There are some diseases that only spread in horses and do not infect humans or other creatures, but they can cause serious health problems or even death to horses. These diseases are often called "horse infectious diseases" or "horse plague". 1. Horse infectious leukemia: This is a disease caused by a pathogen called the " leukemia virus ". It usually spreads in horses but does not cause human infection. 2. Horse Encealment: This is a disease caused by a pathogen called the Encealment Virus. It usually spreads in horses and does not cause human infection. 3. Salmonella-like infection of horses: This is a disease caused by a pathogen called "salmonella-like bacteria" that usually spreads among horses and does not cause human infection. It is important to note that these diseases are usually transmitted in horses and have a serious impact on the health of horses. Therefore, when writing a novel or creating a novel, you can consider using these diseases to show the tension between horses and the interaction between humans and horses.