Estimating the time of infection for African swine fever in pig farms in Korea.

African swine fever (ASF) is a highly contagious and lethal disease with characteristics of hemorrhagic fever. ASF outbreaks in pig farms significantly damage the entire pork industry. Understanding the transmission dynamics of ASF is crucial to effectively respond. Notably, it is important to know when the infection started on the outbreak farm. This study aimed at establishing a procedure for estimating the time of infection on pig farms affected by the ASF outbreak in Korea. The protocol for sampling to detect ASF virus infection, the estimation of the time interval between infection and detection, and the estimation of the infection stage parameters for the simulation model were described. After infection, fattening sheds (9.8 days in median) had the longest detection time compared with pregnant (8.6 days) or farrowing sheds (8.0 days). The intervals were 8.8 days for farrow-to-finisher farms, 7.0 days for farrow-to-weaning farms, and 9.5 days for fattening farms. The findings of this study provide valuable insights into ASF outbreaks in pig farms thus, improving the disease control ability.

Big data-based risk assessment of poultry farms during the 2020/2021 highly pathogenic avian influenza epidemic in Korea.

Outbreaks of H5-type highly pathogenic avian influenza (HPAI) in poultry have been reported in various parts of the world. To respond to these continuous threats, numerous surveillance programs have been applied to poultry raising facilities as well as wild birds. In Korea, a surveillance program was developed aimed at providing a preemptive response to possible outbreaks at poultry farms. The purpose of this study is to comprehensively present the risks of HPAI evaluated by this program in relation to actual outbreak farms during the epidemic of 2020/2021. A deep learning-based risk assessment program was trained based on the pattern of livestock vehicles visiting poultry farms and HPAI outbreaks to calculate the risk of HPAI for farms linked by the movement of livestock vehicles (such farms are termed "epidemiologically linked farms"). A total of 7,984 risk assessments were conducted, and the results were categorized into four groups. The proportion of the highest risk level was greater in duck farms (13.6%) than in chicken farms (8.8%). Among the duck farms, the proportion of the highest risk level was much greater in farms where breeder ducks were raised (accounting for 26.4% of the risk) than in farms where ducks were raised to obtain meat (12.8% of the risk). A higher risk level was also found in cases where the species of the outbreak farm and epidemiologically linked farms were the same (proportion of the highest risk level = 13.2%) compared to that when the species between the two farms were different (7.9%). The overall proportion of farms with HPAI outbreaks among epidemiologically linked farms (attack rate, AR) was 1.7% as HPAI was confirmed on 67 of the 3,883 epidemiologically linked farms. The AR was highest for breeder ducks (15.3%) among duck farms and laying hens (4.8%) among chicken farms. The AR of the pairs where livestock vehicles entered the inner farm area was 1.3 times (95% confidence interval: 1.4-2.9) higher than that of all pairs. With the risk information provided, customized preventive measures can be implemented for each epidemiologically linked farm. The use of this risk assessment program would be a good example of information-based surveillance and support decision-making for controlling animal diseases.

Arthropods as potential vectors of African swine fever virus outbreaks in pig farms in the Republic of Korea.

The seasonality of African swine fever (ASF) in the summers and outbreaks in farms with high biosecurity levels suggest that the ASF virus (ASFV) may be transmitted by arthropod vectors. Arthropods were collected in this study from 14 pig farms with ASF outbreaks in Korea in 2019 to explore the role of arthropods as potential ASFV vectors. A total of 28,729 arthropods, including 28,508 (99.2%) Diptera, were collected using blacklight traps, insect nets and yellow sticky strips. All arthropod samples were negative for ASFV genomic DNA according to laboratory tests using real-time polymerase chain reaction. This result may reflect the effects of immediate control measures following the detection of farms with ASF outbreaks in the early phase of infection in Korea.

Epidemiological Characteristics of Foot-and-Mouth Disease in the Republic of Korea, 2014-2019.

This study describes the epidemiological characteristics of six epidemics of foot-and-mouth disease (FMD) in the Republic of Korea between 2014 and 2019. A total of 223 outbreaks had been confirmed in 40 municipalities across nine provinces. Most farms with FMD (194, 87%) were located in three densely populated livestock areas (Chungcheongnam-do, Gyeonggi-do, and Chungcheongbuk-do). More cases of FMD were found in farms with more than 1,000 pigs or 50 cattle (risk ratios = 1.27 for pigs; 9.46 for Korean native cattle) and fattening pigs. In farms affected by FMD, the proportion of animals with vaccine antibodies was low (5%-50% for Korean native beef cattle farms with FMD in 2017 vs. 97.5% in the surveillance in 2016). Effective control of FMD can be achieved through strict biosecurity measures, proper vaccination, regionalized management, and instilling awareness of FMD prevention in farmers.

