Model specifications for the pig products imported legally
A quantitative stochastic risk assessment for ASF introduction into South Korea via pig products imported legally was conducted using an approach similar to that used in the previous studies (Herrera-Ibatáet al. , 2017; Mur, 2010). 20 countries which exported pig products to South Korea in the last decade were subjected for the assessment (Table 1).
Similar to the previous pathway, four major assumptions were used: 1) If there were no ASF notifications in the country of origin for the study period, the probability of ASF outbreak in the country was estimated 1 outbreak in 1,000 years as maximum; 2) In order to estimate the number of ASF outbreaks during the HRP, all of the origin countries were assumed to have the same level of surveillance and export animal product quarantine capacity; 3) ASFV will be always present in an acute form based on the characteristic of the current ASFV in Eurasia; 4) ASFV can survive regardless of the types of pig products.
Similar to the live pig pathway, the probability of release (Pre ) and exposure (Pex)to a susceptible pig population was assessed. The final probability (Pf(trade of pig products)) here reflects the probability that an ASFV contaminated pig product from a country of origin o is imported to a country of destinationd (in this case South Korea) and results in ASFV transmission. This probability was modelled using a binomial process as follows:
\begin{equation} P_{f(trade\ of\ pig\ products)}=\ \sum{1-{\left(1-P_{\text{re}}\times P_{\text{ex}}\right)\ }^{n_{\text{odm}}}}\nonumber \\ \end{equation}
In this formulation nodm is the quantity (kg) of pig products (i.e. chilled and frozen pork, pork products, fat, and offal) legally imported from the country of origin to South Korea during the month m . The sterilized pork products with heat treatment at 121 °C for 15-20 min according to Range and criteria for sterilization, pasteurization and process of designated quarantine products (Notification of APQA No. 2018-24, Enforcement on 13 Sep 2018) and hog casings that were treated for at least 30 days either with dry salt or with saturated brine or with phosphate supplemented dry salt at 12 °C above following the procedure outlined by the OIE (2018b) were excluded from this study.