Epidemic situation and control measures of African Swine Fever Outbreaks in China 2018–2020

Abstract

As of 21 April 2020, 176 ASF outbreaks have occurred in China. For each outbreak, an investigation was conducted, including historical data retrieval and traceability of potential contacts. The purpose of this study is to conduct a preliminary analysis of the data obtained from the outbreak investigations, including an investigation of the possible contributing factors of the spread of ASF in China. Based on the epidemic situation and the policies issued, the entire epidemic can be divided into three phases. 71 outbreaks were reported between 3 August 2018 and 17 November 2018; 44 outbreaks between 19 November 2018 and 30 March 2019; and 61 outbreaks between 4 April 2019 and 12 April 2020. Based on the reported outbreaks, the proportional rate of outbreaks in small farms (livestock ≤ 500, 127/168) is significantly higher than that of medium (501 ≤ livestock < 2,000, 14/168; 2001 ≤ livestock ≤ 5,000, 9/168) and large farms (livestock ≥ 5,001, 18/168). The odds of infection related to swill feeding (OR = 2.5, 95% CI, 1.5–4.3) and the mechanical dissemination of vehicles and personnel (OR = 2.7, 95% CI, 1.6–4.5) are significantly higher than those of pigs and pig production transportation. Swill feeding is the major contributing factor for small farms while mechanical dissemination of vehicles and personnel is the major contributing factor for large farms. The average duration from the beginning of the infection to the official outbreak report is gradually decreasing, which means that response speed of industry entities and the animal husbandry and veterinary departments from the beginning of the infection to the outbreak report is gradually increasing. Based on the analysis for ASF outbreaks, some policies and suggestions were put forward, such as improving the biosecurity level of the farms, as well as strengthening the supervision of breeding, transportation and slaughter.

Beyond Numbers: Determining the Socioeconomic and Livelihood Impacts of African Swine Fever and Its Control in the Philippines

“…The scale of this disparity has been evidenced with the spread of ASF through Southeast Asia. In China, the proportional rate of outbreaks in smaller farms has been much greater than in medium or large farms ( 36 ). The resultant collapse of the smallholder farming sector, which produces more than 80 percent of China's pork, has created big “winners” from the crisis in the form of large pig production firms ( 35 ).…”

Genotype I African swine fever viruses emerged in domestic pigs in China and caused chronic infection

“…ASF was first described in Kenya in 1921 [ 1 ] and spread throughout sub-Saharan Africa ( www.ioe.int ). ASFVs are classified into different genotypes based on the 3′-end sequences of the B646L gene, which encodes the major capsid protein p72 [ 3 , 4 ]. To date, 24 different ASFV genotypes have been identified in Africa.…”

“…In 2018, Georgia-07-like genotype II ASFV emerged in China, and spread to 15 other Asian countries ( www.oie.int ) [ 10–12 ]. This virus causes very acute disease with near 100% mortality, and has been prevalent in China for almost three years ( www.oie.int ) [ 4 , 10 , 12–14 ]. A subsequent surveillance study found that lower virulent genotype II ASFVs emerged in China in 2020 due to natural mutations in the genomes of the highly virulent viruses [ 15 ].…”

African Swine Fever, the forgotten pandemic

“…Investigations into ASF outbreaks in China have identified three phases, with outbreaks more likely to affect small farms. Spread has been linked with swill feeding and the movement of vehicles and personnel, rather than transportation of live pigs (Gao et al, 2021).…”