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Budgerigar fledgling disease (BFD) is a contagious disease caused by avian polyomavirus (APV) in psittacine birds and causes high mortality rates. Here, eight APV-positive cases were confirmed from dead parrots or parrot tissue samples by polymerase chain reaction (PCR). Full-length genome sequencing showed high nucleotide identity (98.84–100%) between the APV strains. Phylogenetic analysis revealed that two genogroups were cocirculating in South Korea. The nucleotide sequences of five strains, collected from different parrot species, were identical; however, pathological lesions were observed in only two parrots, both aged 2 months. Pathology included necrotic spots in the liver, subcutaneous haemorrhage, hepatomegaly, ascites, intranuclear inclusion bodies, hepatocyte karyomegaly, hepatic necrosis, and bile duct proliferation. This suggests that the pathogenicity of APV might be host age-dependent regardless of the host species. This study improves our understanding of APV pathogenicity and provides a more detailed genetic characterization of APV strains. RESEARCH HIGHLIGHTS Eight APV strains were identified in South Korea from 2019 to 2021. By phylogenetic analysis, South Korean APV strains were classified into two clades. [ABSTRACT FROM AUTHOR]

Avian chlamydiosis is an acute or chronic disease of birds after infection by Chlamydia. Although Chlamydia psittaci is the primary agent of the disease, two additional species, Chlamydia avium and Chlamydia gallinacea, have also been recognized as potential disease agents. Therefore, the diagnosis of avian chlamydiosis requires differential identification of these avian Chlamydia species. The objective of the present study was to develop a multiplex real-time polymerase chain reaction (PCR) assay to rapidly differentiate between these three species of avian Chlamydia (C. psittaci, C. avium, and C. gallinacea) as well as to detect the genus Chlamydia. Specific genetic regions of the three species were identified by comparative analysis of their genome sequences. Also, the genus-specific region was selected based on 23S rRNA sequences. PCR primers and probes specific to the genus and each species were designed and integrated in the multiplex real-time PCR assay. The assay was highly efficient (94.8–100.7%). It could detect fewer than 10 copies of each target sequence of the genus and each species. Twenty-five Chlamydia control and field DNA samples were differentially identified while 20 other bacterial strains comprising 10 bacterial genera were negative in the assay. This assay allows rapid, sensitive, and specific detection of the genus and the three species of avian Chlamydia in a single protocol that is suitable for routine diagnostic purposes in avian diagnostic laboratories. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Campylobacterspecies cause human gastrointestinal infections worldwide. They commonly inhabit intestines of avian species including wild birds. They might play a role in the spread of infections to humans and other bird species. The prevalence ofCampylobacterspecies in 2164 faecal samples of wild birds (representing 71 species and 28 families) captured across the Korean peninsula was evaluated in this study. The overall prevalence was 15.3% (332/2164). Bird species belonging to the familyCharadriidaehad the highest isolation rate (30.0%), followed by those belonging to the familiesArdeidae(26.4%),Turdidae(21.9%), andAnatidae(15.3%). The prevalence ofCampylobacterspp. differed significantly according to migratory habit. Stopover birds were the most commonly infected (19.0%), followed by winter migratory (16.7%) and summer migratory birds (12.3%). However, indigenous birds showed very low prevalence (2.7%). Antimicrobial susceptibility tests were performed for 213 isolates. Results showed thatCampylobacter jejuniisolates (n = 169) exhibited resistance to nalidixic acid (5.3%), ciprofloxacin (3.0%), and tetracycline (1.8%), whileCampylobacter lari(n = 1) displayed resistance to nalidixic acid and ciprofloxacin. However, allCampylobacter coliisolates (n = 20) were susceptible to all antimicrobials tested. This is the first report on the prevalence ofCampylobacterspecies in wild birds that seasonally or indigenously inhabit the Korean peninsula. Our results indicate that the overall prevalence ofCampylobacterin wild birds is moderate. Therefore, birds might serve as significant reservoirs forCampylobacterpathogens. [ABSTRACT FROM PUBLISHER]

Duck hepatitis can be caused by four types of viruses: duck hepatitis virus (DHV) type 1 (DHV-1), DHV-1a (a variant strain of DHV-1), DHV-2 and DHV-3. In Korea, duck hepatitis has been associated with two types of DHV-1, original DHV-1 type-specific strain (DHV-1s) and the recently reported DHV-1 variant strains (DHV-1v). The pathogenicity and pathological findings of ducklings infected with the recent DHV-1v isolates, AP-04114 and AP-04203, were almost identical to those infected with members of the DHV-1s, DHV-HS and the type-specific strain DRL-62. To be able to monitor the epidemiological patterns exhibited by the two Korean types, a specific gene-based differential diagnostic method based on multiplex polymerase chain reaction was developed. The primers selected were designed to bind to and amplify conserved regions within the RNA-dependent RNA polymerase (3D) gene, the complete capsid (P1) region or the 5'-untranslated region to distinguish between the DHV-1s and DHV-1v groups. The described multiplex polymerase chain reaction method was able to selectively recognize ducklings infected with either of the two groups of Korean isolates. The method was also able to distinguish between DHVs and other avian-originated RNA viruses. The detection limit of the diagnostic method was determined to correspond to 103 copies viral RNA and 100 pg used as starting template. As a result, the use of this test allows rapid and early diagnosis of two different virus types affecting the commercial duckling industry. [ABSTRACT FROM AUTHOR]

The present study reports the clinical, virological and pathological findings observed in a natural outbreak of highly pathogenic avian influenza in farmed commercial ducks. The ducks developed clinical signs, including mild respiratory distress, depression, mild diarrhoea, loss of appetite and increasing mortality (up to 12%). Al necropsy, multifocal mottled necrosis was commonly found in the pancreas with splenomegaly, hepatomegaly, and swollen kidneys. Microscopically, there was necrotized pancreatitis and hepatitis, and lymphocytic meningoencephalitis and myocarditis. Influenza viral antigen was demonstrated in areas closely associated with histopathological lesion. Avian influenza virus was isolated from the caecal tonsil, faeces, and kidney of the domestic ducks. The isolated virus was identified as a highly pathogenic H5N1, with a haemagglutinin proteolytic cleavage site deduced amino acid sequence of... QRHKRKKR/GLFGAIAG ... In order to determine the pathogenicity of the isolate, eight 6-week-old specific pathogen free chickens were inoculated intravenously with the virus, and all birds died within 24 h after inoculation. This is the first report of an outbreak of highly pathogenic avian influenza with clinical signs in commercial domestic ducks in South Korea. [ABSTRACT FROM AUTHOR]