Feline Retroviruses

Feline Immunodeficiency Virus

• Lentivirus.
• Five subtypes-> A in the UK.
• Most common in older males, outside cats or sick cats. 

Pathogenesis:

1. Bite wound.
2. Replication in leucocytes.
3. Tissue localisation e.g. CNS.
4. 6-8 weeks. Lymphadenopathy, neutropenia and decreased CD4:CD8 ratio.
5. Prolonged asymptomatic period.
6. Immunosuppression.

Clinical signs-> Immunosuppression resulting in secondary bacterial infections. Direct virus effects e.g. CNS disease. May also result in tumours.

Epidemiology:

• Persistant infective antibody positive.
• Uninfected antibody positive.
• Test-> 90% sensitivity and 98% specificity, not used well for positive tests at low prevalence hence in house tests should be repeated by an independent test. 

Diagnosis:

• PCR- problems as not all strains recognised and problems with sensitivity.
• Diagnosis- viral isolate.
• Antibody e.g. western blotting. 
• All kittens may be virus positive and retest as there is the MDA to consider. 

Transmission:

• Virus in saliva- bites/fights. 
• Transplacental.
• Birth- milk.
• Does not survive well in the environment.

Prevention and control:

• Isolate infected cats.
• Vaccine-> killed vaccine with 2 FIV strains/adjuv vaccine. 
• Prevent cats fighting.

Feline Leukaemia Virus

• RNA genome with P27 protein core. Envelope and GP70 spikes. Only group A transmitted. 

Clinical Signs:

• Neoplastic disease of myeloid and lymphoid. Results in lymphomas- mediastinal (90% FeLV positive), multicentric, ailmentary and extranodal e.g. spinal/renal. 
• Leukaemia-> erythroleukaemia, and reticuloendotheliosis.
• Anaemia, immunosuppression, infertility and neurological disease.

Transmission:

• Inactivated in the environment.
• Congenital infection.
• Oronasal- virus shed in saliva. 
• Prolonged intimate contact e.g. grooming.

Pathogenesis:

• Transient viraemia- neutralising antibody limits the spread of infection. Up to 8 weeks and infection may spread to bone marrow. Normally mounts effective immunity.
• Latent infection- bone marrow, short lived. Blood tests are FeLV negative.
• Persistent viraemia- grave prognosis. Ineffective immunity mounted. Replicates in bone marrow cells. Virus and P27 ag in bood. <16 week old cats, high viral dose, previous infection, vaccination or maternal antibodies.

Epidemiology:

• Age related resistant to development of persistent viraemia.
• 2-4 years old generally.
• Multicat houshold with prolonged contact. Endemic infection= 30% cats persistent viraemic. 

Diagnosis:

• Non specific tests e.g. anaemia.
• Detect virus/viral antigen P27- ELISA, rapid immunomigratory assay, immunoflourescence.
• Viral plasma isolate.  
• Detect FeLV neutralising antibody- detects immune cats.

Control:

• Pets- vaccinated and not high risk.
• Breeding- vaccination not 100%. Regular test and remove and remove any new cats.
• In house tests, possible false positives, so retest all confirm +ve with a second test and retest any positives on the second test. Tested by viral isolation/IF. 

Vaccination:

• Problems= adverse reactions and lack of efficacy.
• Test before vaccination- high risk cats.
• Protects against persistent infection. 12 months. Not 100%. A, B and C types. Canarypox vector. 
• Inactive/virus particles with recombinant gp70 adjuvinated.