Tae-Hyun Lim

An emerging recombinant cluster of nephropathogenic strains of avian infectious bronchitis virus in Korea.

Abstract The infectious bronchitis virus (IBV) is continuously evolving through point mutation and recombination of their genome, subsequently the emergence of IBV variants complicates disease control. The objective of this study was to investigate genetic characterization of new IBV variants isolated from commercial chicken flocks in Korea collected between 2005 and 2010. Phylogenetic analysis revealed that all new IBV isolates belonged to Korean group II (K-II), which included the nephropathogenic IBV strains. However, the isolates formed a new gene cluster that was distinguished from the two distinct K-II subgroups (KM91-like and QX-like). Recombination events were identified in the S1 gene, with their putative parental strains being the KM91-like or QX-like subgroup. In addition, two crossover sites were observed in the S1 gene of IBV isolates. These results suggest that natural genetic recombination between heterologous strains classified into different genetic groups has occurred and may have caused the emergence of new IBV strains. This finding provides important information on IBV evolution and is essential for the effective control of IB in Korea.

Prevalence and antimicrobial resistance of Salmonella species isolated from chicken meats produced by different integrated broiler operations in Korea

Prevalence and antimicrobial resistance profiles of Salmonella serotypes isolated from 7 chicken meat brands produced by different integrated broiler operations in Korea were determined. In total, 210 samples were collected from retail supermarkets in Seoul, South Korea, and analyzed for the presence of Salmonella. Of 210 chicken meat samples, overall Salmonella prevalence was 22.4%. Salmonella Enteritidis was the dominant serovar, with an isolation rate of 57.4% from the Salmonella-positive chickens, followed by Salmonella Montevideo. Salmonella isolates frequently were resistant to various antibiotics, including 100% to erythromycin, 87% to cephalothin, 85% to nalidixic acid, and 70% to streptomycin. Of the 47 isolates, 41 (87.2%) isolates were resistant to 3 or more antibiotics. Moreover, the Salmonella profiles of each chicken meat brand were different by broiler operation. Brand A showed the highest prevalence of Salmonella (18 isolates, 60%), whereas brand G showed the lowest prevalence (one isolate, 3.3%). Eight among the 18 isolates of brand A were resistant to 11 antibiotics, whereas 5 of the 6 brand C isolates were resistant to only 2 antibiotics. This study demonstrates that a high proportion of chicken meat in Korea is contaminated with Salmonella and the prevalence and antimicrobial resistance patterns of Salmonella of chicken meat differ significantly according to the integrated broiler operation.

An inactivated oil-emulsion fowl Adenovirus serotype 4 vaccine provides broad cross-protection against various serotypes of fowl Adenovirus.

The number of clinical cases of inclusion body hepatitis (IBH) and hydropericardium-hepatitis syndrome (HHS) has been increasing, resulting in considerable economic losses in many countries. Currently, only fowl Adenovirus (FAdV) serotype 4 (FAdV-4) has been reported as the causative agent of HHS, whereas IBH can be caused by all 12 serotypes of FAdV. For protection against HHS, various live and killed FAdV serotype 4 vaccines have been developed. However, there is a concern whether these vaccines composed of FAdV-4 alone could provide protection against IBH, which is caused by other serotypes of virulent FAdVs. To date, there have been no reports evaluating the protective efficacy of the FAdV-4 vaccine against other serotypes of FAdV. Thus, we investigated the cross-protection efficacy of an inactivated oil-emulsion FAdV-4 vaccine against various serotypes of FAdV field isolates. Our study demonstrated that the inactivated oil-emulsion FAdV-4 vaccine could provide broad cross-protection against various serotypes of FAdV in not only vaccinated birds, but also the progenies of vaccinated breeder. Therefore, we conclude that the inactivated oil-emulsion FAdV-4 vaccine could be effective in preventing the spread of various other serotypes of FAdV as well as FAdV-4 infection in the poultry industry.

Identification and virulence characterization of fowl adenoviruses in Korea.

