Isolation and Molecular Characterization of Lumpy Skin Disease Virus from Four Selected Area of Active Outbreaks in Oromia Region, Central Ethiopia

Abstract

Lumpy skin disease (LSD) is an economically important notifiable viral disease of cattle caused by the Lumpy skin disease virus (LSDV). A live attenuated vaccine strain Kenya sheep and goat pox O-180 (KS -1) is used for immunization of cattle in Ethiopia. But, outbreaks of the disease have been repeatedly reported in different parts of the country. The cause of these outbreaks while animals were receiving the vaccine was not investigated and documented. Therefore, this study was aimed to explore the cause of LSD outbreaks, isolate and molecularly characterize the virus and the genetic diversity of the LSDV strains that caused the outbreaks in cattle in, four selected area of Oromia region, central Ethiopia. For these purpose, a cross-sectional study was conducted on active LSD outbreaks in four selected area namely; Batu, Bishoftu, Sululta, and Mojo Oromia region, central Ethiopia. Purposive sampling methods were used to collect skin nodules and swabs from animal with suspected LSD clinical signs such as skin nodules covering the entire body of the animal, high fever, nasal discharge, lacrimation, leg swelling, salivation, decreased appetite, reduced milk production, and weight loss. 8.49% of morbidity rate and 1.3% of mortality rate were recorded in this study. Total of 32 samples were collected in universal bottle with virus transport media and transported to National veterinary institute (NVI) for molecular detection, virus isolation and sequencing. Out of total collected sample 25 samples were detected using conventional polymerase chain reaction (PCR) and real- time PCR and nineteen (19) positive samples were obtained. Eight field samples and one KS-1 vaccine were used for virus isolation on embryonic sheep kidney cell line and six LSD field viruses were isolated. During virus isolation cytopathic effect(CPE) was observed started from passage one on day four for the field isolates, whereas the KS-1 revealed CPE on day three of passage one. Four isolated virus were sequenced, sequences were deposited in National center of biotechnology institute (NCBI) data basis and the following accession number were obtained PQ119823, PQ119824, PQ119825 and PQ119826. Sequence comparisons were done between the current isolates, KS-1 vaccine and previous Ethiopian isolates. Sequence variation were observed at nucleotide positions 41 A/C and 292 T/C, as well as amino acid sequence variations at 14N/P and 98S/P between 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 current isolate and previous isolates in Ethiopia. Phylogenetic tree analysis indicates current isolate grouped to LSDV and identical to each. The findings confirmed that the outbreaks were caused by LSDV. Targeting full-genome sequencing to capture the full genetic diversity of LSDV strains in Ethiopia were recommended.