Anthrax outbreak investigation in Tengwe, Mashonaland West Province, Zimbabwe, 2022

by Theresa Hamutyinei Dhliwayo, Prosper Chonzi, Collen Madembo, Tsitsi Patience Juru, Addmore Chadambuka, Notion Tafara Gombe, Silvester Chikerema, Gerald Shambira, Chukwuma David Umeokonkwo, Mufuta Tshimanga

Background

Anthrax continues to be a disease of public health concern in Zimbabwe. Between December 2021 and February 2022, Tengwe reported 36 cases of human anthrax. Gastrointestinal anthrax has the potential to cause serious outbreaks leading to loss of human life. We investigated the outbreak, identified the risk factors using one health approach to inform outbreak control.

Materials and methods

We conducted descriptive analysis of the outbreak and a 1:2 unmatched case control study to identify risk factors for anthrax. A case was any Tengwe resident who developed an ulcer and/or abdominal symptoms and epidemiologically linked to a confirmed environmental exposure. Validated, structured interviewer-administered questionnaires were used to collect data from the cases and neighbourhood controls. Soil and dried meat samples were collected for laboratory investigations. District preparedness and response was assessed using a checklist. Data was analysed using Epi Info version 7.2.5. The odds of exposure were calculated for each risk factor examined. Multivariable logistic regression analysis was performed to identify the independent factors associated with contracting anthrax.

Results

Through active case finding we identified 36 cases, 31 were interviewed. Twenty-one (67.7%) were males. The median age was 33 years (Inter quartile range: 22–54). Nineteen (61.2%) cases presented with abdominal symptoms with zero deaths reported. The independent risk factor for contracting anthrax was eating under-cooked meat (aOR = 12.2, 95% CI: 1.41–105.74, p = 0.023). All samples collected tested positive for anthrax. No livestock vaccinations or zoonotic meetings were being conducted prior to the outbreak. Notification of the outbreak was done 11 days after index case presentation however one health response was instituted within 24 hours.

Conclusion

The anthrax was confirmed in Tengwe. Consumption of under-cooked meat was associated with gastrointestinal anthrax. The timely one health response resulted in excellent outcomes. Using one health approach in managing zoonotic threats is encouraged.