Ringworm is a skin infection caused by a dermatophyte (skin 'loving') fungus of which there are several different species. The fungi that cause ringworm in horses include the Microsporum and Trichophyton species, that can infect not only horses but other animal species, including humans.
Tetanus is a bacterial disease that can affect most animals and humans. Horses are particularly susceptible because of their environment and tendency to suffer injuries.
West Nile Fever is a disease caused by a virus (WNV) carried by mosquitoes. It causes encephalitis (inflammation of the brain and spinal cord) that can affect humans and other animals as well as horses.