Transmission Dynamics of African Swine Fever Virus, South Korea, 2019

Yoo, Dae sung; Kim, Younjung; Lee, Eune Sub; Lim, Jun‐Sik; Hong, Seong Keun; Lee, Il Seob; Jung, Chung Sik; Yoon, Hachung; Wee, Sung‐Hwan; Pfeiffer, Dirk U.; Fournié, Guillaume

doi:10.3201/eid2707.204230

Cited by 25 publications

(30 citation statements)

References 20 publications

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“…Due to the timely implementation of excessive control measures, no further ASF outbreaks have been reported in the pig industries during the study period (October 2019-June 2020). A recent modelling study also indicated that the transmission of ASF from domestic pigs to WB population was unlikely during early phase of ASF outbreak in South Korea (Yoo et al, 2021).…”

Section: Discussionmentioning

confidence: 98%

“…Due to the timely implementation of excessive control measures, no further ASF outbreaks have been reported in the pig industries during the study period (October 2019‐June 2020). A recent modelling study also indicated that the transmission of ASF from domestic pigs to WB population was unlikely during early phase of ASF outbreak in South Korea (Yoo et al., 2021). Similar to other European countries, these suggest that ASF persists in South Korea primarily via the WB‐habitat cycle (Chenais et al., 2019), and therefore, we believe the lack of consideration about the transmission between domestic pigs and WBs would have only a limited impact in this study.…”

Section: Discussionmentioning

confidence: 99%

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Understanding the transmission of African swine fever in wild boars of South Korea: A simulation study for parameter estimation

Han

Yoo

Pak

et al. 2021

Transbounding Emerging Dis

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Since the introduction of African swine fever (ASF) to Georgia in 2007, the disease has spread to many other countries including South Korea. Initial detection of ASF from wild boars (WB) in South Korea was reported in early October 2019. Since then, more than a thousand WB samples collected from the northern part of the country have been confirmed as ASF positive (2.9% of ASF positivity among WB samples collected until June 2020), indicating that the disease is endemic in the WB populations. To control the disease, multiple layers of fence‐lines have been erected. Nevertheless, outbreaks continuously occurred across the fence, requiring a better understanding of the spatial transmission mechanism of ASF in WBs. Hence, we developed a novel ASF transmission model to estimate ecological and epidemiological parameters related to the spread of the disease in the WB population of South Korea. The results showed that roads and rivers were effective to prevent the spread, reducing the transmission rate to approximately 37% on average. Only a limited level of reduction was indicated via fence‐lines, implying erection of fences might be considered as a temporary measure to delay the spread. This study also revealed that the probability of ASF transmission to adjacent habitats considerably decreased with increasing distance, supporting the slow spatial transmission speed reported from other European countries. Considering that elucidation of ASF dynamics in WB is crucial to mitigate the impact of the disease, we believe this study provides some useful ecological and epidemiological implications to control the disease in future.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Understanding the transmission of African swine fever in wild boars of South Korea: A simulation study for parameter estimation

Han

Yoo

Pak

et al. 2021

Transbounding Emerging Dis

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“…The first ASF outbreak in China was reported in August 2018, and sequencing result revealed a genotype II ASFV ( 2 , 3 ). Currently, ASF has raged in Asia and spread over 16 countries including Korea ( 4 ), Indonesia ( 5 ), and Vietnam ( 6 ). Pigs intramuscularly inoculated with epidemic strain Pig/HLJ/18 demonstrated acute clinical symptoms including fever, loss of appetite, depression, lethargy, respiratory distress, vomiting, and death in all of the pigs ( 3 ).…”

