![]() ![]() In the advanced stages of infection, humoral immunity is also adversely affected. The host then remains asymptomatic for an indefinite period until cell-mediated immunity is disrupted by a decrease in the production of Th1 cytokines. Viraemia peaks at 7-8 weeks and then declines, but increases again in the terminal stages of disease 1. After several months of infection, an absolute reduction in CD4+ is appreciable.Īpproximately three weeks after infection, cats may show the "primary phase" of FIV infection with malaise, lymphadenopathy and pyrexia 2. This initially results in a change in the ratio of CD4+ to CD8+ cells, from roughly 2:1 to less than 1:1 5. Although both CD4+ and CD8+ cells can be infected by FIV and lysed in culture, the virus appears to preferentially destroy CD4+ cells. In acute infection, the virus spreads from the site of entry to the lymphoid tissues and thymus, where it first infects T-lymphocytes and then macrophages. ![]() FIV gains entry to the cell via feline CD134, a surface molecule, and uses various chemokine receptors as secondary receptors 5. For all strains, feline lymphocytes and macrophages are the preferred cells for virus replication, and so FIV disrupts the function of the immune system. The pathogenicity of FIV is strain dependent, and can vary widely. Overall it appears that if fighting among cats housed together is rare, the prevalence of FIV is likely to be low 4.įIV infection is prevalent worldwide, with between 1 and 14% of healthy cats and up to 44% of sick cats harboring the virus 4. ![]() It is clearly possible that horizontal transmission can occur within multi-cat households, but in some households only a single cat in a group may be FIV positive, whereas in others nearly every cat may be infected. The potential role of blood-sucking insects, such as fleas, in spreading infection is unknown 2. The likelihood of infected kittens being born to a FIV-infected mother depends on the stage of infection: up to 70% of kittens are born infected if the queen suffers acute infection during pregnancy, but chronic infection of the mother rarely results in transplacental transmission 4. Vertical transmission can occur, either transplacentally or via milk 2, but venereal transmission has not been reported. Less commonly, salivary transmission can occur via shared food bowls and mutual grooming. High levels of virus are found in the saliva of infected cats, particularly those in the stages of acute or terminal infection 3. Therefore, those cats showing territorial aggression are most at risk of contracting FIV. The major route of transmission is via saliva, particularly through biting 2, 3. However, despite these similarities, FIV is specific to cats, and people cannot become infected with the virus. Subsequently it has been shown that FIV has been present in the cat population since the late 1960s, and that the virus is very similar to the human retrovirus, HIV. For general information about the family see Retroviridae Overview.įIV was first discovered in a cat rescue facility in the United States where cats had been showing similar clinical signs to people with acquired immunodeficiency syndrome 2. Feline immunodeficiency virus is a retrovirus that causes immunodeficiency disease in the domestic cat.įIV is a member of the genus of the Retroviridae family. ![]()
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