Molecular Detection of Avipoxvirus in Wild Birds in Central Italy

Molecular and pathological screening of the current circulation of fowlpox and pigeon pox virus in backyard birds

Avian pox is a disease that has devastating impacts on both poultry and wild bird species. Avian pox is caused by various strains of avipoxviruses (APV). Nevertheless, the virus has been detected in pigeons and chickens that are raised in backyard areas, leading to substantial financial damage for small-scale producers. There is a lack of comprehensive information regarding the transmission of APV among birds in the backyards and residential areas. Hence, the present investigation closely monitored and observed APV in domesticated birds residing in backyard areas, with the aim of impeding the transmission of the virus to nearby poultry farms. In 2023, a total of fifty backyard flocks were surveyed for the presence of avian pox disease. Sixteen backyards (14 pigeons and 2 chickens) exhibited warty nodular lesions on their heads and nonfeathered body parts. APV was confirmed in nodular lesions by polymerase chain reaction (PCR) amplification and genetic sequencing. All samples from the lesions showed successful amplification of the p4b locus (core protein p4b). Four confirmed samples were tested for pathogenicity on the chicken embryo chorioallantoic membrane (CAM). Histopathological examination revealed ballooning degeneration and numerous intracytoplasmic inclusion bodies (Bollinger bodies) in the ectoderm of the infected CAM. Phylogenetic analysis revealed that the strains clustered into main clade A, with 11 in subclade A2 and 5 in subclade A1. Amino acid identity showed 100% similarity between the vaccine (fowlpox/VSVRI/Egypt) and some detected strains (PP537574 and PP537575). In addition, the PP537576.1 to PP537580.1 and PP537582.1 to PP537585.1 had 2-point mutations compared to the fowlpox/VSVRI/Egypt vaccine. The overall finding of low biosecurity levels in the investigated backyard birds emphasizes the significance of establishing sanitary measures and control vectors to reduce virus transmission routes and disease severity. In conclusion, it is necessary to emphasize the tracking of APV in backyard birds. Concurrently, we advised enhancing hygiene protocols, vector management, and subsequent vaccination to restrict the occurrence of APV outbreaks and prevent their transmission to neighboring poultry farms. Furthermore, it is crucial to incorporate molecular studies in order to enhance the vaccine seeds for disease management.

Snapshot of the Phylogenetic Relationships among Avian Poxviruses Circulating in Portugal between 2017 and 2023

Avipoxvirus (APV), a linear dsDNA virus belonging to the subfamily Chordopoxvirinae of the family Poxviridae, infects more than 278 species of domestic and wild birds. It is responsible for causing avian pox disease, characterized by its cutaneous and diphtheric forms. With a high transmission capacity, it can cause high economic losses and damage to the ecosystem. Several diagnostic methods are available, and bird vaccination can be an effective preventive measure. Ten APV-positive samples were analyzed to update the molecular characterization and phylogenetic analysis of viruses isolated in Portugal between 2017 and 2023. A P4b gene fragment was amplified using a PCR, and the nucleotide sequence of the amplicons was determined using Sanger sequencing. The sequences obtained were aligned using ClustalW, and a maximum likelihood phylogenetic tree was constructed. With this study, it was possible to verify that the analyzed sequences are distributed in subclades A1, A2, B1, and B3. Since some of them are quite similar to others from different countries and obtained in different years, it is possible to conclude that there have been several viral introductions in Portugal. Finally, it was possible to successfully update the data on Avipoxviruses in Portugal.