• Journal of Veterinary Clinics
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• v.25 no.6
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• pp.435-439
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• 2008

We evaluated the patterns of serology and fecal viral shedding for any differences by hemagglutination inhibition (HI) and real-time PCR on Korean CPV-2 isolates (CPV-2a-I, CPV-2a-V and CPV-2b). We successfully detected fecal viral shedding from samples extracted 2-3 d.p.i., regardless of the onset of clinical signs. In addition, the pattern of viral shedding differed depending on the CPV-2 isolates used for inoculation. We also observed differences in the serological pattern that was also depended on the CPV-2 isolates inoculated. The onset and amount of fecal viral shedding were not correlated with the level of antibody titers in this study. Our study is a valuable resource for understanding the different pathobiology of the CPV-2 isolates and the correlation between the patterns of serum antibody titer and fecal viral shedding.

• Clinical and Experimental Pediatrics
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• v.64 no.12
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• pp.652-660
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• 2021

Background: Viral load and shedding duration are highly associated with the transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. However, limited studies have reported on viral load or shedding in children and adolescents infected with sudden acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Purpose: This study aimed to investigate the natural course of viral load in asymptomatic or mild pediatric cases. Methods: Thirty-one children (<18 years) with confirmed SARS-CoV-2 infection were hospitalized and enrolled in this study. Viral loads were evaluated in nasopharyngeal swab samples using real-time reverse transcription polymerase chain reaction (E, RdRp, N genes). cycle threshold (Ct) values were measured when patients met the clinical criteria to be released from quarantine. Results: The mean age of the patients was 9.8 years, 18 (58%) had mild disease, and 13 (42%) were asymptomatic. Most children were infected by adult family members, most commonly by their mothers. The most common symptoms were fever and sputum (26%), followed by cough and runny nose. Nine patients (29%) had a high or intermediate viral load (Ct value≤30) when they had no clinical symptoms. Viral load showed no difference between symptomatic and asymptomatic patients. Viral rebounds were found in 15 cases (48%), which contributed to prolonged viral detection. The mean duration of viral detection was 25.6 days. Viral loads were significantly lower in patients with viral rebounds than in those with no rebound (E, P=0.003; RdRp, P=0.01; N, P=0.02). Conclusion: Our study showed that many pediatric patients with coronavirus disease 2019 (COVID-19) experienced viral rebound and showed viral detection for more than 3 weeks. Further studies are needed to investigate the relationship between viral rebound and infectiousness in COVID-19.

• Korean Journal of Poultry Science
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• v.46 no.4
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• pp.271-277
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• 2019

In recent years, consumers have recognized the issue of and expressed concern over farm animal welfare. Therefore, worldwide, chicken farms are transitioning from traditional caged breeding systems to welfare-oriented breeding systems. In this study, we further analyzed and compared the prevalence and protection rate of various diseases by challenging chickens under conventional and welfare-oriented breeding conditions with low pathogenic avian influenza. Ten chickens were randomly selected from each farm (conventional and welfare) from which Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) were identified and isolated. Additionally, low pathogenic avian influenza (LPAI) were challenged to broilers from each farm and samples were collected from these chickens using oral and cloacal swabs to investigate viral shedding and titer. The results showed that Mycoplasma infection did not significantly differ between breeding systems. Initially, LPAI viral shedding and titer significantly differed between breeding systems post-challenge, but as the experiment progressed, there was ultimately no significant difference.

• Korean Journal of Veterinary Service
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• v.37 no.1
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• pp.11-18
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• 2014

Porcine reproductive and respiratory syndrome (PRRS) causes a significant economic loss in the swine industry not only in Korea but also all over the world. Andong and Hapcheon region were selected for Area Regional Control (ARC) programme to reduce the shedding of PRRS virus (PRRSV) and decrease PRRS outbreaks. Before conducting the PRRS ARC, sera of pigs were tested for both antibody using ELISA and antigen using RT-PCR, then phylogenetic classifications was analysed. Pigs of 138/275 (50.2%) in Andong and 352/425 (82.8%) in Hapcheon were seropositive. Also, the RT-PCR results revealed that 27 heads (8.2%) in Andong, 112 heads (22.0%) in Hapcheon were positive for PRRSV antigen. PRRSVs were mainly detected between the ages of 40 to 60 days. PRRSV ORF5 regions were used to determine genetic clusters based on previous report. All PRRSV type I detected in both Andong and Hapcheon were classified as Cluster I. The PRRSV type II isolates in Andong were assorted to Cluster II, whereas the PRRSV type II isolates in Hapcheon were the viruses were unassembled into any cluster except one identified to Cluster III. Phylogenetic analysis indicated that new clusters of PRRSVs type II were prevalent in Hapcheon.

