Epidemiology and Investigation of Foot‐and‐Mouth Disease (FMD) in the Republic of Korea

This chapter describes about the experience of dealing with FMD outbreaks in the Republic of Korea. We explain what is FMD, the concept of epidemiological investigation on outbreak sites of FMD, including the episode of detecting the index case for seven epidemics occurred since 2000, and information obtained from investigation in Korea. In any case, farmers’ attitude (recognize clinical signs and report suspected cases) played the essential role in determining size and duration of epidemics. A rapid and correct diagnosis including clinical examination and laboratory test for confirmation is also important

Estimating the time of infection for African swine fever in pig farms in Korea

African swine fever (ASF) is a highly contagious and lethal disease with characteristics of hemorrhagic fever. ASF outbreaks in pig farms significantly damage the entire pork industry. Understanding the transmission dynamics of ASF is crucial to effectively respond. Notably, it is important to know when the infection started on the outbreak farm. This study aimed at establishing a procedure for estimating the time of infection on pig farms affected by the ASF outbreak in Korea. The protocol for sampling to detect ASF virus infection, the estimation of the time interval between infection and detection, and the estimation of the infection stage parameters for the simulation model were described. After infection, fattening sheds (9.8 days in median) had the longest detection time compared with pregnant (8.6 days) or farrowing sheds (8.0 days). The intervals were 8.8 days for farrow-to-finisher farms, 7.0 days for farrow-to-weaning farms, and 9.5 days for fattening farms. The findings of this study provide valuable insights into ASF outbreaks in pig farms thus, improving the disease control ability

Protection of chickens from Newcastle disease with a recombinant baculovirus subunit vaccine expressing the fusion and hemagglutininneuraminidase proteins

Recombinant baculoviruses containing the fusion (F) and hemagglutinin-neuraminidase (HN) glycoprotein gene of the viscerotropic velogenic (vv) Newcastle disease virus (NDV) isolate, Kr-005/00, and a lentogenic La Sota strain of the NDV were constructed in an attempt to develop an effective subunit vaccine to the recent epizootic vvNDV. The level of protection was determined by evaluating the clinical signs, mortality, and virus shedding from the oropharynx and cloaca of chickens after a challenge with vvNDV Kr-005/00. The recombinant ND F (rND F) and recombinant HN (rND HN) glycoproteins derived from the velogenic strain provided good protection against the clinical signs and mortality, showing a 0.00 PI value and 100% protection after a booster immunization. On the other hand, the combined rND F + HN glycoprotein derived from the velogenic strain induced complete protection (0.00 PI value and 100% protection) and significantly reduced the amount of virus shedding even after a single immunization. The rND F and rND HN glycoproteins derived from the velogenic strain had a slightly, but not significantly, greater protective effect than the lentogenic strain. These results suggest that the combined rND F + HN glycoprotein derived from vvNDV can be an ideal subunit marker vaccine candidate in chickens in a future ND eradication program

Serosurveillance for Japanese encephalitis virus in wild birds captured in Korea

Climate change induced by recent global warming may have a significant impact on vector-borne and zoonotic diseases. For example, the distribution of Japanese encephalitis virus (JEV) has expanded into new regions. We surveyed the levels of hemagglutination-inhibition (HI) antibodies against JEV (Family Flaviviridae, genus Flavivirus) in wild birds captured in Korea. Blood samples were collected from 1,316 wild birds including the following migratory birds: Oceanodroma castro (n = 4), Anas formosa (n = 7), Anas penelope (n = 20), Fulica atra (n = 30), Anas acuta (n = 89), Anas crecca (n = 154), Anas platyrhynchos (n = 214), Aix galericulata (n = 310), and Anas poecilorhyncha (n = 488). All were captured in 16 locations in several Korea provinces between April 2007 and December 2009. Out of the 1,316 serum samples tested, 1,141 (86.7%) were positive for JEV. Wild birds captured in 2009 had a higher seroprevalence of ant-JEV antibodies than those captured in 2007. Wild birds with an HI antibody titer of 1 : 1,280 or higher accounted for 21.2% (280/1,316) of the animals tested. These findings indicated that wild birds from the region examined in our study have been exposed to JEV and may pose a high risk for introducing a new JEV genotype into Korea

Spring migration of mallards (Anas platyrhynchos) tracked with wild-trackers in East Asia

Mallard is a dominant waterfowl species wintered in Korea. We researched the mallard spring migration route, stopover sites, and breeding sites. We used cannon nets in Central Korea to catch and attach 10 wild trackers (WT-200). The mallards’ spring departure dates were from the end of March to early April. The spring migration route varied by individual mallards, with most moving through the North Korean east coast. Breeding sites were distributed among the interior of Northeastern China. The average distance to the breeding areas was 1,265 km [standard deviation (SD)=491 km] and the average days spent from wintering site to breeding site was 25.3 days (SD=19.2 days). The mallards used several stopover sites when on the spring migration route (average 3.3±2.1, range 2–9). The time spent at the stopover sites was a minimum of 1 day to a maximum of 16 days. Wintering mallards in Korea showed various individual trends regarding spring migration timing, migration route, stopover sites, and usage days

Home range differences by habitat type of raccoon dogs Nyctereutes procyonoides (Carnivora: Canidae)

From July 2013 to November 2014, this research was conducted to secure baseline data to find long-term preventive measures against epidemics from the analysis of home range and movement characteristics of raccoon dogs, which are known as carriers of zoonosis. Researchers conducted a follow-up study with 12 raccoon dogs, each attached with a Global Positioning System mobile transmitter. Analysis of home range used the minimum convex polygon (MCP) method and kernel density estimation (KDE) with accumulating data of time-based locations. Except for three animals that showed unique behavior, the researchers analyzed nine animals and calculated their average home range. As a result, average home range was 0.48±0.35 km2 (MCP method), and KDE result analysis was verified as 0.65±0.66 km2 (95%), 0.31±0.35 km2 (75%), and 0.23±0.28 km2 (50%). Based on the MCP method, acted in range of minimum 0.07 km2 and maximum 1.08 km2, and the core habitat, KDE 50% level showed activity range in 0.02 km2 to 0.37 km2. Three individuals of unique behavior were classified into two types. Two individuals moved 10–20 km and settled at a place different from the existing habitat, and one individual kept moving without a regular sphere of influence. Generally, raccoon dogs are not considered to move if they secure their area of influence; animals in urban areas have a wider area of influence than those living in areas with a rich source of food such as forest and agricultural land

Control of Foot-and-Mouth Disease during 2010–2011 Epidemic, South Korea

An outbreak of foot-and-mouth disease caused by serotype O virus occurred in cattle and pigs in South Korea during November 2010–April 2011. The highest rates of case and virus detection were observed 44 days after the first case was detected. Detection rates declined rapidly after culling and completion of a national vaccination program

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

An outbreak of highly pathogenic avian influenza, caused by a novel reassortant influenza A (H5N8) virus, occurred among poultry and wild birds in South Korea in 2014. The aim of this study was to evaluate the pathogenesis in and mode of transmission of this virus among domestic and wild ducks. Three of the viruses had similar pathogenicity among infected domestic ducks: the H5N8 viruses were moderately pathogenic (0%–20% mortality rate); in wild mallard ducks, the H5N8 and H5N1 viruses did not cause severe illness or death; viral replication and shedding were greater in H5N8-infected mallards than in H5N1-infected mallards. Identification of H5N8 viruses in birds exposed to infected domestic ducks and mallards indicated that the viruses could spread by contact. We propose active surveillance to support prevention of the spread of this virus among wild birds and poultry, especially domestic ducks