• Clinical and Experimental Vaccine Research
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• v.13 no.1
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• pp.54-62
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• 2024

Purpose: Accidental vaccination with a live attenuated low-virulence strain of Miyagi (LOM) vaccine led to the reemergence of classical swine fever virus (CSFV) in Jeju province, South Korea in 2014. To control the continual outbreaks of LOM-derived CSFV, the provincial government launched a provincial mass vaccination project using a CSF-E2 subunit vaccine. We conducted this study to assess the herd immunity level and outcomes of E2 vaccine-based immunization in breeding and growing herds on Jeju Island during 2020-2021. Materials and Methods: A large-scale vaccination trial using the Bayovac CSF-E2 vaccine investigated its efficacy in breeding and growing herds under farm application conditions (10 CSFV-affected and three CSFV-naïve swine farms). Results: The level of herd immunity in each farm was classified into three (S1-S3) and six (G1-G6) profiles in breeding and growing herds, respectively. Immunity monitoring revealed a remarkable improvement in the herd immunity status in all farms. The majority (10/13) of farms, including CSFV-free farms, showed the S1G1 immunity profile in 2021, indicating the appropriate implementation of the advised vaccination regime. Moreover, there were significant decreases in E^rns seropositivity from 100% to 50% and 25.9% to 4.3% at farm and pig levels, respectively. In particular, all farms were confirmed as CSFV free in the growing-finishing herds. Conclusion: Our large-scale trial demonstrated the effectiveness of the E2 subunit vaccine in establishing herd immunity stabilization and eliminating CSFV circulation in the affected farms and highlighted the need for a provincial vaccination policy to regain the CSF-free status on Jeju Island.

• Korean Journal of Veterinary Research
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• v.47 no.4
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• pp.429-435
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• 2007

The risk of an outbreak of classical swine fever (CSF) was evaluated in relation to the vaccination and seroprevalence of antibodies. Blood samples were collected from 60 piggeries throughout Korea and information regarding CSF vaccination habits was also obtained via in-person interviews with pig farmers. The results of the survey indicated that 51 out of 60 farms were regularly performing CSF vaccinations in reproductive herds. Farmers preferred to vaccinate their reproductive pigs before weaning (41 farms) than on (9 farms) or after weaning (1 farm). In growing herds, however, double vaccinations as recommended were implemented for only 40 farms (66.7%) and vaccine schedules were identified as being frequently ignored. Moreover, many farms (18/40) were found to vaccinate earlier or later than the recommended time. According to antibody seroprevalence levels, only 36 farms (60%) were considered to be safe regarding potential risk for a CSF outbreak. Among the remaining pig farms, 6 were at low-risk (10%), 12 were at medium-risk (20%), and another 6 were at high-risk (10%). Antibody levels were found to be consistent with vaccination status obtained from personal interview surveys. Our findings demonstrate the importance of vaccinations regarding the prevention of a CSF outbreak, suggesting that vaccinations must be promoted toward pig raisers and practitioners.

• Journal of Korean Public Health Nursing
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• v.35 no.3
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• pp.384-400
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• 2021

Purpose: This study aimed to investigate COVID-19 vaccination intention among college students in Korea and verify the factors influencing vaccination. Methods: From April 28 to May 3, 2021, an online survey was conducted on a total of 323 college students. Measures included the 5C scale and the vaccine literacy scale. A logistic regression analysis was performed to identify the factors associated with COVID-19 vaccination intention among students. Results: Among the respondents, 47.7% had the intention to receive the vaccine following the government vaccination plan. Influencing factors of intention to COVID-19 vaccination included the higher level of confidence and collective responsibility and the lower level of constraints and calculation. However, vaccine literacy, socio-demographics, the influence of others, the contents and main source of information about the COVID-19 vaccine, health status and COVID-19-related experiences did not influence the intention to vaccination. The content analysis on self-reported reasons for the decreased vaccination intention resulted in three main categories, including "anxiety about the vaccine", "distrust in the government" and "no need of vaccination." Conclusion: In order to increase COVID-19 vaccination acceptance among college students and form herd immunity, it is necessary to increase the trust in vaccines and emphasize the importance of herd immunity.

