Research Note: Evaluation of the cross protective efficacy of a subtype B aMPV vaccine against virulent subtype A aMPV by different administration routes.

Avian metapneumovirus (aMPV) causes respiratory and reproductive diseases in birds, including chickens. In the chicken industry, live vaccines against aMPV subtypes A and B, which are the major aMPV subtypes, are widely used to control disease caused by aMPV. In this study, we evaluated the cross protective efficacy of a live aMPV subtype B vaccine administered via 3 different routes (nasal, spray, and oral) against virulent aMPV subtype A in chickens. At 3 wk after vaccination of 1-wk-old specific-pathogen-free chickens, we measured the serological responses. On the same day, we challenged the birds with aMPV subtype A. Protection was evaluated by viral gene detection and histopathological examination at 3 and 5 days postchallenge. Although there were differences in the serological responses according to administration route, all vaccinated birds showed complete protection at 5 days postchallenge. Regardless of administration route, genome of challenge virus was not detected in vaccinated group, and there were significant differences between vaccinated birds and control group. Overall, our results demonstrated that a subtype B aMPV vaccine can provide cross protection against virulent subtype A aMPV in chickens.

Genetic Characterization and Pathogenicity Analysis of Recently Isolated Fowl Adenovirus 8b in Korea.

A Korean field strain of fowl adenovirus (FAdV) 8b was isolated from chickens showing high mortality. Isolated FAdV-8b strains with the hexon and fiber genes were genetically analyzed. The Korean FAdV-8b (K194/19) strain isolated in 2019 showed higher sequence identity with the FAdV-8b strain isolated in China but lower sequence identity with the Korean FAdV-8b (K187/08) strain isolated in 2008. The K194/19 strain formed a distinct subcluster within the FAdV-8b cluster in a phylogenetic tree based on hexon and fiber genes. FAdV can infect day-old chicks through vertical transmission, and so blood samples were obtained from 54-, 60-, and 63-wk-old parent chickens. FAdV-specific antibody levels were investigated with ELISA and virus neutralization (VN) tests with the K194/19 and K187/08 strains as antigens. In VN tests, all sera neutralized the K187/08 strain. However, the K194/19 strain was neutralized by sera collected from 60- and 63-wk-old chickens but not sera obtained from 54-wk-old chickens, indicating natural infection. Finally, to determine the pathogenicity of the K194/19 strain, 1-day-old and 4-wk-old specific-pathogen-free birds were infected with the K194/19 and K187/08 strains. No significant difference in pathogenicity was observed between the two strains. Although the K194/19 strain showed similar pathogenicity with the K187/08 strain, differences in nucleotide and amino acid sequences of the hexon and fiber genes may determine the evasion ability of the K187/08 neutralizing antibody, indicating the need for development of a novel FAdV vaccine.

Nota de investigación­Caracterización genética y análisis de patogenicidad de un adenovirus del pollo 8b aislado recientemente en Corea. Se aisló una cepa de campo coreana de adenovirus del pollo (FAdV) 8b de aves que mostraban una alta mortalidad. Se analizaron genéticamente cepas de FAdV-8b aisladas mediante los genes de hexón y de la fibra. La cepa coreana FAdV-8b (K194/19) aislada en 2019 mostró una mayor identidad de secuencia con la cepa FAdV-8b aislada en China, pero una menor identidad de secuencia con la cepa coreana FAdV-8b (K187/08) aislada en 2008. La cepa K194/19 formó un subgrupo distinto dentro del grupo de adenovirus del pollo 8b en un árbol filogenético basado en los genes de las fibras y hexones. El FAdV puede infectar a pollitos de un día a través de la transmisión vertical, por lo que se obtuvieron muestras de sangre de pollos reproductores de 54, 60 y 63 semanas de edad. Los niveles de anticuerpos específicos de FAdV se investigaron con ELISA y pruebas de neutralización de virus (VN) con las cepas K194/19 y K187/08 como antígenos. En las pruebas de neutralización, todos los sueros neutralizaron a la cepa K187/08. Sin embargo, la cepa K194/19 fue neutralizada por sueros recolectados de pollos de 60 y 63 semanas de edad, pero no por los sueros obtenidos de pollos de 54 semanas de edad, lo que indica una infección natural. Finalmente, para determinar la patogenicidad de la cepa K194/19, se infectaron aves libres de patógenos específicos de un día y cuatro semanas de edad con las cepas K194/19 y K187/08. No se observaron diferencias significativas en la patogenicidad entre las dos cepas. Aunque la cepa K194/19 mostró una patogenicidad similar con la cepa K187/08, las diferencias en las secuencias de nucleótidos y aminoácidos de los genes del hexón y de la fibra pueden determinar la capacidad para evadir los anticuerpos neutralizantes K187/08, lo que indica la necesidad de desarrollar una nueva vacuna contra adenovirus del pollo.

