. However, in general, young animals and those with weakened immune systems are more vulnerable. For example, puppies and kittens that haven't had a chance to develop a strong immune system are more susceptible to infections. Similarly, older animals or those with underlying health conditions may have compromised immune systems, making them more susceptible as well.
Furthermore, certain populations of dogs and cats may be more vulnerable due to their living conditions. Animals in crowded or unsanitary environments, such as shelters or puppy mills, are at a higher risk of infectious diseases due to the close proximity and potential for exposure to pathogens.
It's also worth noting that specific breeds or species may have genetic factors that make them more susceptible to certain diseases. For example, certain dog breeds may be more prone to respiratory infections, while specific cat breeds may be more susceptible to viral diseases.