Pit Viper Venom Affects the Brain

June 6, 2003 Some snakes have venom that is used for defense or to capture prey. Some venoms attack the circulatory system; others attack the nervous system. Pit vipers belonging to the genus Bothrops are common venomous snakes found along the Pacific coast of Central and South America. Although the venom of these snakes is not neurotoxic, it is still extremely dangerous. Bothrops venom contains chemicals that prevent blood from clotting and can damage the walls of blood vessels. These factors may cause brain bleeding and stroke. A stroke occurs when the blood supplying the brain is stopped. Researchers in Ecuador recently reviewed the medical records of patients who were bitten by Bothrops snakes. Of the 309 snakebite patients, eight (2.6%) suffered strokes, most often because of brain bleeding within the white matter below the cerebral hemispheres. The venoms of snakes such as the sea snake, Australian common brown snake, krait and green mamba target the nervous system directly. Bothrops venom, however, does not attack the nervous system directly. Instead, this venom can cause brain bleeding that leads to damage of the nervous system. Although Bothrops bites rarely cause strokes, the complications of such brain injuries are severe: of the eight patients who had strokes, five died and three suffered permanent disabilities.