Epidemic models on disease spread attempt to simulate disease transmission and associated control processes. This study reviewed published papers on epidemiological models for the management of foot-and-mouth disease in the world. In addition, an individual animal-based, spatially-explicit, stochastic disease transmission model, the Davis Animal Disease Simulation (DADS) model, was described in the frame of an international collaborative research project participating three countries: Republic of Korea, USA, and New Zealand. In this project, the Korean team is aiming at developing the most appropriate parameters for livestock and epidemiology of foot-and-mouth disease outbreaks. On the other hand, the purpose of foreign counterparts is validating their models: DADS (USA) and InterSpread Plus (New Zealand). Classification of farm types and preliminary estimations on the frequency of intra-herd contacts were also presented. This research project is expected to provide precious information to plan a strategy that will facilitate the eradication of foot-and-mouth disease from Korea.
We investigated the prevalence of the Listeria monocytogenes from livestock processed products in processing plants and retail markets of Korea from 2010 to 2011. A total of 1,380 samples were collected; Meat processed products such as cooked ham and sausage, jerked meat, and meat extract products. Milk processed products such as milk, butter, cheese, and ice cream. Egg processed products such as whole egg liquid and pidan. L. monocytogenes were isolated from samples using listeria enrichment broth, fraser broth and Oxford agar, and counted in Oxford agar. The three of L. monocytogenes strains (1.16%) were isolated from sausages, two (0.73%) from mixed pressed ham and one (0.51%) from jerked meat, respectively. The colony forming unit (CFU) of L. monocytogenes from all samples were below 10 CFU/g. The four isolates (66.6%) were 1/2b except two isolates (1/2a) in the serotypes. Further studies are needed to understand the transmission route of L. monocytogenes, including a survey of food handlers, environments of retail markets, and all potential risk factors in cooked sausages, mixed pressed hams, and jerked meat processing.
Random amplified polymorphic DNA (RAPD) and fluorescent amplified fragment length polymorphism (FAFLP) analyses were executed on a total of 28 Salmonella spp., including 6 ATCC reference strains, 2 isolates from outbreaks of food poisoning in Gwangju, and 20 isolates from carcasses. For RAPD analysis, four primers, named P1254, 23L, OPA-4, OPB-17 were used producing amplification fragments ranged from 0.18kb to 2.6kb. As a result, 5 types using P1254, 5 types using 23L, 3 types using OPA-4, and 6 types using OPB-17 and a total of 18 RAPD types were achieved. For FAFLP analysis, bacterial genomic DNA was digested with endonucleases EcoRⅠ and MseⅠ, site-specific adaptors were ligated, and PCR amplification was carried out with an EcoR1 adaptor-specific primer labelled with fluorescent dye. Amplified fragments, which were separated on a polyacrylamide sequencing gel ranged from 35bp to 300bp were analysed. Results were displayed as a dendrogram with genetic distance. Twenty two Salmonella isolates and 6 reference strains were divided into 14 groups in a level of 0.136 genetic distance. In conclusion, Salmonella isolates of chicken carcasses have different genetic properties when compared to reference strains and isolates from outbreak of food poisoning.
Staphylococcus aureus is an important food-borne pathogen, which is present on the skin and mucosa of animals. Some of the S. aureus strains are causative agent of food poisoning syndrome. The aim of this study was to investigate the antimicrobial resistance of S. aureus isolates from raw meats in slaughterhouses during 2010. From 17,874 raw meat samples tested, a total of 190 S. aureus were isolated, for which antimicrobial susceptibility to 17 agents was examined using broth dilution method. Among isolates from beef, chicken and pork, 20 (51.3%), 20 (24.7%) and 9 (12.9%) were sensitive to all antimicrobials tested, respectively. Isolates from pork and chicken meats showed much higher resistance, compared to isolates from beef. Penicillin resistance was the most frequent among isolates from beef (35.3%) and pork (75.7%), while tetracycline resistance was among those from chicken meats (48.1%). A total of 3 methicillin resistant S. aureus (MRSA) were detected from beef (5.1%, 2/39) and pork (1.4%, 1/70). Although the prevalence of MRSA was low, the presence of antimicrobial resistant S. aureus such as MRSA suggests that further investigation and strict surveillance on MRSA and antimicrobial resistance are needed.
