Hee-Soo Lee

Novel Reassortant Influenza A(H5N8) Viruses, South Korea, 2014

To the Editor: Highly pathogenic avian influenza (HPAI) viruses have caused considerable economic losses to the poultry industry and poses potential threats to animal and human health (www.oie.int/en/ and www.who.int/en/). Since 2003, influenza A(H5N1) viruses with a hemagglutinin (HA) gene derived from A/goose/Guandong/1/96–like viruses have become endemic to 6 countries (Bangladesh, China, Egypt, India, Indonesia, and Vietnam) (1) (www.cdc.gov/). Furthermore, HPAI viruses with an H5 subtype continue to undergo substantial evolution because of extensive genetic divergence and reassortment between other subtypes of influenza viruses. Especially in China, novel subtypes of H5 HPAI virus, such as influenza A(H5N2), influenza A(H5N5), and influenza A(H5N8) viruses, were reported during 2009–2011 (2,3).

Highly pathogenic avian influenza virus (H5N8) in domestic poultry and its relationship with migratory birds in South Korea during 2014.

Highly pathogenic H5N8 avian influenza viruses (HPAIVs) were introduced into South Korea during 2014, thereby caused outbreaks in wild birds and poultry farms. During the 2014 outbreak, H5N8 HPAIVs were isolated from 38 wild birds and 200 poultry farms (up to May 8, 2014). To better understand the introduction of these viruses and their relationships with wild birds and poultry farm, we analyzed the genetic sequences and available epidemiological data related to the viruses. Genetic analysis of 37 viruses isolated from wild birds and poultry farms showed that all of the isolates belonged to clade 2.3.4.6 of the hemagglutinin (HA) gene, but comprised two distinct groups. During the initial stage of the outbreak, identical isolates from each group were found in wild birds and poultry farms near Donglim Reservoir, which is a resting site for migratory birds, thereby indicating that two types of H5N8 HPAIVs were introduced into the lake at the same time. Interestingly, the one group of H5N8 HPAIV predominated around Donglim Reservoir, and the predominant virus was dispersed by wild birds among the migratory bird habitats in the western region of South Korea as time passed, and it was also detected in nearby poultry farms. Furthermore, compared with the results of the annual AIV surveillance of captured wild birds, which has been performed since 2008, more HPAIVs were isolated and H5 sero-prevalence was also detected during the 2014 outbreak. Overall, our results strongly suggest that migratory birds played a key role in the introduction and spread of viruses during the initial stage of the 2014 outbreak.

Novel Reassortant Influenza A(H5N8) Viruses among Inoculated Domestic and Wild Ducks, South Korea, 2014

Inoculated wild ducks showed few symptoms but transmitted H5N8 viruses to other ducks.

Effects of Forsythia suspensa Extract on Growth Performance, Nutrient Digestibility, and Antioxidant Activities in Broiler Chickens Under High Ambient Temperature

A 42-d trial was conducted with 252 broiler chickens (d 1 of age, 38.8 +/- 1.3 g of BW) to determine the effects of Forsythia suspensa extract on growth performance, nutrient digestibility, and antioxidant activities under high ambient temperature (32 +/- 1 degrees C). The feeding program consisted of a starter diet from d 1 to 21 of age and a finisher diet from d 22 to 42 of age. Dietary treatments included a negative control group (NC) fed a cornsoybean meal based diet without vitamin C or Forsythia suspensa extract, a positive control group fed a diet with 200 mg of vitamin C/kg, and a test group (FS) fed with 100 mg of Forsythia suspensa extract/kg. There were 14 cages per treatment and 6 birds per cage during the study. Birds had free access to diets and water during the entire period. Body weight and feed intake were measured at d 21 and 42. Blood and tissue samples were collected at d 21 and 42 for assay of antioxidant indices. Growth performance did not differ among treatment groups during the starter period. In the finisher phase, birds in FS had greater (P < 0.05) average daily gain, feed conversion, and apparent digestibility of energy, CP, calcium, and phosphorus than birds in NC. Furthermore, birds in FS had greater (P < 0.05) total antioxidant capacity and superoxide dismutase activity and lower (P < 0.05) malondialdehyde activity in the serum than birds in NC. The FS birds had greater (P < 0.05) muscle superoxide dismutase activity and lower (P < 0.05) malondialdehyde than NC birds. During the entire period, hepatic superoxide dismutase activity of FS birds was greater (P < 0.05) than that of NC birds. Dietary supplementation with Forsythia suspensa extract can enhance nutrient digestibility and growth performance possibly by reducing oxidative stress of broiler chickens under high ambient temperatures.

The first detection of methicillin-resistant Staphylococcus aureus ST398 in pigs in Korea.

In order to determine the presence of methicillin-resistant Staphylococcus aureus (MRSA) in pigs in Korea, a total of 657 nasal swabs were collected from pigs on 66 different pig farms nationwide during February 2008-May 2009. The prevalences of MRSA positive samples in pigs and farms were 3.2% (21/657) and 22.7% (15/66), respectively. Two different types were found among the 21 MRSA isolates: 17 strains of livestock-associated type (LA; ST398 or ST541/spa t034) and 4 strains of human-associated type (HA; ST72/spa t664 or t2461). The most prevalent type of MRSA strain was ST398/t034 (12/21, 57%), followed by ST541/t034 (5/21, 23.8%). The rest of the isolates were ST72/t664 (n=2) and ST72/t2461 (n=2), respectively. Our data provide evidence for the existence of not only LA types (ST398 and ST541) but also HA type (ST72) MRSA in pigs in Korea. This survey provides the first evidence of LA type MRSA in animals in Korea. In addition, the presence of human MRSA clones in pigs observed in this study suggests an additional reservoir for human MRSA infection, and vice versa.

