Which of the following is an example of a zoonotic disease?

Rabies is a well-known example of a zoonotic disease, which refers to diseases that can be transmitted from animals to humans. Rabies is caused by a virus that is typically spread through the saliva of an infected animal via bites. It poses a significant risk not only to domestic animals like dogs and cats but also to wildlife, and it can lead to severe neurological symptoms in humans if left untreated after exposure.

In contrast, the other diseases listed (Feline Leukemia, Canine Parvovirus, and Heartworm Disease) are primarily specific to cats and dogs and do not transmit to humans. Feline Leukemia is a viral disease affecting cats; Canine Parvovirus is a highly contagious virus that causes gastrointestinal illness in dogs; while Heartworm Disease, caused by parasitic worms transmitted through mosquito bites, primarily affects dogs and some other canids, but not humans. Thus, rabies stands out distinctly as the only zoonotic disease among the options provided.