Difference between revisions of "Feline Leukaemia Virus"

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Also known as '''''FeLV
+
Feline Leukemia Virus is commonly abbreviated to 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==
+
====Antigenicity====
−
[[Image:Kinetics of FeLV 2.jpg|thumb|right|200px|Kinetics of FeLV - Copyright Dr Brian Catchpole BVetMed PhD MRCVS]]
+
*Main envelope protein: gp70
−
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:  
+
*3 antigenic subgroups:
−
*FeLV-A -natural strain
+
*Group A
−
*FeLV-B which formed through FeLV-A recombining with endogenous retroviral sequences in the feline genome.
+
**is transmitted between cats
−
*FeLV-C which formed from the spontaneous mutation of FeLV-A
+
**is monotypic: one vaccine covers all isolates
 +
**causes '''lymphosarcoma'''
 +
*Group B:
 +
**is recombinant with transmissible FeLV-A
 +
**increases the chance of '''thymic tumors'''
 +
*Group C:
 +
**is a mutant of A
 +
**isolates are rare, and occur as A+C mixtures
 +
**increases chances of '''anemia'''
  
−
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====
 +
*FeLV is the "disease of friends": transmission usually occurs through '''mutual grooming'''
 +
*From the oropharynx, virus spreads to most tissues in the body to replicate, notably:
 +
**Bone marrow
 +
**Thymus
 +
**Salivary glands
 +
**Reproductive tract
 +
*Most kittens but only 30% of adults become '''viremic''' for life without producing antibody
 +
**20% of viremic cats die of tumors
 +
**30% of viremic cats die of FeLV-associated disease
 +
**80% die within three years of exposure
 +
*30% of adults exposed become '''latently infected''' and can become viremic when immunosuppressed
 +
*40% of exposed adults remain healthy and develop Ab and CD8+ Tcells after clearing the virus, without becoming reinfected or silent carriers
  
−
==Pathogenesis==
+
Clinical Signs:
−
FeLV is the "disease of friends": transmission usually occurs through mutual grooming. From the oropharynx, the virus spreads to most tissues in the body to replicate, notably:
+
*'''Leukemia'''
−
*Bone marrow
 
−
*Thymus
 
−
*Salivary glands
 
−
*Reproductive tract
 
−
Most kittens but only 30% of adults become '''viraemic''' for life without producing antibody. The condition progresses in various forms:
 
−
*20% of viraemic cats die of tumors
 
−
*30% of viraemic cats die of FeLV-associated disease
 
−
*80% die within three years of exposure
 
−
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.
 
−
 
 
−
==Clinical Signs==
 
−
*'''Leukemia''' - a neoplastic increase in blood cell numbers - usually white blood cells
 
 
*'''Multicentric lymphosarcoma''': B or T cell tumors, which may be palpable as enlarged lymph nodes (particularly mesenteric)
 
*'''Multicentric lymphosarcoma''': B or T cell tumors, which may be palpable as enlarged lymph nodes (particularly mesenteric)
−
*'''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
 +
**Results in dyspnoea
 +
**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 viraemic kittens with thymic aplasia
+
*'''Reproductive failure''': FeLV crosses the placenta, causing fetal resorption or viremic kittens with thymic aplasia
−
 
 
−
==Epidemiology==
 
−
Vertical transmission of FeLV-A occurs from mother to kittens either via placenta, grooming, or milk. Horizontal transmission occurs via saliva during mutual grooming. FeLV is of particular concern for intensively bred cats because of close living conditions shared with other cats.
 
−
 
 
−
Recovery is linked to age and the presence of maternal antibody
 
−
 
 
−
==Antigenicity==
 
−
Viral subgroups have been categorised based on the different abnormalities detected in the host cellular envelope protein gp70. This protein interacts with a cellular receptor, and can prevent already infected cells from being targeted by further viral organisms.
 
  
−
There are 3 antigenic subgroups which are defined by the gp70 regulated viral response:
+
====Epidemiology====
−
*Group A is transmitted between cats and is monotypic: one vaccine covers all isolates. Infection with this viral subgroup leads to '''[[Lymphoma|lymphosarcoma]]'''.
+
*Vertical transmission of FeLV-A from mother to kittens either via placenta, grooming, or milk
−
*Group B is recombinant with transmissible FeLV-A; infection with viruses of this subgroup increases the chance of developing '''[[Thymus Neoplasia|thymic tumours]]'''.
+
*Horizontal transmission occurs via saliva during mutual grooming
−
*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]]'''.
+
*Recovery linked to age and presence of maternal antibody
 +
*Particular concern for intensively bred cats because of crowding, etc.
  
