Epidemiology of snake envenomation in Taiwan

Abstract

There are six major venomous snakes in Taiwan including 3 crotalids, Trimeresurus (Viridovipera) stejnegeri, Protobothrops mucrosquamatus, and Deinagkistrodon acutus; 1 viperid, Daboia russelli siamensis; and 2 elapids, Naja atra and Bungarus multicinctus. The annual incidence of these venomous snakebites has increased from 361.3 to 965.5 cases in the past 70 years, while the incidence rate declines from 8.8 to 4.3 cases per 100,000 person-years. Overall, the highest frequency of bites is observed for, in descending order, T. stejnegeri, P. mucrosquamatus, B. multicinctus, N. atra, D. acutus, and D. r. siamensis. However, the distribution of snakebites varies throughout the country and between hospitals and has changed with time. In northern and southern Taiwan, T. stejnegeri and P. mucrosquamatus snakebites account for the majority of cases; in central Taiwan, cases of N. atra bites predominate, whereas cases of D. r. siamensis bites only scattered in the southern and eastern areas. In Sawai’s studies dining 1960s–1970s, the case fatality rate for T. stejnegeri, P. mucrosquamatus, N. atra, and B. multicinctus bites was 0%, 1.4%, 1.6%, and 7.1%, respectively. In a recent study, three deaths were reported among 3,862 snakebite cases during 2002–2005. Snakebite is an occupational and environmental disease in Taiwan, generally involving middle-aged males, with a ratio of male to female victims of 2–3:1. Snakebites usually occur in the warm season (April–October) on farmlands, in homes, or on roads. Knowledge of the habitats and habits of venomous snakes could be helpful in the identification of offending snakes and the prevention of snakebites.