Fine-scale tracking of wild waterfowl and their impact on highly pathogenic avian influenza outbreaks in the Republic of Korea, 2014-2015.

Wild migratory waterfowl are considered one of the most important reservoirs and long-distance carriers of highly pathogenic avian influenza (HPAI). Our study aimed to explore the spatial and temporal characteristics of wild migratory waterfowl's wintering habitat in the Republic of Korea (ROK) and to evaluate the impact of these habitats on the risk of HPAI outbreaks in commercial poultry farms. The habitat use of 344 wild migratory waterfowl over four migration cycles was estimated based on tracking records. The association of habitat use with HPAI H5N8 outbreaks in poultry farms was evaluated using a multilevel logistic regression model. We found that a poultry farm within a wild waterfowl habitat had a 3-8 times higher risk of HPAI outbreak than poultry farms located outside of the habitat. The range of wild waterfowl habitats increased during autumn migration, and was associated with the epidemic peak of HPAI outbreaks on domestic poultry farms in the ROK. Our findings provide a better understanding of the dynamics of HPAI infection in the wildlife-domestic poultry interface and may help to establish early detection, and cost-effective preventive measures.

Risk Assessment Program of Highly Pathogenic Avian Influenza with Deep Learning Algorithm.

OBJECTIVES: This study presents the development and validation of a risk assessment program of highly pathogenic avian influenza (HPAI). This program was developed by the Korean government (Animal and Plant Quarantine Agency) and a private corporation (Korea Telecom, KT), using a national database (Korean animal health integrated system, KAHIS). METHODS: Our risk assessment program was developed using the multilayer perceptron method using R Language. HPAI outbreaks on 544 poultry farms (307 with H5N6, and 237 with H5N8) that had available visit records of livestock-related vehicles amongst the 812 HPAI outbreaks that were confirmed between January 2014 and June 2017 were involved in this study. RESULTS: After 140,000 iterations without drop-out, a model with 3 hidden layers and 10 nodes per layer, were selected. The activation function of the model was hyperbolic tangent. Precision and recall of the test gave F1 measures of 0.41, 0.68 and 0.51, respectively, at validation. The predicted risk values were higher for the "outbreak" (average ± SD, 0.20 ± 0.31) than "non-outbreak" (0.18 ± 0.30) farms (p < 0.001). CONCLUSION: The risk assessment model developed was employed during the epidemics of 2016/2017 (pilot version) and 2017/2018 (complementary version). This risk assessment model enhanced risk management activities by enabling preemptive control measures to prevent the spread of diseases.

Clinical symptoms of African swine fever in domestic pig farms in the Republic of Korea, 2019.

This study describes the clinical characteristics of the African swine fever (ASF) outbreaks in 14 domestic pig farms in the Republic of Korea. ASF outbreak was identified by farmers' notifications in 11 farms and by active surveillance in the remaining three. At the time of notification, farmers reported sudden death, abortion and anorexia in sows. Death was the primary symptom identified by farmers in fattener pigs. The number of animals exhibiting clinical symptoms did not exceed four heads at notification, and the number of asymptomatic virus positives was four heads per farm on average. As ASF virus was detected only in the same pig house (in a pen for fattener pigs) in each of 14 ASF outbreak farms, there has been no evidence of house-to-house viral spread within any of the ASF outbreak farms. This in turn supports our hypothesis that infection was successfully detected during its initial phase.

Financial Impact of Foot-and-mouth disease outbreaks on pig farms in the Republic of Korea, 2014/2015.

The financial impact of foot-and-mouth disease (FMD) that occurred in 180 piggeries (100 farrow-to-finish and 80 fattening farms) confirmed infected during the 2014/2015 epidemic in the Republic of Korea was estimated at the farm level. The median loss due to slaughtering of pigs prior to their expected market weights was US$ 71.8 (uncovered compensation-compensation loss) plus US$ 57.3 (foregone net gain) per pig. Median loss per farm was US$ 27,487 (55.6% of total loss) for compensation and US$ 15,925 (44.4%) for foregone net gain. The total loss per farm (median, 25th-75th percentile) was US$ 43,822 (9,767-115,893), which represented 49.4% (11.5-112.8) of the annual net gain of pig farms. The total financial loss in 180 FMD outbreak pig farms was US$ 25.2 million, which was nearly one-half of the control cost (US$ 58.3 million) spent by the Korean government on this epidemic. The findings in this study should help planning to help reduce the impact at the farm level in the Republic of Korea in the future.

