The feline distemper virus is a “parvovirus.” Many people are familiar with this term as parvovirus infection is a very real concern for dogs, especially puppies. In fact, canine parvovirus is very closely related to the feline distemper virus and much of the information regarding canine parvovirus holds true for feline distemper. The feline distemper virus, however, is more difficult to remove from the environment and more lethal in its victims than its canine counterpart.
INFECTION AND DISEASE
An infected cat sheds large amounts of virus in all body secretions including feces, vomit, urine, saliva, and mucus. The virus persists long after evidence of the original body secretion has faded away. The virus enters the victim's body and proceeds to seek and infect rapidly dividing cells. The lymph nodes of the throat are first and from there, over the next 2-7 days, the virus rushes to the bone marrow and intestine.
In the bone marrow, the virus suppresses production of the entire white blood cell line, hence the term “panleukopenia” (literally, “all-white-shortage”). The white blood cells are the immune cells that are needed to fight the infection and without them the victim is completely vulnerable to the advance of the virus. In other words, the first order of the virus' business is to eliminate its host's defenses. From there it continues to the intestinal tract.
In the intestine, the virus infects the intestinal cells, causing ulceration leading to diarrhea and life-threatening dehydration as well as bacterial infection as the barrier between the body and intestinal bacteria is lost. The patient dies from either dehydration or secondary bacterial infection. The infection can be so rapidly overwhelming that death occurs before the vomiting and diarrhea even begins.
Because most cats are exposed to this virus to some extent, it is unusual for a kitten to have no immunity whatsoever. Further, the vaccine is so effective that even one dose can provide long lasting protection. As a result, infection is largely limited to unvaccinated younger animals kept in groups such as a colony of barn cats, feral cats or even a group of shelter cats. Viral numbers must be large enough to overwhelm partial immunity but once virus laden diarrhea begins to accumulate in the environment, necessary numbers are achievable. Mortality of the sick is typically considered 90%, though it has been said that a kitten that survives the first 5 days is likely to survive the infection.
Recovered kittens are considered contagious for six weeks following recovery.
DIAGNOSIS OF INFECTION
The infected cat can recover if he/she can be kept alive until his/her immune system recovers from the panleukopenia and can throw off the infection. This means that invading intestinal bacteria must be kept at bay with antibiotics and aggressive fluid therapy must control dehydration. Hospitalization is required as fluids and medications must be given intravenously. Blood sugar must be supported as well and control of pain, nausea and hypothermia is crucial. This is essentially the same therapy as for canine parvovirus infection, though the feline experience seems to be more lethal. There is little chance of survival without hospitalization.
If a cat is lucky enough to recover from this infection, generally no permanent damage is retained and the cat goes on with lifetime immunity.
There is no way to adequately disinfect the environment; any new cats being introduced should simply be vaccinated.
Vaccination after age 12 weeks is generally effective in generating immunity against this infection, though immunity gained from mother’s milk may inactivate the vaccine through age 14-16 weeks. Most vaccine protocols call for at least two doses of vaccine to be given 2-4 weeks apart with the last dose being received at or after age 14 weeks.
Vaccination is generally given every 1-3 years depending on the protocol of the animal hospital. Vaccination can be given in a nasal form or in an injection (either modified live or killed virus vaccine) given in the right front leg area. Killed virus vaccine has been associated with development of vaccination-associated fibrosarcoma (an aggressive cancer) in rare individuals. Research is continuing in this area; however, killed virus vaccine has largely been supplanted by modified live virus vaccine which is not felt to have this problem.
Page last updated: 3/11/2022