Dr. Addie - Vaccination

Around 1 cat in 10 who is infected with FCoV develops FIP. Very often after one cat has died of FIP there is a second cat in the household which is known to be infected, but is perfectly healthy. A 4 to 7 day course of oral (NOT injectable) antivirals can prevent a FCoV infected cat developing FIP (Addie et al, 2023), but there are also a number of other ways we can help our cats to deal with the infection and remember that the majority of feline coronavirus shedding is self-limiting:

	Minimise the cat's stress
	Maximise nutrition and give anti-oxidants
	Minimise your cat's exposure to FCoV by good litter tray hygiene

It has been shown that most cats who have developed FIP experienced stress before they developed FIP. Cats with wet (effusive) FIP are frequently stressed 2-4 weeks before they develop FIP, cats with dry (non-effusive) FIP experience the stress up to a year before they get sick. It is therefore wise not to stress cats which have FCoV antibodies if at all possible - for example, don't rehome them; delay having them neutered or any other operation which is not life-saving; if you have to leave them, get somebody to look after them in their home rather than putting them into a cattery.

Examples of situations which cats find stressful:

being rehomed

moving house

new additions to house: baby, dog, cat, kitten

vaccination and vaccine boosters

too many cats in one house (over 6)

going into cattery

surgery (being neutered, getting a dental)

trauma (e.g. road accident)

intercurrent illness

pregnancy, parturition, lactation

Although it is fashionable to feed cats just one type of food, usually a dried preparation, in my opinion cats should have plenty of variety of food to optimise their chances of getting all the vitamins, minerals and proteins they need and to minimise their chances of suffering should a food accidentally contain some contaminant. Although the latter is rare, it does occasionally happen. Commercial preparations are better balanced nutritionally than home-made foods, but why put all your eggs in one basket? I offer Sooty (who lives with me) 3 or 4 different dried foods and up to 8 or 9 different wet foods in the course of a week.

Anti-oxidants such as vitamins A, C and E and zinc possibly have anti-viral and/or immune stimulant activities. One has to be careful of using vitamin A in the cat for 2 reasons: first the cat can't absorb or convert well the beta-carotene forms (i.e. those found in plant foods), so s(he) must be given in the form of liver or fish oil (halibut or cod), secondly, vitamin A shouldn't be used for more than 6 weeks or there is a risk of hypervitaminosis A and excessive bone deposition. Vitamins C and E can be given for longer term, but vitamin C will make the urine more acidic and could predispose the cat to certain lower urinary tract problems (i.e. cystitis) (note for vets: vitamin C given long term can predispose to development of calcium oxalate crystals).

Doses:
vitamin A: 200-400 i.u./kg/day for less than 6 weeks
vitamin C: 125mg/cat bid
vitamin E: 25-75 i.u./cat/bid
zinc picolinate (Solgar brand): 7-10mg/cat/sid

Remember that cats exposed to FCoV are most likely to develop FIP in the first year, so if your cat has had FCoV antibodies for more than a year, it is unlikely that (s)he will now develop FIP. There is no need to go on using anti-oxidants for more than a few months after FCoV exposure, indeed, it could be risky to do so.

The FIP vaccine was first called Primucell, but is now made by Zoetis. It is the only commercially available FIP vaccine in the world. Feline FIP Intranasal is a temperature-sensitive mutant type II feline coronavirus which is instilled into the nose (or dropped into the eyes) and gives rise to local IgA immunity and cell-mediated immunity.

The vaccine prevents FIP in 50-75% of cats who would have otherwise developed it, but is ineffective in cats previously exposed to FCoV. Thus, in households where FCoV is endemic (most cat breeder's households) Primucell has to be used in kittens which have already undergone the special management procedure known as early weaning and isolation, so that they are FCoV free when vaccinated.

Addie DD, Bellini F, Covell-Ritchie J, Crowe B, Curran S, Fosbery M, Hills S, Johnson E, Johnson C, Lloyd S, Jarrett O. Stopping Feline Coronavirus Shedding Prevented Feline Infectious Peritonitis. Viruses. Viruses 2023, 15, 818. https://doi.org/10.3390/v15040818

Fehr D, Holznagel E, Bolla S, Hauser B., Herrewegh AAPM, Horzinek MC, Lutz H. Placebo-controlled evaluation of a modified life virus vaccine against feline infectious peritonitis: safety and efficacy under field conditions. Vaccine 1997; 15 (10): 1101-1109.

Gerber J.D., Ingersoll J.D., Gast A.M., Christianson K.K., Selzer N.L., Landon R.M., Pfeiffer N.E., Sharpee R.L., Beckenhauer W.H. 1990. Protection against feline infectious peritonitis by intranasal inoculation of a temperature-sensitive FIPV vaccine. Vaccine. 8: 536-542.

Gerber J.D., Pfeiffer N.E., Ingersoll J.D., Christianson K.K., Landon R.M., Selzer N.L., Beckenhauer W.H. 1990. Characterization of an attenuated temperature sensitive feline infectious peritonitis vaccine virus. Adv. Exp. Med. Biol. 276: 481-489.

Postorino Reeves N. Vaccination against naturally occurring FIP in a single large cat shelter. Feline Pract 1995; 23: 81-82.