H5N8 Highly Pathogenic Avian Influenza in the Republic of Korea: Epidemiology During the First Wave, from January Through July 2014.

OBJECTIVES: This study describes the outbreaks of H5N8 highly pathogenic avian influenza (HPAI) in Korea during the first wave, from January 16, 2014 through July 25, 2014. Its purpose is to provide a better understanding of the epidemiology of H5N8 HPAI. METHODS: Information on the outbreak farms and HPAI positive wild birds was provided by the Animal and Plant Quarantine Agency. The epidemiological investigation sheets for the outbreak farms were examined. RESULTS: During the 7-month outbreak period (January-July 2014), H5N8 HPAI was confirmed in 212 poultry farms, 38 specimens from wild birds (stools, birds found dead or captured). Ducks were the most frequently infected poultry species (159 outbreak farms, 75.0%), and poultry in 67 (31.6%) outbreak farms was asymptomatic. CONCLUSION: As in the previous four H5N1 epidemics of HPAI that occurred in Korea, this epidemic of H5N8 proved to be associated with migratory birds. Poultry farms in Korea can hardly be free from the risk of HPAI introduced via migratory birds. The best way to overcome this geographical factor is to reinforce biosecurity to prevent exposure of farms, related people, and poultry to the pathogen.

Novel reassortant influenza A(H5N8) viruses among inoculated domestic and wild ducks, South Korea, 2014.

An outbreak of highly pathogenic avian influenza, caused by a novel reassortant influenza A (H5N8) virus, occurred among poultry and wild birds in South Korea in 2014. The aim of this study was to evaluate the pathogenesis in and mode of transmission of this virus among domestic and wild ducks. Three of the viruses had similar pathogenicity among infected domestic ducks: the H5N8 viruses were moderately pathogenic (0%-20% mortality rate); in wild mallard ducks, the H5N8 and H5N1 viruses did not cause severe illness or death; viral replication and shedding were greater in H5N8-infected mallards than in H5N1-infected mallards. Identification of H5N8 viruses in birds exposed to infected domestic ducks and mallards indicated that the viruses could spread by contact. We propose active surveillance to support prevention of the spread of this virus among wild birds and poultry, especially domestic ducks.

Epidemiology of brucellosis among cattle in Korea from 2001 to 2011.

In the present study, the outbreak patterns of bovine brucellosis in Korea from 2000 to 2011 were analyzed to understand the epidemiological evolution of this disease in the country. A total of 85,521 brucella reactor animals were identified during 14,215 outbreaks over the 12-year study period. The number of bovine brucellosis cases increased after 2003 and peaked in 2006 before decreasing thereafter. The majority of the bovine brucellosis cases were Korean native cattle, Han Woo. The numbers of human brucellosis cases and cattle outbreaks increased and decreased in the same pattern. The correlation coefficient for human and bovine cases per year was 0.96 (95% confidence interval = 0.86 ˜ 0.99; p < 10⁻³). The epidemiological characteristics of bovine brucellosis appeared to be affected by the intensity of eradication programs that mainly involved a test- and-slaughter policy. Findings from the present study were based on freely available statistics from web pages maintained by government agencies. This unlimited access to information demonstrates the usefulness of government statistics for continually monitoring the health of animal populations.

Prevalence of antibodies to Toxoplasma gondii in South Korean wild boar (Sus scrofa coreanus).

Abstract Toxoplasma gondii is an obligate intracellular protozoan parasite and a commonly encountered pathogen in humans and animals. The wild boar (Sus scrofa coreanus) is considered a good indicator when monitoring environmental contamination by T. gondii. We surveyed the prevalence of antibodies against T. gondii in wild boars from South Korea. Blood samples were collected from 426 wild boars captured in eight provinces of South Korea during the hunting seasons in 2008-12. Antibodies against T. gondii were detected using an indirect enzyme-linked immunosorbent assay in samples from 152 of boars, indicating an overall antibody prevalence of 36% (95% confidence interval=31-40%).

