Feline Leukemia Virus (FeLV)
Feline leukemia virus (FeLV) remains a significant threat to cats. Infection with FeLV may lead to lifelong persistence of
the virus, and causes immunosuppression, degenerative conditions such as anemia, and/or proliferative diseases such as lymphoma
and leukemia. Investigations of FeLV infection using molecular detection techniques have identified four stages of infection.
In this study, a small % of cats positive by genetic detection were negative by antigen (p27) detection using ELISA. Other
studies detecting proviral DNA in whole blood found ~5% were negative by antigen ELISA. It is not know if this is a stage
in clearance of the virus, or if the provirus remains. A recent study evaluating risk factors for FeLV infection found that
adults, sexually intact males, and outdoor cats were at higher risk for infection.
Various investigations have compared in-house tests for diagnosis of FeLV. A study by Hartmann and others (2001) evaluated
six FeLV tests, with results shown in this table:
A more recent study by Hartmann and others (2007) compared eight FeLV tests, with results shown in this table:
Thus, reliable and accurate detection of FIV infection by molecular assays is difficult. Recently, a report by Levy and others
(2008) has shown promising results with an antibody assay able to distinguish vaccinal response from that of natural infection.
This discriminant ELISA may prove to be useful for accurate testing of vaccinated cats.
P. Cynda Crawford, Julie K. Levy, DVM. 2007. New Challenges for the Diagnosis of Feline Immunodeficiency Virus Infection.
Vet Clin Small Anim 37 (2007) 335–350.
Crawford, P. Cynda, Margaret R. Slater, Julie K. Levy. Accuracy of polymerase chain reaction assays for diagnosis of feline
immunodeficiency virus infection in cats. JAVMA, Vol 226, No. 9, May 1, 2005, 1503-1507.
Gomes-Keller, M. A., E. Gonczi, R. Tandon, F. Riondato, R. Hofmann-Lehmann, M. L. Meli, and H. Lutz. 2006. Detection of Feline
Leukemia Virus RNA in Saliva from Naturally Infected Cats and Correlation of PCR Results with Those of Current Diagnostic
Methods. JOURNAL OF CLINICAL MICROBIOLOGY, Mar. 2006, 44(3): 916–922.
Grosenbaugh,DeborahA.,Tim Leard, M. Camila Pardo.2006.Protection from challenge following administration of a canarypox virus–vectored
recombinant feline leukemia virus vaccine in cats previously vaccinated with a killed virusvaccine.JAVMA,Vol 228,No.5,March
Hartmann, K, RM Werner, H Egberink, and O Jarrett. 2001. Comparison of six in-house tests for the rapid diagnosis of feline
immiunodeficieny and feline leukaemia virus infections. The Veterinary Record, September 15, 2001, 317-320.
Hofmann-Lehmanna, Regina, Valentino Cattori, Ravi Tandon, Felicitas S. Boretti, Marina L. Meli, Barbara Riond, Andrea C. Pepin,
Barbara Willi, Pete Ossent, Hans Lutz. 2007. Vaccination against the feline leukaemia virus: Outcome and response categories
and long-term follow-up. Vaccine 25 (2007) 5531–5539.
Kusuhara, Hajime, Tsutomu Hohdatsu, Mayuko Okumura, Kayoko Sato, Yumi Suzuki, Kenji Motokawa, Tsuyoshi Gemma, Rie Watanabe,
Chengjin Huang, Setsuo Arai, Hiroyuki Koyama. 2005. Dual-subtype vaccine (Fel-O-Vax FIV) protects cats against contact challenge
with heterologous subtype B FIV infected cats. Veterinary Microbiology 108 (2005) 155–165.
Levy, Julie K., H. Morgan Scott,Jessica L. Lachtara, P. Cynda Crawford. 2006. Seroprevalence of feline leukemia virus and
feline immunodeficiency virus infection among cats in North America and risk factors for seropositivity. JAVMA, 228(3): 371-376.
Levy, J. K., P. C. Crawford, H. Kusuhara, K. Motokawa, T. Gemma, R. Watanabe, S. Arai, D. Bienzle, and T. Hohdatsu. 2008.
Differentiation of feline immunodeficiency virus vaccination, infection, or vaccination and infection in cats. J Vet Intern Med, 22(2):330-4.
Phadke, Anagha P., Andres de la Concha-Bermejillo, Alice M. Wolf, Philip R. Andersen, Veerabhadran Baladandayuthapani, Ellen
W. Collisson. 2006. Pathogenesis of a Texas feline immunodeficiency virus isolate: An emerging subtype of clade B. Veterinary
Microbiology 115 (2006) 64–76.
Richards, James R. 2005. Feline immunodeficiency virus vaccine: Implications for diagnostic testing and disease management.
Biologicals 33 (2005) 215