Comparative assessment of two in-house-built isothermal assays for visual detection of African swine fever virus.

Owing to the lack of effective vaccines, current control measures and eradication strategies for the African swine fever virus (ASFV) rely on early detection and stringent stamping-out procedures. In the present study, we developed two independent isothermal amplification assays, namely, loop-mediated isothermal amplification (LAMP) and polymerase spiral reaction (PSR), for quick visualization of the ASFV genome in clinical samples. Additionally, a quantitative real-time PCR (qRT-PCR)-based hydrolysis probe assay was developed for comparative assessment of sensitivity with the developed isothermal assays. The analytical sensitivity of the LAMP, PSR, and qRT-PCR was found to be 2.64 ×105 copies/µL, 2.64 ×102 copies/µL, and 2.64 ×101 copies/µL, respectively. A total of 165 clinical samples was tested using the developed visual assays. The relative accuracy, relative specificity, and relative diagnostic sensitivity for LAMP vs PSR were found to be 95.37% vs 102.48%, 97.46% vs 101.36%, and 73.33% vs 113.33%, respectively.

Novel estimation of African swine fever transmission parameters within smallholder villages in Lao P.D.R.

African Swine Fever (ASF) disease transmission parameters are crucial for making response and control decisions when faced with an outbreak, yet they are poorly quantified for smallholder and village contexts within Southeast Asia. Whilst disease-specific factors - such as latent and infectious periods - should remain reasonably consistent, host, environmental and management factors are likely to affect the rate of disease spread. These differences are investigated using Approximate Bayesian Computation with Sequential Monte-Carlo methods to provide disease parameter estimates in four naïve pig populations in villages of Lao People's Democratic Republic. The villages represent smallholder pig farmers of the Northern province of Oudomxay and the Southern province of Savannakhet, and the model utilised field mortality data to validate the transmission parameter estimates over the course of multiple model generations. The basic reproductive number between-pigs was estimated to range from 3.08 to 7.80, whilst the latent and infectious periods were consistent with those published in the literature for similar genotypes in the region (4.72 to 6.19 days and 2.63 to 5.50 days, respectively). These findings demonstrate that smallholder village pigs interact similarly to commercial pigs, however the spread of disease may occur slightly slower than in commercial study groups. Furthermore, the findings demonstrated that despite diversity across the study groups, the disease behaved in a consistent manner. This data can be used in disease control programs or for future modelling of ASF in smallholder contexts.

Advancing vaccine development: Evaluation of a mannose-modified lipid nanoparticle-based candidate for African swine fever p30 mRNA vaccine eliciting robust immune response in mice.

The African swine fever virus (ASFV) continues to pose significant economic and pandemic risks. Consequently, discovering new, efficient vaccines is crucial. Messenger RNA (mRNA) vaccines have emerged as promising candidates, providing minimal risk of insertional mutagenesis, high safety profiles, effectiveness, rapid scalability in production, and cost-effectiveness. In this study, we have developed an ASF p30 mRNA vaccine candidate (mRNA/Man-LNP) employing mannose-modified lipid nanoparticles (LNPs). The mRNA/Man-LNP exhibited effective antigen presentation and facilitated dendritic cells (DCs) maturation. Notably, it elicited strong IgG titers and activated CD4+ and CD8+ T-cells in immunized mice, all while adhering to stringent biosafety standards. This investigation demonstrates that mRNA/Man-LNP can trigger both humoral and cellular immune responses, suggesting its potential as a potent and promising vaccine candidate for controlling African swine fever (ASF).

Epidemiological investigation of ASF outbreaks in Kerala (India): detection, source tracing and economic implications.

