Characterization of African swine fever outbreaks in Hong Kong SAR, winter 2023 to 2024
Abstract
Hong Kong veterinary authorities responded to a series of suspected outbreaks of African swine fever in domestic pigs in the New Territories of the Hong Kong Special Administrative Region from November 2023 to January 2024. Cases were identified on 10 farms, with one farm having a single pig with an inconclusive result. Subsequent genetic analysis suggested a more complicated picture than initially considered. Full genome sequencing identified a genotype II virus with a novel deletion in the left of the genome, as well as a genotype I/II hybrid virus similar to those previously reported in the Chinese mainland, Vietnam, and Russia. The replication kinetics of the two viruses were compared to reference strainsin vitro, and the virulence of the genotype I/II hybrid was testedin vivoalongside an African genotype XV virus. Both viruses caused high fever and inappetence, with animals reaching severe humane endpoints within 6 days.
Importance
African swine fever virus causes a lethal hemorrhagic disease in domestic and wild pigs that is present in Africa, Asia, Europe, Oceania, and the Caribbean island of Hispaniola. The virus is a serious threat to pig farmers, global food security, and biodiversity. The virus has been circulating in Eurasia for nearly 20 years, and both small and large changes in the genome have been observed, including a new recombinant virus that emerged in 2021. Full genome sequencing of viruses is required to identify any changes that are important for understanding the epidemiology of the virus, as well as guiding vaccine design and selection. Here, we report genomic data from outbreaks in Hong Kong SAR during Winter 2023/2034 and evaluate the pathogenicity of a hybrid-recombinant virus. We show that minor changes to the hybrid-recombinant genome do not influence virulence and show that this virus, along with a previously uncharacterized isolate from Africa, can be used to test vaccine efficacy in future studies.