Genomic Analysis of Avian Infectious Bronchitis Viruses Recently Isolated in South Korea Reveals Multiple Introductions of GI-19 Lineage (QX Genotype).

Infectious bronchitis virus (IBV) was first identified in the 1930s and it imposes a major economic burden on the poultry industry. In particular, GI-19 lineage has spread globally and has evolved constantly since it was first detected in China. In this study, we analyzed S1 gene sequences from 60 IBVs isolated in South Korea. Two IBV lineages, GI-15 and GI-19, were identified in South Korea. Phylogenetic analysis suggested that there were six distinct subgroups (KM91-like, K40/09-like, and QX-like I to IV) of the South Korean GI-19 IBVs. Among them, QX-type III and IV subgroups, which are phylogenetically different from those reported in South Korea in the past, accounted for more than half of the total. Moreover, the phylogeographic analysis of the QX-like subgroups indicated at least four distinct introductions of GI-19 IBVs into South Korea during 2001-2020. The efficacy of commercialized vaccines against the recently introduced QX-like subgroups should be verified, and continuous international surveillance efforts and quarantine procedures should be enhanced to prevent the incursion of viruses.

Thermal Image Scanning for the Early Detection of Fever Induced by Highly Pathogenic Avian Influenza Virus Infection in Chickens and Ducks and Its Application in Farms.

Highly pathogenic avian influenza (HPAI) is considered as one of the most devastating poultry diseases. It is imperative to immediately report any known outbreaks to the World Organization for Animal Health. Early detection of infected birds is of paramount importance to control virus spread, thus minimizing the associated economic loss. In this study, thermal imaging camera devices were used to detect change in the maximum surface temperature (MST) of chickens (n = 5) and ducks (n = 2) as an early indicator of experimental HPAI infection. The MST of both chickens and ducks increased at least 24 h before the manifestation of clinical signs of HPAI infection, depending on the severity of the infection. The basal MST was recorded for broiler chickens housed under small pen and normal farm conditions without intentional infection. A threshold cutoff of MST was established based on the circadian rhythm of normal MST. This study suggests that thermal imaging of chickens and ducks is a promising tool to screen any potential HPAI-infected flock in order to expedite HPAI diagnosis.

Efficacy of a novel avian metapneumovirus live vaccine candidate based on vaccination route and age.

This article describes a series of animal studies for the development of an avian metapneumovirus (aMPV) live vaccine. Although aMPV causes continual economic loss in the poultry industry, there are no live aMPV vaccines available in Korea. Furthermore, information is limited with respect to standard field practices for vaccinations at an early age. Here, the development of an aMPV live vaccine was attempted, and its efficacy was investigated with respect to the vaccination route and age to develop a method for controlling aMPV. Before vaccine development, an animal challenge model was established using the aMPV field isolate to identify the most effective time and site for collecting samples for evaluation. After attenuation of the virulent aMPV in Vero cells, a safety and efficacy test was conducted for the vaccine candidate. As a novel aMPV live vaccine candidate, aMPV K655/07HP displayed sufficient safety in day-old chicks with 10 vaccine doses. The efficacy test using 1-week-old chicks showed weaker humoral immune response than that in 4-week-old chicks. However, the candidate vaccine provided complete protection against infection caused by the challenge virus for all ages of vaccinated chicks. In conclusion, an effective aMPV challenge model was established for studying aMPV in chickens, which offered important, insightful information. The safety and efficacy study suggested that the new aMPV candidate vaccine could be used to effectively reduce the economic losses incurred because of aMPV infection.

