False Positive Distemper in Cats

Feline distemper is caused by a form of parvovirus, a very hardy virus that can last a year or more when shed by an infected kitty into the environment through bodily fluids, according to WebMD. It's highly contagious among cats who haven't been vaccinated against it, common in feral and outdoor furry felines who may encounter an infected kitty or their feces. The disease attacks a kitty's white blood cells and causes symptoms including vomiting, diarrhea, decreased appetite, fever and severe abdominal pain. Although this condition is potentially fatal, if a kitty does survive it he'll develop antibodies to the disease and won't become reinfected later in life. This works much like a vaccination would for your furry friend, although a vaccination won't actually cause the illness or its symptoms.

If your kitty is exhibiting symptoms of feline distemper, your vet may administer a common SNAP Fecal ELISA test, according to Veterinary Partner. This diagnostic test quickly detects the presence of the virus in your furry friend's stool and is generally considered accurate, although it is labeled for use only in dogs. If your kitty has received a vaccine 5 to 12 days prior to this type of test, it can result in a false positive result because of the virus contained in the vaccine itself, according to the Mar Vista Animal Medical Center. In this case, if an incorrect result is suspected, there are several other tests available, including those to measure the amount of antibodies in the blood and a test to isolate the virus in the blood plasma. These tests may help rule out a false positive result.

In addition to a SNAP Fecal ELISA test, your kitty's blood can be tested by your vet for a white blood cell count, which is typically lower in those with distemper. The polymerase chain reaction test may also be administered, which detects the DNA of the virus itself in either a blood or fecal sample. It can detect the disease in a earlier stage than an antibody test, allowing for proper treatment much sooner, VetInfo says. While the chance of a false positive is lessened by the use of this test, the possibility still exists that it could occur. In fact, residual DNA from a virus in a kitty that has recovered from such an infection could result in false positive result, according to the Cat Group. Contamination of the sample can also result in a false positive.

While a false positive result is possible with many of the tests available to test for the feline distemper virus, a combination of tests can be used to rule out such a result. This, along with a physical exam to check for symptoms and signs of the disease, can help to determine if a kitty is suffering from it. A recently vaccinated kitty who isn't exhibiting symptoms should be only be tested more than 12 days after the vaccination to prevent a vaccine-induced false positive. Those with some symptoms should be isolated and re-checked within one week of the original test, recommends Felinexpress. With proper vaccination of a kitten, starting at 8 to 12 weeks of age, your furry friend likely won't have to worry about becoming infected or having to be tested for feline distemper during his lifetime.