Which sign is commonly associated with listeriosis?

Listeriosis is a serious infection caused by the bacterium Listeria monocytogenes, which can affect various species, including animals and humans. One of the significant effects of listeriosis, particularly in pregnant animals or those in the reproductive phase, is the potential for abortion. This occurs due to the bacteria's ability to cross the placental barrier, leading to severe complications for the fetus. The presence of blood-tinged vaginal discharge during an abortion indicates an infection or complication related to listeriosis, making it a critical sign to identify.

In contrast, the other options do not align with the primary symptoms or consequences associated with listeriosis. Skin infections with discoloration or fur loss focus on local infections or superficial issues that are not characteristic of listeriosis. Symptoms like diarrhea and rapid death are more indicative of other diseases or infections, while the loss of fur around the eye does not correlate with the systemic effects of listeriosis, which primarily affects pregnant females leading to abortion. Thus, the connection between listeriosis and abortion with blood-tinged vaginal discharge is the clear indicator of the disease in this context.