−
==Diagnosis==
+
====Diagnosis====
−
*FeLV should be suspect in any cat with '''recurrent bacterial infections''', '''anemia''' or '''weight loss'''. Diagnostic tests available for confirmation of disease status include:
+
*FeLV should be suspect in any cat with '''recurrent bacterial infections''', '''anemia''' or '''weight loss'''
−
*'''[[ELISA testing|ELISA]]''' for FeLV antigens (capsid protein p27 or envelope protein gp70)
+
*'''ELISA''' for '''Antigen''' (capsid protein p27 or envelope protein gp70)
−
*'''Immunochromatography''' is now preferred as ELISA testing can give false positives
+
*'''Immunochromatography''' is now trusted 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 now be performed to confirm a positive diagnosis
−
*[[Immunofluorescence]]
 
−
*PCR
 
−
*Rapid-Immuno-Migration
 
−
*[[Western blot|Western Blot]]
 
  
−
==Infection Control==
+
====Control====
−
Antigen positive cats with significant symptoms require euthanasia. Healthy positive cats should have the diagnosis confirmed by a second alternate testing method.  
+
*Antigen positive sick cats should be destroyed
 +
*Healthy positive cats should have diagnosis confirmed  
 +
*Vaccination:
 +
**Should take place once antigen-negative status has been determined
 +
**'''Leukogen''': 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
  
−
===Vaccination===
+
(FeLV)
−
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.
+
[[Image:FeLV Electron Micrograph.jpg|thumb|right|150px|FeLV Electron Micrograph [http://phil.cdc.gov/phil/home.asp Public Health Image Library] Image #5610]]
 +
[[Image:Kinetics of FeLV 2.jpg|thumb|right|150px|Kinetics of FeLV - Copyright Dr Brian Catchpole BVetMed PhD MRCVS]]
 +
*Oncogenic retrovirus
 +
*Causes neoplasia (lymphoma), myelosuppression (anaemia) and immunosuppression (of [[Lymphocytes#T cells|T cells]])
 +
*2 strains:
 +
**FeLV-A
 +
***Natural strain
 +
**FeLV-B
 +
***Formed through FeLV-A recombining with endogenous retroviral sequences in the feline genome
 +
***Increases the risks of lymphoma
 +
**FeLV-C
 +
***Formed from the spontaneous mutation of FeLV-A
 +
***Is more myelosuppressive
 +
*Virus replicates in the oropharyngeal lymphoid tissue causing a viraemia (virus circulating in the bloodstream) which then spreads to the systemic lymphoid tissue
 +
*Shed in saliva
 +
*Passed by oronasal route, e.g. mutual grooming
 +
*Kittens between 6 weeks and 6 months are most susceptible
 +
*60% of cats will become immune to the disease and recover
 +
*Cats that are persistently viraemic will progress to develop FeLV-associated diseases
 +
*Some cats will become viraemic again if treated with corticosteroids or stressed if the infection lies dormant in the [[Bone Marrow - Anatomy & Physiology|bone marrow]]
 +
*Diagnosis:
 +
**ELISA
 +
**Rapid-Immuno-Migration
 +
**Western Blot
 +
**Virus Isolation
 +
**Immunofluorescence
 +
**PCR
 +
*Treatment:
 +
**Antibiotics for secondary infection
 +
**Anti-retroviral therapy
 +
*For vaccinations see [[Vaccines#Cat Vaccinations|here]]
  
−
==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 Viruses]][[Category:Lymphoreticular and Haematopoietic Diseases - Cat]][[Category:Alimentary Diseases - Cat]][[Category:Secondary Immunodeficiency]]
+
[[Category:Mammalian Type C retrovirus ]][[Category:Cat]][[Category:Secondary Immunodeficiency]]
−
[[Category:Lymphoreticular and Haemopoietic Diseases]]
+
[[Category:To_Do_-_Clinical/Viruses]]
−
[[Category:Anaemia|6]]
+
[[Category:To Do - Blood]][[Category:Lymphoreticular and Haemopoietic Diseases]]
−
[[Category:Integumentary System - Viral Infections]]
 