SUMMARY. Since 2007, 55 adenovirus strains have been isolated from commercial chicken flocks in Korea and have been identified and the pathogenicity of these isolates was confirmed in specific-pathogen-free chickens of different age. Based on sequencing analysis of the hexon gene, 55 FAdV isolates were genetically related to the IBH-2A strain of FAdV3 (4 isolates, 99.2% to 100%), the KR5 strain of FAdV4 (22 isolates, 97.9% to 99.2%), the 764 strain of FAdV9 (11 isolates, 99.1% to 99.3%), and the 1047 strain of FAdV11 (18 isolates, >99%). Experimental infections with four serotypes of FAdV resulted in high mortality of 18-day-old chicken embryos and 1-day-old chicks with marked liver necrosis similar to those observed in the natural outbreaks. Notably, specific hydropericardium was observed in chicks challenged with the K531 strain (serotype 4). However, 3-wk-old chickens challenged with FAdVs, regardless of serotype, did not show any clinical signs or mortality except histologic lesions of focal hepatocytic necrosis with mild lymphocytic infiltration. The results indicate that four FAdV serotypes (3, 4, 9, and 11) are the dominant serotypes of FAdVs in the Korea and are pathogenic enough to cause clinical disease in young chicks. The present investigation provides important information on the epidemiology and pathogenesis of FAdVs and highlights the importance of control strategies against FAdV infection in Korea.

Use of bacteriophage for biological control of Salmonella Enteritidis infection in chicken

Bacteriophage ΦCJ07 with broad host ranges for Salmonella strains isolated from sewage effluent were used to reduce Salmonella Enteritidis (SE) infection in chickens. One-day-old chicks challenged with 5×10(7) colony-forming units/bird of SE were cohabitated with contact chicks and treated with three concentrations (10(5), 10(7) and 10(9) plaque forming units (PFU)/g) of bacteriophage prepared as a feed additive for 21days after challenge. Salmonella in the intestine was quantified and environmental contamination level was examined at 1, 2 and 3weeks after challenge. All treatments reduced intestinal SE colonization in challenged and contact chickens and reduced the environmental contamination level, but the reductions produced by 10(7) and 10(9)PFU/g of bacteriophage were significant (P<0.05) as compared with untreated controls. In addition, seven out of 10 (70%) contact chickens treated with 10(9)PFU/g of bacteriophage had no detectable intestinal Salmonella at 3weeks after treatment, suggesting that bacteriophage therapy significantly prevented the horizontal transmission of SE. These results provide important insights into preventive and control strategies against SE infection in poultry and indicate that the use of bacteriophage could reduce the incidence of Salmonella food poisoning.

Outbreak of gizzard erosion associated with fowl adenovirus infection in Korea

The pathogenicity of a fowl adenovirus serotype-1 (FAdV-1, K181 strain) isolated from a case of gizzard erosion in layer chickens was investigated in specific-pathogen-free (SPF) chicks. One-week-old SPF chicks were inoculated orally or intramuscularly with the isolate of FAdV-1 and euthanized for necropsy at 7, 14, and 21 d postinoculation. Although there were no clinical signs after inoculation, gizzard erosions were observed grossly and the virus was recovered from the gizzards in the inoculated chickens. Histologically, in the chickens that were infected orally, the lesions found in the gizzard consisted of severe degeneration and necrosis of glandular epitheliums and eosinophilic inclusion bodies. These results indicate that the Korean FAdV-1 isolate could induce gizzard lesions in chickens. Moreover, the present investigation reproduced an outbreak of gizzard erosion caused by FAdV-1 infection and, for the first time, described the isolation of FAdV-1 from chickens in Korea. These findings provide important information on the epidemiology and pathogenesis of FAdV-1 infection in chickens.

Live attenuated nephropathogenic infectious bronchitis virus vaccine provides broad cross protection against new variant strains

ABSTRACT Infectious bronchitis virus (IBV) infections cause great economic losses to the poultry industry worldwide, and the emergence of new variant strains complicates disease control. The present study investigated the genetic and protectotypic features of newly emerged Korean IBV strains. A phylogenetic analysis showed that several recent isolates formed 2 different clusters (new cluster 1 and 2), which were distinct from other preexisting clusters. New cluster 1 IBV strains represented recombinants between Korean nephropathogenic strain KM91 and the QXIBV strain. New cluster 2 IBV strains showed low amino acid homology (<58.7%) compared with previous isolates. We evaluated the protective efficacy of commercial IBV vaccines (H120 and K2 strain) against these new isolates. In cross-protection studies, the H120 strain did not provide sufficient protection against these variants. However, highly attenuated nephropathogenic IBV vaccine, K2 strain, provided significantly higher levels of protection against variants compared with chickens vaccinated with H120 (P < 0.05 or better). These results indicate that the K2 vaccine could be helpful for the reduction of economic losses caused by newly evolving IBV recombinants (new cluster 1) and variants (new cluster 2).

Evidence of intercontinental transfer of North American lineage avian influenza virus into Korea.

