INTRODUCTION
African swine fever (ASF) was
described by Montgomery in Kenya in 1921 for the first time. Since then,
the disease has been considered endemic in most of the Sub-Saharan
countries. The first period of ASF epidemics out of Africa started in
1957 in Portugal and lasted until 1999. However, the ASF epidemiological
situation dramatically changed in 2007 when an ASF outbreak was
unexpectedly reported in Georgia (Rowlands et al. , 2008). From
there, ASF spread to the other Caucasian countries and to the southern
part of the Russian Federation in one year (Gogin et al. , 2012).
Despite surveillance and control measures in the Russian Federation, ASF
continues to spread in the country with significant economic
consequences that were estimated to be 0.8-1 billion USD until October
2009 (USDA, 2010). A report indicated that ASFV was isolated from wild
boars in Iran in 2008 (Rahimi et al. , 2010). The virus also moved
to northwestern countries like Ukraine and Belarus in 2012 and 2013,
respectively. European Union member states such as Lithuania, Latvia,
Estonia and Poland were affected by the movements of the infected wild
boars in 2014. There were notifications regarding ASF outbreaks in
Romania and in the Czech Republic in 2017. In August of 2018, ASF was
introduced in China, a country with particularly close socio-economic
ties with South Korea (OIE, 2019) and other countries like Mongolia,
Vietnam, Cambodia, North Korea, and Laos which have just became
infected. South Korea reported the first ASF case in 17 September 2019.
Until 9 October 2019, 14 cases occurred in the Northern region of the
country. In spite of comprehensive epidemiological investigations, the
source of infection is not determined yet.
The movement of live animals and their products is an important route of
entry and transmission of ASF. Considering this, the World Trade
Organization (WTO) and the World Organization for Animal Health (OIE)
encourage member countries to refer to the guidelines of the Sanitary
and Phytosanitary Measures Agreement (SPS) and create relevant policies
after conducting the necessary risk assessments. According to the
guidelines of the SPS, live pigs and pig products from ASF infected
zones or countries are not allowed to be traded with ASF-free nations or
areas (OIE, 2018a). Once a region reports an ASF outbreak, an immediate
ban of the movement of live pigs and their products is implemented.
However, live pigs and pig products with ASFV can escape freely from the
infected region and be imported to other ASF-free countries legally
during the HRP (High Risk Period) (i.e., which means the time period
from the first ASF case (index case) in one country/region to the
detection and notification of the disease in that country/region, before
international trade is banned), which is the period of time from the
initial infection of the index farm to the official detection and
notification of an ASF outbreak (Horst et al. , 1998). Only 1 or 2
weeks have been shown to be sufficient for the extensive spreading of
FMD and CSF during the HRP through the movements of animals in some
European countries in recent epidemics
(Bouma et al. , 2003;
Greiser-Wilke et al. , 2000).
Considering the historical transcontinental and transboudnary
transmissions of ASF, there are several routes of ASF entry that need to
be considered: legal or illegal import of live pigs or pig products or
feed, introduction of food waste from international airplanes/ships and
their use for swill feeding, movement of infected wild boars, other
potential contaminated materials carried by foreign workers, vehicles or
other fomites. Though the movement of infected wild boars is of major
concerns in South Korea now, it is necessary to assess the probability
of ASF introduction by each possible route in order to block its entry
into the country effectively. This study aimed at assessing the
probability of ASF introduction into South Korea through legal import of
live pigs and pig products during the high risk period (HRP) using a
quantitative stochastic approach during 2009-2018.