This highly infectious and almost fatal disease is caused by a group of viruses known as retro viruses. Although the virus may be present in the blood, faeces, mucus and saliva of cats, it is mainly spread through saliva.
Symptoms include chronic weight loss, fever, vomiting, diarrhoea, difficulty in breathing etc but these may occur only after months and years after infection. Most commonly the only visible symptom after infection will be slight listlessness which may very well go unnoticed.
There is preventive vaccination for the disease, but once infected, the vaccination is of no use and there is no drugs available for treatment. Isolation is needed for preventing the spread of the disease to other cats.
Feline enteritis
This virus causing Feline enteritis or Panleukopaenia can damage a number of tissues including intestines and bone marrow and can survive outside a cats body for up to one year.
Symptoms include diarrohea ( sometimes bloody), vomiting, high fever, pain if touched etc.
There is a vaccination against the disease for kittens. The highly contagious disease which strikes quickly and even lead to death but those cats which survive get lifelong immunity.