Feline Leukemia Virus in the Florida Panther

Feline leukemia virus (FeLV) most commonly affects house cats but can be fatal to panthers. The Florida panther, as well as other North and South American puma populations, has historically not been infected by this virus. However, testing has shown increasing exposure of Florida panthers to the virus over the past 30 years, with many panthers developing active infections. While some panthers may be able to control and eventually clear a FeLV infection, many succumb to the disease. Of greatest concern is that once the virus crosses the species barrier, infection then could spread from panther to panther.

Between 2002 and 2004, an outbreak of FeLV resulted in the deaths of at least five Florida panthers, and since 2010, infections have been diagnosed in six additional panthers. Through genetic analyses of the infecting virus, biologists determined the outbreak likely came from a cross-species transmission from a domestic cat. Panthers are known to prey upon domestic cats that roam freely outdoors.

The clinical diseases resulting from FeLV infection in panthers, including anemia and septicemia, appear similar to those seen in domestic cats. However, progression of the clinical diseases appears to be quite rapid in panthers that are persistently infected, and most will die within a few months of infection.

Surveillance and management of FeLV in panthers

Blood test results for a Florida PantherBlood test reveals that this panther is infected with feline leukemia

All panthers older than 2 months that are handled (alive or dead) by panther biologists are tested for FeLV.  Veterinarians developed a protocol for live-captured panthers that test positive for FeLV in the field. Infected panthers are transported to a holding facility for care, treatment and re-testing. They only will be released back into the wild if a veterinarian verifies the panther cleared of the virus.

 All live-handled panthers older than 2 months are vaccinated against FeLV. Initially, biologists targeted the area where FeLV positive panthers were first discovered. However, the vaccination protocol now calls for biologists to vaccinate all kittens older than 2 months and all adult panthers they handle.

What you can do to prevent this disease

Given the increasing urban-wildlife interface and the increasing Florida panther population, panthers are far more likely to encounter house cats. House cats should be raised as inside pets and never allowed to roam freely outdoors. Cat owners should also make sure their pet’s vaccinations, including FeLV if the cat spends time outdoors, are current. Each house cat that is protected from the virus and direct contact with panthers is one less threat to panther conservation.

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