EFFECTS OF LA-CROSSE VIRUS-INFECTION ON PREGNANT DOMESTIC RABBITS ANDMONGOLIAN GERBILS

The transplacental transmission of La Crosse virus (LACV) was evaluate d in domestic rabbits (Oryctolagus cuniculus) and Mongolian gerbils (M eriones unguiculatis) as a potential mechanism for the maintenance of the virus. Rabbits were infected with LACV at different times of gesta tion by injection of viral suspensions or by exposure to LACV transova rially (TO) infected Aedes triseriatus. Pregnant gerbils were exposed between 16-24 days of gestation to LACV TO- infected Ae. triseriatus. Our results indicate that LACV can infect gerbils in utero. The LACV w as isolated from the brain of suckling gerbils that died 3-5 days afte r birth from LACV-esposed mothers, representing the first evidence of LACV transplacental transmission. Microgliosis was found histologicall y in the cerebral cortex. In addition, LACV infection of both pregnant gerbils and rabbits resulted in in utero and neonatal mortality. La C rosse virus was not detected in surviving young of infected rabbits ev en after immunosuppression by administration of cyclophosphamide. Thus , there was no evidence of persistent infection of rabbits following i n utero exposure. Surprisingly, some of the infected pregnant gerbils developed progressive paralysis 9-14-days postexposure, and LACV was i solated from the brains of these animals. Histopathologic studies of t hese tissue samples showed acute meningoencephalitis. The effects of n atural LACV infection should be studied in pregnant amplifying hosts, such as chipmunks and squirrels, and in pregnant women.