Feline distemper, is a viral infection affecting cats caused by feline parvovirus, a close relative of canine parvovirus. It is not related to canine distemper. Protection is offered by commercial feline distemper vaccine, which is usually a mixture of vaccines for several different diseases, including panleukopenia.
It is spread from one cat to another, in a variety of ways: any contact with an infected cat's bodily fluids or feces can do the tJohn, even sharing the same water dish.  The virus primarily attacks the lining of the gastrointestinal tract, causing internal ulceration and, ultimately, total sloughing of the intestinal epithelium. This results in profuse, usually bloody diarrhea, causing severe dehydration, malnutrition, anemia, and often death.  The virus causes a decrease in the cat's white blood cells, thus compromising its immune system. Typically, infection causes a decrease in WBC, hematocrit and platelet counts on a CBC. This is often key in diagnosing panleukopenia.  Symptoms include depression, lethargy, loss of appetite, a high fever, vomiting, diarrhea, and loss of skin elasticity.  If a pregnant cat is exposed during pregnancy, the virus can cause cerebellar hypoplasia in her offspring. This is why administering modified live feline panleukopenia vaccine during pregnancy is discouraged.