Abstract
Background: Lumpy skin disease (LSD) is endemic in Egypt despite the Egyptian authorities’ annual mass vaccination of animals with sheep pox vaccine (Veterinary Serum and Vaccine Research Institute, Egypt), and the LSD virus (LSDV) continues to thrive practically every summer. The disease has a huge economic impact on the trade of the animal and its by-product.
Aim: This paper study the molecular characterization of LSDV strains that have been circulating in Sharkia Governorate, Egypt, during 3 successive years (2018, 2019, and 2020).
Methods: A total of 61 specimens (26 skin nodules and 35 oculonasal swabs) were collected from a clinic in the hospital of veterinary medicine, Zagazig University, during the summer months (July, August, and September) of three outbreaks in 2018, 2019, and 2020. These were examined by polymerase chain reaction (PCR) based on open reading frame 103 (ORF103) gene to confirm the suspected cases and determine the degree of homology between the three different outbreaks during 3 successive years between each other and between the derived sequences of GenBank.
Results: Cattle is thought to be infected with LSDV due to the presence of scattered local or diffuse circumscribed skin nodules along with fever and lymph node enlargement and sometimes leg edema. The PCR approach proved rapid, sensitive, and specific for the detection of the (LSD) virus and confirmative diagnosis of disease. Forty-six were detected to be positive by PCR (75.4%). The seven sequenced samples were translated to amino acid and registered in GenBank under accession number MW357655-MW357661. A single nucleotide mutation and amino acid variation mutation were observed at positions 161 C/T and 54 P/L between the outbreak in 2020 and those in 2018 and 2019, respectively. The field LSDV isolates from Egypt cattle were more closely related to other LSDV sequences from Africa (Kenya), Asia, Europe, and the United States.
Conclusion: These findings highlight the necessity of ongoing surveillance and characterization of circulating strains and the need to improve procedures for distinguishing vaccine strains from field viruses.

Key words: Lumpy skin disease, Egypt, cattle, Phylogenetic analysis, PCR