Experimental Hendra virus infection in pregnant guinea-pigs and fruit bats(Pteropus poliocephalus)

Antibodies to Hendra virus (HeV) have been found in a high percentage of fr uit bats (Pteropus spp.) in Australia, indicating a possible reservoir for the virus. The aim of the experiments reported here was to investigate tran splacental infection as a possible mode of transmission of the virus in fru it bats and other animals. In a first experiment, 18 pregnant guinea-pigs i n the mid-stage of gestation were inoculated with HeV, as an experimental m odel in a conventional laboratory animal. Nine developed HeV disease as con firmed by viral isolation, histopathology and immunohistochemistry. In five of the nine clinically affected guinea-pigs there was necrosis and strong positive immunostaining in the placentas in an indirect immunoperoxidase (I PX) test for HeV antigen. One of these five guinea-pigs aborted and HeV was isolated from its three fetuses, one of which was also positive to the IPX test. In three other sick guinea-pig darns, virus was isolated from fetuse s, and there was positive immunostaining in two of the latter. In a second experiment, four fruit bats were inoculated with a Similar dose of HeV. (A further four guinea-pigs inoculated at the same time developed severe disea se, indicating adequate virulence.) Two bats were killed at 10 days post-in oculation and two were killed at 21 days. In these bats, no overt clinical disease was observed, but subclinical disease occurred, as indicated by vir al isolation, seroconversion, vascular lesions and positive immunostaining. Transplacental transmission was indicated by positive immunostaining in tw o placentas and confirmed by isolation of virus from one of the associated fetuses. (C) 2000 Harcourt Publishers Ltd.