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.

Molecular characterization of foot-and-mouth disease virus O/SKR/2000.

Molecular cloning and sequencing of the genome of foot-and-mouth disease virus (FMDV) O/SKR/2000, one of PanAsia strain, were performed from FMDV infected cattle. From the poly (C) tract of the 5' nontranslated region (NTR) to the 3' NTR including 14 base pairs (bp) of poly (A) tail, 7813 bp sequences comprising approximately 95% of the whole genome were obtained by reverse transcription polymerase reaction (RT-PCR). The deduced amino acid sequences of the structural and nonstructural proteins (NSP) of the O/SKR/2000 virus were analyzed for the sequence similarity among type O strains. Comparison between FMDV O/SKR/2000 and other strains indicates that overall the number of amino acids appears to be conserved without any deletion in either NSP or capsid proteins, thus, suggesting that O/SKR/2000 evolved with minor difference from preexisting strains.

A case of chronic wasting disease in an elk imported to Korea from Canada.

A seven-year-old male elk (Cervus elaphus nelsoni) was euthanized and necropsied after having a 3-week history of body weight loss, emaciation, excessive salivation, teeth grinding, fever, anorexia, and respiratory distress. The elk was imported into Korea from Canada on March 9, 1997. Gross pathologic findings were restricted to a diffuse fibrinous pneumonia. Microscopic lesions included mild neuronal vacuolation and spongiform change in the neuropil of selected brain stem nuclei and generalized astrocytosis. Immunohistochemistry for protease-resistant prion protein (PrP(res)) was positive in all brain sections but more pronounced in the section of the obex of the medulla. And the PrP(res) was also detected by western immunoblotting in the brain and spinal cord. All the remaining elk and deer that had been in contact with this elk were destroyed and negative for chronic wasting disease (CWD). To our knowledge, this is the first case of CWD occurring outside of the U.S.A. and Canada.

Identification and isolation of foot-and-mouth disease virus from primary suspect cases in Korea in 2000.

The Republic of Korea had been free from foot and mouth disease (FMD) since 1934, until a recent outbreak in 2000. From March to April 2000, a total of 15 FMD outbreaks due to the serotype O virus were recorded. Coincidental outbreaks of FMD in cattle or pigs by the serotype O virus were reported in the region, including Taiwan, China, Japan, Russia and Mongolia. In this report, the results of emergency investigations of FMD cases on a dairy farm located approximately 5-km from the demilitarized zone in Korea are described. The causative agent of the disease was identified as the FMD virus O by reverse transcription-polymerase chain reaction (RT-PCR) assays using primers derived from the 3D polymerase, internal ribosome entry site (IRES), 1D/2B regions, enzyme-linked immunosorbent assay (ELISA) for antigen detection and typing. Sequence data of the partial 1D/2B region obtained from vesicular fluid showed close similarity (98% sequence identity) to the Kinmen isolate of the FMD virus O in Taiwan. The causative virus was isolated using black goat fetal lung cells following propagation in unweaned mice.

Molecular epidemiological investigation of foot-and-mouth disease virus in Korea in 2000.

The genetic relatedness of 7 Korean type O field strains of foot-and-mouth disease virus (FMDV) in clinical specimens collected from 5 different geographic locations in 2000 was investigated. The sequence of 162 nucleotides (nt 478-639) at the 3' end of the 1D (VP1) genes was determined from amplified cDNA fragments, and subjected to the analysis for the sequence identity/divergence and phylogenetic relationship. The overall nucleotide sequence divergence among the 7 field strains was 0 to 3.8%, suggesting that they are closely related to each other. Phylogenetic analysis with the known Middle East-South Asia (ME-SA) topotype strains showed that the 7 Korean field strains formed two distinct clusters within the same lineage of the ME-SA topotype strains. Cluster 1 consisted of the strains of the primary foci of infection (Paju and Hongseong), and closely related to the strains prevailed in the Far East. Cluster 2 comprised those of subsequently affected regions (Boryeong, Yongin, and Chungju), and was further diverged from the Cluster 1. The result of phylogenetic analysis indicated that the Korean strains may have evolved from a common ancestor of the Pan Asia strains, and that at least 2 phylogenetically clustered variants within the same lineage were prevalent during the epidemic. The potential origin and sources of the virus introduction to Korea were discussed.

Development of a foot-and-mouth disease NSP ELISA and its comparison with differential diagnostic methods.

The gene encoding the nonstructural protein (NSP) of O/SKR/2000 foot-and-mouth disease virus (FMDV) was constructed to express under the polyhedron promoter of baculovirus. The expression of NSP was confirmed by indirect immunofluorescence assay (IFA) and Western blotting. The expressed NSP was applied as a diagnostic antigen for indirect-trapping ELISA (I-ELISA). An I-ELISA using monoclonal antibody (Mab) against 3A as trapping antibody was developed to differentiate infected from vaccinated cattle. The diagnostic efficiency of Mab linked I-ELISA was compared and evaluated with baculovirus expressed 3ABC I-ELISA from USDA and Mab (3A) linked E. coli expressed 3ABC I-ELISA from IZSLE through retrospective sero-surveillance. Compared with the two different I-ELISA methods, Mab (3A) linked I-ELISA using baculovirus expressed NSP showed the same level of sensitivity and specificity, indicating that this method is suitable for a differential diagnostic method in cattle.