Difference between revisions of "Feline Leukaemia Virus"

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Also known as '''''FeLV
 
Also known as '''''FeLV
  
−
====Antigenicity====
+
==Introduction==
−
*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====
+
==Pathogenesis==
 
*FeLV is the "disease of friends": transmission usually occurs through '''mutual grooming'''
 
*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:
 
*From the oropharynx, virus spreads to most tissues in the body to replicate, notably:
Line 30: Line 17:
 
*40% of exposed adults remain healthy and develop Ab and CD8+ Tcells after clearing the virus, without becoming reinfected or silent carriers
 
*40% of exposed adults remain healthy and develop Ab and CD8+ Tcells after clearing the virus, without becoming reinfected or silent carriers
  
−
Clinical Signs:
+
==Clinical Signs==
 
*'''Leukemia'''
 
*'''Leukemia'''
 
*'''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)
Line 42: Line 29:
 
*'''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 viremic kittens with thymic aplasia
  
−
====Epidemiology====
+
==Epidemiology==
 
*Vertical transmission of FeLV-A from mother to kittens either via placenta, grooming, or milk
 
*Vertical transmission of FeLV-A from mother to kittens either via placenta, grooming, or milk
 
*Horizontal transmission occurs via saliva during mutual grooming
 
*Horizontal transmission occurs via saliva during mutual grooming
Line 48: Line 35:
 
*Particular concern for intensively bred cats because of crowding, etc.
 
*Particular concern for intensively bred cats because of crowding, etc.
  
−
====Diagnosis====
+
==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'''
 +
 
 +
 
 +
==Diagnosis==
 
*FeLV should be suspect in any cat with '''recurrent bacterial infections''', '''anemia''' or '''weight loss'''
 
*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)
 
*'''ELISA''' for '''Antigen''' (capsid protein p27 or envelope protein gp70)
 
*'''Immunochromatography''' is now trusted as ELISA testing can give false positives
 
*'''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
 
*'''Virus isolation''' from heparinised blood can now be performed to confirm a positive diagnosis
 +
ELISA
 +
**Rapid-Immuno-Migration
 +
**Western Blot
 +
**Virus Isolation
 +
**Immunofluorescence
 +
**PCR
  
−
====Control====
+
==Infection Control==
 
*Antigen positive sick cats should be destroyed
 
*Antigen positive sick cats should be destroyed
 
*Healthy positive cats should have diagnosis confirmed  
 
*Healthy positive cats should have diagnosis confirmed  
Line 83: Line 92:
 
*Cats that are persistently viraemic will progress to develop FeLV-associated diseases
 
*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]]
 
*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
+
==Treatment==
−
**Rapid-Immuno-Migration
 
−
**Western Blot
 
−
**Virus Isolation
 
−
**Immunofluorescence
 
−
**PCR
 
−
*Treatment:
 
 
**Antibiotics for secondary infection
 
**Antibiotics for secondary infection
 
**Anti-retroviral therapy
 
**Anti-retroviral therapy

Revision as of 15:12, 30 October 2010

Also known as FeLV

Introduction

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.

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


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

ELISA

    • Rapid-Immuno-Migration
    • Western Blot
    • Virus Isolation
    • Immunofluorescence
    • PCR

Infection 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

Treatment

    • Antibiotics for secondary infection
    • Anti-retroviral therapy
  • For vaccinations see here
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