Antibodies to Hendra virus (HeV) have been found in a high percentage of fruit bats (Pteropus spp.) in Australia, indicating a possible reservoir for the virus. The aim of the experiments reported here was to investigate transplacental infection as a possible mode of transmission of the virus in fruit bats and other animals. In a first experiment, 18 pregnant guinea-pigs in the mid-stage of gestation were inoculated with HeV, as an experimental model in a conventional laboratory animal. Nine developed HeV disease as confirmed 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 (IPX) 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 dams, virus was isolated from fetuses, 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 disease, indicating adequate virulence.) Two bats were killed at 10 days post-inoculation and two were killed at 21 days. In these bats, no overt clinical disease was observed, but subclinical disease occurred, as indicated by viral isolation, seroconversion, vascular lesions and positive immunostaining. Transplacental transmission was indicated by positive immunostaining in two placentas and confirmed by isolation of virus from one of the associated fetuses.

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PubMedDate not supplied

Encephalitis caused by a Lyssavirus in fruit bats in Australia.

This report describes the first pathologic and immunohistochemical recognition in Australia of a rabies-like disease in a native mammal, a fruit bat, the black flying fox (Pteropus alecto). A virus with close serologic and genetic relationships to members of the Lyssavirus genus of the family Rhabdoviridae was isolated in mice from the tissue homogenates of a sick juvenile animal.

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PubMedDate not supplied

Absence of a role for selenium deficiency in the runting syndrome of broiler chickens in Australia.

The role of selenium deficiency in the etiology of the runting-stunting syndrome (RSS) of broiler chickens in Australia was investigated. Commercial broiler chickens maintained on selenium-deficient developed signs consistent with selenium deficiency of exudative diathesis and markedly reduced plasma glutathione peroxidase activity, but they did not develop pancreatic atrophy and fibrosis or elevated plasma amylase activity, which are the other lesions associated with RSS. Supplementation of the diets of birds from a RSS-susceptible flock with a mixture of selenium, vitamin E, cysteine, and sulfate had no effect on the incidence of runting in the treated birds. In field outbreaks of RSS there were no observable differences between affected and unaffected birds in the concentration of selenium in tissue samples. Furthermore, evidence is presented which suggests that in cases of RSS, pancreatic atrophy and elevations in plasma amylase precede reductions in plasma glutathione peroxidase activity.

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PubMedDate not supplied

Observations on the relationship in chickens between the virulence of some avian influenza viruses and their pathogenicity for various organs.

Comparative histological and immunocytochemical studies were conducted on formalin-fixed tissues from chickens infected with avian influenza viruses of varying virulence. Results showed a distinct pattern of disease that depended on the virulence of the virus and the susceptibility of the birds. At 3 days post-intranasal inoculation with a highly virulent H7N7 virus, all 6-to-8-week-old specific-pathogen-free (SPF) birds were affected, and all developed pancreatic necrosis and encephalitis associated with specific immunoperoxidase staining. Other same-aged SPF birds were only occasionally affected 6 to 8 days after intravenous inoculation with almost avirulent H4N4, H6N2, or H3N8 virus. Specific lesions and immunoperoxidase staining were noted in the kidneys only. The H7N7 virus in older commercial birds and an H7N3 virus in young SPF and older commercial birds caused intermediate mortality rates at 4 to 11 days postinoculation, and there was a broad range of lesions and specific immunoperoxidase staining in the pancreas, brain, kidney, heart, and skeletal muscle. Two exceptional birds had immunostaining of small blood vessels throughout their bodies with or without lesions or staining in the tissues, which may have represented a transitory pre-localizing phase occurring in many birds. There was necrosis without virus antigen detection in the bursae, thymuses, and cecal tonsils, possibly secondary to stress or only transitory infection of virus. These data indicate that rapid, retrospective diagnosis of avian influenza in fixed tissues is possible by using an immunoperoxidase test on pancreas, brain, and kidney.

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