Search

Avian chlamydiosis is an acute or chronic bacterial disease of birds. Chlamydia psittaci is the primary agent of the disease. It is also an important zoonotic pathogen. Chlamydia avium and Chlamydia gallinacea have also been recognized as potential causative agents of the disease. Clinical signs of this disease can vary in severity. Asymptomatic infections of Chlamydia have commonly been reported in various birds worldwide. In this study, we investigated the distribution of Chlamydia species in healthy psittacine birds in Korea. A total of 263 samples (pharyngeal/cloacal swabs and faeces) were collected from psittacine birds of 26 species in five zoos, five parrot farms and seven parrot cafes between 2020 and 2021. Ages of these birds had a wide range (1 month to 30 years). During sample collection, no bird showed any clinical signs indicating diseases such as chlamydiosis. Samples were tested for the presence of Chlamydia spp. using real-time PCR assays. Chlamydia spp. were detected in 168 (63.9%) samples and C. psittaci was detected in 96 (36.5%) samples. However, C. avium and C. gallinacea were not detected. There were no significant differences in the prevalence of asymptomatic infections in birds among three types of housing environments. Regarding ompA genotypes, 87 C. psittaci-positive samples had genotype A based on sequence analysis (n = 28) and genotype-specific real-time PCR (n = 59). Other positive samples were untyped (n = 9). Overall findings showed high prevalence of asymptomatic infections of C. psittaci in psittacine birds in Korea, posing a significant hazard to public health., (© 2023 Wiley-VCH GmbH. Published by John Wiley & Sons Ltd.)

Infectious bronchitis virus (IBV) is a major pathogen in poultry. The genotypes of IBV vary considerably, and their antigenicity may differ. Nationwide surveillance in South Korea was performed to determine the prevalence and distribution of IBV and its genotypes. By both active and passive surveillance, a total of 939 samples were collected and tested for IBV detection by pathogen-specific reverse transcriptase-PCR. IBV RNA-positive samples were inoculated in embryonated eggs for virus isolation. IBV was genotyped and analyzed phylogenetically based on a partial nucleotide sequence of the S1 gene. A total of 114 IBV strains were isolated; 34 (30.9%) of the 110 samples obtained by passive surveillance, and 80 (9.7%) of the 829 samples obtained by active surveillance, were positive. Most IBVs in both groups were isolated from broilers. Five genotypes (QX-like, B4-like, KM91-like, K40/09-like, and 20AD17-like) were observed in South Korea, with the QX-like genotype being the most common, and the 20AD17-like genotype being a novel genotype. These findings will help to maximize protection against IBV infection by providing a reference for the selection of an avian vaccine for IBV in South Korea.

Infectious bronchitis viruses (IBVs) are evolving continuously via genetic drift and genetic recombination, making disease prevention and control difficult. In this study, we undertook genetic and pathogenic characterization of recombinant IBVs isolated from chickens in South Korea between 2003 and 2019. Phylogenetic analysis showed that 46 IBV isolates belonged to GI-19, which includes nephropathogenic IBVs. Ten isolates formed a new cluster, the genomic sequences of which were different from those of reference sequences. Recombination events in the S1 gene were identified, with putative parental strains identified as QX-like, KM91-like, and GI-15. Recombination detection methods identified three patterns (rGI-19-I, rGI-19-II, and rGI-19-III). To better understand the pathogenicity of recombinant IBVs, we compared the pathogenicity of GI-19 with that of the rGI-19s. The results suggest that rGI-19s may be more likely to cause trachea infections than GI-19, whereas rGI-19s were less pathogenic in the kidney. Additionally, the pathogenicity of rGI-19s varied according to the genotype of the major parent. These results indicate that genetic recombination between heterologous strains belonging to different genotypes has occurred, resulting in the emergence of new recombinant IBVs in South Korea.

A total of 116 Escherichia coli isolates from cecal contents of 81 indigenous wild birds in Korea were tested for antimicrobial susceptibility. Seventy-one isolates from sparrows (Passer montanus) and one isolate from doves (Columba livia) were resistant to three antimicrobials, including streptomycin, sulfonamide, and tetracycline (SSuT). PCR and subsequent sequence analysis revealed the SSuT gene cluster region (approximately 13 kb) harboring genes encoding resistance to streptomycin (strA and strB), sulfonamide (sul2), and tetracycline (tetB, tetC, tetD, and tetR). In particular, tetracycline resistance genes were located on the transposon Tn10-like element. The SSuT element-harboring E. coli can be an important source of the transmission of antimicrobial resistance to other pathogenic bacteria. Therefore, strict sanitary measures in human and animal environments are necessary to prevent the spread of resistant bacteria through fecal residues of wild birds.

