Thrombotic stroke following snake bites by the "Fer-de-Lance"Bothrops lanceolatus in Martinique despite antivenom treatment: a report of three recent cases.

BACKGROUND: The severity of envenoming from Bothrops lanceolatus is determined by the development of cerebral, myocardial or pulmonary infarctions, and occasionnaly by serious local envenoming. Introduction of specific antivenom has resulted in a dramatic improvement in the prognosis of this envenoming. Against this background, we report 3 recent cases of patients bitten by B. lanceolatus who developed cerebral infarctions despite early administration of antivenom.
METHODS: In 1991 a protocol was designed to apply the same evaluation and treatment to all envenomed patients. The clinical results have been continuously monitored.
RESULTS: Between April 1993 and July 2003, 128 envenomed patients (age 6-83 (mean 45) years) were treated. No coagulopathy, thrombotic complication or death occurred in patients who were given early antivenom therapy--up to 6h following the bite--and 126 patients recovered. Between August 2003 and October 2004, 10 additional patients (18-66 (mean 46) years) were given antivenom at the time of admission at hospital. Of these, 3 developed cerebral infarctions within 24h. Effectiveness of antivenom was tested on mouse, and found to be lower than specified by the manufacturer. DISCUSSION: Our data shows that recently the antivenom may have lost some of its efficacy. Possible mechanisms include variability in venom composition or loss of activity of the antibodies produced more than 15 years ago. The question is whether we should attempt to produce improved antivenom. This could include activity against the venom of Bothrops caribbaeus from the neighbouring island of St Lucia, which shares a monophyletic group with B. lanceolatus and whose venom produces a similar thrombotic syndrome.
CONCLUSION: Prevention of systemic vessels thrombosis remains the main therapeutic challenge of B. lanceolatus envenoming in Martinique.