Investigation of an anthrax outbreak in Makoni District, Zimbabwe

Anthrax continues to be a disease of public health importance in Zimbabwe, with sporadic outbreaks reported annually in many parts of the country. A human anthrax outbreak occurred in wards 22 and 23 of Makoni District from mid-June 2013 to end of January 2014, following cattle deaths in the wards. Laboratory tests confirmed anthrax as the cause for the cattle deaths. This study investigated the clinical characteristics, distribution of cases (places, person and time) and risk factors for contracting the anthrax disease. We also assessed the environment, district preparedness and response, and outbreak prevention and control measures.

We conducted an outbreak investigation using a mixed-methods design. A 1:1 case-control study was used to assess risk factors for contracting anthrax. The controls were frequency matched to cases by sex. Data were collected using a structured interviewer-administered questionnaire. Environmental assessment, district preparedness and response, and outbreak prevention and control measures were assessed using a checklist, observations, and key informant interviews. Multivariable unconditional logic regression analysis was performed to identify independent risk factors associated with contracting anthrax.

We interviewed 37 of the 64 cases, along with 37 controls. All the cases had cutaneous anthrax, with the hand being the most common site of the eschar (43%). Most of the cases (89%) were managed according to the national guidelines. Multivariable analysis demonstrated that meat sourced from other villages [vs butchery, OR = 15.21, 95% CI (2.32-99.81)], skinning [OR = 4.32, 95% CI (1.25-14.94)], and belonging to religions that permit eating meat from cattle killed due to unknown causes or butchered after unobserved death [OR = 6.12, 95% CI (1.28-29.37)] were associated with contracting anthrax. The poor availability of resources in the district caused a delayed response to the outbreak.

The described anthrax outbreak was caused due to contact with infected cattle meat. Although the outbreak was eventually controlled through cattle vaccination and health education and awareness campaigns, the response of the district office was initially delayed and insufficient. The district should strengthen its emergency preparedness and response capacity, revive zoonotic committees, conduct awareness campaigns and improve surveillance, especially during outbreak seasons.