Colibacillosis caused by avian pathogenic Escherichia coli (APEC) is the most common bacterial disease in poultry, resulting in significant economic losses. Resistance to fluoroquinolones has been found to be high in APEC worldwide, which has increased concerns about risks to human health as well as poultry production. In the present study, we determined the prevalence, genetic traits, and fitness traits of fluoroquinolone-resistant APEC isolated from chickens in Korea using a total of 286 APEC isolates collected between 2014 and 2017. The APEC isolates were highly resistant to nalidixic acid (86.0%), ampicillin (71.7%), tetracycline (69.6%), and sulfisoxazole (61.2%), and 132 (46.2%) of the isolates were resistant to both enrofloxacin and ciprofloxacin. These fluoroquinolone-resistant isolates showed eight mutation combinations including single- or double-point mutations in the gyrA , parC , or parE genes. The isolates with double mutations (codons 83 and 87) in gyrA and additional mutations in parC and parE showed high-level fluoroquinolone resistance (minimum inhibitory concentrations, 16-128 µg/ml). The isolates fell into four phylogenetic groups, and groups A (47/132, 35.6%) and B1 (47/132, 36.4%) were the most predominant. Nine isolates (6.8%) belonged to group B2 and included major lineages of extraintestinal pathogenic E. coli , sequence type (ST) 95 ( n  = 3) and ST69 ( n  = 2). The isolates varied in their virulence-associated gene content, biofilm formation, and intramacrophage survival. Overall, fluoroquinolone-resistant APEC in poultry poses a potential risk to public health and represents a highly diverse group of the resistant bacteria that varied in their genetic and fitness traits.

Infectious bursal disease (IBD) is one of the most important immunosuppressive diseases of young chickens, causing considerable economic losses to the poultry industry. More than 30 years ago, an antigenic variant (av) pathotype of the IBD virus (IBDV) was reported to originate in, and subsequently spread among, poultry farms in the USA. Recently, a novel avIBDV lineage was identified in China and was shown to exhibit clear differences in its pathogenicity as well as molecular characteristics compared with the previously isolated variant strains. In this study, we conducted a passive surveillance of chicken carcasses submitted to our research division from June-December 2019, and detected the IBDV strains by reverse transcription PCR. Five avIBDV strains were isolated, and their pathogenicity was determined by necropsy and molecular analysis. Additionally, a coinfection field case involving an avIBDV strain and a very virulent IBDV (vvIBDV) strain was identified. Multiple sequence alignment and phylogenetic analysis of partial viral protein 1 (VP1) and hypervariable region (hv) VP2 genes revealed that those strains originated from two different avIBDV lineages. The co-occurrence of two sub-groups of avIBDVs in South Korea confirms for the first time the evolution of antigenic variant IBDV strains, and highlights the urgency for the development of new strategies for IBDV intervention in South Korea. RESEARCH HIGHLIGHTS Five avIBDV strains were identified in South Korea by passive surveillance test in 2019.A coinfection between two IBDV strains from different genogroups was reported in a field case.By phylogenetic analysis, Korean avIBDVs belonged to two distinct lineages of antigenic variant genogroup.

We performed viral metagenomics analysis of Japanese quail affected with enteritis to elucidate the viral etiology. Metagenomics generated 21,066,442 sequence reads via high-throughput sequencing, with a mean length of 136 nt. Enrichment in viral sequences suggested that at least three viruses were present in quail samples. Coronavirus and picornavirus were identified and are known as pathogens causing quail enteritis that match the observed morphology. Abundant reads of coronavirus from quail samples yielded four fragment sequences exhibiting six genomes of avian coronavirus. Sequence analysis showed that this quail coronavirus was related to turkey coronavirus and chicken infectious bronchitis virus. Quail picornavirus 8177 bp in size was identified and was similar to the QPV1/HUN/01 virus detected in quails without clinical symptoms in Hungary with 84.6% nucleotide and 94.6% amino acid identity. Our results are useful for understanding the genetic diversity of quail viruses. Further studies must be performed to determine whether quail coronavirus and quail picornavirus are pathogens of the digestive tract of quails.

