Overview of Feline AIDS and Leukaemia
Feline Immunodeficiency Virus (FIV)
Feline immunodeficiency virus is a lentivirus that causes an acquired immunodeficiency syndrome (AIDS) in domestic cats. FIV shares many characteristics with human immunodeficiency virus (HIV) although no evidence links FIV infection to any human disease, including AIDS. Cats that are free roaming in areas of high cat density have an increased opportunity for exposure, largely because bite wounds are the most common way that the disease is transmitted. Male cats are infected 2-4 times more frequently than females, and the prevalence is higher in adult cats. Adult male cats living outdoors consistently compose the majority of FIV-infected cats, and the risk is highest for sexually intact males.
FIV infection progresses through several stages, much like HIV infection in humans. Clinical stages in cats include an acute phase, a clinically asymptomatic phase of variable duration, and a terminal phase. No sharp distinction is seen between the phases in cats and not all stages will be apparent. The clinical disease caused by FIV is dependent on age and health at the time of infection, dose and route of virus inoculation and virus strain. Many FIV-infected cats are healthy: others have a history of recurrent illnesses. The most common disease syndromes seen are stomatitis (severe inflammation of the mouth and gums), myelosuppression (a condition in which bone marrow activity is decreased), tumours or neurologic disease.
Diagnosis of FIV involves a simple and quick in house blood test which can be performed in every veterinary practice. Unfortunately there is no vaccine against the disease currently available. FIV can be best prevented by keeping cats out of environments that encourage high-risk behaviour and neutering is strongly recommended. In most naturally infected cats, FIV infection does not cause a severe clinical syndrome. With proper care, FIV-infected cats can live many years and, in fact, may die in older age from causes unrelated to their FIV infection. Survival time is long and quality of life is usually good. The most important life-prolonging advice is to keep FIV-infected cats strictly indoors, not only to prevent spread to other cats but also to prevent exposure of the immunosuppressed cat to infectious agents carried by other animals. Secondary infections not only cause clinical signs in FIV-infected cats but also lead to progression of FIV infection.
Feline Leukaemia Virus
Feline Leukaemia Virus, FeLV is a retrovirus that is present throughout the world’s domestic cat population. It is spread both vertically (from mother to foetus) and horizontally (from cat to cat) with prolonged close contact. FeLV is slightly more common among male cats than females. The virus is shed in high amounts in the saliva and milk and to a lesser extent in urine and other secretions. Sharing food and water dishes, mutual grooming, and using common litter areas all contribute to virus spread. The wandering and fighting behaviour of unneutered males is an additional risk factor for infection in this group.
Many cats can carry the FeLV infection and never show signs of disease. However, when clinical signs do occur, they can be varied and nonspecific depending on the organ system involved and the presence of secondary diseases. Weight loss is the most common clinical sign in symptomatic cats followed by fever, dehydration, rhinitis (inflammation of the nose), diarrhoea, conjunctivitis, oral infections, enlarged lymph nodes and abscesses. Infected cats are also highly susceptible to bone marrow disorders and neoplasia (cancer). Lymphoma is the most common cancer affecting FeLV positive cats with the alimentary (digestive tract) form being the most recognised.
Unfortunately there is no cure for cats who are diagnosed with the virus. However, all veterinary practices have the ability to perform a rapid and reliable in-house blood test to determine if a cat is a carrier for the disease. There is also a vaccine which is highly effective against the disease and which is given on an annual basis. It is recommended that all cats be tested for FeLV prior to immunization because vaccination of infected cats is not believed to be of benefit.