Prevalence of Severe Fever with Thrombocytopenia Syndrome Virus in Ticks Collected from National Parks in Korea.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral disease in East Asian countries, including China, Japan, and the Republic of Korea (ROK). The causative agent of SFTS is the SFTS virus (SFTSV), which is transmitted by ticks. To investigate the prevalence of SFTSV in the ROK, a total of 9744 ticks were collected from vegetation in five national parks between July and November 2015. Of the collected adult and nymph ticks, Haemaphysalis longicornis (68.44%) was the most abundant, followed by Haemaphysalis flava (29.66%), Ixodes nipponensis (1.56%), and Amblyomma testudinarium (0.34%). Collected larval ticks were of the genera Haemaphysalis (99.61%) and Ixodes (0.39%). One-step RT-PCR and nested PCR were used to detect SFTSV-specific genes from each individual adult and nymph tick and pooled larval ticks. SFTSV was detected in 4.77% (48/1006) in H. longicornis, 1.15% (5/436) in H. flava, 0% (0/23) in I. nipponensis, and 20% (1/5) in A. testudinarium. The infection rate of SFTSV in adult and nymph ticks was 3.61%. The prevalence of SFTSV in adult and nymph ticks was relatively high, compared with previous reports. In larval ticks, the minimum infection rate was 0.31%. SFTSV was detected in ticks collected from both trail and nontrail areas in the national parks, and up to 800 meters above sea level. The sequences obtained showed 99.4-99.7% homology with SFTS virus S segment sequences from Chinese and Japanese ticks.

Serological evidence of H5-subtype influenza A virus infection in indigenous avian and mammalian species in Korea.

In Korea, H5-subtype highly pathogenic avian influenza (HPAI) has caused huge economic losses in poultry farms through outbreaks of H5N1 since 2003, H5N8 since 2013 and H5N6 since 2016. Although it was reported that long-distance migratory birds may play a major role in the global spread of avian influenza viruses (AIVs), transmission from such birds to poultry has not been confirmed. Intermediate hosts in the wild also may be a potential factor in viral transmission. Therefore, a total of 367 serum samples from wild animals were collected near major migratory bird habitats from 2011 to 2016 and tested by AIV-specific blocking ELISA and hemagglutination inhibition (HI) test. Two mammalian and eight avian species were seropositive according to the ELISA test. Among these, two mammalian (Hydropotes inermis and Prionailurus bengalensis) and three avian (Aegypius monachus, Cygnus cygnus, and Bubo bubo) species showed high HI titres (> 1,280) against one or two H5-subtype AIVs. As H. inermis (water deer), P. bengalensis (leopard cat), and B. bubo (Eurasian eagle owl) are indigenous animals in Korea, evidence of H5-subtype AIV in these animals implies that continuous monitoring of indigenous animals should be followed to understand interspecies transmission ecology of H5-subtype influenza viruses.

Molecular prevalence and genotyping of Chlamydia spp. in wild birds from South Korea.

Wild birds are reservoirs for Chlamydia spp. Of the total 225 samples from wild birds during January to September 2016 in Korea, 4 (1.8%) and 2 (0.9%) showed positive for Chlamydia psittaci and Chlamydia gallinacea, respectively. Phylogenetic analyses and comparisons of sequence identities for outer-membrane protein A (ompA) revealed that Korean C. psittaci fall into three previously known genotypes; genotype E, 1V and 6N, whereas the Korean C. gallinacea were classified as new variants of C. gallinacea. Our study demonstrates that wild birds in South Korea carry at least two Chlamydia species: C. psittaci and C. gallinacea, and provides new information on the epidemiology of avian chlamydiosis in wild birds.

Review of Avian Influenza Outbreaks in South Korea from 1996 to 2014.

