Feline LeukemiaErin O’RileyKatie Colbrook

Feline Leukemia• Usually abbreviated as FeLV• First discovered in domestic cats in Scotland • 1964

• Cross-species concern• Domestic/feral cats(natural hosts) Wild Felids

• No reports of infection in humans• Although human (and canine) tissue cultures grown in labs can

be infected with disease

Animals affected:• Felids• Both domestic and wild

• Seen in house cats, feral cat populations, Iberian lynx, captive bobcats, Florida panthers and wild cougars

• Any age• Biased towards males• Virulent virus more common in domestic cats and wild felids of male

gender usually do to higher aggressiveness

FeLV Genetic/Virus Characteristics• Carried in RNA• Gammaretrovirus• Is a genus of the retroviridae family• Known for causing sarcomas and different

types of leukemia• Total genome is about 9,600 base pairs• This virus causes a disease which is a form

of cancer of blood cells called lymphocytes

Structure of FeLV Virus

Process of Infecting Host Cell

Transmission Dynamics• Horizontal Transmission (Direct Contact)• Saliva

• Cats are social animals constantly grooming each other

• Urine• Blood

• Free floating in blood plasma so mechanical vectors (blood sucking parasites) a possible concern

Stages of FeLV

There are 6 stages of FeLV infection:•Stage One: The virus enters the cats system and infects the epithelial cells then moves to different types of white blood cells called lymphocytes and macrophages. These white blood cells then move to the lymph nodes where the virus begins to replicate.

•Stage Two: The virus enters the blood stream where it is spread throughout the body.

•Stage Three: The virus enters the lymphoid system spreading further though the felines body.

Stages Continued• Stage Four: This is the main point of infection in the feline

where if the cat's immune system does not fight off the virus, then it continues on to stage five

• Stage Five: The bone marrow becomes infected. When this occurs the virus will stay with the cat for the rest of its life. Then it is released from the bone marrow to further take over the felines body.

• Stage Six: Feline becomes overwhelmed by infection and mucous and glandular epithelial cells become infected. When this occurs the virus can be easily transferred to other felines.

FeLV mortality• Felids who contract FeLV have 3 possible outcomes:• The cat produces neutralizing antibodies to eliminate virus• The cat can remain latently infected• The virus is virulent and the cat shows symptoms immediately

• No curative treatment• Vaccine makes virus go into latency

• FeLV causes:• Lymphoma• Anemia • Immunosuppression

• These secondary infections are typically the cause of death

Signs of Infection• Loss of appetite• Slow weight loss• Poor coat condition• Enlarged lymph nodes• Persistent fever• Pale and inflamed gums• Infections of the skin, urinary bladder, and upper respiratory

tract• Persistent diarrhea• Seizures, behavior changes, and other neurological disorders• A variety of eye conditions• Spontaneous abortions in pregnant females

FeLV Detection• PCR• Polymerase Chain Reaction• Detects virulent and latent infection

• ELISA• This tests for the antigen present when cats are infected

virulently with FeLV

Iberian Lynx• FeLV was rarely reported and/or detected in wild felids until

the year 2007 when an outbreak occurred in the Iberian Lynx population in Doñana (located in Spain).

• Even before the outbreak…• The Iberian lynx is the most critically endangered felid species

in the world• Due to predators losing population density because of:

• Human/wildlife conflict• Over harvesting• Prey decline• Habitat loss due to human encroachment

• Conservation measures were implemented to sustain the species

Conservation of Iberian Lynx• Since the Iberian lynx was known to be in trouble due to such

low densities (~160 individuals ) conservation efforts were imposed• Beginning of breeding season in ‘06-’07 in the CRS (Coto del Rey

subpopulation)• 7 feeding stations were outfitted• 12 drinking stations available

Before the Outbreak• Positive for FeLV viremia Lynx discovered in December 2006• Past knowledge of FeLV did not lead managers to find great risk

in releasing the infected individual • Infection was probably due to contact with an infected feral cat

• Large populations of feral cats surround this area

Beginning of Outbreak (2007)• Two more lynx were found dead and tested positive for FeLV

viremia• This lead to construction of an FeLV Control Program specified

for the Iberian Lynx

FeLV Control Program• Goals:• 1. Control FeLV focus and stop spread across all of the Doñana

population• 2. Remove virus from population• 3. Minimize possibility of a new outbreak

• Objectives: • 1. Remove FeLV viremia positive lynx from wild• 2. Give FeLV vaccine to all uninfected individuals• 3. Modify management feeding/drinking stations• 4. Reduce the feral cat population

FeLV Control Program• Domestic cats were captured in lynx distribution areas • ELISA tests done• All viremic cats euthanized • Cats not infected were returned to owners or rescue center after

being vaccinated• All Lynxes were captured and transported to a clinic• ELISA and PCR tests done• If ELISA test was positive (conclusive to a viremic lynx) they were

moved to a rescue center until infection became latent• All latent lynx returned to wild after being vaccinated• Recapture and a second dose of vaccine was administered for as

many lynx as possible to achieve best results

Interpretation• FeLV outbreak in the Doñana area probably due to interaction

of lynx with feral/domestic cats• Spread of FeLV occurred because of • Breeding season increases intraspecies contact• Feeding and Drinking stations increased intraspecies contact• High pathogenicity of the FeLV strain in the lynx• High density of the subpopulation

FeLV Prevention• Decreasing interactions between domestic cats from wild

felids• Side note: “green belt” areas made for wildlife should be farther

away from suburban areas to limit these interactions• Should latent felids be released back into wild? • Could cause new outbreak in future

• Vaccinate high risk populations of wild felids• Stricter vaccination policies of domestic cats• Don’t define threat level of a virus because its unpredictable• Critically think out conservation actions• i.e. feeding stations that encourage saliva transfer

Sources• Alexander, K.A. (2009). Successful intervention in a disease outbreak

in the endangered Iberian lynx: what can we learn? Animal Conservation,12.183-4.

• Hardy, W.D., Old, L.J., Hess, P.W., Essex, M. and Cotter, S. (1973).Horizontal Transmission of Feline Leukaemia Virus.Nature,244.266-8.

• Hoopes, J., Baines B., Smyth, T., and Nugent, C. (2009). Overview of feline leukemia virus and symptoms. http://homepage.usask.ca/~vim458/virology/studpages2009/retroviruses/plfelv.html

• Lopez, G., Lopez-Parr, M., Fernandez, L., Martinez-Granados, C., Martinez, F., Meli, M.L., Fil-Sanchez, J.M., Viqueira, N., Diaz-Portero, M.A., Cadenas, R., Lutz, H., Vargas, A. and Simon, M.A. (2009). Management measures to control a feline leukemia virus outbreak in the endangered Iberian lynx. Animal Conservation, 12. 173-8.

Sources Continued• Luaces, I., Domenech, A., Garcia-Montijano, M., Collado, V.M.,

Sanchez, J., Tejerizo, G., Galka, M., Fernandez, P. and Gomez-Lucia, E. (2008). Detection of feline leukemia virus in the endangered Iberian lynx. J Vet Diagn Invest 20, 381-5.