We saw our first case of feline distemper in many years at our clinic this week. Personally, I had previously never seen distemper in all of my 21 years of practice. Many people have heard of feline distemper only because the distemper vaccine is part of the regular recommended core vaccines for all cats. Some cat insurance companies, like Pets Best Insurance, even help pay for a portion of this vaccine with their wellness plans.
Because the vaccine is highly effective, most cat owners do not have experience with the disease or even hear much about the actual feline distemper infection. The 4-month-old kitten that we saw was from a group of strays being fed and cared for by one of our kind-hearted clients. Kittens are especially susceptible to feline distemper because their immune systems are underdeveloped, and, despite our best efforts, the kitten declined very rapidly and died within 24 hours.
Distemper, also known as feline panleukopenia virus, is caused by a parvovirus and is seen worldwide in cats. It is closely related to the canine parvovirus, but does not harm dogs. The virus is extremely stable in the environment, and it can survive indoors at room temperature for a year. It is resistant to many disinfectants, but, fortunately, a 10 minute soak in bleach (diluted 1 part bleach in 32 parts water) exposure will kill it.
Feline distemper is spread through contact with an infected cat or an infected cat’s secretions such as feces, urine, vomit, or saliva. It can also be spread through contact with anything contaminated with an infected cat’s secretions including bedding, food and water dishes, and litter boxes. In addition, humans can infect a cat if their clothes or hands are contaminated with the fluids of an infected cat. Most free-roaming cats are exposed to the virus during their first year of life, so kittens can acquire immunity from their mothers, but the protection does not last long. Infection is largely limited to unvaccinated cats, usually kittens and young adults, living in groups. Barn cats and feral colonies, like the one that our kitten came from, are at high risk for outbreaks.
Symptoms typically show up within 10 days of infection. The first symptoms are usually a high fever and loss of appetite. The virus attacks the bone marrow which suppresses the production of white blood cells, hence the term “panleukopenia” (literally, “all-white-shortage”). White blood cells are immune cells needed to fight the infection, and without them the patient is completely vulnerable to the advance of the virus. In the intestine, the virus causes ulceration leading to diarrhea, life threatening dehydration and secondary bacterial infection.
A special syndrome occurs if infection happens during pregnancy. If the infection is in mid or early pregnancy, the kittens simply abort. If the kittens are fairly far along, the part of the brain called the cerebellum is involved resulting in cerebellar hypoplasia. The cerebellum controls unconscious balance and movement. Without a normal cerebellum, the kitten is born with marked intention tremors. Whenever the kitten focuses on purposeful movement like putting his head toward the food bowl to eat, the tremors are so much that normal movement is impossible. The head wobbles and shakes making eating and other activities difficult.
A diagnosis of distemper is based on compatible clinical signs and the presence of panleukopenia (very low white blood cell count). There are also special tests available that can be used in the clinic to show the presence of the virus in the feces.
Feline distemper requires aggressive treatment if the cat is to survive. There is little chance of survival without hospitalization. Treatment is through supportive care with antibiotics and aggressive fluid therapy to control dehydration. Other medications are added as necessary. If a cat is lucky enough to recover from infection, generally no permanent damage is retained and the cat goes on with lifetime immunity. Virus is shed for up to 6 weeks after recovery, so precautions still need to be taken to prevent spreading of the virus.
Vaccination is the most effective method of prevention. Excellent vaccines that provide solid, long-lasting immunity are available. I recommend starting vaccinations at 6-8 weeks of age with repeated doses every 3-4 weeks with the last dose given at or after age 16 weeks to avoid interference of immunity gained from the mother’s milk. The vaccine is repeated in one year and every 3 years thereafter.