Spatial analysis of human and livestock anthrax in Dien Bien province, Vietnam (2010-2019) and the significance of anthrax vaccination in livestock

Keywords: anthrax, human, livestock, spatial analysis, Vietnam, medical geography
Abstract Type: Paper Abstract

Abstract

Anthrax is a serious zoonosis caused by Bacillus anthracis, which primarily affects herbivorous animals with spillover into humans. The disease occurs nearly worldwide but is poorly reported in Southeast Asian countries including Vietnam. This study examines spatio-temporal distribution of human and livestock anthrax, epidemiological characteristics of human anthrax, and the role of livestock vaccination in reducing human anthrax in Dien Bien province, Vietnam using historical data from 2010-2019. Spatial rate smoothing and spatial clustering analysis were performed using Local Moran’s I in GeoDa and the Poisson Space-time scan statistic in SaTScan. We found temporal and spatial overlap of human and livestock anthrax with hotspots of human anthrax in the east of the province. We identified three significant space-time clusters of human anthrax persisting from 2010 to 2014 in the east and southeast, each with high relative risk. Most of the human cases were male (69%), aged 15-59 years (80%), involved in processing or eating meat of sick or dead livestock (96.9%) but environmental and unknown exposures were also reported. Animal reports were limited compared to humans and at coarser spatial scale, but in areas with human case clusters. In years when livestock vaccination was high (>~25%), human incidence was reduced, with the opposite effect when vaccine rates dropped. This indicates livestock vaccination reduce anthrax burden in both humans and livestock, though livestock surveillance needs immediate improvement. These findings suggest further investigation and measures to strengthen the surveillance of human and animal anthrax for other geographic regions with similar disease context.