[Snake bite epidemiology in Benin]

The incidence and the severity of envenomations in the savannah area of Central and Northern Benin were evaluated between 1985 and 1997 following 3 methods. i) Retrospective surveys were carried out in 9 hospitals, including a sugar-cane infirmary, covering a 3 to 10 year period according to locality. The average annual incidence was approximately 200 envenomations per 100,000 inhabitants (range 20-450) and the lethality was 3.1% (range 0-9.7%). In the plantation, the annual incidence was 1,300 bites per 100,000 workmen with a lethality below 1.5%. ii) Household surveys were conducted in 13 villages inhabited by 2,500 people. The average annual incidence was 430 bites, including dry-bites i. e. without envenomation, per 100,000 inhabitants (range 215-650). Lethality was 3.3%, iii) Finally, a prospective investigation was performed over 3 years in 7 villages involving 1,300 residents. The average annual incidence was 440 bites, including dry-bites, per 100,000 inhabitants and the lethality was 5.9%. The majority of the bites occurred during the rainy season. During this period, envenomations represented up to 20% of hospitalised patients. However, the village surveys showed that 80% of the patients first consulted traditional practitioners, reducing the proportion of patients consulting in hospitals to less than a third of snakebite victims. The population at risk was made up primarily of active males. The sex ratio was 2.3 men to 1 woman and more than 60% of snakebite patients were aged 21 to 50 years. The evaluation of the frequency of clinical syndromes was as follows: oedema (66%), haemorrhage (12%) and necrosis (5%). Neurological disorders seemed to be rare.