The distemper shot for cats is a vaccine that protects against feline panleukopenia, also known as feline distemper. Feline panleukopenia is a highly contagious and life-threatening viral disease caused by the feline parvovirus. Cats can become infected with feline panleukopenia by coming into contact with blood, urine, stool, or fleas from another infected cat. Kittens can also be infected in utero or via breast milk when feeding from their mother. The virus is resistant to many disinfectants and can live in the environment for months or years. Symptoms of feline panleukopenia include depression, lethargy, loss of appetite, high fever, vomiting, severe diarrhea, nasal discharge, or dehydration. The vaccine for feline panleukopenia is included in the standard combination vaccine given to all kittens, known as the FVRCP vaccine. The vaccine is highly effective in preventing feline panleukopenia infections in cats if used and boostered properly. The American Association of Feline Practitioners considers the distemper vaccine a core or necessary vaccine for all cats. It is recommended that cats receive initial primary courses of vaccination against feline panleukopenia as kittens, followed by yearly boosters.