the test will change color. These give a definitive diagnosis, but it cannot differentiate between acute or persistent infections. Therefore, it is recommended that the cat be retested in three to four months after the positive result to determine if the virus has been cleared from the body. Diagnosis can also be made by reference lab testing, using an immunofluorescence (IFA) test. The IFA test uses a blood sample and will detect the virus once it is in the bone marrow by detecting the virus's presence in white blood cells. IFA testing will not give positive results for transient, primary infections - the infection must be persistent to get a positive result on this test. Other than ELISA and IFA testing, routine laboratory blood work may show changes that indicate infection but cannot be used as a definitive diagnosis. There may be blood cell count changes like leukopenia, decreased Packed Cell Volume (PCV) and Total Protein (TP) levels due to anemia, hemoconcentration and hypoglycemia due to vomiting and diarrhea, electrolyte imbalance caused by dehydration and anorexia, and recurrent urinary tract infections. Cats diagnosed as persistently infected by ELISA testing may die within a few months or may remain asymptomatic for longer; median survival time after diagnosis is 2.5 years. FeLV is categorized into four subgroups. FeLV-A is responsible for the immunosuppression characteristic of the disease. The vast majority of cats with FeLV has FeLV-A. An exception was reported in 2013. FeLV-B causes an additional increase in the incidence of tumors and other abnormal tissue growths. About half of FeLV infected cats have FeLV-B. It forms by recombination of FeLV-A and cat endogenous FeLV (enFeLV). FeLV-C causes severe anemia. Approximately 1% of FeLV infected cats have FeLV-C. It forms by mutation of FeLV-A. FeLV-T leads to lymphoid depletion and immunodeficiency. It forms by mutation of FeLV-A. The fatal diseases are leukemias, lymphomas, and non-regenerative anemias. Although there is no known cure for the virus infection, in 2006 the United States Department of Agriculture approved Lymphocyte T-Cell Immunomodulator as a treatment aid for FeLV (see Treatment). Prevention Three types of vaccines for FeLV are available: an adjuvanted killed virus noninfectious vaccine, an adjuvanted subunite vaccine and a nonadjuvanted canarypox virus-vectored recombinant infectious vaccine (ATCvet code QI066AA01 and various combination vaccines), though no currently available vaccine offers 100% protection from the virus. Vaccination is recommended for high-risk cats: those that have access to