Which of the following diseases is known to be viral?

Rabies is correctly identified as a viral disease. It is caused by the rabies virus and primarily manifests in mammals, including humans. The disease is primarily transmitted through the saliva of infected animals, usually through bites or scratches. Rabies affects the central nervous system, leading to severe neurological symptoms and is almost invariably fatal once clinical signs appear.

In contrast, the other choices represent conditions caused by different agents. Tetanus is a bacterial infection caused by Clostridium tetani, which produces a potent neurotoxin. Coccidiosis is caused by protozoan parasites in the genus Eimeria, affecting the intestines of many animals, particularly in young livestock. Rocky Mountain Spotted Fever is a tick-borne illness caused by the bacterium Rickettsia rickettsii, leading to systemic illness and various symptoms such as fever and rash. Understanding the differences between these diseases is crucial for proper diagnosis and treatment in veterinary practice.