Professor
Dang Duc Anh
National Insitute of Hygiene and Epidemiology, Vietnam
Title of the talk: A Lesson from a Spatiotemporal Dynamics of Bacillus anthracis Infection Transmission
Abstract
Bacillus anthracis is a zoonotic pathogen causing anthrax outbreaks in northern Vietnam. In April 2022, an outbreak in Son La occurred after the butchering of a water buffalo, followed by infections in Ha Giang, Lai Chau, and Dien Bien provinces. This study aims to analyze the transmission dynamics and origins of B. anthracis strains in human patients and their source animals within the endemic region.
In 2022-2023, 83 human, buffalo, and soil samples were collected during anthrax outbreaks across four provinces. Processing involved inoculating human samples on 5% Horse Blood Agar (HBA), suspending soil in 1x PBS, and incubating at 65oC before plating on Polymyxin-Lysozyme-EDTA-Thallous-acetate agar. Buffalo hide was washed, homogenized, and plated on HBA. Then, the typical B. anthracis colonies were stuck for isolated colonies on HBA. DNA extraction and qPCR confirmed 31 specimens as B. anthracis. Whole genome sequencing on Illumina Miseq and Multi-locus variable number tandem repeat analysis (MLVA-25) were conducted to explore relationships between human, soil, and cattle strains. Genetic analysis revealed high genetic homogeneity among the strains in Dien Bien and Ha Giang, which belonged to the A.Br.011/009 canSNP lineage, primarily consisting of trans-Eurasian (TEA) group strains. In Son La, epidemiological investigations suggested a single animal was responsible for all exposures. B. anthracis isolates recovered from human clinical cases and associated samples were classified under the A.Br.001/002 lineage, not previously identified in Vietnam but reported in neighboring countries. MLVA-25 revealed surprising genetic diversity among the isolates, indicating multiple potential sources of the outbreak. This diversity contrasts with previous literature and suggests the outbreak likely originated from multiple and potentially undetected animal sources.
The study emphasizes the need for intensive surveillance of additional animal cases and molecular epidemiological traceback methods to identify pathogen sources for effective prevention and control strategies in future outbreaks.
Biography
Prof. Dang Duc Anh was the Director of the National Institute of Hygiene and Epidemiology, Hanoi, Vietnam. He has published more than 250 papers in international journals and has been serving as an editorial in chief of the Journal of Preventive Medicine
Publications: Researchgate.