An atypical clinicopathological manifestation of fowlpox virus associated with reticuloendotheliosis virus in commercial laying hen flocks in Brazil

• Published in: Transboundary and emerging diseases Vol. 67; no. 6; pp. 2923 - 2935
• Main Authors: Chacón, Ruy D., Astolfi‐Ferreira, Claudete S., De la Torre, David I., Sá, Lilian R. M., Piantino Ferreira, Antonio J.
• Format: Journal Article
• Language: English
• Published: Germany Hindawi Limited 01-11-2020
• Subjects: Abnormalities; Animals; Brazil; Chickens; Data integration; Female; Fowlpox; Fowlpox - pathology; Fowlpox - virology; fowlpox virus; Fowlpox virus - physiology; Genomes; Integration; Long terminal repeat; molecular characterization; Outbreaks; phylogenetic analysis; Poultry; Poultry Diseases - pathology; Poultry Diseases - virology; reticuloendotheliosis virus; Reticuloendotheliosis Viruses, Avian - physiology; Reticuloendotheliosis, Avian - pathology; Reticuloendotheliosis, Avian - virology; sequencing; Viruses; Brazil; fowlpox virus; integration; phylogenetic analysis; molecular characterization; reticuloendotheliosis virus; sequencing
• ISSN: 1865-1674; 1865-1682
• DOI: 10.1111/tbed.13668

Fowlpox (FP) is a common epitheliotropic disease in chickens that is usually controlled by live attenuated vaccines. However, there have been some reports of outbreaks of FP in recent years, even in vaccinated flocks, presenting as atypical lesions and feathering abnormalities in chickens. These findings can be associated with fowlpox virus (FPV) with the reticuloendotheliosis virus (REV) integrated into its genome. In the present study, outbreaks of atypical FP were explored in vaccinated commercial laying hen flocks to determine the nature of the causative agent by histopathologic and molecular approaches. FPV and REV were detected and classified into subclade A1 of the genus Avipoxvirus and subtype 3 of REV (REV3), respectively. Additionally, heterogeneous populations of FPV with partial (containing only a remnant long terminal repeat—LTR) or total (all functional genes) integration of REV were identified by heterologous PCRs and detected considering reference integration sites. These results indicate the mechanism of chimeric genome FPV‐REV associated with outbreaks and atypical clinicopathological manifestations in commercial laying hens for the first time in Brazil and in South America. In addition, this study demonstrates the emergence of REV integrated in the FPV genome in Brazilian chicken flocks.