Epidemiological Survey of the Snakebite Problem in Human in the Terai Region of Nepal, 1996/97

Abstract

In this survey the team visited 13 zonal or district hospitals, veterinary hospitals, and municipalities across the Terai and gathered a variety of informations. Epidemiological data on snakebite incidence was collected for 1996 & 1997 from all these hospitals. Information on treatment protocols for snakebite by medical staff, availability and cost to the patient of ASV, and awareness of the rural populations about first aid treatment for snakebite was gathered. Age & sexwise venomous snakebite cases were recorded in Nepal for the year 1996/1997. The case fatility rate is higher in children: 8% in 1996 and 3% in 1997, than adults: male 3% & female 4%. The 1994 study demonstrated a total of 1917 bites by venomous snakes in the Terai area and a total of 151 deaths, the mortality rate being 8% over a period of 6 years. Morbidity was highest in Mechi, Koshi, Sagarmatha, Bharatpur and Lumbini hospitals respectively. The peak season for snakebite was from June to September, during and following the monsoon, when snakes are most abundant. It has been shown that a breakdown of snakebite morbidity by age and sex for 10 years (1985/86 - 1994/95) from Bharatpur hospital, Chitwan. The case fatality rate exceeded 20% in this district.

Mortality and injury to both humans and livestock due to the bites of venomous snakes is a serious public health problem in much of the developing world, and particularly in Southeast Asia where there are abundant venomous snakes (Navy, 1965a). It has been estimated that there are on average 3000 reported human deaths per year from snakebites (Sawai, 1993), and this figure is probably underestimated. Several prior epidemiological studies (Joshi 1982, 1983, 1994) have demonstrated that mortality and morbidity caused by snakebite is a significant problem in the Terai region of Nepal. Studies in neighbouring India have identified 4 species of snake responsible for the majority of fatal bites: the Indian cobra (Naja naja), common krait (Bungarus caeruleus), Russell's viper (Vipera russellii), and saw-scaled viper (Echis carinatus) (Gaitonde, 1979). The polyvalent anti-snake-venin (ASV) produced in India by the Haffkine Institute and Serum Institute of India, and currently purchased by His Majesty's Government for use in Nepal, is directed against the venom of these four snakes. Recent studies (Joshi et al., 1996) in Nepal suggest that the Indian cobra and common krait are the problem snakes in the Terai region, whilst Russell's viper and the green pit viper (Trimeresurus albolabris) constitute a threat in the hill and mountain forest areas of Nepal.

Fear and dislike of snakes often leads to indiscriminate killing of snakes on sight, even though the great majority of snakes are non-venomous. In addition to the ecological impact of decimating snake populations, there are economic impacts to farmers of such actions. It has been suggested that 20 - 50% of India's grain crop is destroyed by rodents (Whitaker, 1975), and snakes constitute one of the most effective natural controls over rodent populations, often multiplying in response to increasing rodent populations. Unfortunately, indiscriminate killing of snakes removes this natural control leading to expanding rodent populations and increased loss or grain and crops.