Illegal African swine fever (ASF) vaccine use in China continues, creating concern in the US swine industry. Per a January 21, 2021, report by Reuters, “A new form of African swine fever identified in Chinese pig farms is most likely caused by illicit vaccines, industry insiders say… Two new strains of African swine fever have infected more than 1,000 sows on several farms owned by New Hope Liuhe, China’s fourth-largest producer, as well as pigs being fattened for the firm by contract farmers, said Yan Zhichun, the company’s chief science officer.” USDA Animal and Plant Health Inspection Service (APHIS) says there is information about at least two ASF vaccines being used in China, a situation they continue to monitor and acknowledge may change. One of these vaccines circulating in China at this stage has a deletion of only the CD2 gene and the other with deletions of the CD2 and the MGF genes. Based on this information, APHIS fully expects available ASF PCR tests deployed in the US to be able to detect both vaccine strains.
The Swine Health Information Center remains vigilant in its monitoring of the situation. While a proven reliable, tested, and approved vaccine for ASF would be welcome, risks associated with any vaccine versions not shown to be safe and effective are great. Anecdotal information from China, prior to the Reuters report, indicated an unapproved two-gene deleted ASF vaccine version in the Asian nation reportedly causes infection and pathology as well as some death, but the majority of pigs live following vaccination, even though there might be chronic lesions and shedding. Consequently, the ability to detect even these types of vaccine strains via PCR is crucial for safeguarding the US swine herd from risk of exposure due to feed, fomites, products, or by purposeful or accidental introductions.
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