Estimation of the Infection Window for the 2010/2011 Korean Foot-and-Mouth Disease Outbreak.

OBJECTIVES: This study aims to develop a method for calculating infection time lines for disease outbreaks on farms was developed using the 2010/2011 foot-and-mouth disease (FMD) epidemic in the Republic of Korea. METHODS: Data on farm demography, the detection date of FMD, the clinical history for the manifestation of lesions, the presence of antibodies against FMD virus (including antibodies against the structural and nonstructural proteins of serotype O), vaccination status (O1 Manisa strain), the number of reactors and information on the slaughter of infected animals were utilized in this method. RESULTS: Based on estimates of the most likely infection date, a cumulative detection probability that an infected farm would be identified on a specific day was determined. Peak infection was observed between late December and early January, but peak detection occurred in mid-January. The early detection probability was highest for pigs, followed by cattle (dairy, then beef) and small ruminants. Nearly 90% of the infected pig farms were detected by Day 11 post-infection while 13 days were required for detection for both dairy and beef cattle farms, and 21 days were necessary for small ruminant (goat and deer) farms. On average, 8.1 ± 3.1 days passed prior to detecting the presence of FMD virus on a farm. The interval between infection and detection of FMD was inversely associated with the intensity of farming. CONCLUSION: The results of our study emphasize the importance of intensive clinical inspection, which is the quickest method of detecting FMD infection and minimizing the damage caused by an epidemic.

Control of foot-and-mouth disease during 2010-2011 epidemic, South Korea.

An outbreak of foot-and-mouth disease caused by serotype O virus occurred in cattle and pigs in South Korea during November 2010-April 2011. The highest rates of case and virus detection were observed 44 days after the first case was detected. Detection rates declined rapidly after culling and completion of a national vaccination program.

A retrospective study of the extensive eradication program for brucellosis outbreaks and control in Korea, 2002-2009.

This study concerns the quantitative analysis of brucellosis outbreaks and the related risk factors and control programs for both domestic cattle and human brucellosis infections in Korea between 2002 and 2009. There were a total of 77,082 infections of bovine brucellosis (BB) in domestic cattle with a prevalence rate (PR) of 13.3 per 1,000 cattle; during the same period there were 620 cases of human brucellosis (HB) with a PR of 0.16 per 100,000 persons. Moreover, the correlation coefficient of brucellosis outbreaks between cattle and humans was highly significant (r = +0.985). The attack ratio of HB cases was 8.04 per 1,000 BB cases. The distribution of brucellosis outbreaks was concentrated in the southeast region of Korea (P < 0.01). Significantly more males were infected than females (86.9% versus 13.1%), and a high incidence of HB was observed in those aged more than 40 years (86.1%). The majority of HB cases occurred primarily among rural inhabitants (92.3%) and among famers and related workers (47.9%). Finally, all of the measures that were applied in the extensive eradication program for brucellosis outbreaks and control were based principally on an intensive test-and-slaughter policy and contributed significantly to the reduction in the outbreaks of brucellosis in Korea.

Serosurveillance for Japanese encephalitis virus in wild birds captured in Korea.

Climate change induced by recent global warming may have a significant impact on vector-borne and zoonotic diseases. For example, the distribution of Japanese encephalitis virus (JEV) has expanded into new regions. We surveyed the levels of hemagglutination-inhibition (HI) antibodies against JEV (Family Flaviviridae, genus Flavivirus) in wild birds captured in Korea. Blood samples were collected from 1,316 wild birds including the following migratory birds: Oceanodroma castro (n = 4), Anas formosa (n = 7), Anas penelope (n = 20), Fulica atra (n = 30), Anas acuta (n = 89), Anas crecca (n = 154), Anas platyrhynchos (n = 214), Aix galericulata (n = 310), and Anas poecilorhyncha (n = 488). All were captured in 16 locations in several Korea provinces between April 2007 and December 2009. Out of the 1,316 serum samples tested, 1,141 (86.7%) were positive for JEV. Wild birds captured in 2009 had a higher seroprevalence of ant-JEV antibodies than those captured in 2007. Wild birds with an HI antibody titer of 1 : 1,280 or higher accounted for 21.2% (280/1,316) of the animals tested. These findings indicated that wild birds from the region examined in our study have been exposed to JEV and may pose a high risk for introducing a new JEV genotype into Korea.

Impact of bovine brucellosis eradication programs in the Republic of Korea.

