Evaluation of long-term consequences among snakebite survivors in rural Kenya including validation of a functional limitations assessment tool

BACKGROUND: Snakebite envenoming, a neglected tropical disease, causes functional limitations and disability, yet the burden and optimal assessment methods remain unclear. We describe the frequency and severity of disability and functional limitation among snakebite survivors in Kenya and validate a tool to evaluate interventions and guide rehabilitation. 

METHODS: Snakebite survivors whose incident occurred at least six months prior to the day of survey and healthy community controls in Kitui County, Kenya, were sampled and assessed using the World Health Organization Disability Assessment Schedule (WHODAS 2.0) and the Buruli Ulcer Functional Limitation Scale (BUFLS). The BUFLS was tested for construct validity based on five a priori hypotheses and discriminant validity. RESULTS: In total, 140 snakebite survivors and 57 community controls were included. Of the 140 survivors, 87 (62.1%) were categorised as having more severe envenoming (SBE) based on reporting multiple clinical symptoms, while 53 (37.9%) were categorised as snakebite only (SB) having reported localised redness or no symptoms at all. Among survivors with more severe envenoming, 49% reported mild disabilities, compared to 32% in the snakebite survivors who presented with less severe symptoms of envenoming. The highest levels of disabilities were observed in the domains of mobility, participation, and life activities. In the control group, 12% reported mild disabilities, reflecting real-world background disability common in rural sub-Saharan African communities. The BUFLS met the predefined construct validity criteria and displayed good discrimination between snakebite survivors and controls. The activities mainly affected were those requiring gross motor skills within the BUFLS domains of food preparation, personal care, work and mobility. 

CONCLUSION: Snakebite survivors exhibit high rates of long-term disability and gross motor skill functional limitations, which must be considered when designing and evaluating public health interventions improving management and rehabilitation. The BUFLS provides a valid tool for assessing functional limitations in regions where cytotoxic envenoming predominates.