FREQUENT PERINATAL TRANSMISSION OF FELINE IMMUNODEFICIENCY VIRUS BY CHRONICALLY INFECTED CATS

Vertical transmission of feline immunodeficiency virus (FIV) was studi ed in cats infected with either of two FIV clinical isolates (FIV-B-25 42 or FIV-AB-2771) prior to breeding and conception. Queens infected 4 to 30 months (mean = 14 months) prior to conception transmitted FIV t o 59 of 83 (71%) kittens; 50.6% were virus positive on the day of birt h. To examine potential routes of FIV transmission from mother to offs pring, kittens were delivered via either vaginal or cesarean birth and nursed by either their virus-infected natural mothers or uninfected s urrogate mothers. Comparison of FN infection rates at birth with those at 6 months of age in kittens delivered by cesarean and surrogate rai sed demonstrated that late in utero transmission occurred in approxima tely 20% of kittens. Comparison of kittens nursed by FIV+ mothers with those by uninfected surrogate mothers demonstrated a 13.5% increase i n infection rate of kittens exposed to milk-borne virus. Isolation of virus from 40% of maternal vaginal wash samples and the slightly great er infection rate in vaginally versus cesarean-delivered surrogate-nur sed kittens suggested that intrapartum transmission may occur. In addi tion, we found that low maternal CD4 count (<200 cells per mu l), long er duration of maternal infection (>15 months), and maternal symptoms of clinical immunodeficiency correlated with increased rates of mother -to-kitten FIV transmission, paralleling observations in human immunod eficiency virus-infected women. We conclude that FIV infection provide s a model in which to explore aspects of human immunodeficiency virus vertical transmission and intervention difficult to address in human p atients.