Objectives Between July 2, 2021, and September 20, 2022, a Mycobacterium bovis outbreak occurred among exhibition animals at a zoo in the Republic of Korea. This study was conducted to assess the likelihood of M. bovis transmission to human contacts through a contact investigation and to implement preventive treatment for latent tuberculosis infection (LTBI). Methods: In this descriptive study, the Korea Disease Control and Prevention Agency conducted a contact investigation, which included interviews, interferon-gamma release assay (IGRA) tests, and chest X-rays. Contacts underwent IGRA testing on 2 occasions: initial testing of 29 contacts (15 in the first cluster of infection and 14 in the second cluster) and follow-up testing of the 15 contacts in the first cluster. Results: The study included 29 participants, 18 of whom were male (62.1%) and 11 female (37.9%). The mean participant age was 37.3 years (standard deviation, 9.6 years). In the initial IGRA tests, 6 of the 29 participants tested positive, indicating a prevalence of 20.7%. Following prolonged exposure, 1 additional positive case was detected in follow-up testing, raising the prevalence of LTBI to 24.1%. None of the contacts had active tuberculosis. Among the 7 individuals with positive results, 2 (28.6%) underwent treatment for LTBI. Conclusion: This study faced challenges in confirming the transmission of M. bovis infection from infected animals to humans in the Republic of Korea. Nevertheless, adopting a One Health approach necessitates the implementation of surveillance systems and infection control protocols, particularly for occupational groups at high risk of exposure.
Objectives
South Koreans receive the bacillus Calmette-Guerin (BCG) vaccination, which influence the result of the tuberculin skin test (TST); however, only a few studies have described the usefulness of the TST and interferon-γ release assay (IGRA) for diagnosing latent TB infection (LTBI). Therefore, our aim was to determine the usefulness of the TST and IGRA for diagnosing LTBI in a household contacts investigation. Methods
We reviewed the 329 household contacts who visited Chung-Ang University Hospital (Seoul, Korea) from May 1, 2011 to February 28, 2014. To evaluate the effectiveness of TST and IGRA for the diagnosis of LTBI, we examined the concordance rate between the two tests, based on age. We also evaluated the risk factors for LTBI. Results
The concordance rate between the two tests in individuals 0–24 years, 25–54 years, and over 55 years were 82.6% (κ = 0.64, p < 0.01), 68.9% (κ = 0.40, p < 0.01), and 68.4% (κ = 0.35, p < 0.01), respectively. The ratio of positive TST to negative IGRA was higher in individuals 25–44 years old, whereas the ratio of negative TST to positive IGRA was higher in individuals older than 55 years old. Based on the TST, the risk factor for LTBI was a cavity (p < 0.01). When using IGRA, the risk factors were contact time (p = 0.04) and age over 55 years old (p = 0.02). Conclusion
The concordance rate between TST and IGRA was not good after the age of 25 years. The IGRA test reflects the known risk factors more exactly.
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