Although it has rapidly decreased since the early 2000s, fowl typhoid still occurs in commercial layer chickens, causing a significant economic loss in Korea. There is growing concern about the emergence of new pathogenic strains of the causative agent, Salmonella Gallinarum, which is able to overcome vaccine immunity. It has also been suspected that the poultry red mite, Dermanyssus gallinae, which is commonly found in layer chicken farms, may be an important cause of the recurrence of fowl typhoid in the farms. This study was conducted to examine changes in the virulence of recent isolates of S. Gallinarum obtained from layer farms and estimate the potential of the disease transmission of D. gallinae in the farms. Clinical and environmental samples and mites collected from layer farms affected by fowl typhoid between 2013 and 2018 were tested for S. Gallinarum. The isolates were characterized by genotypic analyses and in vitro virulence assays with chicken-derived cell lines. Vaccine protection against recent isolates was examined in the chickens. A total of 45 isolates of S. Gallinarum were collected and there was no evidence of changes in their virulence. It has also been demonstrated that the S. Gallinarum 9R vaccine strain widely used in Korea is still effective in controlling fowl typhoid if the susceptibility of birds to the disease is not increased by stress. Salmonella Gallinarum isolated from the outer and inner parts of D. gallinae, environmental dust, and dead birds of the same farm showed the same or closely related genotypes. Consequently, the present study indicated that the horizontal transmission and environmental persistence of S. Gallinarum and the increased disease susceptibility of chickens in layer farms could be mediated by D. gallinae, causing persistent outbreaks of fowl typhoid., (Copyright © 2020. Published by Elsevier Inc.)

Background and Aims: Runting-stunting syndrome (RSS) in chickens, also known as malabsorption syndrome, which is characterized by mild to severe enteritis and diagnosed through typical histopathologic examination as well as clinical signs, results in considerable economic losses. Despite the many studies carried out over decades to determine the etiologic agents of RSS involved in the disease, several outbreaks remained without the elucidation of, potentially multiple, etiologies involved., Methods: We performed comparative analysis of viral metagenomes from four chicken flocks affected with RSS using next-generation sequencing. Primers for the detection of chicken enteric viruses were designed from the sequencing data obtained with metagenomics. Multiplex reverse transcription-polymerase chain reaction (PCR) and PCR were performed to detect a variety of etiological agents previously described in natural cases of RSS., Results: The most abundant viral families identified in this study were Astroviridae, Picornaviridae, Parvoviridae, Caliciviridae, Reoviridae and Picobirnaviridae. Chicken astrovirus sequences were present in all four samples, suggesting an association between chicken astrovirus and RSS and chicken astrovirus as a candidate pathogen responsible for RSS. Picobirnavirus and the newly identified chapparvovirus were found in chickens in the Republic of Korea for the first time, and the genetic diversity of enteric viruses and viral communities was showed., Conclusions: Chicken astrovirus was consistently detected in broilers affected with RSS and the result of this study may contribute to knowledge of enteric diseases and viruses in chickens.

In 2017, for the first time in Asia, we reported the isolation of variants of Avibacterium paragallinarum with atypical NAD dependency. The present study was conducted to characterize the genotypes of 24 isolates of Av. paragallinarum in Korea, including the four variants reported previously. Most of the typical isolates (19/20) showed a unique ERIC-PCR pattern with no ERIC-PCR patterns in common between the typical isolates and the variants. Furthermore, the variants shared no ERIC-PCR patterns among themselves. All the typical NAD-dependent isolates belonged to the same phylogenetic group based on both 16S rRNA and hagA gene sequences. The four variants were placed in several groups distinct from the typical isolates. In the 16S rRNA phylogenetic analysis, two of the variants were not closely aligned to any other Av. paragallinarum, isolate although they were clearly members of the genus Avibacterium . The other variants were clustered together with NAD atypical isolates from geographically diverse global locations. Compared with the Modesto reference strain AY498870, all the variants lacked a TTTTT stretch at positions 182-186 in the 16S rRNA gene and the same deletion was shown in most of the reported variants. The typical isolates and variants shared 97.3-98.2% and 95.2-97.2% nucleotide sequence similarity, for 16S rRNA and hagA , respectively. In addition, the similarities among variants were within 98.3-100% and 96.5-98.4% for the two genes, respectively. Our results indicate that the Av. paragallinarum variants with altered NAD growth requirements were genetically different and highly divergent from the typical NAD-dependent isolates. RESEARCH HIGHLIGHTS NAD variant Korean Av. paragallinarum isolates show genetic diversity, whereas typical Korean Av. paragallinarum isolates do not.The Korean variants were not closely aligned to all other Av. paragallinarum in the 16S rRNA phylogeny.NAD atypical isolates from geographically diverse global locations clustered together.Almost all variants, including all Korean variants of Av. paragallinarum , lack a specific fragment of the 16S rRNA gene.

