Quantitative risk assessment of African swine fever virus introduction to Japan via pork products brought in air passengers’ luggage

Abstract

The spread of African swine fever (ASF) has reached pandemic levels over the last decade, and outbreaks of this disease in China, Mongolia, Vietnam and Cambodia in 2018 and 2019 could accelerate its transmission to neighbouring Asian territories. Thus, the risk that the ASF virus (ASFV) will be introduced to disease‐free territories increases each year. Since Japan is an island nation, the most likely way in which ASFV would be introduced is via pork products brought in air passengers’ luggage (PPAP). Therefore, in the present study, we assessed the risk of ASFV introduction to Japan via PPAP. For the purposes of this analysis, we considered 214 international commercial flights travelling from 47 origin territories to 31 destination airports as potential routes of ASFV introduction via PPAP. The risk was estimated quantitatively through a stochastic model that considered the volume of air passengers’ luggage, the amount of confiscated pork products that were carried in air passengers’ luggage and the disease status of the origin territory. The overall mean annual probability of ASFV introduction to Japan via PPAP was found to be 0.941 [95% confidence interval (CI), 0.661–1.000], which approximately corresponds to one introduction every 1.06 years. At the origin territory level, Mongolia was led as the highest risk territory, with a risk of 0.864 (95% CI, 0.434–1.000), followed by China (0.697; 0.223–0.999), Vietnam (0.662; 0.196–0.998) and the Russian Federation (0.136; 0.018–0.401). At the destination airport level, Narita International Airport had the highest risk (0.905; 0.537–1.000), followed by Kansai International Airport (0.496; 0.109–0.961), Tokyo International Airport (0.389; 0.072–0.879) and Chubu Centrair International Airport (0.338; 0.058–0.816). This information will help improve risk management activities and monitoring systems to prevent the introduction of ASFV to Japan.

Assessing the risk of ASFV entry into Japan through pork products illegally brought in by air passengers from China and fed to pigs in Japan

“…Although not totally comparable because of the methodological difference, the risk calculated in our study was lower than the risk calculated previously by Ito et al: they predicted that the annual risk of ASFV introduction from China into Japan via pork product brought in in air passenger's luggage is 0.67 (95% PI: 0.223-0.999) [37]. This is mostly because that they only considered the release risk in assessing the risk of introduction while in our current model we took account of both release and exposure risk.…”

“…Illegal importation or smuggling of meat and meat products is a serious issue which could greatly compromise a country's import regime in preventing the introduction of diseases. Its effect on the risk of entry of ASF and other TADs has been evaluated in various QRA [34][35][36][37][38][39][40]. Most recently, Jurado et al (2019) and Ito et al (2019) assessed the risk of ASF introduction into the US and Japan respectively through smuggling of pork products in air passenger https://doi.org/10.1371/journal.pone.0232132.g007…”

“…luggage [36,37]. They both calculated the risk using two main inputs without considering the exposure assessment, namely, i) number of prohibited swine products of air passengers confiscated at airports and ii) number of air passengers arriving in the US and Japan via international commercial flights.…”

Modelling the transmission and persistence of African swine fever in wild boar in contrasting European scenarios

“…Model studies have also been used to undertake a risk assessment for the spread of ASF. These studies have used statistical data fitting approaches to determine the risk of ASF introduction through contaminated pork products 24,25 , have linked ASF infection data to meteorological records to make global predictions of ASF outbreaks 26 , and have identified risk factor indicators to predict the spread of ASF in Europe 27,28 , with wild boar density classified as a key indicator. These model approaches have not focused on determining the underlying epidemiological processes responsible for infection.…”

Current status of African swine fever

“…In China ASF detections at road barriers and abattoirs are considerably more frequently reported than elsewhere (Disease information-Immediate notifications 2005-2020). An additional phenomenon since ASF was detected in China were reports emanating from several countries, namely Australia, Japan, Northern Ireland, Philippines, South Korea, Taiwan and Thailand of infected pork products being introduced by airline passengers Ito et al 2020;Jurado et al 2019). In most cases the origin of the meat was specified to be travellers from China.…”