Serological evidence for human exposure to Bacillus cereus biovar anthracis in the villages around Taï National Park, Côte d'Ivoire

PLoS Negl Trop Dis. 2020 May 14;14(5):e0008292. doi: 10.1371/journal.pntd.0008292. eCollection 2020 May.

Abstract

Bacillus cereus biovar anthracis (Bcbva) is an untypical anthrax-causing pathogen responsible for high wildlife mortality in Taï National Park (TNP), Côte d'Ivoire. However, nothing is known about its effect on the rural population living in the region bordering TNP. Contact to bushmeat is a known risk factor for exposure to a variety of zoonotic pathogens, but no human infections with Bcbva were noted so far. Therefore, we performed a retrospective seroprevalence analysis with sera from 1,386 study volunteers. We used assays which detect antibodies against the protective antigen PA, which is synthesized by both Bcbva and classic B. anthracis, and against the recently described antigen pXO2-60, a 35-kDa protein only produced by Bcbva. We found a high seroprevalence (22.37%) of antibodies against PA, and approximately half of those sera (10.46%) were also positive for the Bcbva-specific antigen pXO2-60. All sera negative for PA were also negative for antibodies against pXO2-60, confirming specificity and suitability of the PA/pXO2-60 combined serological assay. The fact that a large fraction of sera was positive for PA but negative for pXO2-60 can most likely be explained by lower immunogenicity of pXO2-60, but exposure to classic B. anthracis cannot be excluded. As only Bcbva has been detected in the TNP area so far, exposure to Bcbva can be suspected from the presence of antibodies against PA alone. In a questionnaire, most study participants reported contact to bushmeat and livestock carcasses. Unfortunately, risk factor analysis indicated that neither animal contacts, sex, age, nor country of origin were significant predictors of Bcbva seroprevalence. Nevertheless, our study added to an assessment of the distribution of Bcbva and its impact on the human population, and our data can serve to raise awareness of anthrax in the affected regions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Antibodies, Bacterial / blood*
  • Antigens, Bacterial / immunology*
  • Bacillus cereus / immunology*
  • Child
  • Child, Preschool
  • Cote d'Ivoire
  • Environmental Exposure*
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Middle Aged
  • Parks, Recreational*
  • Retrospective Studies
  • Risk Factors
  • Rural Population*
  • Seroepidemiologic Studies
  • Surveys and Questionnaires
  • Young Adult

Substances

  • Antibodies, Bacterial
  • Antigens, Bacterial

Grants and funding

This study was funded by the Deutsche Forschungsgemeinschaft (DFG) grant KL 2521/1-1 and LE 1813/4-1. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.