SUMMARY. Here, we report three detections of H7N1 low pathogenicity avian influenza viruses (LPAIV) from poultry in Missouri ( n = 2) and Texas ( n = 1) during February and March 2018. Complete genome sequencing and comparative phylogenetic analysis suggest that the H7 LPAIV precursor viruses were circulating in wild birds in North America during the fall and winter of 2017 and spilled over into domestic poultry in Texas and Missouri independently during the spring of 2018.

SUMMARY The H9N2 subtype of low pathogenic avian influenza (LPAI) virus is the most prevalent LPAI in domestic poultry. We previously reported the natural reassortant H9N2 viruses between North American and Eurasian lineages isolated from wild birds in Korea. These viruses were identified in China and Alaska, providing evidence of intercontinental dispersal. In this study, we evaluated the infectivity, transmissibility, and pathogenic potential of these H9N2 viruses and Eurasian H9N2 virus identified from wild birds using specific-pathogen-free chickens. Three-week-old chickens were infected intranasally. All of these reassortant H9N2 viruses could not be replicated and transmitted in chickens. On the other hand, three out of eight chickens inoculated with the Eurasian H9N2 virus shed detectable levels of virus and showed seroconversion but did not show contact transmission of the virus. Although all reassortant H9N2 viruses could not be replicated and transmitted in chickens, and although there are no reports on reassortant H9N2 virus infection in poultry farms until now, monitoring of reassortant H9N2 viruses should be continued to prepare for the advent and evolution of these viruses.

SUMMARY 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. RESUMEN Reporte de Caso— Diagnóstico de la infección en Leucocytozoon caulleryi en rereproductores pesados comerciales en Corea del Sur. Este informe confirma un brote reciente de la infección con Leucocytozoon caulleryi en un lote comercial de reproductoras pesadas en Corea del Sur. Se realizó la necropsia de siete reproductores de 18 días de edad ( Gallus gallus ) que tenían una historia de depresión, muerte repentina y hemorragias subcutáneas. A la necropsia, se identificaron hemorragias subcutáneas en las alas y las piernas, los músculos pectorales y del muslo, el timo, epicardio, páncreas y los riñones. A la histopatología, se observaron numerosos esquizontes y merozoitos de Leucocytozoon sp. especialmente en el corazón, bazo, hígado, riñones, timo y en la bolsa de Fabricio. El análisis molecular del gene mitocondrial citocromo b oxidasa confirmó que el agente causal era Leucocytozoon caulleryi . Aunque L. caulleryi fue diagnosticado previamente en Corea del Sur, no había reportes de L. caulleryi durante las últimas décadas.

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 10 3.5 50% egg infective dose (EID 50 ). Three weeks after immunization all the birds were challenged with seven different strains at 10 4.5 EID 50 . 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 10 3.5 dosis infectantes en embrión de pollo 50% (EID50). Tres semanas después de la vacunación, todas las aves fueron desafiadas con siete cepas diferentes, con 10 4.5 EID 50 . 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.

SUMMARY A Salmonella Gallinarum (SG)-specific bacteriophage isolated from sewage effluent was used to prevent horizontal transmission of SG in commercial layer chickens. Six-week-old chickens, each challenged with 5 × 10 8 colony-forming units of SG, cohabited with contact chickens treated with 10 6 plaque-forming units/kg of bacteriophage, prepared in feed additives, for 7 days before, and 21 days after challenge with SG. Mortality was observed for 3 wk after challenge and SG was periodically re-isolated from the liver, spleen, and cecum of chickens. SG re-isolation from organs was decreased and a significant ( P < 0.05) reduction in mortality was observed in contact chickens treated with the bacteriophage, as compared to untreated contact chickens, indicating that bacteriophage administration in feed additives significantly prevented the horizontal transmission of SG. These results provide important insights into prevention and control strategies against SG infection and suggest that the use of bacteriophages may be a novel, safe, and effectively plausible alternative to antibiotics for the prevention of SG infection in poultry.