Salmonella is one of the most common foodborne pathogens worldwide. Salmonella infections in humans are mainly associated with consumption of poultry products contaminated with this foodborne pathogen. Therefore, strict sanitary measures are necessary to control Salmonella contamination during the slaughtering process of poultry. The objective of this study was to determine the occurrence and transmission of Salmonella at a series of steps in the slaughtering process of chicken. A total of 601 samples were collected from a series of slaughtering steps (10 sampling sites) of 26 chicken slaughterhouses throughout Korea. Salmonella was isolated from samples and its distribution was analyzed along the slaughtering process. Isolates from each sampling site were tested for susceptibility to 15 antibiotics by the broth microdilution method. They were also genotypically characterized by pulsed-field gel electrophoresis (PFGE). Salmonela was isolated from 168 out of 601 samples. Sixteen serotypes were identified while six isolates were untypable. Salmonella enterica serovars Montevideo (n = 29) and Virchow (n = 27) were the most common serotypes out of 119 nonredundant isolates. Relatively high contamination rates of Salmonella were found in shackles (75.0%), feathers near plucking machine (68.5%), and feces from crates (44.0%). Twenty-three antibiotic resistance patterns were recognized and 40 (33.6%) isolates were resistant to five or more antibiotics. The same serotypes of Salmonella were distributed along the slaughtering process of each Salmonella-positive slaughterhouse. Most of those isolates belonging to the same serotype had identical or closely related PFGE profiles. They also shared common antibiotic resistance patterns. Overall findings of this study indicated that Salmonella were sequentially transmitted through the chicken slaughtering process. PRACTICAL APPLICATION: This study provides useful information on the distribution and transmission of Salmonella serotypes through the chicken slaughtering process. Overall findings indicated the need for routine microbiological monitoring along the slaughtering process. This study also showed that on-farm control of Salmonella is needed to obtain Salmonella-free chicken carcasses., (© 2019 Institute of Food Technologists®.)

Thirty-nine human isolates of Campylobacter jejuni obtained from a national university hospital during 2007-2010 and 38 chicken isolates of C. jejuni were collected from poultry farms during 2009-2010 in South Korea were used in this study. Campylobacter genomic species and virulence-associated genes were identified by PCR. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to compare their genetic relationships. All isolates were highly resistant to ciprofloxacin, nalidixic acid, and tetracycline. Of all isolates tested, over 94% contained seven virulence associated genes (flaA, cadF, racR, dnaJ, cdtA, cdtB, and cdtC). All isolates were classified into 39 types by PFGE clustering with 90% similarity. Some chicken isolates were incorporated into some PFGE types of human isolates. MLST analysis for the 39 human isolates and 38 chicken isolates resulted in 14 and 23 sequence types (STs), respectively, of which 10 STs were new. STs overlapped in both chicken and human isolates included ST-21, ST-48, ST-50, ST-51, and ST-354, of which ST-21 was the predominant ST in both human and chicken isolates. Through combined analysis of PFGE types and STs, three chicken isolates were clonally related to the three human isolates associated with food poisoning (VII-ST-48, XXII-ST-354, and XXVIII-ST-51). They were derived from geographically same or distinct districts. Remarkably, clonal spread of food poisoning pathogens between animals and humans was confirmed by population genetic analysis. Consequently, contamination of campylobacters with quinolone resistance and potential virulence genes in poultry production and consumption may increase the risk of infections in humans.

