What is a pathogen, and how does it cause disease?
Innate immunity protects the host in the early stages of infection, but many pathogens have evolved measures to prevent elimination and prolong survival. Furthermore, the animal’s immune response can be weakened by environmental factors, increasing the risk of infection.
The nature of an infection can vary significantly depending on the causative pathogen and its location in the host. A number of infectious agents cause diseases with significant impact for livestock.
Adaptive immunity, once established, provides a more robust defense against such pathogens compared with innate immunity.