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Also known as '''''FeLV
Also known as '''''FeLV
[[Image:FeLV Electron Micrograph.jpg|thumb|right|175px|FeLV Electron Micrograph [http://phil.cdc.gov/phil/home.asp Public Health Image Library] Image #5610]]
==Introduction==
==Introduction==
[[Image:Kinetics of FeLV 2.jpg|thumb|right|200px|Kinetics of FeLV - Copyright Dr Brian Catchpole BVetMed PhD MRCVS]]
FeLV is an oncogenic mammalian type C 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-B which formed through FeLV-A recombining with endogenous retroviral sequences in the feline genome.
*FeLV-C which formed from the spontaneous mutation of FeLV-A
The virus replicates in the oropharyngeal lymphoid tissue causing a viraemia (the virus circulates in the bloodstream) which then spreads to the systemic lymphoid tissue.
==Pathogenesis==
==Pathogenesis==
*Salivary glands
*Salivary glands
*Reproductive tract
*Reproductive tract
Most kittens but only 30% of adults become '''viremic''' 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.
*'''Thymic lymphosarcoma''': T cell tumors, with only the thymus enlarged -this may result in dyspnoea and can be confirmed by radiography
*'''Thymic lymphosarcoma''': T cell tumors, with only the thymus enlarged -this may result in dyspnoea and can be confirmed by radiography
*'''Alimentary lymphosarcoma''': B cell tumors of the Peyer's patches
*'''Alimentary lymphosarcoma''': B cell tumors of the Peyer's patches
*Cutaneous horns on foot pads
*Epidermal and follicular epithelial hyperplasia, epidermal giant cells, dyskeratosis, necrosis, ulceration
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==
There are 3 antigenic subgroups which are defined by the gp70 regulated viral response:
There are 3 antigenic subgroups which are defined by the gp70 regulated viral response:
*Group A is transmitted between cats and is monotypic: one vaccine covers all isolates. Infection with this viral subgroup leads to '''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 '''thymic tumors'''.
*Group B is recombinant with transmissible FeLV-A; infection with viruses of this subgroup increases the chance of developing '''[[Thymus Neoplasia|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 '''anemia'''.
*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''' 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
*'''Virus isolation''' from heparinised blood can be performed to confirm a positive diagnosis
*'''Virus isolation''' from heparinised blood can be performed to confirm a positive diagnosis
*Immunofluorescence
*[[Immunofluorescence]]
*PCR
*PCR
*Rapid-Immuno-Migration
*Rapid-Immuno-Migration
*Western Blot
*[[Western blot|Western Blot]]
==Infection Control==
==Infection Control==
===Vaccination===
===Vaccination===
Ideally, this should take place once antigen-negative status has been determined by laboratory testing. '''Leukogen''' is a subunit vaccine (using envelope protein gp70) produced in ''E. coli'' mixed with Quill-A and alhydrogel. Others include inactivated virus and canarypox recombinants, but all MUST include FeLV-A.
Ideally, this should take place once antigen-negative status has been determined by laboratory testing. 'Leukogen' is a subunit vaccine (using envelope protein gp70) produced in ''E. coli'' mixed with Quill-A and alhydrogel. Others include inactivated virus and canarypox recombinants, but all MUST include FeLV-A.
==Treatment==
==Treatment==
Where treatment is undertaken, anti-retroviral therapy is indicated with antibiotics to control secondary infections. Prevention is a key element in the control and treatment of FeLV overall.
{{Learning
|Vetstream = [https://www.vetstream.com/felis/Content/Disease/dis60141 Feline leukemia virus disease]
}}
[[Category:Mammalian Type C retrovirus ]][[Category:Cat]][[Category:Secondary Immunodeficiency]]
[[Category:Mammalian Type C retrovirus ]][[Category:Cat Viruses]][[Category:Lymphoreticular and Haematopoietic Diseases - Cat]][[Category:Alimentary Diseases - Cat]][[Category:Secondary Immunodeficiency]]
[[Category:To_Do_-_Clinical/Viruses]]
[[Category:Lymphoreticular and Haemopoietic Diseases]]
[[Category:To Do - Blood]][[Category:To Do - Clinical]][[Category:Lymphoreticular and Haemopoietic Diseases]]
[[Category:Anaemia|6]]
[[Category:Integumentary System - Viral Infections]]