Transmission and Persistence of Methicillin-Resistant Staphylococcus aureus in Milk, Environment, and Workers in Dairy Cattle Farms

The aim of this study was to determine the presence and persistence of methicillin-resistant Staphylococcus aureus (MRSA) in milk, farm environment, and farmers on 22 dairy cattle farms in Korea during 2008-2009. Genetic relatedness among the MRSA isolates was also investigated. Of 1146 samples examined, 35 of 559 (6.3%) quarter milk samples from 371 cows, four of 86 (4.7%) hand and nose samples from 43 farmers, and 6 of 501 (1.2%) farm environment samples were MRSA positive. Except for three isolates, all MRSA were classified into ST72-spa t324-SCCmec IV with PVL negative, the most predominant clonal type among community-associated MRSA in South Korea. All 35 MRSA-positive milk samples from 19 cows were obtained from a single farm (Farm G) out of 22 (4.5%) farms tested. The farm G was revisited 1 year later and milk samples were collected for examination of MRSA again. Two of six previous MRSA-positive cattle that had been kept on the farm still harbored MRSA genetically identical to MRSA strains, which were isolated from the same farm a year ago. The results of this study provide the evidence of transmission of MRSA among cattle, farm environment, and farmers and also long-term persistence of MRSA in animals.

CTX-M-Type β-Lactamase in Escherichia coli Isolated from Sick Animals in Korea

About 408 Escherichia coli were isolated from sick farm animals and pets during 2003-2006. Of these isolates, four strains showed resistance to third-generation cephalosporins. The bla(CTX-M-14) gene was encountered in three E. coli strains, each of which were isolated from two cows and a dog, respectively, and bla(CTX-M-15) was identified in an E. coli isolated from a pig. All bla(CTX-M) genes were found to be transferred. The pulsed-field gel electrophoresis pattern indicated that the CTX-M-type beta-lactamase-producing E. coli isolates were genetically diverse. This study shows the emergence of CTX-M-type beta-lactamase-producing E. coli in animals for the first time in Korea. Study results suggest the need for awareness and comprehensive monitoring of extended-spectrum beta-lactamases in animals because gene transfer can occur between animals as well as humans.

Genetic and phylogenetic analysis of South Korean sacbrood virus isolates from infected honey bees (Apis cerana)

Sacbrood virus (SBV) is one of the most destructive honey bee viruses. The virus causes failure to pupate and death in both larvae and adult bees. Genetic analysis of SBV infected honey bees (Apis cerana) from five different provinces was carried out based on three nucleotide sequences; one partial structural protein coding sequence and two non-structural protein coding sequences. Sequences amplified by three specific primer pairs were aligned and compared with reference sequences deposited in the GenBank database. Sequence alignments revealed a low level of sequence variation among Korean isolates (≥ 98.6% nucleotide identity), regardless of the genome regions studied or the geographic origins of the strains. Multiple sequence comparisons indicated that Korean SBV isolates are genetically closely related to Chinese and other Asian strains. Interestingly, the Korean SBV isolates showed a number of unique nucleotides and amino acids that had not been observed in other published strains. Korean and other Asian isolates from the host A. cerana and the UK, European and Japanese strains from the host Apis mellifera showed differences in nucleotide and deduced amino acid identities. This suggests that host-specificity exists among SBV strains isolated from different species. Phylogenetic relatedness between compared sequences was analyzed by MEGA 4.1 software using the neighbor-joining (NJ) method with a boot-strap value of 1000 replicates. Obtained topologies were in agreement with previous studies, in which a distinct group of SBV was formed by UK and European genotypes and another group was comprised of Asian genotypes including strains that originated from China, Japan (japonica), India and Nepal. However, phylogeny based on a partial protein structural coding sequence grouped all Korean SBV isolates identified in A. cerana as a separate cluster. Our findings suggest that further study, including Korean SBV isolated from A. mellifera, is needed.

Pathologic Changes in Wild Birds Infected with Highly Pathogenic Avian Influenza A(H5N8) Viruses, South Korea, 2014

Susceptibility to infection varies by species, and asymptomatic birds could be carriers.

Characterization of Clade 2.3.2.1 H5N1 Highly Pathogenic Avian Influenza Viruses Isolated from Wild Birds (Mandarin Duck and Eurasian Eagle Owl) in 2010 in Korea

Starting in late November 2010, the H5N1 highly pathogenic avian influenza (HPAI) virus was isolated from many types of wild ducks and raptors and was subsequently isolated from poultry in Korea. We assessed the genetic and pathogenic properties of the HPAI viruses isolated from a fecal sample from a mandarin duck and a dead Eurasian eagle owl, the most affected wild bird species during the 2010/2011 HPAI outbreak in Korea. These viruses have similar genetic backgrounds and exhibited the highest genetic similarity with recent Eurasian clade 2.3.2.1 HPAI viruses. In animal inoculation experiments, regardless of their originating hosts, the two Korean isolates produced highly pathogenic characteristics in chickens, ducks and mice without pre-adaptation. These results raise concerns about veterinary and public health. Surveillance of wild birds could provide a good early warning signal for possible HPAI infection in poultry as well as in humans.