Final answer:
A larger number of prey animals can lead to denser populations that facilitate the spread of pathogens, disrupting normal host-parasite relationships and possibly increasing pathogen loads. This change can be exacerbated by the loss of large predators, leading to possible pandemics and population collapses.
Step-by-step explanation:
A larger number of prey animals in an ecosystem can contribute to a changed pathogen load in several ways. First, an increased prey population can lead to more dense and crowded conditions, which greatly facilitate the transmission of parasites and pathogenic microbes among individuals. This proximity can disrupt the typical host-parasite relationships and can result in a higher incidence of infections within the population. In addition, the principle of epidemiology suggests that when animal populations exceed the numbers found in their evolutionary environment, disturbances in host-parasite relationships are likely. For example, parasites might encounter bottlenecks in their genetic variation, or they might thrive due to the abundance of hosts, potentially leading to greater virulence or resistance to the host's immune responses. A larger prey base could also attract more predators, potentially increasing the spread of pathogens if those predators are carriers. The significant loss of big predators, as has been observed in recent centuries, can lead to increased pathogen loads and thus pandemics and population collapses among prey species. These effects highlight the complex interaction between prey density, predator populations, and pathogen dynamics within ecosystems.