Revision as of 14:33, 12 August 2010

Feline Leukemia Virus is commonly abbreviated to FeLV

Antigenicity

  • Main envelope protein: gp70
  • 3 antigenic subgroups:
  • Group A
    • is transmitted between cats
    • is monotypic: one vaccine covers all isolates
    • causes lymphosarcoma
  • Group B:
    • is recombinant with transmissible FeLV-A
    • increases the chance of thymic tumors
  • Group C:
    • is a mutant of A
    • isolates are rare, and occur as A+C mixtures
    • increases chances of anemia

Pathogenesis

  • FeLV is the "disease of friends": transmission usually occurs through mutual grooming
  • From the oropharynx, virus spreads to most tissues in the body to replicate, notably:
    • Bone marrow
    • Thymus
    • Salivary glands
    • Reproductive tract
  • Most kittens but only 30% of adults become viremic for life without producing antibody
    • 20% of viremic cats die of tumors
    • 30% of viremic cats die of FeLV-associated disease
    • 80% die within three years of exposure
  • 30% of adults exposed become latently infected and can become viremic when immunosuppressed
  • 40% of exposed adults remain healthy and develop Ab and CD8+ Tcells after clearing the virus, without becoming reinfected or silent carriers

Clinical Signs:

  • Leukemia
  • Multicentric lymphosarcoma: B or T cell tumors, which may be palpable as enlarged lymph nodes (particularly mesenteric)
  • Thymic lymphosarcoma: T cell tumors, with only the thymus enlarged
    • Results in dyspnoea
    • Confirmed by radiography
  • Alimentary lymphosarcoma: B cell tumors of the Peyer's patches

FeLV-associated disease:

  • Immunodepression causing secondary disease
  • Reproductive failure: FeLV crosses the placenta, causing fetal resorption or viremic kittens with thymic aplasia

Epidemiology

  • Vertical transmission of FeLV-A from mother to kittens either via placenta, grooming, or milk
  • Horizontal transmission occurs via saliva during mutual grooming
  • Recovery linked to age and presence of maternal antibody
  • Particular concern for intensively bred cats because of crowding, etc.

Diagnosis

  • FeLV should be suspect in any cat with recurrent bacterial infections, anemia or weight loss
  • ELISA for Antigen (capsid protein p27 or envelope protein gp70)
  • Immunochromatography is now trusted as ELISA testing can give false positives
  • Virus isolation from heparinised blood can now be performed to confirm a positive diagnosis

Control

  • Antigen positive sick cats should be destroyed
  • Healthy positive cats should have diagnosis confirmed
  • Vaccination:
    • Should take place once antigen-negative status has been determined
    • Leukogen: 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

(FeLV)

FeLV Electron Micrograph Public Health Image Library Image #5610
Kinetics of FeLV - Copyright Dr Brian Catchpole BVetMed PhD MRCVS
  • Oncogenic retrovirus
  • Causes neoplasia (lymphoma), myelosuppression (anaemia) and immunosuppression (of T cells)
  • 2 strains:
    • FeLV-A
      • Natural strain
    • FeLV-B
      • Formed through FeLV-A recombining with endogenous retroviral sequences in the feline genome
      • Increases the risks of lymphoma
    • FeLV-C
      • Formed from the spontaneous mutation of FeLV-A
      • Is more myelosuppressive
  • Virus replicates in the oropharyngeal lymphoid tissue causing a viraemia (virus circulating in the bloodstream) which then spreads to the systemic lymphoid tissue
  • Shed in saliva
  • Passed by oronasal route, e.g. mutual grooming
  • Kittens between 6 weeks and 6 months are most susceptible
  • 60% of cats will become immune to the disease and recover
  • Cats that are persistently viraemic will progress to develop FeLV-associated diseases
  • Some cats will become viraemic again if treated with corticosteroids or stressed if the infection lies dormant in the bone marrow
  • Diagnosis:
    • ELISA
    • Rapid-Immuno-Migration
    • Western Blot
    • Virus Isolation
    • Immunofluorescence
    • PCR
  • Treatment:
    • Antibiotics for secondary infection
    • Anti-retroviral therapy
  • For vaccinations see here
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