Molecular investigation of infection sources and transmission chains of brucellosis in Zhejiang, China

Emerg Microbes Infect. 2020 Dec;9(1):889-899. doi: 10.1080/22221751.2020.1754137.

Abstract

In the present study, a total of 7793 samples from 5 different types of hosts were collected and tested, with a seroprevalence of 2.4% (184/7793). Although the seroprevalence of human and animal brucellosis is relatively low, numbers of human brucellosis cases reported have increased continuously from 2004 to 2018. A total of 118 Brucella strains containing 4 biotypes were obtained, including Brucella melitensis bv.1 (n = 8) and bv.3 (n = 106), Brucella abortus bv.3 (n = 3) and bv.7 (n = 1). Twenty-one shared MLVA-16 genotypes, each composed of 2 to 19 strains obtained from different hosts, suggest the occurrence of a brucellosis outbreak epidemic with multiple source points and laboratory infection events. Moreover, 30 shared MLVA-16 genotypes were observed among 59.6% (68/114) B. melitensis isolates from Zhejiang and strains from other 21 different provinces, especially northern provinces, China. The analysis highlighted the imported nature of the strains from all over the northern provinces with a dominant part from the developed areas of animal husbandry. These data revealed a potential transmission pattern of brucellosis in this region, due to introduced infected sheep leading to a brucellosis outbreak epidemic, and eventually causing multiple laboratory infection events. It is urgent to strengthen the inspection and quarantine of the introduced animals.

Keywords: B. abortus; B. melitensis; MLVA; Zhejiang province; laboratory infection; trace-back.

MeSH terms

  • Animals
  • Bacterial Typing Techniques
  • Brucella / classification*
  • Brucella abortus / genetics
  • Brucella melitensis / genetics
  • Brucellosis / epidemiology*
  • Brucellosis / transmission*
  • China / epidemiology
  • DNA, Bacterial / genetics
  • Disease Outbreaks
  • Genetic Variation
  • Genotype
  • Humans
  • Laboratory Infection / microbiology*
  • Minisatellite Repeats
  • Multilocus Sequence Typing
  • Phylogeny
  • Seroepidemiologic Studies
  • Sheep / microbiology*

Substances

  • DNA, Bacterial

Grants and funding

This study was supported by Hangzhou Science and Technology Development Program (grant number 20160533B49 and 20140633B23), Hangzhou Health Science and Technology Program (grant number 2013A53), National Key R&D Program of China (grant number 2019YFC1200705), the China Special Grant for the Prevention and Control of Infectious Diseases (grant number 2018ZX10734401 and 2018ZX10734404), and the Nature Science Fund of Inner Mongolia Autonomous Region (No. 2018MS08004). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.