Avian influenza viruses (AIV) can be genetically distinguished by geographical origin. The present study found evidence of intercontinental transfer of North American lineage AIV into Asia via migratory bird populations. The North American lineage genes were detected in live animal markets during avian influenza surveillance, seemed to have reassorted with Eurasian AIV in wild bird habitats, and had transmitted to live animal markets. Enhanced AIV surveillance is required to understand the influence of newly transferred North American lineage AIV genes on AIV evolution in Asia and to investigate AIV ecology in various transcontinental migrant species.

Cross-Protective Immune Responses Elicited by a Korean Variant of Infectious Bronchitis Virus

SUMMARY Infectious bronchitis virus (IBV) infections cause great economic losses to the poultry industry worldwide. IBVs continuously evolve by developing mutations in antigenic sites; therefore, an IBV vaccine that provides broad cross-protection can be a highly relevant and practical method in IBV control strategies. Although some IBV vaccine strains are known to provide protection against multiple IBV serotypes, in general commercially available IBV vaccine strains provide protection against antigenically related viruses but not distinct heterologous viruses. In the present study we characterized the Korean variant IBV K40/09 strain with regard to its immunogenicity and protective efficacy against seven currently circulating IBV serotypes. Three-week-old specific-pathogen-free chickens were intraocularly immunized with the IBV K40/09 strain at 103.5 50% egg infective dose (EID50). Three weeks after immunization all the birds were challenged with seven different strains at 104.5 EID50. Chickens immunized with the IBV K40/09 strain showed significantly high levels of protection against all challenge viruses at the trachea and kidney levels. Our results suggest that IBV K40/09 could be useful to ensure IBV vaccine effectiveness owing to its cross-protective ability. Therefore, the IBV K40/09 strain merits consideration as a vaccine candidate to prevent infection as well as the spread of new IBV strains and many IBV variants that have been reported worldwide. RESUMEN Nota de Investigación—Respuesta inmune protectora cruzada provocada por una variante coreana del virus de la bronquitis infecciosa. Las infecciones por el virus de bronquitis infecciosa (IBV) causan grandes pérdidas económicas a la industria avícola en todo el mundo. Los virus de la bronquitis infecciosa evolucionan continuamente mediante el desarrollo de mutaciones en sitios antigénicos, por lo tanto, una vacuna contra el virus de bronquitis infecciosa que proporciona una amplia protección cruzada puede ser un método altamente relevante y práctico dentro de las estrategias de control contra este virus. Aunque algunas cepas vacunales del virus de bronquitis proporcionan protección contra múltiples serotipos del virus, en general, las cepas vacunales disponibles comercialmente proporcionan protección contra virus antigénicamente relacionados pero no contra virus heterólogos distintos. En el presente estudio se caracterizó la cepa variante coreana IBV K40/09 con relación a su inmunogenicidad y eficacia protectora contra siete serotipos que circulan actualmente. Aves libres de patógenos específicos de tres semanas de edad, fueron inmunizadas por vía intraocular con la cepa IBV K40/09 con 103.5 dosis infectantes en embrión de pollo 50% (EID50). Tres semanas después de la vacunación, todas las aves fueron desafiadas con siete cepas diferentes, con 104.5 EID50. Los pollos inmunizados con la cepa K40/09 mostraron niveles significativamente altos de protección contra todos los virus de desafío en la tráquea y en riñón. Nuestros resultados sugieren que la cepa IBV K40/09 podría ser útil y eficaz como vacuna contra el virus de bronquitis infecciosa debido a su capacidad de protección cruzada. Por lo tanto, la cepa K40/09 merece consideración como un candidato a vacuna para prevenir la infección y la propagación de nuevas cepas del virus de la bronquitis infecciosa y variantes que han sido reportadas en todo el mundo.

Surveillance and Isolation of HPAI H5N1 from Wild Mandarin Ducks (Aix galericulata)

Highly pathogenic avian influenza (HPAI) H5N1 virus circulates among a variety of free-ranging wild birds and continually poses a threat to animal and human health. During the winter of 2010–2011, we surveyed Korean wild bird habitats. From 728 fresh fecal samples, 14 HPAI H5N1 viruses were identified. The isolates phylogenetically clustered with other recently isolated clade 2.3.2 HPAI H5N1 viruses isolated from wild birds in Mongolia. All HPAI-positive fecal samples were analyzed by DNA barcoding for host-species identification. Twelve of the 14 HPAI-positive samples were typed as Mandarin Duck (Aix galericulata). The high incidence of HPAI subtype H5N1 viruses in wild Mandarin Duck droppings is a novel finding and underscores the need for enhanced avian influenza virus surveillance in wild Mandarin Ducks. Further investigation of the susceptibility of Mandarin Ducks to HPAI H5N1 clade 2.3.2 virus would aid the understanding of HPAI ecology and epidemiology in wild birds.