A stray cat diagnosed with FIV
Feline Immunodeficiency Virus (FIV) is a lentivirus that progressively disrupts the normal immune system of a cat. This leaves the cat susceptible to many other infections. Cats affected by FIV often appear normal for many years. However, over time they often fall ill to pathogens which may otherwise be harmless to healthy cats.
The main mode of transmission of FIV is when a cat infected with the virus bites another cat. As such free-roaming, aggressive male cats are most frequently infected. Indoor cats have a lower likelihood of contracting the disease. Transmission between household cats that do not fight is not common but possible. Infected queens can rarely infect kittens.
In data collected by IDEXX over the years, prevalance of FIV in Singapore was estimated to be at 18%.
Symptoms of FIV
During early infection, the virus after inoculation is carried to nearby lymph nodes. It reproduces in the white blood cells there and then spread to the other lymph nodes throughout the body. This usually results in enlargement of the lymph nodes and fever. The virus then spreads to other organs including the kidneys, bone marrow, lung, brain and intestinal tract.
Symptoms of disease are often due to opportunistic secondary infections rather than the FIV. Diarrhoea may occur from bacterial overgrowth and inflammatory lesions in the gastrointestinal tract. Pneumonia can result from bacterial, fungal or protozoal infections in the lungs.
Other symptoms of cats infected with FIV include enlarged lymph nodes, fever, anaemia, poor coat, conjunctivitis, inflammation of gums and mouth (stomatitis). The nervous system can be affected in some cases resulting in uncoordinated gait, altered behaviour and seizures.
Infected cats have progressive weight loss and often have cancer (lymphoma or leukemia) and other blood diseases eg Feline Leukemia virus.
B-cell lymphoma is the most common cancer found in FIV-infected cats and are thought be caused directly by the virus. In these cats, findings may include enlarged peripheral lymph nodes, abdominal growths and weight loss.
Diagnosis
FIV testing is recommended in the following cases:
- sick cats, even if previous serology tests have been negative
- cats and kittens when first brought into the clinic. A negative test should be confirmed 60 days later.
- annual testing of cats living with other FIV infected cats.
- cats that will be receiving vaccination against FIV
- cats that are used for blood donation
- cats with recent exposure to another cat of unknown status especially bite wound present. A negative test should be confirmed 60 days later.
To diagnose FIV, blood is collected from the leg or the neck of the cat and tested for the presence of antibodies to FIV virus. An in-house test using enzyme-linked immunoabsorbent assay (ELISA) is often carried out in the clinic. Results are often obtained in less than 15 minutes. This method of detection is dependent on the cat mounting an immune response to the infection or if the cat has had sufficient time after exposure to mount a response. Most cats have detectable antibody levels within 60 days of infection.
A negative result indicates that the cat’s body has not produced antibodies towards any possible FIV infection. It is important to note that it can about 8-12 weeks for antibodies to develop in a cat after infection. As a result, testing during this interval may result in false negatives. If the degree of suspicion of FIV is high in a cat although the test has yielded a negative result, repeat testing should be carried out 2-3 months later. This includes cases whereby cats have had contact with FIV-positive cats or cats of unknown status. ELISA tests are ideal for screening situations.
Polymerase chain reaction (PCR) tests are highly accurate tests that are able to detect virus levels in the cat. These tests detect presence of virus unlike ELISA tests which detect antibody response. While PCR tests are highly sensitive, there have been false positives reported in FIV-vaccinated cats. PCR allows quantity of virus to be measured in the bloodstream as well. These tests are usually expensive as samples have to be sent overseas and results may take a couple of days .
A complete blood count (CBC) is often carried out to check for any possible abnormalities as a result of FIV infection. These include low red blood cell level (anaemia), low platelet levels (thrombocytopaenia) and low white blood cell level. Cats that are asymptomatic may not show any changes on a CBC.
A biochemistry panel is included as well to diagnose any concurrent organ issues. The incidence of chronic kidney disease is higher in cats with FIV infection as compared to uninfected cats. High protein levels are often seen in affected cats.
A urinalysis may reveal signs of protein loss which is indicative of reduced kidney function.
Therapy
Supportive therapy is usually initiated with the aim of making the cat more comfortable. Erythropoietin can be given as a subcutaneous injection every 48 hours until the desired red blood cell volume is achieved. The frequency of dosing is then tapered to maintain an acceptable red blood cell volume.
Antibiotics may be given to treat any secondary bacterial infections.
Glucocorticoids and other immunosuppressive drugs are avoided so that the already compromised immune system is not weakened further.
There is no specific treatment for the disease itself as it is similar to HIV in humans. Interferon which has some antiviral and immunomodulatory effects are sometimes prescribed by vets.
Preventative measures
Keeping cats indoors helps limit exposure to other cats. Testing of cats in multicat household is recommended so that the FIV-positive cats can be separated from the FIV-negative cats and spread can be contained. Stray trap and neuter programs limit the spread of the virus by reducing fights between territorial male entire cats.
FIV is unstable in the environment. Regular cleaning with common detergents and disinfectants will easily inactivate the virus. Boarding facilities should ensure cats are individually housed especially when the FIV-status of the cat is unknown. Caretakers should ensure proper hygiene is maintained.
Vaccination
The FIV vaccine is not available in Singapore and is not considered a core vaccine.