Lumpy skin disease (LSD) is a severe disease of bovine characterized by nodules on the skin, mucous membranes, and profuse nasal discharge which causes severe economic losses. In October 2020, an LSD outbreak case was found in Inner Mongolia Autonomous Region, China. A total of 1,206 cattle were sold from the same imported animal quarantine field to 36 farms after the quarantine period finished, and over 30 farmers reported symptoms such as skin scabs found in newly arrived cattle shortly after that. A large-scale LSD outbreak investigation was launched after laboratory diagnosis confirmed LSD. The clinical samples of 1,206 cattle from 36 farms, including 1,206 whole blood, 1,206 oral and nose swabs, and 355 scabs, were collected for the qRT-PCR test. The result showed that 51 whole blood samples (4.23%), 580 swab samples (48.09%), and 350 skin scabs (98.59%) were lumpy skin disease virus (LSDV) positive, 33 of 36 farms were affected. This study aims to provide a basis for LSD epidemiological traceability, movement control, and measures for prevention and control.
Background
Lumpy skin disease (LSD) is an acute or subacute infectious disease caused by lumpy skin disease virus (LSDV) of genus Capripoxvirus. The outbreaks of LSD were confirmed in the Yili area of the Xinjiang autonomous region in August 2019 and the Fujian province in June 2020. We detected LSDV in our daily monitoring work, then isolated, identified and sequenced the virus, and analyzed the whole genome characteristics of the isolated strain.
Results
Whole genome sequencing revealed that the strains isolated were all LSDV and were named as LSDV XJ201901 and LSDV FJ2019. The results showed that the identity based on whole genome sequences between LSDV XJ201901 and LSDV FJ2019 was 100% and the identity based on whole genome sequences between the two isolated strains and the global LSDV strains was 97.28%-99.99%, with the strain LSDV72/PrachuapKhiriKhan/Thailand/2021 (99.99%) having the highest sequence identity. Analysis of potential recombination events revealed that a total of 18 potential recombination events were identified in strains LSDV XJ201901 and LSDV FJ2019. The two strains are a recombination of Neethling vaccine LW 1959 (GeneBank: AF409138.1) with KSGP 0240 (GeneBank: KX683219.1). It was observed that Neethling vaccine LW 1959 (11/18) and KSGP 0240 (10/18) are involved in most of the potential recombination events.
Conclusions
The virus isolate in this study was LSDV and was identified as a vaccine recombinant strain. The most likely potential parent strains of the two strains in this study are Neethling vaccine LW 1959 and KSGP 0240. The strains in this study are very similar to those isolated in East and Southeast Asia since 2019.
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