The course of the disease is comparable to HIV. The virus affects the immune system (immunosuppression) of the cat, making it susceptible to all kinds of infections.
After infection with the FIV virus there are a number of stages:
- Acute stage. This stage can occur without disease symptoms. Sometimes only some fever is observed.
- Asymptomatic phase. In this stage, the cat shows no symptoms of the disease. This period can last several years, sometimes even longer than five years. The cat can infect other cats.
- Phase with vague, general symptoms such as recurring fever, eye infections (uveitis) reduced appetite, and emaciation.
- AIDS-related stage. This is the stage when the owner notices that the cat is not well. Common symptoms are gum inflammation, eye inflammation, emaciation, lymph node swelling, shortness of breath, and diarrhea. These symptoms get worse over a few months.
- AIDS. Eventually, some of the cats will reach a stage similar to AIDS in humans. The cat emaciates, gets chronic disease problems, and all kinds of secondary infections he can’t overcome. Pneumonia and neurological symptoms (nervous disorders) are often observed in cats with AIDS.
Due to the long period (5 years on average) between infection with the virus and the development of disease symptoms, cats with FIV have a better prognosis than cats with FeLV. They can usually have a good life for a number of years before they become too sick. Unfortunately, even a cat with AIDS will eventually die from complications of the disease.