Unraveling the Dynamics of the 2023 Anthrax Outbreak: Insights from Spatial and Temporal Analysis in the Kariba Ecosystem, Zambia

The 2023 anthrax outbreak in the Lake Kariba ecosystem of Zambia, particularly in the Sinazongwe district, heralded a significant threat to both animal and human populations. This study aimed to unravel the spatial and temporal distribution of anthrax deaths, identify the sources of the outbreak, and analyze the factors contributing to its spread. Through meticulous investigation and analysis of data collected from June to November 2023, we uncovered critical insights into the dynamics of the outbreak. Spatially, the outbreak affected 25 locations, with the highest concentration of anthrax-related cattle deaths observed in Chimonselo, Chiyabi, and Dengeza villages. Temporally, the first livestock case emerged in June 2023, with vaccination efforts commencing in August and covering over 68,000 cattle by November 2023. Concurrently, sightings of dead hippos along the shores of Lake Kariba underscored the potential role of wildlife in disseminating anthrax. Tissue samples from a hippo carcass tested positive for anthrax, suggesting a zoonotic transmission pathway. Climate change emerged as a critical factor exacerbating the outbreak, with prolonged droughts impacting water availability and pasture quality, rendering livestock more susceptible to diseases. Additionally, illegal livestock trade across Lake Kariba and collusion between coal truck drivers and livestock traders facilitated the spread of anthrax-contaminated meat, circumventing veterinary checkpoints. The chronology of events leading to the outbreak elucidated the cascade of factors contributing to its delayed detection and control. The contamination of Lake Kariba by anthrax-infected hippo carcasses emerged as a primary source of the outbreak, with contaminated pastures also playing a significant role. It is probable that the outbreak in Sinazongwe district was epidemiologically linked to simultaneous outbreaks in neighboring Zimbabwe. The absence of anthrax vaccination programs and a deficient animal disease early warning system exacerbated the vulnerability of livestock populations. The outbreak spread across a wide geographical area, particularly affecting villages along the shores of Lake Kariba, highlighting the significance of waterborne transmission. In conclusion, this study provides critical insights into the complex interplay between wildlife, livestock, humans, and the environment in anthrax outbreaks. By implementing the recommended control measures, enhancing disease surveillance, and fostering cross-border collaboration, future outbreaks can be mitigated, safeguarding public health, livestock, and wildlife in the Lake Kariba ecosystem of Zambia.