This study investigates suspected African swine fever (ASF) outbreaks in two villages of Kannur district in Kerala, India, with the aim of identifying the causative agent and its genotype, the source of infection, and estimating the economic losses due to the outbreaks. Clinically, the disease was acute with high mortality, while gross pathology was characterized by widespread haemorrhages in various organs, especially the spleen, which was dark, enlarged and had friable cut surfaces with diffuse haemorrhages. Notably, histopathological examination revealed multifocal, diffuse haemorrhages in the splenic parenchyma and lymphoid depletion accompanied by lymphoid cell necrosis. The clinico-pathological observations were suggestive of ASF, which was confirmed by PCR. The source of outbreak was identified as swill and it was a likely point source infection as revealed by epidemic curve analysis. The phylogenetic analysis of p72 gene identified the ASFV in the current outbreak as genotype-II and IGR II variant consistent with ASFVs detected in India thus far. However, the sequence analysis of the Central Variable Region (CVR) of the B602L gene showed that the ASFVs circulating in Kerala (South India) formed a separate clade along with those found in Mizoram (North East India), while ASFVs circulating in Arunachal Pradesh and Assam states of India grouped in to different clade. This study represents the first investigation of ASF outbreak in South India, establishing the genetic relatedness of the ASFV circulating in this region with that in other parts of the country. The study also underscores the utility of the CVR of the B602L gene in genetically characterizing highly similar Genotype II ASFVs to understand the spread of ASF within the country.

Assessment of different factors on the influence of glass wool concentration for detection of main swine viruses in water samples.

Viruses existed in wastewaters might pose a biosecurity risk to human and animal health. However, it is generally difficult to detect viruses in wastewater directly as they usually occur in low numbers in water. Therefore, processing large volumes of water to concentrate viruses in a much smaller final volume for detection is necessary. Glass wool has been recognized as an effective material to concentrate multiple in water, and in this study, we assessed the use of glass wools on concentrating pseudorabies virus (PRV), African swine fever virus (ASFV), and porcine epidemic diarrhea virus (PEDV) in water samples. The influence of pH values, water matrix, water volume, filtration rate, temperature on the effect of the method concentrating these viruses for detection was evaluated in laboratory. Our results revealed that glass wool was suitable for the concentration of above-mentioned viruses from different water samples, and demonstrated a good application effect for water with pH between 6.0-9.0. Furthermore, glass wool also showed a good recovery effect on concentrating viral nucleic acids and viral particles, as well as living viruses. In addition, combining use of glass wool with skim milk, polyethylene glycol (PEG)-NaCl, or ultracentrifuge had good effects on concentrating ASFV, PRV, and PEDV. Detection of wastewater samples (n = 70) collected from 70 pig farms in 13 regions across Hubei Province in Central China after glass-wool-concentration determined one sample positive for ASFV, eighteen samples positive for PRV, but no sample positive for PEDV. However, these positive samples were detected to be negative before glass wool enrichment was implemented. Our results suggest that glass wool-based water concentration method developed in this study represents an effective tool for detecting viruses in wastewater.

Fuzzy model for quantitative assessment of the epidemic risk of African Swine Fever within Australia.

African Swine Fever (ASF) has spread rapidly across different continents since 2007 and caused huge biosecurity threats and economic losses. Establishing an effective risk assessment model is of great importance for ASF prevention, especially for those ASF-free countries such as Australia. With a vast territory and an economy heavily relying on primary industry, Australia faces a threat from the spread of ASF. Although ordinary quarantine measures have been well-performed throughout Australia, there is still a need to develop an effective risk assessment model to understand the spread of ASF due to the strong transmission ability of ASF. In this paper, via a comprehensive literature review, and analyzing the transmission factors of ASF, we provide a fuzzy model to assess the epidemic risk of Australian states and territories, under the assumption that ASF has entered Australia. As demonstrated in this work, although the pandemic risk of ASF in Australia is relatively low, there is a risk of irregular and scattered outbreaks, with Victoria (VIC) and New South Wales (NSW) - Australia Capital Territory (NSW-ACT) showed the highest risk. The reliability of this model was also systematically tested by a conjoint analysis model. To our knowledge, this is the first study to comprehensively analyze the ASF epidemic risk in a country using fuzzy modeling. This work can provide an understanding of the risk ASF transmission within Australia based on the fuzzy modeling, the same methodology can also provide insights and useful information for the establishment of fuzzy models to perform the ASF risk assessment for other countries.

