Feline infectious peritonitis (F.I.P.) is a disease caused by a virus called coronavirus. The F.I.P. disease entity is only one variation of what can happen when a cat comes across the coronavirus for the first time. FIP is transmitted by the faeco-oral route – therefore during sharing of litter trays and food bowls, mutual grooming and close contact.

The possibilities after infection are listed below:

Virus enters blood – cat’s immune system attacks virus and destroys it, normally after a bout of diarrhoea (very approximately 80-90%). These cats may not be immune to further insult with coronavirus Virus enters blood – cat’s immune system prevents further internal injury but the cat becomes a intermittent, persistent shedder of the virus, completely asymptomatic, but dangerous to other cats which have not met the virus before (5-10% again very approximately). Virus enters blood – cat’s immune system is not strong enough to neutralize the virus and the virus – the disease starts. (5-10% of cases)

Diagnosis is complicated.

This can involve assessment of feline coronavirus titre, the serum albumin:globulin ratio, the AGP acute phase protein level, full haematology, cytology of effusions; histopathology of biopsy samples in addition to the clinical signs.

The disease is characterised by two forms, again dependent on the state of the cat’s immune system:

‘WET’ form – poor immune response, virus runs riot, immune system attacks virus in blood vessels all around the body, and the resultant damage causes the blood vessels to leak fluid into blood cavities – abdomen and thorax, poor prognosis, severe malaise and normally fatal.

‘DRY’ form – better immune response means less prolific and immediate damage – virus can localize anywhere causing damage wherever it is. Typical signs are sore cloudy looking eyes, weight loss, persistent intermittent high temperature, liver damage, kidney damage, neurological signs (fitting/ blindness), and/or anaemia. This form is usually fatal also, but continues over a much longer period of time. There are treatment protocols for this form, which should be considered at best palliative.

An expensive drug, feline interferon omega (Virbagen Omega) can help (not cure) around 25-33% of cats. There is not yet available a vaccine for FIP in the NZ, though one is in use in the USA.