Campylobacterosis is the most common food borne bacterial disease in many countries. Food animals and animal products are considered to be the reservoir of the Campylobacter species. The aim of this study was to investigate the antimicrobial resistance of Campylobacter spp. from food animals and raw meats in slaughterhouses. A total of 90 Campylobacter jejuni (C. jejuni) and 127 Campylobacter coli (C. coli) were isolated, for which antimicrobial susceptibility was examined using broth dilution method. Resistance to macrolide antimicrobials was higher among C. coli isolates than among C. jejuni. Among both C. jejuni and C. coli isolates, the most frequently observed resistance was to nalidixic acid, ciprofloxacin, and tetracycline. No erythromycin resistance was observed among C. jejuni isolates from cattle, pig and beef. However, 28.3% (n=13) and 25% (n=3) of C. coli isolates from pigs and pork showed resistance to erythromycin, respectively. The predominant profile of multiple resistance among C. jejuni and C. coli isolates was ciprofloxacin/tetracycline/nalidixic acid resistance (46.7%) and ciprofloxacin/nalidixic acid resistance (31.5%), respectively. This finding has important implication for food safety and public health.
Salmonellosis constitutes an important public health problem in both developing and developed countries, including Korea. The aims of present study were to investigate the serovar and antimicrobial resistance of Salmonella isolated from food animals and animal products in slaughterhouses and farms. A total of 323 Salmonella were isolated from food animals (n=277) and meats (n=46) during 2010. Of the isolates, 21 different serovars were identified. The predominant serovars were S. Rissen (35%) and S. Montevideo (24.3) in healthy pigs, while S. Enteritidis (25.5%) in healthy chicken. S. Typhimurium (88.8%) was predominant in disease pigs, while S. Gallinarum (29.2%) and S. Montevideo (26.9%) were in diseased chickens. Among meat samples, S. Typhimurium (57.1%) was the most common serovar in pork but S. Enteritidis (38.7%) and S. Montevideo(32.3%) were in chikcen meats. Analysis of antimicrobial resistance patterns revealed that 20.7% of the isolates were sensitive to all the 15 drugs tested. The isolates were frequently resistant to nalidixic acid (47.7%), tetracycline (38.4%), streptomycin (33.7%), and ampicillin (32.8%). The resistance to quinolone and 3rd generation cephalosporins was higher in chicken and chicken meat isolates. Of the 323 isolates, 174 (53.9%) were resistant to one or more CLSI subclass, and 117 (36.2%) showed multiple-resistance. Our findings showed that multiple resistant Salmonella organism are widespread in animals and animal products in Korea. To prevent the transmission or exposure for consumers of antimicrobial resistant Salmonella, policies and guidelines aiming at prudential use of critical antimicrobials for humans are needed.
Ruminant pestiviruses of bovine viral diarrhea virus (BVDV) and border disease virus (BDV) are closely related to classical swine fever virus (CSFV) and all belong to the genus of Pestiviruses. BVDV is one of the most important viral pathogen of cattle and has been recorded in most countries where cattle are raised. Natural host for BVDV is cattle, but BVDV is able to infect pigs as well. The purpose of this study was to investigate the prevalence for antibodies against BVDV in domestic pig farms in South Korea from 2009 to 2011. In this study, 2,755 pigs in 239 farms in South Korea's inland and 5,293 pigs in 613 farms in Jeju province (CSF free region) were investigated for antibodies against two pestiviruses, BVDV and CSFV by a virus neutralization test (VNT). The seroprevalences on the individual level and on herd level against BVDV were 5.3 % and 21.2 % in South Korea's inland, 5.2 % and 6.5 % in Jeju province, respectively. Based on the ratio of respective antibody titers by the comparative VNT, 273 pigs in Jeju province with BVDV infection were detected and they were distinctly negative to CSF. It is recognized that porcine infections with BVDV naturally occurred in Jeju province. Whereas, antibody titers against BVDV of South Korea's inland were cross-reactivity with CSFV.