This study concerns a quantitative analysis of the bovine brucellosis eradication program in the Republic of Korea to provide insight into how to plan better future control strategies. In 2004, an active bovine brucellosis eradication program, based principally on intensive test-and-slaughter, was implemented in Korea. With more intensive testing on cattle, the reported incidence rate at herd level increased significantly, becoming 61 times higher in 2006 (225.1 per 10,000 farms) than in 2003 (3.7 per 10,000 farms). Since 2006, when the greatest numbers of infected farms and animals were detected, the incidence rate has been decreasing. All control measures applied in the brucellosis eradication program contributed significantly to the reduction in the incidence of brucellosis. The continuation of the current control strategies, combined with new, innovative measures, may facilitate the eradication of bovine brucellosis in Korea in the near future.

The development of a selective medium for the Brucella abortus strains and its comparison with the currently recommended and used medium.

The Brucella spp. are fastidious and relatively slow-growing organisms. The isolation of such strains in a variety of specimens often requires the use of a selective medium to reduce or eliminate the growth of unexpected microorganisms. The modified Brucella selective (MBS) medium, which contains improved antibiotic mixtures, erythritol as the only carbon source, and neutral red as a pH indicator, showed good selectivity for the Brucella abortus strains, including the RB51 vaccine strain. Erythritol in the MBS medium was able to promote and/or recover the delayed growth of the B. abortus strains through the antibiotic mixtures. The Brucella colonies, which assumed a pinkish color at their central part, were easily differentiated from other organisms. The MBS medium also allows the isolation of the Brucella strains even in contaminated specimens and/or in specimens containing small numbers of viable organisms. Moreover, this medium can be applied to environmental samples for the isolation of the Brucella strains, and it can thus offer epidemiologic traceback sources for the dissemination or transfer of diseases. Therefore, the MBS medium can be applied as a useful tool of important control measures in the eradication programs.

Protection of chickens from Newcastle disease with a recombinant baculovirus subunit vaccine expressing the fusion and hemagglutininneuraminidase proteins.

Recombinant baculoviruses containing the fusion (F) and hemagglutinin-neuraminidase (HN) glycoprotein gene of the viscerotropic velogenic (vv) Newcastle disease virus (NDV) isolate, Kr-005/00, and a lentogenic La Sota strain of the NDV were constructed in an attempt to develop an effective subunit vaccine to the recent epizootic vvNDV. The level of protection was determined by evaluating the clinical signs, mortality, and virus shedding from the oropharynx and cloaca of chickens after a challenge with vvNDV Kr-005/00. The recombinant ND F (rND F) and recombinant HN (rND HN) glycoproteins derived from the velogenic strain provided good protection against the clinical signs and mortality, showing a 0.00 PI value and 100% protection after a booster immunization. On the other hand, the combined rND F + HN glycoprotein derived from the velogenic strain induced complete protection (0.00 PI value and 100% protection) and significantly reduced the amount of virus shedding even after a single immunization. The rND F and rND HN glycoproteins derived from the velogenic strain had a slightly, but not significantly, greater protective effect than the lentogenic strain. These results suggest that the combined rND F + HN glycoprotein derived from vvNDV can be an ideal subunit marker vaccine candidate in chickens in a future ND eradication program.

[Inter-observer agreement on histological diagnosis of colorectal polyps: the APACC study]. / Reproductibilité inter-observateurs du diagnostic anatomo-pathologique des polypes colorectaux.

INTRODUCTION: Adenomas are considered as precursors of colorectal adenocarcinomas. After polypectomy, surveillance depends on the histological analysis of the excised polyps. The aim of the study was to evaluate the reproducibility of the histological diagnosis performed by pathologists from participating centers in the APACC study. Their interpretations were compared to those of the study's consensual diagnosis performed by two reference pathologists. METHODS: The agreement proportion and the concordance coefficient (kappa) were estimated for 326 polyps obtained from the first 148 patients included. RESULTS: A concordant diagnosis for the adenomatous nature was shown for 246 of the 255 adenomas (96%). The diagnosis of both the histological type and the degree of dysplasia was concordant for only 92 of the 255 adenomas (36%). Kappa values were 0.67 for the adenomatous nature, 0.46 for the histological types, and 0.26 for the degree of dysplasia. CONCLUSION: A high degree of agreement was obtained for the diagnosis of the adenomatous nature. By contrast, high variations were observed for the interpretations of the histological type and the degree of dysplasia.