• Korean Journal of Veterinary Service
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• v.44 no.4
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• pp.291-297
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• 2021

Severe outbreaks of porcine epidemic diarrhoea virus (PEDV) have continued to re-emerge worldwide. Because of the high mortality rate of suckling piglets in PEDV outbreaks, the disease causes significant economic losses in the pig industry. The limited pre-existing immunity against this virus is thought to cause an explosive increase in infection in pig farms. This study aimed to evaluate the clinical symptoms of PEDV after intentional exposure (feedback). During the first few days of the outbreak in a breeding pig farm, 14 sows showed watery diarrhoea, and the disease subsequently spread rapidly throughout the barn. Pigs that were intentionally exposed to PEDV (n=251) showed watery diarrhoea (46.6%), reduced appetite (17.5%), and vomiting (6.0%). However, 75 exposed pigs (29.9%) showed no clinical signs of disease. Four weeks after the feedback challenge, 34 sows gave birth to litters of piglets, which survived with no diarrhoea. Five weeks after the start of the outbreak, PEDV was not detected in any of the examined samples, including environmental swabs. Thus, early diagnosis, prompt establishment of herd immunity, and strict application of biosecurity are good practices to reduce the mortality rates among new-born piglets and control economic losses in pig farms showing PEDV outbreaks.

• Journal of Veterinary Science
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• v.24 no.4
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• pp.58.1-58.25
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• 2023

Porcine epidemic diarrhea virus (PEDV) has posed significant financial threats to the domestic pig industry over the last three decades in South Korea. PEDV infection will mostly result in endemic persistence in the affected farrow-to-finish (FTF) herds, leading to endemic porcine epidemic diarrhea (PED) followed by year-round recurrent outbreaks. This review aims to encourage collaboration among swine producers, veterinarians, and researchers to offer answers that strengthen our understanding of PEDV in efforts to prevent and control endemic PED and to prepare for the next epidemics or pandemics. We found that collaboratively implementing a PED risk assessment and customized four-pillar-based control measures is vital to interrupt the chain of endemic PED in affected herds: the former can identify on-farm risk factors while the latter aims to compensate for or improve weaknesses via herd immunity stabilization and virus elimination. Under endemic PED, long-term virus survival in slurry and asymptomatically infected gilts ("Trojan Pigs") that can transmit the virus to farrowing houses are key challenges for PEDV eradication in FTF farms and highlight the necessity for active monitoring and surveillance of the virus in herds and their environments. This paper underlines the current knowledge of molecular epidemiology and commercially available vaccines, as well as the risk assessment and customized strategies to control PEDV. The intervention measures for stabilizing herd immunity and eliminating virus circulation may be the cornerstone of establishing regional or national PED eradication programs.

• Korean Journal of Veterinary Research
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• v.58 no.2
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• pp.73-79
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• 2018

Outbreaks of porcine reproductive and respiratory syndrome virus (PRRSV) in vaccinated sow herds from occurrence to stabilization were monitored and analyzed in terms of serology and reproductive performance. Three different conventional pig farms experienced severe reproductive failures with the introduction of a type 1 PRRSV. These farms had adopted mass vaccination of sows using a type 2 PRRSV modified live vaccine (MLV). Therefore, to control the type 1 PRRSV, an alternative vaccination program utilizing both type 1 and type 2 MLV was undertaken. Following whole herd vaccinations with both types of MLV, successful stabilization of PRRS outbreaks was identified based on serological data (no viremia and downward trends in ELISA antibody titers in both sows and suckling piglets) and recovery of reproductive performance. Additionally, through comparison of the reproductive parameters between outbreak and non-outbreak periods, it was identified that PRRSV significantly affected the farrowing rate and the number of suckling piglets per litter at all three pig farms. Comparison of reproductive parameters between periods when the different vaccination strategies were applied revealed that the number of piglets born in total and born dead per litter were significantly increased after the introduction of the type 1 PRRS MLV.