A total of 2,423 nonduplicate isolates of Escherichia coli recovered from wild birds (n=793) and chickens (n=1,630) in South Korea were investigated for plasmid-mediated quinolone resistance (PMQR) genes. Altogether, 56 isolates with PMQR genes were identified, including 25 (3.2%) from wild birds and 31 (1.9%) from chickens, which were further characterized using molecular methods. Among them, qnrS, aac(6')-Ib-cr, qnrB, and qepA genes were detected in 47 (1.9%), 6 (0.24%), 2 (0.08%), and 1 (0.04%) isolates, respectively. The most prevalent gene, qnrS, was identified in 21 (0.9%) and 26 (1.1%) isolates from wild birds and chickens, respectively. The qnrB gene was identified in two chicken isolates, which included qnrB19 and a novel qnrB44 gene. Plasmid isolation and Southern hybridization revealed that qnrS1 was located on a large (>200 kbp) plasmid. The spread of the PMQR genes was attributed to a combination of horizontal dissemination and clonal expansion. The horizontal dissemination of PMQR genes was mostly mediated by IncK plasmids. Molecular typing demonstrated that the majority of the PMQR-positive isolates were genetically diverse. Only one chicken isolate belonged to ST131, which harbored an additional CMY-2 gene. Our findings suggest that the wild birds could serve as reservoirs of PMQR genes and spread them over long distances through migration. To our knowledge, this is the first report of PMQR genes in Korean wild birds. This study also reports qnrS2, qnrB19, qnrB44, and qepA genes for the first time in animal E. coli isolates from South Korea.

Salmonellosis is one of the most prevalent foodborne illnesses. The outbreak of this disease is often associated with eggs. In this study, the prevalence and characteristics of Salmonella was surveyed in layer farms in Korea. In addition, the risk factors affecting the prevalence of Salmonella in these farms were also assessed. Of the 32 farms and 67 flocks examined, 19 farms (59.3%) and 34 flocks (50.7%) were observed to be positive for Salmonella contamination. Salmonella was detected in the surrounding environment such as feces (41.8%), dust (40.3%), egg shells (17.2%), as well as the internal egg contents (5.2%). The incidence of Salmonella positives were tended to increase when the flock size is larger (P = 0.021). Differences in the provinces also affected Salmonella prevalence (P < 0.001). The most frequently observed Salmonella serovars in the flocks were Salmonella Bareilly (41.2%), Salmonella Mbandaka (32.4%), and Salmonella Rissen (17.6%). Twenty of the flocks revealed multi-serovar contamination, with the isolation of 2 to 4 serovars. Antimicrobial susceptibility testing revealed that 93 out of 101 isolates were susceptible to the 17 tested antimicrobial agents. The remaining isolates displayed resistance to ampicillin (4.0%), nalidixic acid (3.0%), tetracycline (1.0%), cephalothin (1.0%), and gentamicin (1.0%). As human salmonellosis has been repeatedly correlated to the consumption of poultry products worldwide, continuous studies are required to effectively minimize the Salmonella contamination in layer farms and egg products., (© 2015 Poultry Science Association Inc.)

Clostridium perfringens produces diverse virulent toxins that cause necrotic enteritis in poultry, resulting in a great negative impact on the poultry industry. To study the characteristics of C. perfringens in chickens, we isolated 88 strains from chickens (1 strain per flock) with necrotic enteritis. The isolated bacterial strains were screened for toxin type and antimicrobial susceptibility. Necropsy of 17 chickens that died from necrotic enteritis revealed that their intestines were dilated with inflammatory exudates and characterized by mucosal necrosis. All the isolated strains were identified as toxin type A using multiplex PCR for toxin typing. We found that the rate of netB-positive strains isolated from dead chickens was significantly higher (8 of 17) than the rate among healthy chickens (2 of 50). We performed antimicrobial susceptibility test with 20 selected antimicrobial agents using the disk diffusion test and found that 30 tested strains were completely resistant to 5 antibiotics and partially resistant to 6 antibiotics whereas all the strains were susceptible to 9 antimicrobial agents. Using pulsed-field gel electrophoresis analysis, the 17 strains were divided into 13 genetic clusters showing high genetic diversity. In conclusion, C. perfringens strains isolated from Korean poultry showed a high resistance to antimicrobial drugs and high genetic diversity, suggesting that continuous monitoring is essential to prevent outbreaks of necrotic enteritis in chickens., (© 2015 Poultry Science Association Inc.)

