The most infectious and serious disease affecting cats is feline parvovirus. The disease occurs wherever there are large numbers of cats and is usually fatal in young animals.
The cause of the disease is a small virus, feline parvovirus (FPV), also known as feline panleukopenia virus, closely related to the virus that causes parvovirus infection in dogs.
The organism is capable of living for long periods outside the animal, which ensures that the virus is present to infect successive litters of kittens from year to year. In catteries and breeding establishments the virus is particularly hard to eliminate.
Infected cats excrete the virus in their saliva, vomitus, urine, and feces. Incubation is quite short – usually about a week from the time of contracting the virus to the appearance of the first signs of the disease.
The cat becomes very quiet, refuses all food, and usually remains hunched over a water bowl. Soon it begins to vomit a bright-yellow bile-stained fluid.
In very young cats, death may occur within only 24 to 36 hours of its first becoming sick. Older cats may have less-severe symptoms and may eventually recover, but not before losing a great deal of weight.
The virus attacks the outer layer of cells in the small bowel, quickly destroying the ability to absorb water and foods. The virus spreads throughout the body, affecting kidney cells and the blood-forming cells in the marrow. It is this property of the virus which makes feline distemper such a serious disease.
In most infectious diseases, the body responds to the infection by increasing the white blood cell component of the blood. These cells help to fight the infection and repair the cellular damage. But in feline distemper, such a response does not occur, and in fact, the number of white cells in the blood actually drops.
The infection of a pregnant cat can result in the birth of abnormal kittens. Infections of very young kittens can result in brain damage in those kittens which survive.
Treatment of such an acute virus disease is very difficult. Blood transfusions and fluid replacement may help kittens in the early stages of the disease, and antibiotics are given to limit secondary bacterial infection of the bowel following the initial viral damage.
Once the disease is well established and most of the bowel has been invaded by the virus, the prognosis is usually very grave.
Recovered cats continue to shed the virus for many weeks and should be kept completely isolated from any young unvaccinated cats.
Fortunately, the disease is preventable with the use of a vaccine. Before the development of an efficient vaccine, veterinarians typically had to deal with epidemics every second year as new groups of susceptible cats bred up from the survivors of the previous epidemic.
Since the widespread use of the vaccine, these epidemics are rare and occur only in isolated pockets where susceptible populations exist, such as on a rural property or small country towns.
Feral cats are probably responsible for the introduction of the virus in these isolated populations.
The modern vaccine is very effective and produces a strong immunity about 10 to 14 days after injection. A preliminary vaccination may be given at 8 weeks of age and repeated when the kitten is 12 to 14 weeks old.
Depending upon the type of vaccine used, re-vaccination is recommended a year later, then either annually or every second year. Feline distemper vaccine is very often given at the same time as the vaccine for feline influenza (cat flu).