• BMB Reports
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• v.48 no.2
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• pp.61-67
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• 2015

Norovirus is a major cause of viral gastroenteritis and a common cause of foodborne and waterborne outbreaks. Norovirus outbreaks are responsible for economic losses, most notably to the public health and food industry field. Norovirus has characteristics such as low infectious dose, prolonged shedding period, strong stability, great diversity, and frequent genome mutations. Besides these characteristics, they are known for rapid and extensive spread in closed settings such as hospitals, hotels, and schools. Norovirus is well known as a major agent of food-poisoning in diverse settings in South Korea. For these reasons, nationwide surveillance for norovirus is active in both clinical and environmental settings in South Korea. Recent studies have reported the emergence of variants and novel recombinants of norovirus. In this review, we summarized studies on the molecular epidemiology and nationwide surveillance of norovirus in South Korea. This review will provide information for vaccine development and prediction of new emerging variants of norovirus in South Korea.

• Journal of Veterinary Clinics
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• v.15 no.1
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• pp.46-55
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• 1998

This study was performed to verify the effect of modified live virus vaccine against canine parvovirus (CPV) infection. Serum hemagglutination inhibition (Hl) test, histopathological and immunohistochemical techniques and polymerase chain reaction were used. The results were as follows: 1. During the experimental terms after vaccination, serum Hl titer was stable. Geometric mean titer (GMT) after the 1st vaccination was 280. After virulent CPV was challenged, GMT was 1,306. 2. After challenge by virulent CPV, the vaccinated group was not shown clinical signs and gross and histopathological findings. 3. After challenge by virulent CPV, the vaccinated group was not detected viral antigens in the small intestine immunohistochemically. 4. After challenge by violent CPV, the vaccinated group was not shown virus shedding in feces. In conclusions the overall results confirmed that modified live virus vaccine was effective on prevention of canine parvovirus infection.

• Journal of Microbiology and Biotechnology
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• v.30 no.12
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• pp.1793-1800
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• 2020

Bifidobacterium strains can provide several health benefits, such as antimicrobial and immunomodulatory effects. Some strains inhibit growth or cell adhesion of pathogenic bacteria, including multidrug-resistant bacteria, and their antibacterial activity can be intensified when combined with certain antibiotics. In addition, some strains of bifidobacteria reduce viral infectivity, leading to less epithelial damage of intestinal tissue, lowering the virus shedding titer, and controlling the release of antiviral substances. Furthermore, bifidobacteria can modulate the immune system by increasing immunoglobulins, and inducing or reducing pro- or anti-inflammatory cytokines, respectively. In particular, these anti-inflammatory effects are helpful in the treatment of patients who are already suffering from infection or inflammatory diseases. This review summarizes the antimicrobial effects and mechanisms, and immunomodulatory effects of Bifidobacterium strains, suggesting the potential of bifidobacteria as an alternative or complementary treatment option.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2133-2140
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• 2018

Norovirus is the most common cause of acute gastroenteritis. Its pathogenesis is poorly understood owing to the difficulty of establishing viral infection in animal models. Here, post-weaning gnotobiotic pigs were infected with human norovirus genogroup II genotype 4 (HuNoV GII.4) to investigate the pathogenesis and replication of the virus. Three groups of four pigs were infected with $1{\times}10^5$, $1{\times}10^6$, or $1{\times}10^7$ genomic equivalent (GE) copies of HuNoV GII.4. Four pigs were used as negative controls. Blood and rectal swab samples were collected after viral infection, and gross legions were examined after necropsy. Diarrhea was induced in 25% and 75% of pigs infected with $1{\times}10^6$ and $1{\times}10^7$ GE copies, respectively. Viral shedding was detected in 50%, 75%, and 50% of pigs infected with $1{\times}10^5$, $1{\times}10^6$, and $1{\times}10^7$ GE copies, respectively. Viremia was detected in 25% of pigs infected with either $1{\times}10^6$ or $1{\times}10^7$ GE copies. When gross lesions of gastroenteritis were investigated, the ileum walls of the infected pigs were thinner than those of the controls. Villi atrophy and inflammatory cell infiltration were identified in the ileum of each infected pig. Viral capsid was identified in the jejunum, ileum, colon, spleen, and mesenteric lymph node. Virus replication was newly verified in the spleen and mesenteric lymph nodes by detection of negative-sense viral RNA. In conclusion, HuNoV GII.4 could induce acute gastroenteritis and replicate in the extra-intestinal lymphoid tissues in post-weaning gnotobiotic pigs. Therefore, such pigs would be a suitable animal model for studying the pathogenesis and replication of HuNoV.