In January 2014, an outbreak of infection with highly pathogenic avian influenza (HPAI) A(H5N8) virus began on a duck farm in South Korea and spread to other poultry farms nearby. During this outbreak, many sick or dead wild birds were found around habitats frequented by migratory birds. To determine the causes of death, we examined 771 wild bird carcasses and identified HPAI A(H5N8) virus in 167. Gross and histologic lesions were observed in pancreas, lung, brain, and kidney of Baikal teals, bean geese, and whooper swans but not mallard ducks. Such lesions are consistent with lethal HPAI A(H5N8) virus infection. However, some HPAI-positive birds had died of gunshot wounds, peritonitis, or agrochemical poisoning rather than virus infection. These findings suggest that susceptibility to HPAI A(H5N8) virus varies among species of migratory birds and that asymptomatic migratory birds could be carriers of this virus.

Transmissible viral proventriculitis (TVP), an infectious disease in chickens, is responsible for economic losses in the commercial poultry industry. The major etiologic agent, however, is unknown. Using metagenomics, we compared the diversity of viruses present in proventriculus samples from flocks diagnosed with TVP to those of healthy flocks in South Korea between 2003 and 2012. Each sample had a mean of 21,538,726 sequence reads generated by high-throughput sequencing, with a mean length of 160 nt. Enrichment in viral sequences suggested that at least three viruses were present in each TVP sample. Although we could not determine a pathogen of TVP that matched the known morphology, picornavirus sequences were present in all five disease samples, suggesting an association with TVP. The five samples yielded 1,045-1,720 bp contigs with 81-84 % nt sequence identity to turkey hepatitis virus (accession number: HM751199). Whole-genome analysis indicated that the QIA01 strain of the novel picornavirus was similar to turkey hepatitis virus in the P2 and P3 regions (82.7 % nt and 95.5 % aa sequence identity), but different in the structural region and partial 2A peptides (56.2 % nt and 23.9 % aa sequence identity). In addition, the QIA01 virus was similar (87.0 % nt and 95.6 % aa sequence identity) to chicken megrivirus, recently detected in chickens with malabsorption syndrome in Hungary. Our results are useful for understanding the genetic diversity of avian picornaviruses and for classifying chicken megrivirus as a pathogen affecting the digestive tract of chickens.

Botulism is a paralytic disease caused by the botulinum neurotoxin produced by Clostridium botulinum. In the summer season in Korea, intensive outbreaks of avian botulism were reported in both poultry and wild birds, including five Korean native chicken farms (HanHyup NO.3), one pheasant (Phasianus colchicus karpowi) farm, and one community of spot-billed ducks (Anas poecilorhyncha). The affected domestic birds showed 24.5% to 58.3% mortality, with specific clinical signs including ataxia, limber neck, and diarrhea. To confirm the botulinum toxin, neutralization tests were performed on sera (four Korean native chicken farms and one pheasant farm) or culture supernatant (spot-billed ducks). Additionally, the contents of the cecum and liver from poultry presenting signs suggestive of botulism were inoculated to isolate the pathogen. The toxin genes were then detected by polymerase chain reaction (PCR). Through the neutralization tests, it was possible to diagnose the botulism and, except in the case of one Korean native chicken farm, to identify the type of pathogen. Using detection by PCR, except in two cases of the Korean native chicken farms, the botulinum toxin gene was found. Additionally, in four cases, it was possible to identify the C/D mosaic type using PCR. This paper reports the first occurrence of avian botulism in domestic birds and the first detection of botulism caused by this mosaic type in Korea.

Clostridium perfringens causes various digestive system disease symptoms in pigs. In the present study, 11 C. perfringens isolates were obtained from diarrheic piglets and 18 from healthy piglets. All of the C. perfringens isolates were shown to be type A using a multiplex PCR assay. The β2 toxin gene was detected in 27/29 C. perfringens isolates, i.e., 81% (9/11) of diarrheic piglets and 100% (18/18) of healthy piglets, and all of the genes had the same sequence. In conclusion, the β2 toxin gene of C. perfringens was distributed widely in Korean piglets regardless of the incidence of diarrhea, and there was no clear relationship with enteric disease. A pulsed-field gel electrophoresis analysis of DNA digested using SmaI demonstrated the non-clonal spread of C. perfringens isolates from piglets.