SUMMARY An outbreak of avian influenza, caused by an H9N2 low-pathogenic avian influenza virus (AIV), occurred in a chicken farm and caused severe economic losses due to mortality and diarrhea. AIV was isolated and identified in a sample from an affected native Korean chicken. Genetic analysis of the isolate revealed a high sequence similarity to genes of novel reassortant H9N2 viruses isolated from slaughterhouses and live bird markets in Korea in 2008 and 2009. Animal challenge studies demonstrated that the replication kinetics and pathogenicity of the isolate were considerably altered due to adaptation in chickens. Vaccine protection studies indicated that commercial vaccine was not able to prevent virus shedding and clinical disease when chickens were challenged with the isolate. These results suggest that the novel H9N2 virus possesses the capacity to replicate efficiently in the respiratory system against vaccination and to cause severe disease in domestic chickens. The results also highlight the importance of appropriate updating of vaccine strains, based on continuous surveillance data, to prevent the possibility of a new H9N2 epidemic in Korea.

SUMMARY Avian influenza is one of the most contagious viral diseases in bird species and, increasingly, interspecies transmission to mammalian species has been reported. Prevention and eradication of avian influenza virus (AIV) infection in birds may require vaccines as part of a comprehensive program including biosecurity, culling, diagnostics, and surveillance. However, for valuable bird species in zoos, novel eradication strategies are needed, including antiviral treatments. The present study evaluated the anti-influenza efficacy of the potent neuraminidase inhibitor oseltamivir in avian species using the orders Galliformes (chickens) and Anseriformes (ducks). Viral replication of low pathogenic AIV was significantly reduced in the chicken model and completely reduced in the duck model. Anti-influenza drug administration to valuable bird species with an appropriate extrapolation approach could be useful for control of AIV in combination with active surveillance and vaccination strategies. Further, evaluation of oseltamivir against highly pathogenic avian influenza (HPAI) using avian models would be needed to optimize the oseltamivir application guideline for HPAI control.

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.

In a previous study, we optimized DNA barcoding techniques for avian influenza virus (AIV) isolation and host identification, using fecal samples from wild birds, for high-throughput surveillance of migratory waterfowls. In the present study, we surveyed AIV in Mongolia during the breeding season and, subsequently, in Korea in winter, to compare prevalent AIV subtypes and hosts using DNA barcoding. In Korea, H4 and H5 subtypes were the most abundantly detected HA subtypes, and most AIVs were isolated from the major population (mallards, Anas platyrhynchos ) of wild bird habitats. On the other hand, in Mongolia, H3 and H4 subtypes were the most abundantly detected HA subtypes, and most AIVs were isolated from a small population of wild bird habitats that were not visible at the sampling site. In conclusion, AIV isolation using fecal samples, accompanied with DNA barcoding techniques as a host bird species identification tool, could be useful for monitoring major and minor populations of wild bird habitats. Further, continuous, and large-scale surveillance could be helpful for understanding the AIV epidemiology, evolution, and ecology in wild waterfowl.

Live bird markets (LBMs) provide an ideal environment for the evolution and interspecies transfer of avian influenza viruses (AIVs). In this study, we analyzed AIVs present in LBMs in Korea during the winter seasons of 2006–08. Sixty-five AIVs that belong to four hemagglutination (HA) subtypes of AIV (H3, H4, H6, and H9) were isolated from 644 pooled tissue or swab samples collected in LBMs. Most H9 subtypes of AIVs were isolated from Galliformes (chickens, silky fowls, pheasants, and guinea fowls), and other subtypes were isolated from Anseriformes (Pekin ducks and mallards). In addition, we obtained a single H3N2 virus from nasal swabs of dogs sold in LBMs, and the virus was genetically identical to the canine influenza virus (CIV) isolated from pet dogs in Korea. Phylogenetic analysis suggests that the Korean H9N2 viruses prevalent in chickens have provided their gene segments to AIVs circulating in ducks. These gene transfers facilitated reassortment events among AIVs and likely generated the ancestors of CIV in Korea. An animal challenge study using chickens, quail, mice, and dogs had shown that the H4 and H6 subtypes could replicate in mice and that some H4 and H6 viruses could replicate in chickens without preadaptation. In addition, two H3 subtype viruses (H3N2 and H3N8) induced interstitial pneumonia that accompanied clinical signs and seroconversion in dogs. Our findings indicate that the newly evolved AIVs have been continuously generated by reassortment in ducks, and these reassortments could result in expanding the host range of AIVs.