Which of the following is true regarding listeriosis in animals?

Listeriosis is primarily associated with ruminants, particularly sheep and cattle. This bacterial infection is caused by Listeria monocytogenes, which can be present in various environments, often related to silage and feed that has become contaminated. Ruminants are particularly susceptible to the disease, leading to neurological issues, reproductive failures, and mastitis among other problems.

The other options do not accurately reflect the nature of listeriosis. While contaminated water can be a transmission route, it is not the only means by which animals can contract the infection; contamination can also occur through feed or the environment. Listeriosis is indeed zoonotic, meaning it can be transmitted from animals to humans, typically through the consumption of contaminated food products. Additionally, there are no effective vaccines available for listeriosis in animals, primarily focusing on preventative measures like proper feed management and hygiene in animal husbandry practices. Therefore, the assertion that it is primarily a concern for ruminants is the most accurate representation of how this disease impacts animal populations.