• Korean Journal of Veterinary Research
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• v.52 no.4
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• pp.223-230
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• 2012

The worldwide distribution and continuing genetic mutation of avian influenza virus (AIV) has been posed a great threat to human and animal health. A comparison of 3 isolates of AIV H9N2, A/chicken/Korea/KBNP-0028/00 (H9N2) (KBNP-0028), A/chicken/Korea/SNU8011/08 (H9N2) (SNU 8011) and an inactivated oil vaccine strain A/chicken/Korea/01310/01 (H9N2) (01310), was performed. The former 2 AIVs were isolated from field cases before and after the application of an inactivated H9N2 vaccine in 2007, respectively. The antigenic relationship, viral shedding, tissue tropism and genetic analysis were examined. The comparison of virus shedding from the cloaca and the oropharynx revealed that both isolates were more frequently isolated from the upper respiratory tract (90~100%) 1 day post inoculation (DPI) compared with isolation 5 DPI from gastrointestinal tracts (10~60%). Moreover, the isolate KBNP-0028 were recovered from all organs including bone marrow, brain and kidneys, indicating higher ability for broad tissue dissemination than that of SNU 8011. KBNP-0028 replicated earlier than other strains and with a higher titer than SNU 8011. In full-length nucleotide sequences of the NA gene and a partial sequence of the HA gene of SNU 8011, we found that there might be significant changes in tissue tropism, virus replication and genetic mutation in AIV H9N2 isolates.

• Pediatric Infection and Vaccine
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• v.30 no.2
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• pp.73-83
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• 2023

Purpose: This study aimed to investigate the viral load dynamics in children with underlying malignancies diagnosed with symptomatic coronavirus disease 2019 (COVID-19). Methods: This was a retrospective longitudinal cohort study of patients <19 years old with underlying hemato-oncologic malignancies that were diagnosed with their first symptomatic severe acute respiratory syndrome coronavirus 2 polymerase chain reaction (PCR)-confirmed COVID-19 infection during March 1 to August 30, 2022. Review of electronic medical records and telephone surveys were undertaken to assess the clinical presentations and transmission route of the patients. Thresholds of negligible likelihood of infectious virus was defined as E gene reverse transcription (RT)-PCR cycle threshold (Ct) value ≥25. Results: During the 6-month study period, a total of 43 children with 44 episodes of COVID-19 were included. Of the 44 episodes, the median age of the patients included was 8 years old (interquartile range [IQR], 4.9-10.5), and the most common underlying disease was acute lymphoid leukemia (n=30, 68.2%), followed by patients post-hematopoietic stem cell transplantation (n=8, 18.2%). Majority of the patients had mild COVID-19 (n=32, 72.7%), and three patients (7.0%) had severe/critical COVID-19. Furthermore, 2.3% (n=1) died of COVID-19 associated acute respiratory distress syndrome. The largest percentage of the patients showed E gene RT-PCR Ct value ≥25 between 15-21 days (n=13, 39.4%), followed by 22-28 days (n=10, 30.3%). In 15.2% (n=5), E gene RT-PCR Ct value remained <25 beyond 28 days after initial positive PCR. Refractory malignancy status (β, 67.0; 95% confidence interval, 7.0-17.0; P=0.030) was significantly associated with prolonged duration of E gene RT-PCR <25. A patient with prolonged duration of E gene RT-PCR Ct value <25 was suspected to have infectivity shown by the transmission of the virus to his mother at day 86 after his initial positive test. Conclusions: Children that acquire symptomatic COVID-19 during refractory malignancy state are at a high risk for prolonged shedding warranting PCR-based transmission precautions in this cohort of patients.