Since the first outbreak of low pathogenic avian influenza (LPAI) in 1996, outbreaks of LPAI have become more common in Korea, leading to the development of a nationwide mass vaccination program in 2007. In the case of highly pathogenic avian influenza (HPAI), four outbreaks took place in 2003-04, 2006-07, 2008, and 2010-11; a fifth outbreak began in 2014 and was ongoing at the time of this writing. The length of the four previous outbreaks varied, ranging from 42 days (2008) to 139 days (2010-11). The number of cases reported by farmers that were subsequently confirmed as HPAI also varied, from seven cases in 2006-07 to 53 in 2010-11. The number of farms affected by the outbreaks varied, from a low of 286 (2006-07) with depopulation of 6,473,000 birds, to a high of 1500 farms (2008) with depopulation of 10,200,000 birds. Government compensation for bird depopulation ranged from $253 million to $683 million in the five outbreaks. Despite the damage caused by the five HPAI outbreaks, efficient control strategies have yet to be established. Meanwhile, the situation in the field worsens. Analysis of the five HPAI outbreaks revealed horizontal farm-to-farm transmission as the main factor effecting major economic losses. However, horizontal transmission could not be efficiently prevented because of insufficient transparency within the poultry industry, especially within the duck industry, which is reluctant to report suspicious cases early. Moreover, the experiences and expertise garnered in previous outbreaks has yet to be effectively applied to the management of new outbreaks. Considering the magnitude of the economic damage caused by avian influenza and the increasing likelihood of its endemicity, careful and quantitative analysis of outbreaks and the establishment of control policies are urgently needed.

Tracking Mallards (Anas platyrhynchos) with GPS Satellite Transmitters Along Their Migration Route Through Northeast Asia.

In this study, Global Positioning System satellite transmitters were attached to three mallards (Anas platyrhynchos) wintering in South Korea to track their migration routes, stopover sites, breeding sites, and migration patterns. We successfully tracked only one mallard (no. 108917) from November 15, 2011, to November 29, 2013, and determined separate migration routes in two cases of spring migration and one case of fall migration. The mallard repeatedly migrated to the same final destination, even though the travel path varied. We identified six stopover sites: Hunhe River, Liaohe River, Yinma River, Yalu River, Songjeon Bay, and Dahuofang Reservoir in China and South Korea. The wintering sites of two migration cases were discovered to be identical (Gokgyo River in Asan, South Korea). The terminal sites, which were presumed to be breeding grounds, were the same in both cases (Hinggan League in Inner Mongolia Autonomous Region, China). On the basis of the migration routes identified in this study, we suggest that future efforts to control highly pathogenic avian influenza (HPAI) should not only include avian influenza surveillance but also implement flyway-based strategies, with regard to all countries affected by potential HPAI outbreaks.

Assessment of the safety and efficacy of low pathogenic avian influenza (H9N2) virus in inactivated oil emulsion vaccine in laying hens.

In Korea, several outbreaks of low pathogenic AI (H9N2) viral infections leading to decreased egg production and increased mortality have been reported on commercial farms since 1996, resulting in severe economic losses. To control the H9N2 LPAI endemic, the Korea Veterinary Authority has permitted the use of the inactivated H9N2 LPAI vaccine since 2007. In this study, we developed a killed vaccine using a low pathogenic H9N2 AI virus (A/chicken/Korea/ADL0401) and conducted safety and efficacy tests in commercial layer farms while focusing on analysis of factors that cause losses to farms, including egg production rate, egg abnormality, and feed efficiency. The egg production rate of the control group declined dramatically 5 days after the challenge. There were no changes in feed consumption of all three groups before the challenge, but rates of the control declined afterward. Clinical signs in the vaccinated groups were similar, and a slight decline in feed consumption was observed after challenge; however, this returned to normal more rapidly than the control group and commercial layers. Overall, the results of this study indicate that the safety and efficacy of the vaccine are adequate to provide protection against the AI field infection (H9N2) epidemic in Korea.

Detection of Severe Fever with Thrombocytopenia Syndrome Virus from Wild Animals and Ixodidae Ticks in the Republic of Korea.

