Abstract
A suspected human cutaneous anthrax epidemic caused by butchering sick cattle occurred in Zhijin County of Guizhou Province, Southwest of China, in 2016. Epidemiological investigation and etiological analysis were performed to provide a scientific basis for the source tracking of the epidemic. The epidemic was epidemiologically investigated, and skin blister samples collected from patients and soil samples collected from the butchering spots were used for Bacillus anthracis isolation. The suspicious B. anthracis isolates were identified using conventional methods and PCR, followed by genotyping using multiple-locus variable-number tandem repeats (VNTRs) analysis (MLVA-15) and canonical single-nucleotide polymorphism (canSNP). The genetic relationship of epidemic strains and isolates collected from other regions was analyzed. Epidemiological investigation results showed that the patients may be infected by B. anthracis during butchering sick cattle. Two suspected B. anthracis strains were isolated from blood samples and blister fluids, respectively. Conventional methods identified the two suspected isolates as B. anthracis, while PCR results showed that anti-protective antigen (PA) and capsule (CAP) gene were positive in the two isolates. MLVA-15 showed that the MLVA profiles of the two isolates were 9-20-12-53-16-2-8-8-8-4-4-4-4-10-4, which is different from the MLVA profiles of representative strains from other regions. CanSNP analysis showed that the two strains belonged to cluster A.Br.001/002. Clustering analysis and minimum spanning tree (MST) demonstrated that the two isolates were clustered with strains previously isolated from Guizhou Province. The results indicated that B. anthracis was the pathogen for this epidemic, and the patients were infected during butchering the sick. The genetic characteristics and the relationship of the B. anthracis isolates to strains from other regions indicated that the epidemic was a local occurrence.
Highlights
Anthrax is a zoonosis caused by the pathogenic bacterium Bacillus anthracis [1]
The results showed the two isolates have the same multiple-locus variablenumber tandem repeat analysis (MLVA)-15 profile (312-228-158-584-524-157-128-139-112271-383-92-194-564-112)
Based on their unique MLVA profile, the two B. anthracis isolates belonged to one MT, which was designated as GZGT8
Summary
Anthrax is a zoonosis caused by the pathogenic bacterium Bacillus anthracis [1]. B. anthracis can form a resistant spore that can survive for decades in soil. Humans can usually become infected when they touch animals infected by B. anthracis or products of infected animals [2]. When endospores of B. anthracis enter the body by ingestion or inhalation, or through skin abrasions, the fatal anthrax often occurs [1, 3]. Humans commonly suffer anthrax by handling infected animals, carcasses of animals, or animal products [4]. Anthrax is a potential agent of bioterrorism and biowarfare, as spores of B. anthracis can be stable for decades and can be readily used as biological weapons [5]
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