Detection and genetic characterization of porcine circovirus 3 from aborted fetuses and pigs with respiratory disease in Korea

A novel porcine circovirus 3 (PCV3) was first detected in pigs showing porcine dermatitis and nephropathy syndrome, reproductive failure, and multisystemic inflammation in the USA. Herein, we report on PCV3 as a potential etiological agent of clinical signs, reproductive failure and respiratory distress on Korean pig farms, based on in situ hybridization, pathological, and molecular findings. Confirmation of the presence of PCV3 may increase co-infection with other causative agents of disease in Korean pig herds, indicating the need for further systemic investigation of pathogenicity and of multiple infections with PCV2 genotypes and bacteria, and the development of an effective PCV3 vaccine.

First detection and genetic characterization of porcine parvovirus 7 from Korean domestic pig farms

Porcine parvovirus 7 (PPV7) was first detected in Korean pig farms in 2017. The detection rate of PPV7 DNA was 24.0% (30/125) in aborted pig fetuses and 74.9% (262/350) in finishing pigs, suggesting that PPV7 has circulated among Korean domestic pig farms. Phylogenetic analysis based on capsid protein amino acid sequences demonstrated that the nine isolated Korean strains (PPV-KA1-3 and PPV-KF1-6) were closely related to the previously reported USA and Chinese PPV7 strains. In addition, the Korean strains exhibit genetic diversity with both insertion and deletion mutations. This study contributes to the understanding of the molecular epidemiology of PPV7 in Korea.

Uracil-DNA glycosylase-treated reverse transcription loop-mediated isothermal amplification for rapid detection of avian influenza virus preventing carry-over contamination

Here, we describe a uracil-DNA glycosylase (UNG)-treated reverse transcription loop-mediated isothermal amplification (uRT-LAMP) for the visual detection of all subtypes of avian influenza A virus (AIV). The uRT-LAMP assay can prevent unwanted amplification by carryover contamination of the previously amplified DNA, although the detection limit of the uRT-LAMP assay is 10-fold lower than that of the RT-LAMP without a UNG treatment. To the best of our knowledge, this is the first successful application of deoxyuridine triphosphate/UNG strategy in RT-LAMP for AIV detection, and the assay can be applied for the rapid, and reliable diagnosis of AIVs, even in contaminated samples.

Genetic diversity of porcine reproductive and respiratory syndrome virus in Korea

The high genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV) has been an obstacle to developing an effective vaccine for porcine reproductive and respiratory syndrome (PRRS). This study was performed to assess the degree of genetic diversity among PRRSVs from Korean pig farms where wasting and respiratory syndrome was observed from 2005 to 2009. Samples from 786 farms were tested for the presence of PRRSV using reverse transcription PCR protocol. A total of 117 farms were positive for type 1 PRRSV while 198 farms were positive for type 2. Nucleotide sequences encoding the open reading frame (ORF) 5 were analyzed and compared to those of various published PRRSV isolates obtained worldwide. Sequence identity of the ORF 5 in the isolates was 81.6~100% for type 1 viruses and 81.4~100% for type 2 viruses. Phylogenetic analysis of the ORF 5 sequences showed that types 1 and 2 PRRSVs from Korea were mainly classified into three and four clusters, respectively. The analyzed isolates were distributed throughout the clusters independent of the isolation year or geographical origin. In conclusion, our results indicated that the genetic diversity of PRRSVs from Korean pig farms is high and has been increasing over time.

Generation and Biological Characterization of a Neutralization-Resistant Mutant of Newcastle Disease Virus

A neutralization-resistant mutant of Newcastle disease virus (NDV) Kr005 strain belonging to class II genotype VII was generated using a neutralizing monoclonal antibody and its biological effects were assessed. The mutant showed single amino acid substitution (E to K) at position 347 of the hemagglutinin-neuraminidase (HN) protein (E347K mutant). The E347K mutant exhibited marked rounding of the cells and few syncytia in infected chicken embryofibroblast (CEF) cells. The hemadsorption and neuraminidase activities of the E347K mutant of the wild-type virus were 118% and 166%, respectively. The mutant produced a rapid elution pattern whereas the wild type had a slow elution pattern. Growth kinetics studies showed that the E347K mutant produced an 80-times higher yield of extracellular virus in CEF cells compared with the wild-type virus. The time-course virus titer showed a marked increase in mutant-infected cells from 6 h to 12 h post infection (pi), which was consistent with the titer pattern time-course for NA activity. The E347K mutant virus showed a slight decrease in virulence compared to the wild-type virus, but there was no change in pathotype when measured by in vivo pathogenicity testing. These results suggest that an E347K mutation in HN protein might be associated with increased NA activity and subsequent enhancement of virus release from infected cells without change in viral pathotype.

