Feline Panleukopaenia or Feline Parvo is a uncommon disease that is  highly contagious and has a very high mortality(100%) in untreated cats.  Even in treated animals mortalitity rates can be as high as 85%.
    

It is a completely preventable disease.  Vaccinate your cat with a Feline 3 vaccine at minimum to ensure protection year around.  

Please use the links below to get more information of Feline Panleukopaenia

1. Wikipedia

2. PetMD

3. AVAMA - American Veterinary Medical Assoc