Burden of snakebite envenoming in northern Benin: A Retrospective Cross-Sectional Study in the Tchaourou District

Technical Summary: Burden of Snakebite Envenoming in Northern Benin

Problem Statement
Snakebite envenoming (SBE) is recognized as the second most deadly neglected tropical disease (NTD) and a priority for the World Health Organization. Despite its global impact—causing an estimated 81,000 to 138,000 deaths annually and leaving hundreds of thousands with disabilities—its incidence and associated burdens in low-income tropical countries are vastly underestimated. In Benin, existing data suggests high incidence rates in specific departments, yet the true disease burden remains poorly characterized at the district level, particularly in rural areas where farming is the primary economic activity. Current statistics often rely on hospital records, which may miss the majority of cases that do not seek formal medical care.

Methodology
This study employed a retrospective, descriptive, and analytical cross-sectional survey conducted in the Tchaourou district of northern Benin, the country's largest district, from October 2018 to October 2023. The research utilized data collected from 264 households (comprising 3,706 individuals) enrolled in the ENABLE 1.0 Lassa research program.

• Sampling: A two-stage cluster sampling method was used to select 34 villages and approximately 63 households per village.
• Data Collection: Face-to-face interviews were conducted with household heads and members using a validated questionnaire to identify snakebite incidents, victim demographics, circumstances of the bite, first aid measures, and treatment pathways.
• Analysis: Statistical analyses included incidence-rate calculations and multivariable logistic regression to identify factors associated with complications. The study focused on victims who reported snakebites during the five-year observation period.

Key Results

• Incidence: Among the study population, 74 individuals reported snakebites, yielding an incidence rate of 399 per 100,000 person-years (95% CI 314–501).
• Victim Profile: The median age of victims was 25.5 years, with a male-to-female ratio of 55% to 45%.
  • Gender Differences: Male victims were predominantly young adults (10–29 years) and were primarily bitten while farming (51%). Female victims were generally older (peak incidence ≥50 years) and were bitten while farming (33%), walking outdoors (27%), or gathering wood (24%).
• Temporal and Environmental Factors: Bites occurred most frequently during the rainy season (June and July), coinciding with peak farming intensity. The most common time of day for bites was the morning (38%).
• Clinical Presentation: The foot or leg was the most frequently bitten body part (74%). The most reported symptoms were local swelling (78%), pain (78%), bleeding (66%), and headache (64%). The sand viper (Cerastes vipera) was the most commonly identified snake (30% of identified cases).
• Management and Care Seeking:
  • First Point of Care: Only 8.1% (6/74) of victims initially sought care at a health center. The majority first consulted a traditional healer (59%) or treated the wound at home (32%).
  • Ultimate Care: Ultimately, only 24% (18/74) of victims attended a health center.
• Complications: 30% (22/74) of victims reported complications.
  • Risk Factors: The risk of complications was 3.0 times higher for female victims compared to males (p=0.032).
  • Care Pathway Impact: Complications were reported by 42% of those treated at home and 27% of those treated by traditional healers, whereas no complications were reported among the six victims who received initial care at a health center.
  • Snake Type: Bites from the Black Mamba were associated with a significantly higher risk of complications (Odds Ratio 11.3) compared to Echid bites, though sample sizes for specific snake types were small.
  • Surgery: Victims who underwent surgery had a 3.6 times higher risk of complications, though the study could not determine if these were pre-existing or surgical consequences.

Significance and Claims
The paper claims that the incidence of snakebites in the Tchaourou district is significantly higher than previous national estimates, likely due to the intensive farming activities in the region and the rigorous surveillance of the household-based study design, which captures cases missed by hospital-based reporting.

The study highlights a critical gap in healthcare access, noting that the vast majority of victims rely on traditional healers or home remedies rather than formal medical care. The authors posit that the high rate of complications, particularly among women and those treated outside health centers, underscores the need for improved immediate access to health facilities. The paper concludes that comprehensive strategies involving the training of healthcare providers, community engagement, and reducing barriers to health center access are essential to reduce the morbidity associated with snakebite envenoming in Benin.

Limitations
The authors acknowledge several limitations: the retrospective nature of the study embedded within a Lassa fever program prevented in-depth assessment of acute complications; complications may have been missed in victims who did not seek follow-up care; and data regarding antivenom usage, family income, and specific medical costs were not collected.