Spatio-temporal analysis of anthrax in livestock at zonal level in Ethiopia, 2008-2020.

Overview

• This study analyzed the patterns of anthrax cases in livestock across different zones in Ethiopia from 2008 to 2020, highlighting the geographic and temporal variations in outbreaks among various animal species.
• The findings help identify specific locations and time periods with high anthrax incidence, which is essential for designing targeted disease control and prevention strategies.

Background and Objective

• Ethiopia has one of the largest livestock populations in Africa and a growing human population, increasing the risk of zoonotic diseases like anthrax.
• Anthrax is a priority zoonotic disease in Ethiopia because it affects both animals and humans, posing health and economic challenges.
• The study aimed to examine the spatio-temporal distribution (variation over space and time) of livestock anthrax cases at the zonal level using retrospective data spanning 13 years (2008-2020).

Data and Methods

• Data collected from 92 zones across Ethiopia documented anthrax cases in livestock between 2008 and 2020.
• Species included in the study were cattle, sheep, goats, camels, and equines.
• The analysis involved several statistical methods:
  • Kruskal-Wallis tests to examine differences in anthrax incidence per 100,000 animals across species, years, regions, and zones.
  • Getis-Ord General G analysis to detect overall clustering patterns of anthrax cases by species and year.
  • Getis-Ord Gi* hotspot analysis to identify specific zones showing significant clustering (‘hotspots’) of anthrax cases.

Key Findings

• Annual anthrax incidence varied widely, with a low of 2,357 cases (3.73%) in 2018 and a high of 8,210 cases (12.98%) in 2019.
• Cattle accounted for the majority of cases (36,104; 57.09%), while cases in sheep, goats, camels, and equines were relatively evenly distributed.
• Significant variation in incidence by species, year, region, and zone was found, with the largest differences observed between zones, indicating strong geographic clustering.
• Species-specific clustering:
  • Cattle hotspots appeared mainly in the Somali region during 2013, 2018, and 2019.
  • Goat hotspots were identified in neighboring zones of the Amhara and Oromia regions in 2009, 2010, and 2012.
  • Sheep hotspots occurred in various locations without geographic restriction during 2013, 2015, 2016, and 2019.
• No hotspots overlapped across multiple species in the same zone and year, indicating species-specific spatial patterns of anthrax outbreaks.

Implications and Importance

• The wide zonal variation suggests that local environmental factors, livestock management practices, or other epidemiological variables influence anthrax occurrence.
• Identifying hotspots allows health authorities to prioritize zones for anthrax surveillance, vaccination campaigns, and public health interventions.
• Species-specific hotspots highlight the importance of tailoring anthrax control measures to the ecology and behavior of different livestock species.
• Better understanding of spatio-temporal patterns assists in coordinating resources efficiently to reduce risks of anthrax transmission to both animals and humans.
• The study contributes to Ethiopia’s zoonotic disease control goals by providing evidence-based insights for targeted anthrax management at multiple administrative levels.