Update on Canine and Feline Blood Donor Screening for Blood-Borne Pathogens

Wardrop, K.J.; Birkenheuer, A.; Blais, M.C.; Callan, M.B.; Kohn, B.; Lappin, M.R.; Sykes, J.

Feline Leukemia Virus. Transmission of Feline Leukemia Virus (FeLV) occurs primarily through saliva, but the virus is present in the blood and can be transmitted by blood transfusion. 100 Screening of donor cats for FeLV using an ELISA that detects soluble circulating core viral antigen p27 in the peripheral blood is recommended, and all cats testing antigen-positive should be excluded as blood donors. With the recognition that cats exposed to FeLV can develop regressive infection (defined as transient or undetectable antigenemia with proviral DNA in the blood), optimally real-time PCR testing for proviral DNA should be performed, because FeLV provirus is infectious. 101, 102 However, PCR assays for FeLV proviral DNA currently available in the United States have not been evaluated for clinical sensitivity and specificity. Regressor cats have detectable proviral DNA and viral RNA in many tissues, including the bone marrow, many years after FeLV exposure, indicating that these cats do not completely clear the virus. 103 Regressor cats can transmit FeLV infection to recipient cats through blood transfusions, and the recipients can then go on to develop progressive infection. g Furthermore, reactivation of FeLV infection in regressor cats with and without immune suppression has been reported. 103 Reactivation of a regressive FeLV infection has the potential to place FeLV-negative donor cats at risk if housed together in a colony situation if reactivation occurs in the interval between routine screening tests (eg, annual screening) and is not detected. Free-roaming cats have constant potential exposure and should be excluded from blood donor programs.