Molecular characterization of fowl and pigeon pox viruses: A recent outbreak in Libya

Abstract

Background: Poxvirus infections in poultry, particularly fowl poxviruses (FPV), pose significant challenges to the global poultry industry. A notable outbreak of cutaneous fowl (FP) and pigeon pox in Libya has primarily affected backyard chickens, pigeons, and some commercial layers, marking the region's first official record of these viruses.

Aim: This study aimed to isolate, identify, and characterize FP and pigeon pox viruses (PPVs) associated with the outbreak.

Methods: Histopathological examinations were conducted alongside clinical observations of lesions in affected chickens and pigeons. Virus isolation was performed using embryonated chicken eggs, and molecular diagnosis was achieved via polymerase chain reaction targeting the P4b core protein gene. Sequencing and phylogenetic analyses were also performed.

Results: Characteristic lesions, such as wart-like growths and scabs, were observed in backyard chickens and pigeons. Histopathological analyses confirmed the presence of eosinophilic intracytoplasmic inclusion bodies. Molecular analysis revealed high genetic similarity among the four FPV isolates, which were 100% identical to selected isolates from Iraq, Iran, and Brazil. The PPV isolates also showed significant genetic homogeneity, with 100% identity to strains from Egypt and India and high similarities to other isolates.

Conclusion: Our findings underscore the need for further investigation into the epidemiology and transmission dynamics of fowlpox and PPVs. Future research should focus on the genetic diversity of PPVs and their implications for pathogenicity and host specificity. Ongoing global surveillance and genetic analysis of avian viruses are crucial for understanding their impact on poultry populations and developing effective disease management strategies.

Keywords: Backyard chicken; Fowl pox; Libya; Pigeon; Pigeon pox.

Fig. 1.. Commercial Novo gen white-laying chickens aged 18 weeks with pox lesions on their combs and wattles.

Fig. 2.. Commercial laying chicken (Hy-line W- 80 white) aged 16 weeks with a wart-like lesion on the tops of their peaks.

Fig. 3.. Backyard chicken aged 40 days suffered from severe pox lesions on the comb, wattles, and around the eyes.

Fig. 4.. Section of sample showing extensive lesions (ballooning degeneration and inclusion bodies) caused by PPV in the skin of C. rupestris pigeons (HE, Bar = 50 μm).

Fig. 5.. Section of sample showing Bollinger bodies displacing the nuclei of keratocyte to the periphery (HE, 20 μm).

Fig. 6.. Section of CAMs harvested from embryonated eggs inoculated with samples from backyard chickens. CAMs showing a membrane, hemorrhage, and pock lesions.

Fig. 7.. Section of the CAM showing thickening of the tissue with infiltration of lymphocytes (arrow), presence of syncytial cells (arrow head) and hemorrhages (HE, Bar = 50 μm).

Fig. 8.. Section of the CAM showing some infected cells (Arrowhead) with intracytoplasmic eosinophilic inclusion bodies and ballooning of other cells (HE, Bar = 50 μm, inlet 100×).

Fig. 9.. Result of PCR showing the positive eight isolates from CAM. Bands of successful amplification of viral DNA (578 bp) compared with the positive and negative controls. A 1,000 bp DNA marker (Ladder) was used to determine the molecular weight of the bands.

Fig. 10.. Phylogenetic analysis of the partial 4b core protein gene of avian pox virus isolates. Isolate names and GenBank accession numbers. Libyan FP isolates from this study are highlighted in red circles, whereas Libyan pigeon isolates are highlighted in blue squares. The phylogenetic tree was constructed in MEGA 11 using the neighbor-joining method with 1,000 bootstrap replicates.