Severe fever with thrombocytopenia syndrome (SFTS) is caused by SFTS virus (SFTSV), a novel bunyavirus reported to be endemic to central-northeastern China, southern Japan, and the Republic of Korea (ROK). To investigate SFTSV infections, we collected serum samples and ticks from wild animals. Using serum samples and ticks, SFTSV-specific genes were amplified by one-step RT-PCR and nested PCR and sequenced. Indirect immunofluorescence assay (IFA) was performed to analyze virus-specific antibody levels in wild animals. Serum samples were collected from a total of 91 animals: 21 Korean water deer (KWD), 3 Siberian roe deer, 5 gorals, 7 raccoon dogs, 54 wild boars (WBs), and 1 carrion crow. The SFTSV infection rate in wild animals was 3.30% (3 of 91 animals: 1 KWD and 2 WBs). The seropositive rate was 6.59% (6 of 91 animals: 5 KWD and 1 WB). A total of 891 ticks (3 species) were collected from 65 wild animals (9 species). Of the attached tick species, Haemaphysalis longicornis (74.86%) was the most abundant, followed by Haemaphysalis flava (20.20%) and Ixodes nipponensis (4.94%). The average minimum infection rate (MIR) of SFTSV in ticks was 4.98%. The MIRs of H. longicornis, H. flava, and I. nipponensis were 4.51%, 2.22%, and 22.73%, respectively. The MIRs of larvae, nymphs, and adult ticks were 0.68%, 6.88%, and 5.53%, respectively. In addition, the MIRs of fed and unfed ticks were 4.67% and 4.96%, respectively. We detected a low SFTSV infection rate in wild animals, no differences in SFTSV infection rate with respect to bloodsucking in ticks, and SFTSV infection for all developmental stages of ticks. This is the first report describing the detection of SFTSV in wild animals in the ROK.

Molecular characterization of highly pathogenic avian influenza H5N8 viruses isolated from Baikal teals found dead during a 2014 outbreak in Korea.

Nineteen highly pathogenic avian influenza (HPAI) H5N8 viruses were isolated from wild birds in the Donglim reservoir in Gochang, Jeonbuk province, Korea, which was first reported to be an outbreak site on January 17, 2014. Most genes from the nineteen viruses shared high nucleotide sequence identities (i.e., 99.7% to 100%). Phylogenetic analysis showed that these viruses were reassortants of the HPAI H5 subtype and the H4N2 strain and that their hemagglutinin clade was 2.3.4.4, which originated from Eastern China. The hemagglutinin protein contained Q222 and G224 at the receptor-binding site. Although the neuraminidase protein contained I314V and the matrix 2 protein contained an S31N substitution, other mutations resulting in oseltamivir and amantadine resistance were not detected. No substitutions associated with increased virulence and enhanced transmission in mammals were detected in the polymerase basic protein 2 (627E and 701D). Non-structural-1 was 237 amino acids long and had an ESEV motif with additional RGNKMAD amino acids in the C terminal region. These viruses caused deaths in the Baikal teal, which was unusual, and outbreaks occurred at the same time in both poultry and wild birds. These data are helpful for epidemiological understanding of HPAI and the design of prevention strategies.

Prevalence of avian influenza virus in wild birds before and after the HPAI H5N8 outbreak in 2014 in South Korea.

Since 2003, highly pathogenic avian influenza (HPAI) virus outbreaks have occurred five times in Korea, with four HPAI H5N1 outbreaks and one HPAI H5N8 outbreak. Migratory birds have been suggested to be the first source of HPAI in Korea. Here, we surveyed migratory wild birds for the presence of AI and compared regional AI prevalence in wild birds from September 2012 to April 2014 for birds having migratory pathways in South Korea. Finally, we investigated the prevalence of AI in migratory birds before and after HPAI H5N8 outbreaks. Overall, we captured 1617 migratory wild birds, while 18,817 feces samples and 74 dead birds were collected from major wild bird habitats. A total of 21 HPAI viruses were isolated from dead birds, and 86 low pathogenic AI (LPAI) viruses were isolated from captured birds and from feces samples. Spatiotemporal distribution analysis revealed that AI viruses were spread southward until December, but tended to shift north after January, consistent with the movement of migratory birds in South Korea. Furthermore, we found that LPAI virus prevalences within wild birds were notably higher in 2013-2014 than the previous prevalence during the northward migration season. The data from our study demonstrate the importance of the surveillance of AI in wild birds. Future studies including in-depth genetic analysis in combination with evaluation of the movement and ecology of migratory birds might help us to bridge the gaps in our knowledge and better explain, predict, and ultimately prevent future HPAI outbreaks.

