Changes

===Laboratory Tests===

===Laboratory Tests===

No typical changes for FIV infection are revealed by routine haematology and biochemsitry. The haemogram may be noraml, or anaemia, lymphopenia or neutropenia can be seen, related to the direct effects of the virus. Secondary infection may result in a neutrophilia. Biochemical changes reflect the associated conditions in indvidual cases⁵.

No typical changes for FIV infection are revealed by routine haematology and biochemsitry. The haemogram may be normal, or anaemia, lymphopenia or neutropenia can be seen, related to the direct effects of the virus. Secondary infection may result in a neutrophilia. Biochemical changes reflect the associated conditions in indvidual cases⁵.

Diagnosis of FIV is made by demonstrating the presence of antibodies against the virus. ELISA tests are available for in-house use, with some kits detecting antibody to the core protein p24 and others detect antibody to the envelope protein gp4l². Non-haemolysed plasma or serum is used for performing the in-house ELISA. Results must be interpreted with caution.  

Diagnosis of FIV is made by demonstrating the presence of antibodies against the virus. ELISA tests are available for in-house use, with some kits detecting antibody to the core protein p24 and others detecting antibody to the envelope protein gp4l². Non-haemolysed plasma or serum is used for performing the in-house ELISA. Results must be interpreted with caution.  

Once a cat acquires FIV infection, the antibodies created persist for life. This means that an ELISA test at any stage after infection should give a positive result. However, the test has a sensitivity of 98%, and so false positives do occur. Because of this, animals that test positive to an in-house ELISA, should be re-tested using a different test. Laboratories offer an immunoblot (Western blot) to confirm the diagnosis in cats that test ELISA-positive. The problem of using a test that detects anitbodies becomes apparent when it is neccessart to test kittens that are born to an FIV-positive queen. Antibodies against FIV are passively acquired via the milk, and can be detected when an ELISA test is used. This makes it imposible to distinguish animals that have been transplacentally infected with virus and are producing their own antibodies from those which have merely acquired pre-formed anitbodies from their mother. Maternally derived anitbodies can persist for up to 6 months², and so animals testing positive before this age should be restested at 8-12 months old⁵.

Once a cat acquires FIV infection, the antibodies created persist for life. This means that an ELISA test at any stage after infection should give a positive result. However, the test has a sensitivity of 98%, and so false positives do occur. Because of this, animals that test positive to an in-house ELISA, should be re-tested using a different test. Laboratories offer an immunoblot (Western blot) to confirm the diagnosis in cats that are ELISA-positive. The problem of using a test that detects anitbodies becomes apparent when it is neccessary to test kittens that are born to an FIV-positive queen. Antibodies against FIV are passively acquired via the milk, and can be detected when an ELISA test is used. This makes it imposible to distinguish animals that have been transplacentally infected with virus and are producing their own antibodies from those which have merely acquired pre-formed anitbodies from their mother. Maternally derived anitbodies can persist for up to 6 months², and so animals testing positive before this age should be restested at 8-12 months old⁵.

   

   

Negative results can be true negatives. Alternatively, they may arise when the cat is infected with FIV but the antibodies produced are not detectable by the test used. Conversely, the cat may be infected but antibodies are not present, for example in the first two months of infection². Therefore, if clinical signs give a strong suspicion of FIV infection, or the cat is known to be at risk (for example, recently bitten by and infected cat), animals should be retested 6-8 weeks later and use of an immunoblot should be considered. Up to 15% of cats completely fail to ever mount an antibody response against FIV infection. Virus isolation can be performed but is not widely available outwith the context of research^{4, 5}. An RT-PCR tests is commercially available and detects virus rather than antibody with high specificity, but variations between strains and laboratories may make this test unreliable^{2, 4, 5}.

Negative results can be true negatives. Alternatively, they may arise when the cat is infected with FIV but the antibodies produced are not detectable by the test used. Conversely, the cat may be infected but antibodies are not present, for example in the first two months of infection². Therefore, if clinical signs give a strong suspicion of FIV infection, or the cat is known to be at risk (for example, recently bitten by and infected cat), animals should be retested 6-8 weeks later and use of an immunoblot should be considered. Up to 15% of cats completely fail to ever mount an antibody response against FIV infection. Virus isolation can be performed but is not widely available outwith the context of research^{4, 5}. An RT-PCR tests is commercially available and detects virus rather than antibody with high specificity, but variations between strains and laboratories may make this test unreliable^{2, 4, 5}.