Development of a Real-Time Recombinase Polymerase Amplification Assay for the Rapid Detection of African Swine Fever Virus Genotype I and II.

African swine fever (ASF) is a contagious viral disease in pigs and wild boars which poses a major threat to the pig industry. Rapid and accurate diagnosis is necessary to control ASF. Hence, we developed a rapid diagnostic method using a recombinase polymerase amplification (RPA) assay targeting the conserved sequences of CP204L (p30) thatcan rapidly detect ASF virus (ASFV) genotype strains I and II. The lower detection limit of the real-time RPA assay was 5 × 101 copies per reaction. The real-time RPA assay effectively detected ASFV isolates and clinical specimens belonging to ASFV genotypes I and II. The sensitivity and specificity of the assay were 96.8% (95% confidence interval (CI): 83.3−99.9) and 100% (95% CI: 88.4−100.0), respectively. The agreement between the real-time RPA assay and a reference commercial real-time quantitative polymerase chain reaction (qPCR) was 100%. The real-time RPA assay had a detection time of 6.0 min (95% CI: 5.7−6.2), which was significantly shorter than that of qPCR (49 min; 95% CI: 47.4−50.6; p < 0.001). Thus, the developed real-time RPA assay is a rapid and accurate diagnostic tool for detecting ASFV genotypes I and II.

Author Correction: Highly pathogenic H5N6 avian influenza virus subtype clade 2.3.4.4 indigenous in South Korea.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Highly pathogenic H5N6 avian influenza virus subtype clade 2.3.4.4 indigenous in South Korea.

The outbreaks of the highly pathogenic avian influenza (HPAI) in 2016-2017 and 2017-2018, caused by novel reassortant clade 2.3.4.4 H5N6 viruses, resulted in the loss of one billion birds in South Korea. Here, we characterized the H5N6 viruses isolated from wild birds in South Korea from December 2017 to August 2019 by next-generation sequencing. The results indicated that clade 2.3.4.4 H5N6 viruses isolated in 2017 and 2019 shared almost identical nucleotide sequences with the HPAI H5N6 viruses from 2016 in South Korea. This repeated detection of evolutionarily identical H5N6 viruses in same region for more than three years may suggest indigenization of the HPAI H5N6 virus in South Korea. Phylogenetic analysis demonstrated that the clade 2.3.4.4 H5N6 viruses isolated in 2017 and 2019 were evolutionarily distinct from those isolated in 2018. Molecular analysis revealed that the H5N6 viruses isolated in 2017 and 2019 had features associated with an increased risk of human infection (e.g. a deletion at position 133 of HA and glutamic acid residue at position 92 of NS1). Overall, these genomic features of HPAI H5N6 viruses highlight the need for continuous monitoring of avian influenza viruses in wild migratory birds as well as in domestic birds.

Seroprevalence of tuberculosis in domesticated elk (Cervus canadensis) in Korea.

Tuberculosis is a contagious disease in animals, primarily cattle, although it also affects wild animals and humans. There are few data on the state of tuberculosis in domesticated elk (Cervus canadensis) in Korea. In order to investigate tuberculosis in elk, the effectiveness of an enzyme linked immunosorbent assay (ELISA) using MPB70 and MPB83 antigens was compared with the tuberculin skin test (TST), and seroprevalence was measured with this assay using serum samples collected from domesticated elk herds in Korea. The respective sensitivities of the MPB70 and MPB83 ELISAs were 51.9% (95% CI 42.0-61.6) and 49.1% (95% CI 39.3-58.9), and their specificities were 100.0% (95% CI 92.6-100.0) and 97.9% (95% CI 88.9-100.0), respectively, in comparison with the TST. The herd prevalence ranged from 50 to 80% and the mean herd seropositive rate was 67.7% (21 of 31). Of 819 serum samples, 163 (19.9%) were seropositive, and the within-region prevalence ranged from 18.5-58.0%. In conclusion, the ELISA using the MPB70 and MPB83 antigens showed moderate sensitivity and high specificity compared to TST in elk, and tuberculosis was assumed to be fairly prevalent in domesticated elk in Korea.

Performance of the SD Bioline TB Ag MPT64 Rapid test for quick confirmation of Mycobacterium bovis isolates from animals.

Mycobacterium (M.) bovis, a bacterium in the M. tuberculosis complex, is a causative agent of bovine tuberculosis, a contagious disease of animals. Mycobacterial culture is the gold standard for diagnosing bovine tuberculosis, but this technique is laborious and time-consuming. In the present study, performance of the SD Bioline TB Ag MPT4 Rapid test, an immunochromatographic assay, was evaluated using reference bacterial strains and M. bovis field isolates collected from animals. The SD MPT64 Rapid test produced positive results for 95.5% (63/66) of the M. bovis isolates from cattle and 97.9% (46/47) of the isolates from deer. Additionally, the test had a sensitivity of 96.5% (95% CI, 91.2-99.0), specificity of 100% (95% CI, 96.7-100.0), positive predictive value of 100% (95% CI, 96.7-100.0), and negative predictive value of 92.9% (95% CI, 82.7-98.0) for M. bovis isolates. In conclusion, the SD MPT64 Rapid test is simple to use and may be useful for quickly confirming the presence of M. bovis in animals.