Isolation and molecular characterization of lumpy skin disease viruses from selected outbreak areas in the Oromia Regional state, Central Ethiopia

Lumpy skin disease (LSD) is an economically important notifiable viral disease of cattle caused by Lumpy skin disease virus (LSDV). In Ethiopia, a live attenuated vaccine strain called Kenyan sheep and goat pox O-180 (KS-1) has been used for immunization of cattle. Disease outbreaks have been repeatedly reported in different parts of the country. However, similar outbreak investigations have not yet been reported or documented in the study area. This study aimed to explore the cause of LSD outbreaks, isolate and molecularly characterize the virus and genetic diversity of the LSDV strains that cause occurrences in cattle in four selected areas of the Oromia regional state, central Ethiopia. A cross-sectional study was carried out on the area of active outbreaks around Batu, Bishoftu, Sululta, and Mojo. Skin nodule and swab samples were collected from the animals revealed high fever, nasal discharge, lacrimation, leg swelling, salivation, decreased appetite, reduced milk production, and weight loss. A total of 32 skin nodule samples were collected using virus transport media and tested for molecular detection, virus isolation, and sequencing. Among the total samples collected, 25 samples were detected using conventional polymerase chain reaction (PCR) and real-time PCR, and 19 samples tested positive. One KS-1 vaccine was used as a control and eight field samples were subjected for viral isolation using an embryonic sheep kidney cell line, and six LSD field viruses were isolated. The cytopathic effect (CPE) was observed starting from passage one on day four for the field isolates, whereas KS-1 revealed a CPE on day three of passage one. Four virus isolates were sequenced, and the sequences were deposited in the GenBank under the accession numbers PQ119823, PQ119824, PQ119825, and PQ119826. Sequence comparisons were conducted between the current isolates, the KS-1 vaccine, and previous Ethiopian isolates. Sequence variation was observed at nucleotide positions 41 A/C and 292 T/C, as well as amino acid sequence variations at 14 N/P and 98 S/P between the current isolate and KS-1 vaccine, whereas single genetic variations at nucleotide position 41 A/C and amino acid 14 N/P were observed between the current isolate and previous isolates in Ethiopia. Phylogenetic tree analysis indicates that the current isolate clustered to LSDV. These findings confirmed that the investigated outbreaks were caused by LSD viruses. The use of full-genome sequencing to capture the genetic diversity of field LSDV strains in Ethiopia is recommended.