Assessment of the Impact of a Toll-like Receptor 2 Agonist Synthetic Lipopeptide on Macrophage Susceptibility and Responses to African Swine Fever Virus Infection.

Toll-like receptor 2 (TLR2) ligands are attracting attention as prophylactic and immunopotentiator agents against pathogens, including viruses. We previously reported that a synthetic diacylated lipopeptide (Mag-Pam2Cys_P48) polarized porcine macrophages towards a proinflammatory antimicrobial phenotype. Here, we investigated its role in modulating monocyte-derived macrophage (moMΦ) responses against African swine fever virus (ASFV), the etiological agent of one of the greatest threats to the global pig industry. Two ASFV isolates were compared: the attenuated NH/P68 and the virulent 26544/OG10. No effect on virus infection nor the modulation of surface markers' expression (MHC I, MHC II DR, CD14, CD16, and CD163) were observed when Mag-Pam2Cys_P48 treated moMΦ were infected using a multiplicity of infection (MOI) of 1. Mag-Pam2Cys_P48 treated moMΦ released higher levels of IL-1α, IL-1ß, IL-1Ra, and IL-18 in response to infection with NH/P68 ASFV compared to 26544/OG10-infected and mock-infected controls. Surprisingly, when infected using a MOI of 0.01, the virulent ASFV 26544/OG10 isolate replicated even slightly more efficiently in Mag-Pam2Cys_P48 treated moMΦ. These effects also extended to the treatment of moMΦ with two other lipopeptides: Mag-Pam2Cys_P80 and Mag-Pam2Cys_Mag1000. Our data suggested limited applicability of TLR2 agonists as prophylactic or immunopotentiator agents against virulent ASFV but highlighted the ability of the virulent 26544/OG10 to impair macrophage defenses.

Identification of Risk Factors for African Swine Fever: A Systematic Review.

African swine fever (ASF) is an internationally-spreading viral pig disease that severely damages agricultural pork production and trade economy as well as social welfare in disease-affected regions. A comprehensive understanding of ASF risk factors is imperative for efficient disease control. As the absence of effective ASF vaccines limits disease management options, the identification and minimisation of ASF-associated risk factors is critical to preventing ASF outbreaks. Here, we compile currently known potential ASF risk factors identified through a systematic literature review. We found 154 observation-based and 1239 potential ASF risk factors, which we were able to group into the following defined risk categories: 'ASF-virus', 'Biosecurity', 'Disease control', 'Environment', 'Husbandry', 'Movement', 'Network', 'Pig', 'Society' and 'Surveillance'. Throughout the epidemiological history of ASF there have been similar risk categories, such as 'Environment'-related risk factors, predominantly reported in the literature irrespective of the ASF situation at the time. While ASF risk factor reporting has markedly increased since 2010, the majority of identified risk factors overall have referred to domestic pigs. The reporting of risk factors for ASF in wild boar mostly commenced from 2016 onwards. The compendium of ASF risk factors presented herein defines our current knowledge of ASF risk factors, and critically informs ASF-related problem solving.

Research progress on the proteins involved in African swine fever virus infection and replication.

African swine fever (ASF) is an acute, hemorrhagic and highly contagious infectious disease caused by African swine fever virus (ASFV), which infects domestic pigs or wild boars. It is characterized by short course of disease, high fever and hemorrhagic lesions, with mortality of up to 100% from acute infection. Up to now, the lack of commercial vaccines and effective drugs has seriously threatened the healthy economic development of the global pig industry. ASFV is a double-stranded DNA virus and genome varies between about 170-194 kb, which encodes 150-200 viral proteins, including 68 structural proteins and more than 100 non-structural proteins. In recent years, although the research on structure and function of ASFV-encoded proteins has been deepened, the structure and infection process of ASFV are still not clear. This review summarizes the main process of ASFV infection, replication and functions of related viral proteins to provide scientific basis and theoretical basis for ASFV research and vaccine development.