Rabies is a zoonotic disease that causes severe destruction to the central nerve system which is usually fatal. It is one of the most important disease around the world and particular in Asia because of the high costs of prevention and post-exposure treatment. After the recurrence of sylvatic rabies in 1993, the number of raccoon dog mediating rabies cases in Korea has maintained annually until 2011. To better understand the current rabies epidemics in Korea, Korean rabies isolate (SKRBV0601GY) from Gyeonggi province in 2006 was compared with previous isolates in Korea and with isolates originating from the North-East Asia, such as Japan, China and Russia, based on complete nucleoprotein (N) gene sequences. By comparison of the N genes among these viruses, SKRBV0601GY revealed that nucleotide similarity ranged from 97.7 to 99.7%, 96.4 to 97.5%, 91.4 to 96.3%, 89.2 to 90% and 86.1 to 88.1% with Korean isolates, "Arctic-like-2" viruses, "Arctic" viruses, Russian group C - E and Chinese isolates, respectively. Phylogenetic analyses of the isolates revealed that the Korean isolate in 2006 belonged to Korean group B. The topology of the phylogenetic tree of Korean isolates related not the species and year of isolation but the geological location of the virus isolates. All of the Korean isolates showed close relationship to the "Arctic-like-2" virus (Russian group B) more than the "Arctic" virus (Russian group A) and all of the Chinese isolates (Chinese group A, B and C). The "Arctic-like-2" virus group contains the Japanese isolate and Russian group B viruses, originating from the south of East Siberia and Far East in Russia. These molecular data demonstrated that the current rabies epizootic in Korea developed independently of Chinese groups and originated from the "arctic-like-2" viruses in detail.
Avian influenza (AI) and Newcastle disease (ND) distress a variety of avian species, especially domestic poultry. Severe syndromes are caused by highly virulent specific virus strains termed highly pathogenic AI and velogenic ND viruses, which are potential agrobioterrorism agents. This outbreak emphasizes the need for continuing cooperation between public health and veterinary medical communities in controlling AI and ND when it has a zoonotic potential. Up to date, the stamping out and burying system were applied for controlling methods against these highly infectious diseases in the ordinary way, however these methods had many environmental problems, including leachat and effluvium. Thus, we assessed that sterilization effect of AI and ND virus dependent on several treatment conditions, such as autoclaving time and cutting types of chicken. As a result, we found that the cutting type of chicken meat revealed a reduced HA titer (20) against both of AI and ND virus after 10 min of autoclaving, while whole chicken showed same titer after 30 and 60 min. Therefore, we propose that the conditions of treatment on infected chicken should be developed for convenient, affordable, and effective prevention methods against for AI and ND.
A rapid, simple and reliable LC-MS/MS method, which can be used on a routine basis, was developed for the simultaneous detection of 8 penicillin antibiotics (amoxicillin, ampicillin, penicillin-G, penicillin-V, oxacillin, cloxacillin, nafcillin and dicloxacillin) in swine muscle and kidney. The antibiotics were extracted from samples with water and methanol. The extract was centrifuged, filtered and analyzed by liquid chromatography coupled with a tandem mass spectrometer (LC-MS/MS), using a C18 reversed phase column with water/acetonitrile gradient containing 0.05 % formic acid. Mass spectral acquisition was achieved in an electrospray positive ion mode by applying multiple reaction monitoring (MRM) of 2 fragment ion transitions to provide a high degree of sensitivity and specificity. The ion rations were consistent and could be used for confirmation of identity of the penicillin antibiotics. Recoveries of eight penicillins at three fortification levels (10, 20 and 40㎍/㎏) ranged from 79.8 to 102.4% and 72.8 to 103.4% in swine muscle and kidney, respectively. The coefficient of variation was than 9% in all samples. The estimated limits of quantification (LOQs) ranged from 1.0 to 3.2㎍/㎏ in swine muscle and kidney, respectively. The LOQs of this method are below the MRLs of penicillin antibiotics in animal tissues established in Korea and other countries.
