What is a reason that older animals might not be suitable as sentinels?

Choosing older animals as sentinels may lead to issues because they often develop nonspecific antibodies. As animals age, their immune responses can change, resulting in the production of antibodies that do not specifically target the pathogens of interest. This can complicate the interpretation of serological tests used to monitor the health status of a population, as it may be difficult to determine whether the presence of these antibodies is due to previous exposure to the disease being studied or from stimuli unrelated to the specific pathogens of concern.

Sentinels are typically younger animals that have not yet been exposed to a broad range of antigens, thus providing clearer data regarding disease presence within a given cohort. In contrast, older animals, with their more complex and sometimes varied immune histories, may not provide reliable information in sentinel studies.