This report confirms a recent outbreak of a Leucocytozoon caulleryi infection in a commercial broiler breeder flock in South Korea. Seven, 18-day-old broiler breeders (Gallus gallus) were necropsied following a history of depression, sudden death, and subcutaneous hemorrhages. On necropsy, subcutaneous hemorrhages were identified in the wings and legs, pectoral and thigh muscles, thymus, epicardium, pancreas, and kidneys. On histopathology, there were numerous schizonts and merozoits of a Leucocytozoon sp. noted in the heart, spleen, liver, kidneys, thymus, and bursa of Fabricius. Molecular analysis of the mitochondrial cytochrome oxidase b confirmed that the causative agent was Leucocytozoon caulleryi. Although L. caulleryi was diagnosed previously in South Korea, there had been no reports of L. caulleryi over the past several decades.

This study was conducted to characterize infectious laryngotracheitis (ILT) viruses isolated from poultry in South Korea using RFLP analysis of PCR products. Seven wild-type Korean isolates from commercial chicken farms collected between 1986 and 2012 were compared with 3 imported commercial vaccine strains [LT Blen (Hudson strain, United States), Laryngo Vac (Cover strain, United States), and Nobilis ILT (Serva strain, France)] and a Korean chicken embryo origin (CEO) vaccine strain [ILT-VAC (Gyeonggi97 strain, Korea)]. Six of the field isolates were highly virulent viruses, and the Kr12AD37 isolate was considered an attenuated type according to Han's RFLP method. These virulent Korean ILT viruses were divided into 3 classes (class I, II, and III). The Kr12AD37 isolate was found to have the same RFLP pattern as the Korean CEO vaccine strain, and both of these strains were different from the 3 foreign vaccine strains. The results suggest that the Korean CEO vaccine strain has been responsible for recent outbreaks, and the characterization of ILT viruses by RFLP was useful for diagnosis by providing epidemiological information.

We identified two distinct bla(CTX-M)-bearing and five distinct bla(CMY-2)-bearing genetic structures located on plasmids from Salmonella enterica and Escherichia coli isolates (n = 35) collected from chickens in South Korea. All Salmonella plasmids shared a common replicon, bla(CTX-M-15) transposon, and core resistance phenotype, while E. coli bla(CTX-M-15) plasmids included four distinct replicons.

Background: The rapid and accurate identification of the H5 and H7 subtypes of avian influenza (AI) virus is an important step for the control and eradication of highly pathogenic AI outbreaks and for the surveillance of AI viruses that have the potential to undergo changes in pathogenicity in poultry and wild birds. Currently, real-time reverse transcription polymerase chain reaction (RRT-PCR) is routinely used for the rapid detection of the H5 and H7 genes, but misidentification is frequent for emergent isolates and viruses isolated from diverse regions due to the high sequence variation among AI viruses., Findings: In this study, an RRT-PCR method was tested for the detection of matrix, H5 and H7 genes from diverse subtypes of AI viruses and from field samples obtained through AI surveillance in South Korea over the last four years. Both RRT-PCR and conventional experiment (virus isolation using egg inoculation followed by reverse transcription polymerase chain reaction) agreed on the virus-positive samples. And the comparison of the results with 174 clinical samples showed a high level of agreement without decreasing the specificity and sensitivity., Conclusions: This assay could be useful tool for the rapid detection of AI using the field samples from domestic poultry and wild birds in South Korea, and continuous regional updates is needed to validate primer sets as the AI virus evolves.

