Investigation and source-tracing of an anthrax outbreak in Gansu Province, China.

Deshan Yu,Huijuan Zhang,Jian He,Yadong Hou,Huimin Zhang,Kongfu Wei,Enmin Zhang,Peng Wang,Faxiang Gou,Dongpeng Liu,Wei Li,Jianchun Wei,Nupur Gangopadhyay

doi:10.1371/journal.pone.0203267

Abstract

Anthrax is an endemic disease in China. Cases are reported every year, especially in the northwestern areas. In August 2016, an outbreak of 21 cutaneous anthrax cases was reported in Min County, Gansu Province, China. In this study, the general characteristics of the anthrax outbreak are described. Two molecular typing methods, canonical single-nucleotide polymorphism (canSNP) and multiple-locus variable-number tandem repeat analysis with 15 markers (MLVA15), were used to investigate the possible source of transmission and to identify the genetic relationship among the strains/samples isolated in this outbreak as well as previous isolates. In this outbreak, all patients were infected through contact with diseased livestock or contaminated animal products. Livestock had been introduced into the local area shortly before the outbreak from Gannan Prefecture (in Gansu Province), Sichuan and Qinghai Provinces. In the molecular typing analysis, there were two canSNP subgroups found in Gansu, A.Br.001/002 and A.Br.Ames, and five MLVA15 genotypes were observed. The strains collected from the anthrax outbreak in Min County in 2016 belonged to the A.Br.001/002 canSNP subgroup and the MLVA15-28 and MLVA15-30 genotype. Strains previously isolated from Sichuan, Inner Mongolia and Maqu County (in Gannan Prefecture, Gansu Province) were clustered with these outbreak-related strains/samples according to the MLVA15-30 genotype. The MLVA15-28 genotype was found in strains isolated from Gansu and Xinjiang in previous studies. Combining the epidemiological investigation and molecular typing results, we conclude that the patients in this outbreak were infected by a local pathogen present in the adjoining area of Gansu, Sichuan and Qinghai Provinces.

Highlights

Anthrax is primarily a disease of herbivores; animals become infected through the uptake of pathogenic spores from the environment
Anthrax outbreak description In August 2016, an outbreak of 21 suspected cutaneous anthrax cases was reported by the health authorities of Min County, Gansu Province
Anthrax cases are reported in Gansu Province every year

Summary

Introduction

Anthrax is primarily a disease of herbivores; animals become infected through the uptake of pathogenic spores from the environment. Bacillus anthracis (B. anthracis), the causative agent of anthrax, is a relatively homogeneous bacterial species; its lack of polymorphisms may be due to its life cycle, which includes long periods of time as dormant endospores [4]. Genetic markers, such as single-nucleotide polymorphisms (SNPs) and variable-number tandem repeats (MLVA), have been used to characterize the phylogenetic and evolutionary relationships of B. anthracis strains [5,6,7] and have been used as source-tracing methods in the event of anthrax outbreaks or bioterrorist attacks [8,9,10]. To determine the relationship among the cases and investigate the infectious sources and possible routes of transmission, epidemiologic investigations and laboratory investigations were performed by the local CDC and China CDC

Ethics statement

Results

Discussion