Name a common disease that affects horses.

Equine Influenza is a highly contagious viral infection that primarily affects horses, leading to respiratory illness. It is caused by the influenza virus, specifically Type A viruses, and is characterized by symptoms such as fever, cough, nasal discharge, and decreased appetite. Vaccination plays a crucial role in preventing the spread of this disease among horse populations, especially in settings where horses are in close contact, such as shows or competitions.

The other listed diseases do not primarily affect horses. Canine Distemper is a disease affecting dogs, Feline Leukemia impacts cats, and Equine Encephalitis, while related to horses, is less common and refers to inflammatory diseases caused by viruses like Eastern, Western, or Venezualan Encephalitis. Therefore, Equine Influenza is the most recognized and prevalent disease impacting horse health directly.