1. Erin O’Riley Katie Colbrook
Feline Leukemia
Erin O’Riley
Katie Colbrook

2. 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

3. 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

4. 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

5. Structure of FeLV Virus

6. Process of Infecting Host Cell

7. 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

8. 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.

9. 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.

10. 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

11. 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

12. FeLV Detection PCR ELISA Polymerase Chain Reaction
Detects virulent and latent infection
ELISA
This tests for the antigen present when cats are infected virulently with FeLV

13. 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

14. 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

15. 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

16. 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

17. FeLV Control Program Goals: Objectives:
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

18. 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

19. 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

20. 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

21. Sources
Alexander, K.A. (2009). Successful intervention in a disease outbreak in the endangered Iberian lynx: what can we learn? Animal Conservation,
Hardy, W.D., Old, L.J., Hess, P.W., Essex, M. and Cotter, S. (1973).Horizontal Transmission of Feline Leukaemia Virus.Nature,
Hoopes, J., Baines B., Smyth, T., and Nugent, C. (2009). Overview of feline leukemia virus and symptoms.
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,

22. 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,