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==Introduction==
==Introduction==
[[Image:Kinetics of FeLV 2.jpg|thumb|right|200px|Kinetics of FeLV - Copyright Dr Brian Catchpole BVetMed PhD MRCVS]]
[[Image:Kinetics of FeLV 2.jpg|thumb|right|200px|Kinetics of FeLV - Copyright Dr Brian Catchpole BVetMed PhD MRCVS]]
FeLV is an ncogenic retrovirus which causes neoplasia ([[Lymphoma|lymphoma]]), myelosuppression ([[Regenerative and Non-Regenerative Anaemias|anaemia]]) and immunosuppression (of [[Lymphocytes#T cells|T cells]]). Three different strains are currently recognised:
FeLV is an oncogenic retrovirus which causes neoplasia ([[Lymphoma|lymphoma]]), myelosuppression ([[Regenerative and Non-Regenerative Anaemias|anaemia]]) and immunosuppression (of [[Lymphocytes#T cells|T cells]]). Three different strains are currently recognised:
*FeLV-A -natural strain
*FeLV-A -natural strain
*FeLV-B which formed through FeLV-A recombining with endogenous retroviral sequences in the feline genome.
*FeLV-B which formed through FeLV-A recombining with endogenous retroviral sequences in the feline genome.
*Reproductive tract
*Reproductive tract
Most kittens but only 30% of adults become '''viraemic''' for life without producing antibody. The condition progresses in various forms:
Most kittens but only 30% of adults become '''viraemic''' for life without producing antibody. The condition progresses in various forms:
*20% of viremic cats die of tumors
*20% of viraemic cats die of tumors
*30% of viremic cats die of FeLV-associated disease
*30% of viraemic cats die of FeLV-associated disease
*80% die within three years of exposure
*80% die within three years of exposure
30% of adults exposed become '''latently infected''' and can become viremic when immunosuppressed.
30% of adults exposed become '''latently infected''' and can become viraemic when immunosuppressed.
40% of exposed adults remain healthy and develop Ab and CD8+ T cells after clearing the virus, without becoming reinfected or silent carriers.
40% of exposed adults remain healthy and develop Ab and CD8+ T cells after clearing the virus, without becoming reinfected or silent carriers.
FeLV-associated disease:
FeLV-associated disease:
*'''Immunodepression''' causing secondary disease
*'''Immunodepression''' causing secondary disease
*'''Reproductive failure''': FeLV crosses the placenta, causing fetal resorption or viremic kittens with thymic aplasia
*'''Reproductive failure''': FeLV crosses the placenta, causing fetal resorption or viraemic kittens with thymic aplasia
==Epidemiology==
==Epidemiology==
*Group A is transmitted between cats and is monotypic: one vaccine covers all isolates. Infection with this viral subgroup leads to '''[[Lymphoma|lymphosarcoma]]'''.
*Group A is transmitted between cats and is monotypic: one vaccine covers all isolates. Infection with this viral subgroup leads to '''[[Lymphoma|lymphosarcoma]]'''.
*Group B is recombinant with transmissible FeLV-A; infection with viruses of this subgroup increases the chance of developing '''[[Thymus - Pathology|thymic tumours]]'''.
*Group B is recombinant with transmissible FeLV-A; infection with viruses of this subgroup increases the chance of developing '''[[Thymus - Pathology|thymic tumours]]'''.
*Group C is a mutant of subgroup A. Isolates are rare, and occur as A+C mixtures, leading to an increased chance of developing '''[[Regenerative and Non-Regenerative Anaemias|anaemia]]'''.
*Group C is a mutant of subgroup A. Isolates are rare, and occur as A+C mixes, leading to an increased chance of developing '''[[Regenerative and Non-Regenerative Anaemias|anaemia]]'''.
==Diagnosis==
==Diagnosis==
*FeLV should be suspect in any cat with '''recurrent bacterial infections''', '''anemia''' or '''weight loss'''. Diagnostic tests available for cinfirmation of disease sttus includes:
*FeLV should be suspect in any cat with '''recurrent bacterial infections''', '''anemia''' or '''weight loss'''. Diagnostic tests available for confirmation of disease status include:
*'''[[ELISA testing|ELISA]]''' for FeLV antigens (capsid protein p27 or envelope protein gp70)
*'''[[ELISA testing|ELISA]]''' for FeLV antigens (capsid protein p27 or envelope protein gp70)
*'''Immunochromatography''' is now preferred as ELISA testing can give false positives
*'''Immunochromatography''' is now preferred as ELISA testing can give false positives