African swine fever (ASF) was first confirmed in South Korea on September 17, 2019. As of September 24, 2019, a total of five ASF cases were found in the southeast Asian country. All the current outbreaks closely neighbor North Korea, by land or sea. The first two ASF cases in South Korea were confirmed in Paju and Yeoncheon. The third was discovered in Gimpo then a fourth was found in Paju. The fifth was just reported in Kanghwa. Dr. Kyoung-Jin Yoon, a professor at Iowa State University’s Veterinary School and staff at its Veterinary Diagnostic Lab, maintains close connections with swine industry experts in his native country and has been monitoring the ASF situation in South Korea closely.
The initial epidemiological investigation launched after the first two ASF diagnoses in South Korea tentatively ruled out the involvement of wild boars. Both index farms had a good fence system for feral hogs and were built in an elevated ground. Additionally, wild boars have not been observed in the area. All wild boars tested in South Korea were negative when surveillance was conducted earlier this summer.
Dr. Yoon said South Korea has implemented a nationwide movement restriction (“standstill”) for 48 hours after the first and third cases, and out-of-province movement of livestock from the impacted province, Gyeonggi and its neighboring province, Kangwon is still restricted. Including Paju, Yeoncheon, Gimpo, and Kanghwa, the federal authority has also designated a total of six counties near the border as tightly controlled zones, subject to a series of quarantine measures to prevent spread of the disease. The South Korean government has mobilized many disinfection vehicles to affected areas, with inspection posts set on all major roads for vehicle disinfection. All affected farms have been depopulated according to OIE standard.
According to Dr. Yoon, the initial epidemiological investigation didn’t reveal any obvious link between the third ASF case farm or the two earlier positive farms. The third farm is about 8.7 miles from the first ASF-affected farm and 28.6 miles away from the second farm. The Han River runs between the counties where the first and third ASF cases were found. The third farm has about 1800 pigs, including 100 sows. The fourth case farm, located in the same province as the first, has about 2400 pigs including sows and is only four miles away from the second case farm. The fourth ASF positive farm is one of 150 farms within a 6.2 miles radius from the farm where the second diagnosis of ASF was confirmed. The fifth ASF positive farm is about 9.3 miles away from the third case farm and has 400 head, including sows.
On the first two farms with confirmed ASF, death was noticed in lactating sows first and then piglets. Elevated body temperatures and inappetence were also noticed in sows. On-site necropsy revealed splenomegaly in all dead pigs. The third farm diagnosed with ASF had abortions overnight before the owner reported it to the authorities and the owner of the fourth ASF-positive farm had three abortions and one dead before reporting it to authorities. The newly affected farms were going through phone surveillance because of their proximity to the first two cases. The fifth farm was found positive by surveillance testing as the farm is at the border area but didn’t have any sick pigs at the time of blood sampling. Feedstuffs supplied to the first and second index farms tested negative for ASF. Water bodies (i.e., rivers, creeks, streams) are sampled for testing as well with results pending.
Dr. Yoon reviewed herd and clinical history of the affected South Korean farms and believes there might have been a three to four day delay in reporting from producers as they tried to treat pigs with fever and inappetence symptoms with usual protocols, until they recognized something different was occurring. This may have delayed very early detection of positive cases. However, he also says overall reporting of sick pigs to South Korean authorities has been better than expected so far. There was no evidence pigs were moved out of the index farms, however, trucks and people have been in and out. Dr. Yoon says these activities emphasize the importance of continuing education for producers and veterinarians on what to do in cases of foreign animal disease incidence.
Laboratory confirmation of ASF positives has been superb in South Korea, in Dr. Yoon’s view, with same day turnaround once reported. South Korea’s federal lab, the equivalent to National Veterinary Services Laboratories (NVSL) here in the US, is the only lab authorized to make the final report. This lab has been suffering from staff shortage and fatigue as it has handled testing all samples from both suspect cases and surveillance samples. Regional labs in South Korea are allowed to use a rapid test kit, but test results have to be confirmed at the reference lab before making any official reports. Private and university-affiliated diagnostic labs in South Korea are not allowed to do testing yet due to the lack of appropriate biosafety containment level.
Dr. Yoon sees evidence of the benefit of producer education on foreign animal disease occurrence in South Korea. Suspect cases are being quickly reported and epidemiological investigations are underway, searching for ASF origin and commonalities between affected farms.
SHIC will continue to monitor this situation along with other global swine disease monitoring efforts, reported online at www.swinehealth.org/global-disease-surveillance-reports/
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