How snakebites kill you (and how science can save your life)
The rattling sound as you’re hiking in the mountains of New Mexico, the desert of Arizona or the Everglades of Florida: it’s enough to frighten anyone, although your odds of survival—of the bite of a rattlesnake or any other poisonous snake in the country—are pretty good. Only about five people die of snakebites in the United States each year. Still, it does happen, and that number would be much higher if the estimated 7,000–8,000 people who are bitten in this country each year did not have access to high-quality medical care and expensive anti-venoms.
And because we are largely safe from dying of snakebites in the developed world—bees and wasps kill more than 10 times more people than snakes do in the United States—it can be easy to forget these animals are still a major safety risk. Around the world, an estimated 125,000 people die each year due to snakebites, and two or three times that many are permanently disabled or disfigured—and those are just the reported cases who do make it to a health care facility.
“I don’t think people realize what a huge problem snakebites are, particularly for women and children,” said Peter J.A. Davies, MD, PhD, professor and director of the Center for Translational Cancer Research at the Texas A&M Institute of Biosciences and Technology in Houston. “It’s one of the largest unmet medical needs in the developing world.”
Access to effective snakebite treatment might soon become a problem in the developed world as well. The anti-venom to coral snakes—a problem in especially Texas and Florida—has become scarce because the manufacturers have decided to stop producing it. In the case of a rattlesnake bite, even if the medication is available, it can cost between $20,000 and $50,000 to treat one snakebite.
However, scientists at Texas A&M are working on solutions. “There is a great deal of interest in developing new treatments,” said Davies, who also holds the position of co-director of the National Natural Toxins Research Center (NNTRC) at Texas A&M University-Kingsville, an NIH-funded center that is home to 450 venomous snakes. There, Davies collaborates with Elda Sanchez, PhD, associate professor and director, and Sara Lucena, PhD, a research assistant professor at the NNTRC, on the Snakebite Mitigation Program. “We are trying to develop new ways to prevent people from dying or suffering terrible injuries from snakebite,” Davies said. “I’m excited that the team of talented scientists Dr. Sanchez and I have assembled at Texas A&M University Health Science Center and Texas A&M University-Kingsville can work together to discover new ways to treat this often neglected but truly devastating disease.”
“We have a unique program involving not only scientists but also students, ranging from high school to master’s level, who play a significant role in assisting the NNTRC in developing new ways to use toxins as therapeutics,” Sanchez added. “Our team is truly dedicated to helping alleviate the devastation caused by venomous snakebites.”
Davies is a physician and pharmacologist whose special interest is the development of new treatments for neglected diseases. In the case of snakebites, the path to new treatments involves developing a better understanding of how the snake venom’s toxins work. “We have a special interest in finding out how snakebites affect the vascular system, especially the effects of the toxins on the lymphatic system,” Davies said. To that end, he’s also collaborating with David C. Zawieja, PhD, regents professor and interim chair of the Department of Medical Physiology at the Texas A&M College of Medicine and director of the Division of Lymphatic Biology, and his team.
“We are contributing our expertise in lymph and blood vessel function to help Dr. Davies and his team understand the pathophysiology of some of the toxins in rattlesnake toxin venom, toxins called cyteine-rich scecretory proteins, or CRISPs,” Zawieja said. “These particular toxins are related to similar proteins that the body’s immune system uses, but we don’t understand how these toxins work and particularly how they are transported beyond the local bite site.”
Although it is clear how the venom acts on the tissue in the immediate area of the bite, more work is needed to understand how it moves through the lymphatic system to the lymph nodes, and from there to the bloodstream where it is then rapidly distributed throughout the body. “In particular, we want to know how these toxin components affect the physiological function of blood and lymphatic vessels in the site of the snakebite,” Davies added.
It’s known, for example, that the venom of pit vipers (including rattle snakes, copperheads and water moccasins, which are also called cotton mouths) makes the walls of the body’s blood vessels ‘leaky,’ allowing toxins in the snake venom to get into the circulatory system and blood components (especially plasma proteins and fluid) to escape into the tissues and cause the gross edema seen at snakebite sites. Eventually, without treatment, the toxins in the snake’s venom affect the function of many of the body’s organ systems—including the blood coagulation and nervous systems as well as the function of the heart and skeletal muscles—effects that all contribute to the paralysis, and ultimately the death, of the snake’s prey.
The goal of the research being conducted by Davies and his colleagues is focused on finding ways to slow or stop the distribution of the venom from the site of the snakebite and to develop ways to inactivate the venom at the site of the bite, without the use of expensive and difficult-to-use anti-venoms.
The earliest part of this work has been funded, in part, by the United States Department of Defense through a grant from the Defense Advanced Research Projects Agency (DARPA). The military is very interested in finding new ways to protect American soldiers, and especially special forces, from the hazards of being bitten by venomous snakes. Their interest is in developing first aid measures for snakebite or other venomous bites that could be used by troops in the field to provide immediate protection from the danger of the bite until the soldier or special forces personnel can receive more traditional medical care after they have been evacuated and treated at an intensive care unit of a modern hospital. “The goal is to discover new ways for treating snakebite that will be more effective, less expensive and more stable than the treatments that are currently available,” Davies said. “It is easy to see how new ways to treat snakebite might be of great value, not only to military personnel but also the hundreds of thousands of ordinary people whose lives are affected by snakebites every year.”