This study was conducted to examine the effect of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) on morphological changes in the developing rat testis. PCB 126 (0.2㎎/㎏/week) in corn oil was weekly i.p. injected into rats from 1 to 11 weeks old. The total body weights and testicular weights were measured at 3, 6, 9 and 12 weeks, respectively. The morphological changes in the rat testes were then analyzed by light microscopy (LM) and transmission electron microscopy (TEM). The results demonstrated that PCB 126 treatment caused significant change in the ratio of testicular weight/body weight at 9 week. The treatment of PCB increased the number of pregonium cells at 3 week and it decreased spermatogenesis of the seminiferous tubules at 6 week. The results of this study suggest that PCB 126 can damage the male reproductive organ of the growing rat and that it might be associated with retardation of development of the testis.
Tuberculosis (TB) is a significant disease for both humans and animals worldwide. The genus Mycobacterium includes several species that cause TB disease in humans and other animals. Amongst the members of the Mycobacterium tuberculosis complex (MTC), M. tuberculosis is mainly a human pathogen, whereas M. bovis has a broad host range and is the principal agent responsible for TB in domestic and wild mammals. M. bovis also infects humans, causing zoonotic TB through ingestion, inhalation. M. bovis accounts for only a small percentage of the reported cases of TB in humans. In recent years, TB in farmed deer has become a disease as public health importance in several countries. Nowadays, there has been rapid outbreak of bovine TB in cattle and deer in Korea. Investigations are needed to elucidate the relative importance of M. bovis on TB incidence in humans, especially in Korea where bovine TB remains a problem. Also, the human sources as the cause of animal infection, M. tuberculosis from the farm workers also important for TB control of animals in Korea. Differentiation between the causative organisms may only be achieved by sophisticated laboratory methods involving bacteriological characteristics, biochemical properties, and routine resistance to pyrazinamide (PZA). M. bovis shows inherently resistant to PZA whereas M. tuberculosis is susceptible to PZA. In this study, we developed a multiplex-PCR assay based on a 12.7-kb fragment for the differential detection of M. bovis and M. tuberculosis. A total of 131 M. tuberculosis complex isolates were randomly obtained from cattle and deers that were PPD positive. they all yielded M. bovis. M. tuberculosis was not isolated from animals. and, a total of 25 M. tuberculosis complex isolates which is resistant to PZA were obtained from patient. PZA resistant MTC in humans was caused entirely by M. tuberculosis. The multiplex-PCR protocol was highly species-specific and time saving for identification of M. bovis and M. tuberculosis. This multiplex-PCR assay will be easily used as a routine monitoring tool in veterinary and medical laboratories.
The aim of this study was to evaluate the TEMPOⓇ STA automated most probable number (MPN) system for the enumeration of Staphylococcus aureus (S. aureus) in comparison with a standard culture method. Artificially inoculated food products with S. aureus - triangle kimbap, sliced spring onion, dried filefish fillet, danpatjuk (sweet red-bean porridge with small rice dumplings)- were tested in this study. Twenty-five grams of each of food samples were added into 225 ㎖ of sterilized phosphate buffered saline in a TEMPOⓇ stomacher bag followed by stomaching for 2 min. One milliliter of the stomached sample was added to a bottle of culture medium. Cards were filled and sealed in the automated filler and then were incubated for 24 h at 37℃. After incubation, the cards were placed in the automated TEMPOⓇ reader and MPN results were generated. For comparison with a culture method, decimal dilutions were prepared from the same homogenized samples described above, transferred onto Baird Parker and Baird Parker-Rabbit Plasma Fibrinogen (BP-RPF) agar plates, and then incubated at 37℃ for 24 h. The performance of TEMPOⓇ STA method is equivalent to the culture method using Baird Parker or BP-RPF agar count plate for the enumeration of S. aureus in foods, eliminating a time-consuming and laborious process.