Pathogens in water deer (Hydropotes inermis) in South Korea, 2010-12.

Water deer (Hydropotes inermis) are among the most common wildlife to approach farmhouses and livestock barns in Korea. We collected 305 water deer from Gangwon (n=168), South Chungcheong (n=89), and Gyeongsang (n=48) provinces in 2010-12 and used PCR and serologic tests to screen the deer for pathogens. In 2010, tests for bovine viral diarrhea virus (BVDV), rotavirus, and Brucella abortus were positive in 8% (5/60), 2% (1/60), and 59% (33/56) of the animals, respectively. In 2010, the water deer were negative for foot-and-mouth disease virus, coronaviruses, and Mycobacterium bovis. All samples collected in 2011 and 2012 were negative for all pathogens analyzed. These results suggest that at least two of the investigated pathogens, BVDV and B. abortus, circulate among water deer in South Korea.

Adiaspiromycosis of an Apodemus agrarius captured wild rodent in Korea.

Adiaspiromycosis is caused by pulmonary infection with Emmonsia. Inhalated spores of Emmonsia cause asymptomatic infection to necrogranulomatous pneumonia, depending on the burden of adiaspore and host immunity. For disease monitoring of wild rodents captured on Jeju Island in Korea, we examined the lung tissue of wild rodents histopathologically. Spores composed of thick three-layered walls were found following histopathological examination and were diagnosed as adiaspiromycosis. Adiaspiromycosis has been found in mammals in many parts of the world. To our knowledge, this is the first report of adiaspiromycosis of an Apodemus agrarius captured in Korea.

Detection of sarcocystic infection in a wild rodent (Apodemus agrarius chejuensis) captured on Jeju island.

Sarcocystis spp is a causative agent of sarcocystosis. They have a characteristic life cycle infecting both prey and predator. Sarcocystis can cause myositis, atrophy of the adjacent cells and abortion in cattle. In mice, sarcocystosis causes mild cellular reactions without clinical disease. Severe haemorrhage and abortion were also reported. For monitoring the disease in wild rodents of the Korean peninsula, we captured Apodemus agrarius chejuensis on Jeju island and examined the specimen histopathologically. Intramuscular cysts were found and diagnosed as Sarcocystis. Sarcocystic infection has been reported in worldwide. There have been many reported infections in cattle and pigs in Korea. To our knowledge, this is the first report of Sarcocystis in Apodemus agrarius chejuensis captured in Korea.

An outbreak of type C botulism in waterbirds: Incheon, Korea.

Five outbreaks of botulism in waterbirds were encountered over a 5-yr period from 2004 to 2008 in Korea. In October 2008, an outbreak of avian type C botulism affected approximately 2,000 wild waterbirds in the Namdong flood control basin, Incheon, South Korea. Ecologic conditions, clinical signs exhibited by moribund birds, and lack of gross pathology and microbial evidence of infectious disease, suggested botulinum intoxication. Type C botulinum toxin was demonstrated in duck sera, liquid culture of intestinal tissue, and an extract of maggots taken from the carcasses. Additionally, 34 of 40 (85.0%) sediment samples from the same area were positive for botulinum toxin by mouse bioassay using multivalent (types A-F) antiserum, indicating that toxigenic Clostridium botulinum was present in the environment. This is the most severe case of avian botulism documented in Korea.