Molecular Identification and Isolation of Avian Poxviruses from Different Bird Species in Iran

Avian pox, a prevalent viral disease among domestic and wild birds, is caused by different species of avipoxviruses belonging to the family Poxviridae. Different avipoxviruses demonstrated a certain degree of host specificity. In the present study, a total of 105 tissue samples were collected from various avian species that exhibited cutaneous or mucosal proliferative and/or necrotic lesions, which bore a resemblance to pox lesions. The molecular detection of poxviruses was accomplished through the implementation of a polymerase chain reaction (PCR) assay that targeted a highly conserved 4b gene. The samples that were positive for the Polymerase Chain Reaction (PCR) were also used for the isolation of the virus by means of chorioallantoic membrane (CAM) inoculation of embryonated chicken eggs. A pox-like lesion was observed in five avian species, and avipoxvirus was subsequently detected in 19 samples of backyard chickens (42.2%), 24 turkey samples (70.5%), a flock of commercial layer chickens, a flock of commercial breeder turkeys, four canaries (23.5%), two pigeons, and two common mynahs (Acridotheres tristis). The propagation of all viruses was conducted on chicken embryo cells (CAM), and the formation of pocks was evident, with the exception of two isolates derived from backyard chickens. A thorough investigation into the genetic relationships among various poxviruses has been conducted through the analysis of partial sequencing of the 4b gene. The study's findings have revealed a notable similarity among poxviruses derived from chickens and turkeys, which have been classified as subclade A1. The present study identified a single instance of pigeon pox in subclade A2. A close proximity of all passerine isolates, including three canarypox viruses and two novel mynahpox viruses from common mynah, was observed in subclade B2. Notwithstanding the long-standing tradition of vaccination, avian pox has been identified in two commercial flocks in disparate provinces, encompassing a layer and a turkey breeder. The present study yielded results indicating the presence of at least three distinct clades of avipoxviruses, which have been identified as the causative agents of avian pox in Galliformes, Columbiformes, and Passeriformes within the Iranian avian population. To the best of the authors' knowledge, this is the inaugural report of molecular typing of mynahpox viruses in Iran.