Evaluation of the economic impact of classical and African swine fever epidemics using OutCosT, a new spreadsheet-based tool.

African swine fever (ASF) and classical swine fever (CSF) are two major transboundary animal diseases of swine with important socioeconomic consequences at farm, subnational and national level. The objective of this study was to evaluate the direct cost of outbreaks and their control at country/regional level in four countries: namely CSF in Colombia in 2015-2016, the retrospective cost of ASF in the Philippines in 2019 and in a province of Vietnam in 2020 and a hypothetical ASF scenario in one region in North Macedonia, using the newly developed Outbreak Costing Tool (OutCosT). The tool calculates the costs of 106 different items, broken down by up to four types of farms, and by who assumes the cost (whether veterinary services, farmers or other stakeholders). The total cost of CSF in Colombia was US$ 3.8 million, of which 88% represented the cost of the vaccination campaign. For ASF, there were wide differences between countries: US$ 8,26,911 in Lao Cai (Vietnam), US$ 33,19,666 in North Macedonia and over US$ 58 million in the Philippines. While in the Philippines and Vietnam, 96-98% of the cost occurred in the affected farms, the highest expenditure in North Macedonia scenario was the movement control of the neighbouring and at-risk farms (77%). These important differences between countries depend on the spread of the disease, but also on the production systems affected and the measures applied. Apart from the financial cost, these diseases have other negative impacts, especially in the livelihoods of smallholder farms. The OutCosT tool also allows users to evaluate qualitatively other important aspects related to the epidemics, such as the impact on human health, the environment, animal welfare, socioeconomic vulnerability, trading and political response. OutCosT, which is a FAO corporate tool (available online at: https://www.fao.org/fileadmin/user_upload/faoweb/animal-health/OutCosT_PIG.xlsx), can be an important tool to support country authorities to rapidly respond to a swine disease outbreak by estimating the associated costs and for advocacy purposes to mobilize resources at national or international levels.

A methodology to assess indirect economic impacts of animal disease outbreaks: A case of hypothetical African swine fever outbreak in Switzerland.

Indirect costs of animal disease outbreaks often significantly exceed the direct costs. Despite their importance, indirect costs remain poorly characterized due to their complexity. In this study, we developed a framework to assess the indirect costs of a hypothetical African swine fever outbreak in Switzerland. We collected data through international and national stakeholder interviews, analysis of national disease control regulations and industry data. We developed a framework to capture the resulting qualitative and quantitative data, categorize the impacts of these regulations, and rank the impacts in order of importance. We then developed a spreadsheet model to calculate the indirect costs of one category of control measure for an individual group of stakeholders. We developed a decision tree model to guide the most economically favourable implementation plan for a given control measure category, under different outbreak scenarios. Our results suggest that the most important measure/impact categories were 'Transport logistics', 'Consumer demand', 'Prevention of wild boar and domestic pig contact' and 'Slaughter logistics'. In our hypothetical scenario, the greatest costs associated with 'Prevention of wild boar and domestic pig contact' were due to assumed partial or total depopulation of fattening pig farms in order to reduce herd size to comply with the simulated control regulations. The model also provides suggestions on the most economically favourable strategy to reduce contact between wild boar and domestic pigs in control areas. Our approach provides a new framework to integrate qualitative and quantitative data to guide disease control strategy. This method could be useful in other countries and for other diseases, including in data- and resource-poor settings, or areas with limited experience of animal disease outbreaks.

A one-pot CRISPR/Cas13a-based contamination-free biosensor for low-cost and rapid nucleic acid diagnostics.

