Estimating the Burden of Snakebite on Public Hospitals in KwaZulu Natal, South Africa

Abstract

We propose a formula as a means to estimate the number and incidence of snakebites treated per annum in KwaZulu Natal (KZN), South Africa. Using an unvalidated formula that includes an antivenom ratio, we crudely estimated the total number of snakebite presentations in KZN. Using antivenom supply data from the central pharmacy, we stratified a sample of 6 hospitals that were surveyed to establish an antivenom ratio, that is, the total number of patients receiving antivenom to the total number of snakebite presentations at hospitals. The antivenom ratio and the average number of antivenom vials for treated snakebites were incorporated into a formula to crudely estimate the number of snakebite presentations. This was then applied to all public hospitals and districts in the region. Seventy-eight percent of public hospitals were included. The mean antivenom ratio derived from the sample hospitals indicated that 12% (95% CI, 10-14%) of snakebite presentations received antivenom. We estimated an annual total of 1680 (95% CI, 1193-2357) snakebite presentations to hospitals. Two thirds of cases (1109 of 1680) were in the low-lying subtropical coastal region. Few cases were in the higher, cooler regions of KZN (87 of 1680) or the metropolitan city of Durban (93 of 1680). The overall incidence for KZN was 16/100,000. The estimated cost of snakebite in KZN was between $1,156,930 and $2,827,848. We propose an alternative method to estimate the annual number of snakebite presentations to hospitals.