How can a healthy cat appear sick?

Your cat suddenly starts to vomit, refuses to eat and looks like as though she's lost interest in life. Your stomach also knots up with with worry, because obviously your cat is unwell. But is she? Recent research suggests that sometimes a cat with all the above symptoms may actually be physically healthy. Vets call this 'sickness behaviour' and as the name says, itís when a cat that has nothing medically wrong acts as though stricken with illness.

Most cats don't like any changes to their life. Why should they, once they have you totally trained and the universe organized to their satisfaction? Once they have life properly sorted out, cats are happiest when every day is just like the one before. So changes in the environment or disruptions to an established routine can cause a lot of stress.

The cat's response is desperately trying to call for attention to the fact that her world has been re-arranged without her permission. Just as human children can vomit or lose their appetite when very excited or upset, some cats just don't take stress well.

The discovery of the sickness behaviour in cats was an unexpected spin-off from research on cats with IC. (This is interstitial cystitis; an infection of the bladder which results in pain and an urgent need to urinate. There is no successful treatment at present).

Judi Stella, a doctorate student in veterinary preventive medicine at Ohio State University was the main caretaker of a colony of IC cats and the healthy control animals. Judi knew that to be happy, cats kept exclusively indoors need an environment rich in stimuli. She spent months making sure that the cats under her care had lots of play time and regular meals. Litter trays were cleaned when it would cause the least inconvenience. In summary, Judi made sure that the cats were comfortable and under minimal stress.

After a while she noticed that the IC cats looked healthier, their coats were shiny, and their eyes clear. They stopped vomiting and - most unexpectedly - the cats stopped urinating outside their litter trays. In fact, although these cats still suffered from IC, they were clearly healthier.

The researchers started to wonder if at least some of the clinical signs of illness were more to do with the environment than the illness itself. Observations over another 77 weeks showed that under regulated conditions, clinical signs of illness in the IC cats were reduced by 75%. Judi started keeping detailed records of changes in behaviour following changes to the environment of her cats. For example, when she went on holiday and someone else took charge of the colonies, her data showed that sickness behaviour clearly increased. But perhaps the most surprising discovery was that not only the IC cats showed sickness behaviour under stress, but also - and equally often - the cats in the healthy colony did as well.

The three most common sickness behaviors (vomiting, missing the litter tray and refusing to eat) accounted for 88 percent of all sickness behavior in healthy cats and 78 percent in IC cats. All these sickness behaviours are frequently seen in places like zoos, boarding kennels and animal shelters - places where cats are often very stressed or in an unfamiliar environment.

So if your cat appears to be sick but the vet canít find anything wrong, consider the possibility of sickness behaviour. Is your cat feeling ignored, or is something different that is causing stress? Sometimes small changes such as regular play time, regular meals, or the introduction of few new toys may be enough to turn a 'sick' cat into a healthy, happy one.


Judi L. Stella, Linda K. Lord, C. A. Tony Buffington. Sickness behaviors in response to unusual external events in healthy cats and cats with feline interstitial cystitis. Journal of the American Veterinary Medical Association, 2011; 238(1): pp 67-73.

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