Influenza A virus infections in commercial turkeys in north east Italy.

During 1973-1979 a marked increase in respiratory disease was seen in turkeys in the province of Verona in north east Italy. The disease was associated with virus isolations and serological evidence of influenza A infection. Seven of the influenza A viruses isolated from affected turkeys were of the Hav6 N2 antigenic subtype and one of the Hav2 N2 subtype. Pathogenicity index tests were done for seven of the virus isolates and indicated they were of low virulence.

Ultrastructural histopathology of chick embryo chorioallantoic membrane infected with an avian reovirus.

The histopathological pattern of chick embryo chorioallantoic membrane infected by an avian reovirus, Crawley strain, has been investigated by semithin sections and transmission electron microscopy of ultrathin sections. The typical virus-induced pock is made up of a crust of necrotic ectodermal cell elements, an ectodermal proliferation and a proliferated, infiltrated, and oedematous mesoderm. Large crystals of virions are present in the ectodermal cells of the pock, where the details of the viral morphogenesis are not clearly revealed. While the virus appears neither to replicate in the mesodermal elements, nor in endodermal cells, it actively replicates in macrophages inside blood vessels. This finding may account for the dissemination of the infection. The pattern of replication of virions in these cells is identical to that described in in vitro tissue cultures.

Inactivation of a turkey herpesvirus by ultra-violet light.

The sensitivity to inactivation by ultraviolet light of the PB 1 strain of herpesvirus of turkeys (HVT) was determined and compared with the relative sensitivity of pseudo-rabies virus (PRV), another member of the herpesvirus group. HVT (PB1) was 6.3 times more resistant than PRV when assayed in chick embryo fibroblasts. The survival curve of HVT (strain PB1) had one component and the survival curve of PRV had two components. Survival curves of HVT and PRV in chick embryo fibroblasts treated with caffeine and in duck embryo fibroblasts are also presented. Evidence was obtained for host cell reactivation of HVT and PRV in chick embryo fibroblasts. Multiplicity reactivation could be clearly demonstrated for UV-irradiated PRV, but not for HVT.

Biological and physico-chemical properties of the infectious bursal disease virus (IBDV).

Some biological properties of an egg-adapted strain of IBDV, PV1, have been studied. By immunofluorescent staining the strain is serologically identical to another egg-adapted strain, MU2, and to three pathogenic strains of IBDV. All five strains do not react with antisera prepared against known avian viruses of various groups, including Reoviruses. The egg-adapted strain PV1 replicates in chick embryo fibro-blasts and in RK13 cells, with the formation of plaques. The PV1 strain, highly neuropathogenic for newborn mice, is not neuropathogenic for newborn chicks. Various physico-chemical characteristics of IBDV have been studied in comparison to Crawley Reovirus, namely resistance to 5-iodo-2-deoxyuridine, heat-resistance, stability over a wide pH range, resistance to photodynamic inactivation and UV irradiation, sensitivity to Actinomycin D. As Reoviruses, IBDV is a naked RNA Virus, sensitive to Actinomycin D. It is more resistant than Reoviruses to heat, UV irradiation and photodynamic in-activation. All these findings are discussed in relationship to the taxonomic position of IBDV. Cytological observations are reported on cells infected with IBDV and the growth curve is described.