Whole-Genome Sequencing Analysis of Salmonella Enterica Serotype Enteritidis Isolated from Poultry Sources in South Korea, 2010-2017.

Salmonella enterica subsp. enterica serotype Enteritidis (SE) is recognized as a major cause of human salmonellosis worldwide, and most human salmonellosis is due to the consumption of contaminated poultry meats and poultry byproducts. Whole-genome sequencing (data were obtained from 96 SE isolates from poultry sources, including an integrated broiler supply chain, farms, slaughterhouses, chicken transporting trucks, and retail chicken meats in South Korea during 2010-2017. Antimicrobial resistance and virulence genes were investigated using WGS data, and the phylogenetic relationship of the isolates was analyzed using single-nucleotide polymorphism (SNP) typing and core genome multilocus sequence typing (cgMLST). All isolates carried aminoglycoside resistance genes, aac (6')- Iaa, and 56 isolates carried multiple antimicrobial resistance genes. The most frequent virulence gene profile, pef-fim-sop-inv.-org-sip-spa-sif-fli-flg-hil-ssa-sse-prg-pag-spv, was found in 90 isolates. The SNP analysis provided a higher resolution than the cgMLST analysis, but the cgMLST analysis was highly congruent with the SNP analysis. The phylogenetic results suggested the presence of resident SE within the facility of processing plants, environments of slaughterhouses, and the integrated broiler supply chain, and the phylogenetically related isolates were found in retail meats. In addition, the SE isolates from different origins showed close genetic relationships indicating that these strains may have originated from a common source. This study could be valuable reference data for future traceback investigations in South Korea.

Molecular characterization and genetic diversity of avian paramyxovirus type 4 isolated in South Korea from 2013 to 2017.

In recent years, avian paramyxovirus type 4 (APMV-4) frequently isolated from wild and domestic bird populations particularly waterfowls worldwide. However, molecular characteristics and genetic diversity of APMV-4 are uncertain, owing to the limited availability of sequence information. A total of 11 APMV-4 strains from 9850 fecal, swab, and environmental samples were isolated during the surveillance program in wintering seasons of 2013-2017 in South Korea. We performed genetic characterization and phylogenetic analysis to investigate the genetic diversity and relatedness between isolates from the region. We report high APMV-4 genetic diversity (multiple genotypes and sub-genotypes) among wild bird and poultry populations in Korea and that the potential virus exchange occurs between neighboring countries via wild bird migration. Furthermore, our study results suggest the possibility of transcontinental transmission of APMV-4 between Asia and Europe.

Molecular Characterization of Avian Paramyxovirus Types 4 and 8 Isolated from Wild Migratory Waterfowl in Mongolia.

Avian paramyxoviruses (APMVs) constitute some of the most globally prevalent avian viruses and are frequently isolated from wild migratory bird species. Using 1,907 fresh fecal samples collected during the 2012 avian influenza surveillance program, we identified two serotypes of APMV: APMV-4 ( n=10) and APMV-8 ( n=1). Sequences for these isolates phylogenetically clustered with Asian APMV-4 and APMV-8 recently isolated from wild birds in Korea, Japan, China, and Kazakhstan. Analysis by DNA barcoding indicated that the Mongolian APMV-4 and APMV-8 strains were isolated from Anseriformes species including Mallards ( Anas platyrhynchos) and Whooper Swans ( Cygnus cygnus). The close genetic relatedness to Asian isolates, and to similar host species, suggested that wild bird species in the Anatidae family might play an important role as a natural reservoir in the spread of APMV-4 and APMV-8. However, we did not find conclusive evidence to support this hypothesis owing to the limited number of strains that could be isolated. Enhanced surveillance of poultry and wild bird populations in Asia is therefore crucial for the understanding of global AMPV transmission, ecology, evolution, and epidemiology.

Complete Genome Sequence of an Avian Paramyxovirus Type 4 Strain Isolated from Domestic Duck at a Live Bird Market in South Korea.

We report here the first full-genome sequence of an avian paramyxovirus type 4 (APMV-4) strain isolated from a domestic mallard duck at a live bird market in South Korea. Phylogenetic analyses provide genetic information on a new genetic clade, APMV-4, isolated from a domestic duck and evidence of APMV-4 exchange between poultry and wild birds.