engleski

Isolation and molecular biological investigations of avian poxviruses from chickens, a turkey, and a pigeon in Croatia

In the last 3 yr several outbreaks of avian poxviruses (APVs) were observed in different parts of Croatia. Four strains of APVs, from chickens, a pigeon and a turkey, were isolated from cutaneous lesions by inoculation on to the chorioallantoic membranes (CAM) of 12-day-old SPF chicken embryos. The resulting proliferative CAM lesions contained eosinophilic cytoplasmic inclusion bodies. The characteristic viral particles of poxvirus were detected in the infected CAM and also in the infected tissues by transmission electron microscopy examination. Further identification and differentiation of the four various APVs were carried out by the use of a polymerase chain reaction (PCR) combined with restriction enzyme analysis. Using one primer set, which framed a region within the APV 4b core protein gene, it was able to detect APV-specific DNA from all four tested isolates. PCR results revealed no recognizable differences in size of amplified fragments between the different APVs from chicken, turkey and pigeon. Restriction enzyme analysis of PCR products using NlaIII showed the same cleavage pattern for turkey and chicken isolates and a different one for the pigeon isolate. Multiplex polymerase chain reaction for direct detection of avian poxvirus (APV) and reticuloendotheliosis virus (REV) was carried out to determine the possible integration of REV in the genome of isolated avian poxviruses. The obtained results revealed that REV was present in chicken’ s and turkey’ s strains of poxviruses, while the pigeon isolate was negative. It is not known whether the avipoxvirus vaccine strain used in Croatia is contaminated with REV or the REV is natural contaminating Croatian field strains of fowlpox virus. It is indicated by the negative REV finding in the pigeon, which was not vaccinated. The results of the present study indicate the reemerging of fowlpox in Croatia, where infections have not been recorded since 1963 and never confirmed etiologically.

avian poxvirus; chicken; pigeon; turkey; reticuloendotheliosis virus

nije evidentirano