Little S, Levy J, Hartmann K, Hofmann-Lehmann R, Hosie M, Olah G, et al. 2020 AAFP Feline Retrovirus Testing and Management Guidelines. J Feline Med Surg [Internet]. 2020 Jan 9 [cited 2020 Jan 13];22(1):5–30.
The is the second half of a two part series on the 2020 retrovirus guidelines published by the AAFP.
Feline Immunodeficiency Virus (FIV)
Diagnosis and pathogenesis of FIV are less complex than FeLV. The major route of infection is from bite wounds that introduces saliva into the blood. Vertical transmission is possible but uncommon in nature. Transmission between cats living together without fighting is rare, and sexual transmission is uncommon.
Initially cats present with transient fever, lymphadenopathy, and lymphopenia. They have a high FIV concentration by culture and PCR. Within a few weeks, CD4 and CD8 T cell concentrations drop, followed by antibody production and suppression of circulating virus, and an increase in CD8 cells to above pre infection levels with inversion of the CD4:CD8 ratio. This persists lifelong, though levels of both T cell types decline with time. There is a long asymptomatic phase that persists for years with progressive dysfunction of the immune system. Cell mediated immunity is more affected than humoral. Neoplasia is 5 times more common in FIV+ cats. Survival time is highly variable but similar to uninfected cats, and several studies have shown no or minimal influence on survival.
Diagnosis is based on detection of antibodies in whole blood, serum, or plasma. These are produced within 60 days of infection. Confirmation of infection is based on Western Blot or PCR. Only PCR reliably differentiates infected from vaccinated animals, though some point of care (POC) tests also may be able to. Some animals with low viral load are PCR negative despite being infected. Confirmation of positive POC testing is recommended in low risk cats, but may not be needed in high risk. Cats in terminal infection may become negative due to antigen-antibody complexes sequestering antigen.
As with FeLV, diagnosis of FIV positive status should never be a sole indicator for euthanasia.
All cats should be screened with a point of care test at the time of adoption, prior to initial vaccination, following exposure to infected cats, or if signs of illness are displayed. Additional testing is recommended for positive results, especially in low risk cats. Confirm with PCR or IFA for FeLV and PCR or Western Blot for FIV.
Antibodies are passively transferred to kittens nursing on infected queens and may persist for 6 months. These kittens rarely become infected. Cats infected as adults who produce antibodies rarely clear the infection and are generally positive for life. Positive antibody tests after 6 months are generally truly infected; but PCR may differentiate prior to 6 months. As with FeLV, infection may be spread iatrogenically through surgical instruments and supplies. Environmental survival is very poor, infected cats in hospitals do not need to be isolated (though may require reverse isolation). Any common disinfectant will kill retroviruses. Needles, IV lines and bags, ET tubes and anesthesia circuits, etc may spread disease. Blood donors should be tested by ELISA.
Positive cats should have preventative healthcare exams every 6 months, with special attention to the oral cavity. Infected animals should not be fed raw meat or dairy products. A CBC, biochemistry panel, and urinalysis by cystocentesis are recommended every 12 months. All infected animals should be neutered. Perioperative antibiotic use should be dictate by the procedure and is no different than for uninfected cats.
Vaccination is available in some countries and is ~50% effective at preventing infection, though may be less effective with some strains. Vaccinated animals will test positive with some POC tests.
Ideally infected cats should be housed indoors, though this may depending on quality of life factors. They do not need to be isolated form negative cats in stable households, but new cats should not be introduced. Risk of transfer of FIV in stable households is negligible. Infected queens should not be used for breeding.
Catteries and Shelters
Prevalence of retroviruses appears to be low, but vigilance is required. Only healthy cats should be bred and the retrovirus status of all cats should be known. All cats introduced to a cattery should be tested, and negative cats retested in 60 days with strict isolation between tests. This also applies to queens sent away for breeding. Cats leaving to attend a cat show do not need test and quarantine as risk of infection is very low. Vaccination is not needed if guidelines are followed.
All cats being adopted through a shelter should be screened for retroviruses. If not practical, recommendations should be made for screening with the new owners. All pets in shelters should be considered at risk for infection regardless of history. Vaccination on shelter entry is not recommended, unless animals are group housed in which case testing and FeLV vaccination is recommended. Pooling samples for POC testing is not recommended due to decreased sensitivity.
Testing of TNR (trap-neuter-return) cats is not recommended as the resources used would be better devoted to TNRing more animals and it is unclear what to do with positive animals.
Sick Viral-Positive Cats
Any disease in a viral positive cat should be classified as either unrelated to viral status, secondary to immunosuppression, or due to direct viral effect. For example, anemia in a FeLV positive cat may be unrelated to viral status (ie due to CKD), due to secondary infection (ie mycoplasmosis) or due to direct viral effect (ie FeLV induced erythrocyte maturation arrest). In cases where clinical illness is thought to be due to retroviral infection, AZT or possibly interferons may be used, though data on efficacy is scant. (MRK)
Kreisler RE, Levy JK, et al. Decrease in Population and Increase in Welfare of Community Cats in a Twenty-Three Year Trap-Neuter-Return Program in Key Largo, FL: The ORCAT Program. Front Vet Sci. 2019 Feb 1;6:7.
feline immunodeficiency virus