Epidemiological characteristics of bovine brucellosis in Korea, 2000~2004 / 대한수의학회지

This paper describes the epidemiological characteristics of bovine brucellosis in Korea during January 2000~September 2004, which encompasses the period when the incidence of bovine brucellosis increased abruptly. Data from the National Animal Infectious Disease Data Management System were used for this study. A range of epidemiological measures was calculated including annual herd and animal incidence. During the study period, there were 1,183 outbreaks on 638 farms. In beef cattle, annual herd incidence increased from 0.2 (2000) to 11.5 (2004, to September) outbreaks per 10,000 and annual animal incidence varied between 3.4 (2000) and 105.8 (2004, to September) per 100,000, respectively. On 401 (62.9%) infected farms during this period, infection was eradicated without recurrence. Recurrence of infection was significantly higher on farms where abortion was reported (53.3%), compared to farms where it was not (30.0%). On beef cattle farms, infection was introduced most frequently through purchased cattle (46.2%). Based on the results of this study, the establishment and spread of brucellosis in the Korean beef cattle population were mainly due to incomplete or inappropriate treatment of aborted materials and the movement of infected cattle.

Development and characterization of stable cell lines constitutively expressing the porcine reproductive and respiratory syndrome virus nucleocapsid protein

Despite global efforts to control porcine reproductive and respiratory syndrome virus (PRRSV) infection, the virus continues to cause economic problems in the swine industry worldwide. In this study, we attempted to generate and characterize a panel of stable BHK cell lines that constitutively express the nucleocapsid (N) protein of type 1 or type 2 PRRSV. The established BHK cell lines were found to react well with N-specific antibodies as well as the hyperimmune serum of pigs raised against each genotype of PRRSV. Taken together, the data implicate a potential usefulness for the newly generated stable cell lines as a diagnostic reagent for PRRSV serology.

Epidemiology and Prevention Strategies of Avian Influenza / 한국역학회지

Natural infections with influenza A viruses have been reported in a variety of animal species including humans, pigs, horses, sea mammals, and birds. Although viruses of relatively few haemagglutinin(HA) and neuraminidase(NA) subtype combinations have been isolated from mammalian species, all subtypes, in most combinations, have been isolated from birds. During the past few years, several subtypes of avian influenza A have been shown to cross the species barrier and infect humans. During an outbreak of a highly pathogenic influenza A(H5N1) virus among poultry in Hong Kong in 1997, 6 of 18 people with confirmed infection died. And a total of 89 human infections with influenza A(H7N7), including 1 resulting in the death of a Dutch veterinarian, occurred during the extensive outbreak in 2003. During late 2003 and early 2004, there were reports of large outbreaks of H5N1 among poultry throughout Asia (including Korea, Japan, Indonesia, Vietnam, Thailand, Laos, Cambodia, and China). In Korea, we had also highly pathogenic avian influenza(HPAI) outbreak in 2003~2004 with a first suspected case reported on 10 December 2003. The case was reported at a parent stock farm for broilers, which was located in Chungbuk province, and the farm was immediately placed under movement restrictions. Laboratory tests confirmed the outbreak of HPAI on 12 December 2003. Up to 20 March 2004, a total of 19 farms were confirmed as having been infected with HPAI virus. No further outbreaks occurred after that date. Fortunately there were no human cases founded in this epidemic in Korea. In January 2004, there was confirmation that influenza A(H5N1) virus had been isolated from patients who had died of a respiratory illness in Vietnam. Total 107 human confirmed cases were reported until June 2005 to WHO, threatening new pandemic outbreak. We reviewed our prevention and control strategies of avian influenza and preparedness to the pandemic outbreak.