Clinical symptoms of African swine fever in domestic pig farms in the Republic of Korea, 2019

Abstract

This study describes the clinical characteristics of the African swine fever (ASF) outbreaks in 14 domestic pig farms in the Republic of Korea. ASF outbreak was identified by farmers' notifications in 11 farms and by active surveillance in the remaining three. At the time of notification, farmers reported sudden death, abortion and anorexia in sows. Death was the primary symptom identified by farmers in fattener pigs. The number of animals exhibiting clinical symptoms did not exceed four heads at notification, and the number of asymptomatic virus positives was four heads per farm on average. As ASF virus was detected only in the same pig house (in a pen for fattener pigs) in each of 14 ASF outbreak farms, there has been no evidence of house‐to‐house viral spread within any of the ASF outbreak farms. This in turn supports our hypothesis that infection was successfully detected during its initial phase.

Insects as potential vectors of African swine fever virus in the Republic of Korea

“…In this study, a total of 28,718 insects were collected in ASF outbreak farms, and no trace of ASFV-DNA was detected by laboratory analysis. This may reflect the effects of cleaning and disinfection, following the detection of ASF outbreak in the early phase of infection [Yoon et al, 2020]. The results of the present study and the experimental research and fieldwork previously conducted in other countries suggest that it is premature to conclude on the role of insects in the transmission of ASFV.…”

Surveillance of ASF-infected pig farms from September to October 2019 in South Korea

“…It is highly possible that there was no evidence of pen-to-pen infection within and across farms. In addition to the fact that the number of animals with clinical signs was less than four heads at the time of notification and that the number of asymptomatic virus-positive cases did not exceed four heads per farm on average [ 13 ], this surveillance also supports the fact that the infection was detected in the initial phase.…”

Neurological signs in African swine fever virus-infected piglets

“…Although clinical signs and lesions by ASFV have been recorded both in previous experimental and field studies (Schlafer and Mebus 1984, Kipanyula and Nong'ona 2017, Nga, Tran Anh Dao et al 2020, Yoon, Hong et al 2020, this is the first report of neurological signs in ASFV-infected neonate piglets. In these piglets, ASFV DNA and a significant amount of ASFV antigen and was found in brain tissues which showed microscopic lesions.…”