The pandemic due to the outbreak of 2019 coronavirus disease (COVID-19) caused by novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has raised significant public health concerns. Rapid, affordable, and accurate diagnostic testing not only paves the way for the effective treatment of diseases, but also plays a crucial role in preventing the spreading of infectious diseases. Herein, a one-pot CRISPR/Cas13a-based visual biosensor was proposed and developed for the rapid and low-cost nucleic acid detection. By combining Cas13a cleavage and Recombinase Polymerase Amplification (RPA) in a one-pot reaction in a disposable tube-in-tube vessel, amplicon contamination could be completely avoided. The RPA reaction is carried out in the inner tube containing two hydrophobic holes at the bottom. After the completion of amplification reaction, the reaction solution enters the outer tube containing pre-stored Cas13a reagent under the action of centrifugation or shaking. Inner and outer tubes are combined to form an independent reaction pot to complete the nucleic acid detection without opening the lid. This newly developed nucleic acid detection method not only meets the need of rapid nucleic acid detection at home without the need for any specialized equipment, but also fulfils the requirement of rapid on-site nucleic acid detection with the aid of small automated instruments. In this study, CRISPR/Cas13a and CRISPR/Cas12a were used to verify the reliability of the developed one-pot nucleic acid detection method. The performance of the system was verified by detecting the DNA virus, i.e., African swine fever virus (ASFV) and the RNA virus, i.e., SARS-Cov-2. The results indicate that the proposed method possesses a limit of detection of 3 copy/µL. The negative and positive test results are consistent with the results of real-time fluorescence quantitative polymerase chain reaction (PCR), but the time required is shorter and the cost is lower. Thus, this study makes this method available in resource-limited areas for the purpose of large-scale screening and in case of epidemic outbreak.

African swine fever risk and plant-based feed ingredients: Canada's approach to risk management of imported feed products.

As a result of unprecedented spread of African swine fever (ASF) since 2018, Canada has taken additional steps to prevent introduction of the virus. While the role of plant-based feed in the transmission of ASF is not completely understood, it was identified that no mitigation measures were in place to address this uncertain risk. A risk analysis process was conducted with collaboration between government and industry, including an assessment of the costs and benefits of various risk mitigation options. Using existing legislative tools, requirements must now be met before the importation of plant-based feed ingredients of concern is permitted. Even with an uncertain risk, countries such as Canada that would suffer severe consequences should ASF be introduced, need to consider appropriate, risk-based mitigation measures.

A stochastic assessment to quantify the risk of introduction of African swine fever virus to Taiwan via illegal pork products carried by international travellers.

The current study quantified the risk of releasing African swine fever virus (ASFV) into Taiwan from pork products illegally carried by international travellers from 157 countries or territories through six international airports and three international seaports. The association between various factors and the number of pork products detected by the border control authorities was also examined. The risk was estimated with a stochastic process after modelling the number of undetected illegal pork products, probability of pork product detection at international airports and seaports and probability of ASFV contamination of pork products from various countries. The overall annual probability of ASFV release to Taiwan was estimated to be 1 [95% confidence interval (CI): 1-1] under no enhanced mitigation measures. All the median airport-level risks were higher than .921, and four of them reached 1. The total annual risk was .570 (95% CI: .109-.937) for international seaports. The country or territory level risk was estimated to be 1 for Vietnam, China, Hong Kong, the Philippines and South Korea, .999 (95% CI: .628-1) for Macao and .967 (95% CI: .359-1) for Indonesia. After the total number of travellers was factored in, the number of detected illegal pork products was the highest in January and February, and travellers from Vietnam [risk ratio to Japan (RR): 80.45; 95% CI: 58.68-110.3], the Philippines (RR: 37.67; 95% CI: 26.9-52.74) and Cambodia (RR: 28.39; 95% CI: 12.69-63.51) were most likely to bring pork products to Taiwan. Our study indicated a high risk of ASFV introduction through international travellers and also identified the factors associated with the risk. This information can be used as empirical evidence for cost-effective risk mitigation practices.

