Testing for Feline Viruses

Virology today provides us with the means to test for many viruses affecting both us and our pets. These techniques are particularly useful in the cat since there are several serious viral infections of felines that can result in immune related problems.

What viruses do we commonly test for?

The most common feline viral tests are those for feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV) and feline coronavirus (FCoV).

What are the diseases associated with these viruses?

• Feline leukaemia virus (FeLV) is responsible for a number of diseases in cats that include leukaemia. It is highly contagious and is transmitted through body fluids and across the placenta in pregnancy.
• Feline immunodeficiency virus (FIV) is often known as feline AIDS. It inhibits the cat's immune system, preventing a protective response to other infectious agents. FIV is highly contagious and can be transmitted via the placenta but the main cause of spread is as a result of cat fights.
• Feline infectious peritonitis (FIP) is caused by a mutated feline coronavirus. FIP again is an immune related disease and often results in the production of fluid in the abdomen and chest cavities. It is transmitted through infected body fluids and via the faeces.

Why is testing for these viruses important?

FeLV and FIV are implicated in a wide variety of diseases including those exhibiting bone marrow and immune dysfunction. Therefore testing for these diseases is a routine procedure for the sick cat particularly if the cat has been in contact with others of unknown FeLV or FIV status. Similarly testing is prudent if a new cat is intended to be introduced into a household with other cats. Testing may be done prior to vaccination to ensure that the cat does not have the disease prior to vaccinating. This is especially important since FIV vaccination is likely to cause a subsequent positive result for FIV testing.

Feline coronaviruses are common and found in the intestinal tract of many healthy cats. The particular strain of FCoV that causes FIP is less common and is caused by an internal mutation of the more common intestinal coronavirus within the body, allowing the virus to become more deadly. Unfortunately at present there is no test that will specifically detect the mutated form of FCoV virus that causes FIP. In addition, the number of cats in the population that carry antibodies to FCoV is high. Therefore testing cats for FCoV is usually restricted to those for which a diagnosis of FIP is strongly suspected due to other clinical information and supporting laboratory data or those cats in which a negative test result may help decrease the suspicion of the cat having FIP.

The tests all involve taking a small blood sample which is tested for either the virus itself or antibodies to the virus. Once we have the results we may advise further testing before confirming whether the cat had or had not the particular viruses.

Summary

All in all, FeLV and FIV are useful screening tests and are routinely carried out in general practice. A test for confirmation of the presence of the condition may sometimes be sent to a specialist laboratory.