Section: Introductionmentioning

confidence: 99%

Development and Application of a Duplex Droplet Digital Polymerase Chain Reaction Assay for Detection and Differentiation of EP402R-Deleted and Wild-Type African Swine Fever Virus

et al. 2022

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African swine fever (ASF) is a highly fatal porcine disease caused by the African swine fever virus (ASFV), and resulting in huge economic losses across the globe. ASF has been raging in China for 3 years, and recently EP402R-deleted ASFV strains emerged, showing sub-acute or chronic symptoms in pigs and providing novel difficulties to monitor and control the disease as EP402R-deleted strains possess no hemadsorption (HAD) ability. In addition, the gene deletion virus with low viral load is prone to results retest or false negative due to the high cycle threshold (Ct) value under the current real-time polymerase chain reaction (PCR) detection method. Thus, a new method is needed to detect and distinguish wild strains and gene-deleted viruses. In this study, a duplex droplet digital polymerase chain reaction (ddPCR) assay based on the ASFV B646L and EP402R genes was established and showed good linearity (R2 > 0.99). The limit of detection for duplex ddPCR was 52 copies per reaction and 8.6 copies per reaction for B646L and EP402R, respectively. No cross-reaction with other porcine viruses [classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), porcine parvovirus (PPV), Japanese encephalitis virus (JEV), and porcine circovirus type 2 (PCV2)] was identified by this assay. In addition, 44 ASFV-suspicious clinical samples as well as EP402R-deleted ASFV were tested in parallel by duplex real-time PCR and ddPCR, indicative of a higher sensitivity which belonged to the duplex ddPCR assay. In summary, this is the first time that duplex ddPCR assay has been successfully developed to provide an efficient method to detect and differentiate ASFV wild-type and gene-deleted strains.

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“…From individual vehicle GPS movement data, we reconstructed networks while considering the elapsed time between farm visits, and the time vehicles spent within each farm to define effective contacts among them. In addition, we considered contact between farms to end once a truck drove through a cleaning station (Figure 1), as previous studies suggest that vehicle disinfection can reduce the probability of pathogens’ introduction into pig farms, e.g., PRRSV (Thakur et al, 2017) and ASFV (Yoo et al, 2021). In the current work, the inclusion of cleaning stations reduced around half the edges of the four types of transportation vehicle networks, which represent valuable information for the analysis of disease transmission given that including or not cleaning stations provide different results of the pathogen dissemination among the farms through vehicles.…”

Section: Discussionmentioning

confidence: 99%

Modelling and assessing additional transmission routes for porcine reproductive and respiratory syndrome virus: vehicle movements and feed ingredients

Galvis¹,

Corzo

Machado³

2021

Preprint

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Porcine reproductive and respiratory syndrome virus (PRRSV) continues to cause substantial economic losses for the North American pork industry. Here we developed and parameterized a mathematical model for transmission of PRRSV amongst the swine farms of one U.S. state. The model is tailored by eight modes of between-farm transmission pathways including farm-to-farm proximity (local transmission), networks comprised of different layers contacts here considered the number of batches of pigs transferred between-farm (pig movements), transportation vehicles used for -- feed delivery, transferring live pigs to farms and to markets, and personnel (crew), in addition to the quantity of feed with animal by-products within feed ingredients, and finally we also accounted for re-break probabilities for farms with previous PRRSV outbreaks. The model was calibrated on weekly PRRSV outbreaks data. We assessed the role of each transmission pathway considering the dynamics of specific types of production. Our results estimated that the networks formed by transportation vehicles were more densely connected than the actual network of pigs moved between-farms. The model estimated that pig movements and farm proximity were the main route of transmission in the spread of PRRSV regardless of production types, but vehicles transporting pigs to farms explained a large proportion of infections (sow = 17.2%; nursery = 11.7%; and finisher = 29.5%). Animal by-products delivered via feed contributed principally to finisher farms, with a significant impact on PRRSV outbreaks on sow farms. Thus, our results support the consideration of transport vehicles and feed meals in order better to understand the transmission dynamic of PRRSV and establish more robust control strategies.

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Transmission Dynamics of African Swine Fever Virus, South Korea, 2019

Cited by 25 publications

References 20 publications

Understanding the transmission of African swine fever in wild boars of South Korea: A simulation study for parameter estimation

Understanding the transmission of African swine fever in wild boars of South Korea: A simulation study for parameter estimation

Development and Application of a Duplex Droplet Digital Polymerase Chain Reaction Assay for Detection and Differentiation of EP402R-Deleted and Wild-Type African Swine Fever Virus

Modelling and assessing additional transmission routes for porcine reproductive and respiratory syndrome virus: vehicle movements and feed ingredients

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