Escherichia fergusonii has been associated with a wide variety of intestinal and extraintestinal infections in both humans and animals. The aim of this study was to demonstrate the presence of heat-labile enterotoxin (LT)-producing E. fergusonii in healthy chickens and its plasmid-mediated LT toxin gene transfer to other Enterobacteriaceae. We tested faecal samples from 184 chicken flocks (consisting of 109 broilers and 75 layers) of 78 commercial chicken farms for the presence of the LT gene using a polymerase chain reaction-based screening and identified samples from 43 flocks (23.4%) as positive for the LT gene. We subsequently isolated and identified E. fergusonii harboring the LT gene from all LT-positive samples and observed 21 various biochemical types. The plasmids encoding LT in 16 (37.2%) of the 43 isolates were conjugally transferred to the recipient strain Escherichia coli J53. Southern hybridization showed that all plasmids from the transconjugants carried the eltAB gene (Ent plasmid) and belonged to the narrow-host-range IncF type. In addition, all the E. fergusonii strains identified were classified into 17 pulsed-field gel electrophoresis (PFGE) types, and it is likely that there was an association between the PFGE types and geographical location or breed of flocks. In conclusion, this is the first study to demonstrate that LT-producing E. fergusonii strains were present in the faeces of healthy chickens and that plasmid-mediated virulence genes can be transferred to E. coli and may have a great potential to cause human disease., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Escherichia coli has commonly been associated with diarrheal illness in humans and animals. Recently, E. albertii has been reported to be a potential pathogen of humans and animals and to be carried by wild birds. In the present study, the prevalence and genetic characteristics of intimin-producing E. coli and E. albertii strains were evaluated in wild birds in Korea. Thirty one of 790 Enterobacteriaceae strains from healthy wild birds were positive for the intimin gene (eaeA) and twenty two of the 31 strains were identified as atypical enteropathogenic E. coli (aEPEC) that did not possess both EAF and bfpA genes. A total of nine lactose non-fermenting coliform bacterial strains were identified as E. albertii by PCR and sequence analysis of housekeeping genes. A total of 28 (90.3%) eaeA-positive strains were isolated from waterfowl. Fifteen aEPEC (68.2%) and two E. albertii (22.2%) strains had a β-intimin subtype and 14 aEPEC strains harboring β-intimin belonged to phylogenetic group B2. AU eaeA-positive E. albertii and 3 aEPEC strains possessed the cytolethal distending toxin gene (cdtB). The eaeA-positive E. coli and E. albertii strains isolated from healthy wild birds need to be recognized as a potential pathogroup that may pose a potential threat to human and animal health. These findings indicate that eaeA-positive E. coli as well as E. albertii can be carried by wild birds, posing a potential threat to human and animal health.

An H7N7 avian influenza virus [A/Magpie/Kr/YJD174/07 (H7N7); Mp/Kr/07 virus] was isolated from magpie feces in the north-western area (Youngjongdo) of South Korea and identified as low pathogenicity by intravenous pathogenic index and amino acid sequence of cleavage site. In genetic analysis, the genome of the Mp/Kr/07 virus was the same as those of two other H7N7 viruses isolated from the Mallard ducks in Ganghwa, 5 km north of Youngjongdo, and grouped under the H7-subtype Eurasian linage with the highest similarity to recent two domestic duck isolates in South Korea. In vivo studies of the chickens and magpies, the Mp/Kr/07 virus, though did not caused any clinical signs with histological changes, could replicate in the oropharynx and cloaca of the chickens and was efficiently transmitted to contact chickens. However, the virus was restrictively identified in oropharynx of the magpies and was not spread to magpies by direct contact. These results suggest that magpie are not a biological amplifier of influenza virus and thus play a minimal role in virus transmission as intermediate host., (Copyright 2009 Elsevier B.V. All rights reserved.)

A variant type of duck hepatitis A virus (DHAV), DHAV-3 was recently discovered in South Korea and China. Sequence analyses verified that the variant is genetically or serologically different from the DHAV-1 and DHAV-2 types. Duck hepatitis had been reported in South Korea since 1985 and an attenuated DHAV-1 vaccine had efficiently prevented epidemics of DHAV-1 until 2002. Despite the DHAV-1 based vaccine in use the novel DHAV-3 circulating in South Korea remains to be a threat to duckling farming. To develop a live attenuated vaccine against DHAV-3, a representative isolate, AP-04203, was therefore attenuated by repeated passages in SPF chicken embryos 100 times. The 100th passaged virus, AP-04203P100, did not cause clinical sign and mortality in 1-day-old ducklings as well as reversion of virulence capacity. The ducklings vaccinated with AP-04203P100 virus (10(3.0)ELD(50)/0.2ml) on 1-day-old age via the intramuscular injection were well protected from 2 days after challenge with pathogenic AP04203P1 virus via the intramuscular route. In addition, the vaccine candidate also exhibited complete protection against currently circulating pathogenic DHAV-3 isolates. In conclusion, we demonstrate that the live attenuated virus, AP-04203P100, is a promising vaccine candidate facilitating the prevention of duck hepatitis caused by DHAV-3 around East Asia including South Korea.