New guidance on testing shelter cats for feline panleukopenia virus

Blue eyed cat resting

Thanks to a new study by the Toronto Humane Society, animal shelters may be less likely to misdiagnose panleukopenia in cats and kittens, resulting in saved lives.

Panleukopenia virus in cats is like parvovirus in dogs; it causes vomiting, diarrhea, and sometimes shock and death. In shelters, young kittens are the most vulnerable. The virus could easily spread through animal shelters if unchecked, so shelters routinely vaccinate cats against panleukopenia. They typically use a “live” vaccine, meaning it uses a weakened form of the virus.

If cats in a shelter exhibit symptoms of panleukopenia, the shelter tests them for the virus. If they test positive, their fate often depends on the shelter’s resources; shelters with sufficient resources isolate and treat them, while shelters without sufficient resources may euthanize them.

The problem is twofold: vomiting and diarrhea is common in shelters, and may be caused by something other than panleukopenia, such as stress and diet change — so many cats who don’t have panleukopenia might be tested for it. And the usual test — a PCR (polymerase chain reaction) assay, which detects genetic material from the virus — may produce false positives when used on cats who have been vaccinated against panleukopenia, due to the use of a live vaccine. For cats at under-resourced shelters, the false positive may be a death sentence.

Researchers at the Toronto Humane Society conducted a study to evaluate the incidence of false positives by testing stool samples from 37 healthy shelter cats and kittens for panleukopenia for four weeks after they were vaccinated. Three days after vaccination, one cat tested positive on the PCR test. On day seven, eight cats tested positive on the PCR test. In comparison, throughout the four weeks, only one cat tested positive on another commonly-used point-of-care (non-PCR) test. None of the cats actually had panleukopenia.

Veterinary JournalThe study showed that using the PCR assay to test cats for panleukopenia after they have been vaccinated against the virus with a live vaccine results in a high proportion of false positives. Dr. Linda Jacobson, Senior Manager of Shelter Medicine Advancement at the Toronto Humane Society and lead author on the project, recommended that shelters should not use the PCR test unless they have a strong suspicion of infection, and if they do test healthy cats from a high-risk environment, this should be done within 24 hours of vaccination (before the cats would have started to shed a small amount of virus due to the live vaccine).

Further, veterinarians should ask for more detailed information from the laboratory to help them interpret positive PCR test results; this might help them recognize a false positive. And generally speaking, cats suspected of having panleukopenia should first be tested with the less sensitive point-of-care test, and only tested with the PCR assay if the point-of-care test is negative and there’s a strong suspicion of panleukopenia infection.

The Parsemus Foundation was proud to pay for open-access publication of this important study, which will make the information more easily available to shelter staff.

For more details, read the full text of the article published in The Veterinary Journal. Additional articles on this topic by the researchers at the Toronto Humane Society include:

Diagnostic testing for feline panleukopenia in a shelter setting: a prospective, observational study
Fecal viral DNA shedding following clinical panleukopenia virus infection in shelter kittens: a prospective, observational study

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