Is the COVID-19 pandemic impacting on the risk of African Swine Fever virus (ASFV) introduction into the United States? A short-term assessment of the risk factors.

African swine fever (ASF) is a contagious disease with high mortality in domestic and feral swine populations. Although it is not a zoonosis, its spread may have severe socio-economic and public health consequences. The activities of veterinary services are essential for controlling ASF outbreaks within a country, but also for diminishing its threat of spread to neighbouring countries, and for recognizing its entry into countries that are currently free. ASF requires quick responses and permanent monitoring to identify outbreaks and prevent spread, and both aspects can be heavily undercut during the COVID-19 pandemic. This paper analyses changing patterns of the main drivers and pathways for the potential introduction of ASFV into the United States during the COVID-19 pandemic, including international movements of people, swine products and by-products. Data on commercial flights and merchant ships was used as a proxy to indirectly assess the flow of illegal products coming from ASF affected countries. Results from this study highlight a decreasing trend in the legal imports of swine products and by-products from ASF affected countries (Sen's slope = -99, 95% CI: -215.34 to -21.26, p-value < 0.05), while no trend was detected for confiscations of illegal products at ports of entry. Additionally, increasing trends were detected for the monthly number of merchant ships coming from ASF affected countries (Sen's slope = 0.46, 95%CI 0.25-0.59), the monthly value of imported goods ($) through merchant ships (Sen's slope = 1513196160, 95%CI 1072731702-1908231855), and the monthly percentage of commercial flights (Sen's slope = 0.005, 95%CI 0.003-0.007), with the majority of them originating from China. Overall, the findings show an increased connection of the United States with ASF affected countries, highlighting the risk posed by ASF during a global public health crisis.

Berbamine Hydrochloride Inhibits African Swine Fever Virus Infection In Vitro.

African swine fever virus (ASFV) causes a viral disease in swine with a mortality rate of approximately 100%, threatening the global pig industry's economic development. However, vaccines are not yet commercially available, and other antiviral therapeutics, such as antiviral drugs, are urgently needed. In this study, berbamine hydrochloride, a natural bis-benzylisoquinoline alkaloid isolated from the traditional Chinese herb Berberis amurensis, showed significant antiviral activity against ASFV. The 50% cytotoxic concentration (CC50) of berbamine hydrochloride in porcine alveolar macrophages (PAMs) was 27.89 µM. The antiviral activity assay demonstrated that berbamine hydrochloride inhibits ASFV in a dose-dependent manner. In addition, a 4.14 log TCID50 decrease in the viral titre resulting from non-cytotoxic berbamine hydrochloride was found. Moreover, the antiviral activity of berbamine hydrochloride was maintained for 48h and took effect at multiplicities of infection (MOI) of 0.01, 0.1, and 1. The time-of-addition analysis revealed an inhibitory effect throughout the entire virus life-cycle. A subsequent viral entry assay verified that berbamine hydrochloride blocks the early stage of ASFV infection. Moreover, similar anti-ASFV activity of berbamine hydrochloride was also found in PK-15 and 3D4/21 cells. In summary, these results indicate that berbamine hydrochloride is an effective anti-ASFV natural product and may be considered a novel antiviral drug.

Dynamical analysis of the spread of African swine fever with the live pig price in China.

