Risk factors for human cutaneous anthrax outbreaks in the hotspot districts of Northern Tanzania: an unmatched case-control study

Abstract

Bacillus anthracis is an aerobic, Gram-positive and spore-forming bacterium, which causes anthrax in herbivores. Humans get infected after coming into contact with infected animals' products. An unmatched case-control study was conducted to identify the importance of demographic, biological and/or behavioural factors associated with human cutaneous anthrax outbreaks in the hotspot areas of Northern Tanzania. A semi-structured questionnaire was administered to both cases and controls. The age range of participants was 1-80 years with a median age of 32 years. In the younger group (1-20 years), the odds of being infected were 25 times higher in the exposed group compared to the unexposed group (OR= 25, 95% CI = 1.5-410). By contrast, the odds of exposure in the old group (≥20 years) were three times lower in the exposed group compared to the unexposed group (OR = 3.2, 95% CI = 1.28-8.00). Demographic characteristics, sleeping on animal's skins, contacting with infected carcasses through skinning and butchering, and not having formal education were linked to exposure for anthrax infection. Hence, a One Health approach is inevitable for the prevention and control of anthrax outbreaks in the hotspot areas of Northern Tanzania.

Keywords: Tanzania; animal and human interactions; cultural practices; cutaneous anthrax.

Figure 1.

Spatial distribution of anthrax cases in the affected wards from hotspot districts, Northern Tanzania 2016.

Figure 2.

The cumulative epidemic curve for identified anthrax cases in the hotspot districts of Northern Tanzania in the period of October–December 2016.

Figure 3.

Demographic characteristics of study subjects in the hotspot districts of Northern Tanzania, 2016.

Figure 4.

Direct acyclical graph (DAG) for the suggested causal pathway of anthrax transmission in the hotspot districts of Northern Tanzania, 2016.