• Journal of Veterinary Science
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• v.23 no.3
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• pp.33.1-33.10
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• 2022

Background: Endemic circulation of human-specific hepatitis E virus (HEV) genotypes 1 and 2 may occult the importance of sporadic zoonotic HEV transmissions in Africa. Increasing numbers of studies reporting anti-HEV antibodies in cattle and the discovery of infectious HEV in cow milk has raised public health concern, but cattle exposure has seldom been investigated in Africa. Objectives: This study aimed at investigating the role of cows in the epidemiology of HEV in Burkina Faso and farmers habits in terms of dairy product consumption as a prerequisite to estimate the risk of transmission to humans. Methods: Sera from 475 cattle and 192 pigs were screened for the presence of anti-HEV antibodies while HEV RNA in swine stools was detected by reverse transcription polymerase chain reaction. Data on mixed farming, dairy product consumption and selling habits were gathered through questionnaires. Results: The overall seroprevalence in cattle was 5.1% and herd seroprevalence reached 32.4% (11/34). Herd seropositivity was not associated with husbandry practice or presence of rabbits on the farms. However, herd seropositivity was associated with on-site presence of pigs, 80.7% of which had anti-HEV antibodies. The majority of farmers reported to preferentially consume raw milk based dairy products. Conclusions: Concomitant presence of pigs on cattle farms constitutes a risk factor for HEV exposure of cattle. However, the risk of HEV infections associated with raw cow dairy product consumption is currently considered as low.

• Journal of Veterinary Science
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• v.22 no.4
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• pp.48.1-48.15
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• 2021

Background: Porcine epidemic diarrhea virus (PEDV) is a swine enteropathogenic coronavirus that has devastated the swine industry in South Korea over the last 30 years. The lack of an effective method to control the endemics has led to a surge in PEDV recurrences in affected farms throughout the country. Objectives: In the first step toward establishing systematic monitoring of and active control measures over the swine populations, we constructed an assessment model that evaluates the status of (1) biosecurity, (2) herd immunity, and (3) virus circulation in each of the PEDV-infected farms. Methods: A total of 13 farrow-to-finish pig farms with a history of acute PEDV infection on Jeju Island were chosen for this study. The potential risk of the recurrence in these farms was estimated through on-site data collection and laboratory examination. Results: Overall, the data indicated that a considerable number of the PEDV-infected farms had lax biosecurity, achieved incomplete protective immunity in the sows despite multi-dose vaccination, and served as incubators of the circulating virus; thus, they face an increased risk of recurrent outbreaks. Intriguingly, our results suggest that after an outbreak, a farm requires proactive tasks, including reinforcing biosecurity, conducting serological and virus monitoring to check the sows' immunity and to identify the animals exposed to PEDV, and improving the vaccination scheme and disinfection practices if needed. Conclusions: The present study highlights the significance of coordinated PEDV management in infected farms to reduce the risk of recurrence and further contribute towards the national eradication of PEDV.

• Journal of Korean Academy of Nursing
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• v.51 no.4
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• pp.395-407
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• 2021

The COVID-19 curve seesawed and reached the fourth pandemic in July 2021. Since the first three waves, the focus has been on achieving herd immunity through vaccination while a lot of manpower is used for quarantine. However, we have not been able to prevent the fourth wave. The causes are thought to be related to people who doubt the safety of the vaccine and refuse it or violate quarantine guidelines such as social distancing. This study examined guidelines for preventing and controlling COVID-19, the accuracy of vaccination-related information, and described quarantine measures including for those who completed vaccination. In conclusion, prevention and vaccination are the most effective countermeasures against COVID-19. We recommend people vaccination with self-quarantine. Also, it is necessary to make large investments to protect and support nurses in future pandemics.

• Korean Journal of Veterinary Service
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• v.38 no.2
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• pp.71-75
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• 2015

Porcine salmonellosis is an economically important disease affecting the global pig industry today. Salmonella (S.) Typhimurium is highly contagious and may rapidly spread within pig populations of herd. To investigate the prevalence of porcine salmonellosis in Jeju, a total of 12,885 blood sera of 96 pig farms from 2009 to 2012 were analyzed by microplate agglutination test. Antibodies to S. Typhimurium were detected in all of pig farms tested in Jeju Province, and the mean of seropositive rate of individual pig was 18.8%. The mean seropositive rate of S. Typhimurium in sows (46.7%) was 7 times higher than that of weaned or growing pigs (6.7%). The lowest seropositive rate (3.0%) was detected in 40 day-old pigs, and this result might be closely associated with the marked decrease of maternal passive immunity. The seropositive rate in winter (42.7%) was higher than in other seasons.