Pork makes up the highest proportion of household expenditure on meat in China and supply and demand have been basically stable in the past decade. However, the catastrophic outbreak of African swine fever (ASF) in August 2018 disrupted the balance and reduced the national herd by half within six months. The consequence was a gross lack of supply to the market and consumer demand was unable to be met. Accordingly, live pig prices rose sharply from 2019. In order to assess the influence of ASF on the price of the live pigs, we use a price function to characterize the relationship between price of the live pigs and the nation's pig stock, and then establish a time delay ASF epidemic dynamical model with the price function. By analyzing the dynamical behaviors of the model, we calculate the basic reproductive number, discuss the stability of equilibrium, and obtain the critical conditions for Hopf bifurcation. The model reasonableness is confirmed by carrying out data fitting and parameter estimation based on price data of the live pigs, the pig stock data and the outbreak data of ASF. By performing sensitivity analysis, we intuitively show the impact of ASF on the price of live pigs and the pig stocks, and assess the key factors affecting the outbreak of ASF. The conclusion is drawn that, with the control measures adopted by related government department in China, the basic reproductive number ($ R_0 = 0.6005 $) means that the ASF epidemic has been controlled. Moreover, the price of the live pig increases linearly with $ R_0 $, while the effect of the number of infected pigs on the subsequent price is non-linear related. Our findings suggest that society and the government should pay more attention to the prevention of animal disease epidemics.

Semi-quantitative risk assessment by expert elicitation of potential introduction routes of African swine fever from wild reservoir to domestic pig industry and subsequent spread during the Belgian outbreak (2018-2019).

Since the introduction in Georgia in 2007 of an African swine fever (ASF) genotype 2 virus strain, the virus has rapidly spread to both Western European and Asian countries. It now constitutes a major threat for the global swine industry. The ongoing European transmission cycle has been related to the 'wild boar habitat' with closed transmission events between wild boar populations and incidental spillovers to commercial and non-commercial (backyard) pig holdings. During the epidemic in Belgium, only wild boar were infected and although the introduction route has not yet been elucidated, the 'human factor' is highly suspected. While ASF was successfully contained in a small region in the Southern part of Belgium without affecting domestic pigs, the risk of spillover at the wild/domestic interface remains poorly assessed. In this study, we used a semi-quantitative method, involving national and international experts, to assess the risk associated with different transmission routes for ASF introduction from wild boar to domestic pig holdings and subsequent dissemination between holdings in the Belgian epidemiological context. Qualitative responses obtained by our questionnaire were numerically transformed and statistically processed to provide a semi-quantitative assessment of the occurrence of the hazard and a ranking of all transmission routes. 'Farmer', 'bedding material', 'veterinarian' and 'professionals from the pig sector' were considered as the most important transmission routes for ASF introduction from the wild reservoir to pig holdings. 'Animal movements', 'farmer', 'veterinarian', 'iatrogenic', 'animal transport truck' and 'animal care equipment' were considered as the most important transmission routes posing a risk of ASF spread between pig holdings. Combined with specific biosecurity checks in the holdings, this assessment helps in prioritizing risk mitigation measures against ASF introduction and further spread in the domestic pig industry, particularly while the ASF situation in Western Europe is worsening.

Quantitative risk assessment of the African swine fever introduction into the Republic of Korea via legal import of live pigs and pig products.

There are several routes of African swine fever (ASF) introduction into a country. Among the possible routes of entry, quarantine policies determine the possibility of introduction by legal import of live pigs and pig products. This study aimed at assessing the probability of ASF introduction through legal import of live pigs and pig products during the high-risk period (HRP) using a quantitative stochastic approach during 2009-2018. The result indicates that the mean annual probability of ASF introduction by legal import of live pig was 1.58 × 10-7 (1.52~1.67 × 10-7 95% CI). The mean annual probability by legal import of pig products was 1.59 × 10-10 (1.55~1.64 × 10-10 95% CI), of which Poland assumed 87.9% of the mean annual risk. The current import quarantine policy of Korean government may be enough to block the release of the virus via legal import of live pigs and pig products, and it should be continually enforced. This result can help to elucidate source of infection and to minimize the catastrophic consequences of the potential ASF reintroduction into South Korea by designing risk mitigation strategies such as risk-based selection of routes to be assessed and prevented and decreased exposure possibility by increased control of food waste and swill feeding practices.