Experts at the Global Snakebite Initiative estimate venomous snakes seriously injure 2.7 million people and kill 125,000 people annually. Most deaths occur in tropical regions of Asia and Africa, where farmers and children in rural communities experience increased exposure to bites and reduced access to proper healthcare and antivenom.

People in the Americas are also at risk. In the lowlands of Central America, the fer-de-lance, a pit viper that can reach lengths of up to six feet, is responsible for more than half of all venomous bites. This quick-to-strike ambush predator can open its jaws up to 180 degrees before hitting prey—or perceived threats—with fangs that are almost an inch long. Its hemotoxic venom spreads through cells and blood vessels, causing swelling and blisters, and destroying tissue as it moves. Bites can lead to infection, amputation, and death.

Steve Rankin, a 51-year-old executive producer for the new Discovery show “Naked and Afraid,” felt the venom’s power while scouting a location in the Costa Rican jungle. Here, Rankin tells the story of how he ran into the country’s most feared snake while searching for the perfect spot for the premiere episode (Sunday, 10:20 EST).

On the morning of March 23 at 8:00 A.M., I hiked into the tropical forest in the Heredia province of Costa Rica with three other members of our production crew, a local guide named Gerhard, and a local wildlife expert named Pomipilio. We needed a solid rainforest location, and this area of Costa Rica offered amazing terrain and loads of biodiversity. Our plan was to trek through a six-mile stretch of jungle to find a starting location and points where the show’s two survivalists might obtain water and food. We also had to find somewhere to land a chopper to extract the couple in case of an emergency. We started about a mile from the nearest river valley and marked interesting points with GPS coordinates.

Our plan was to trek through a six-mile stretch of jungle to find a starting location and points where the show’s two survivalists might obtain water and food.

The Costa Rican jungle was thick and impressive. Huge trees rooted themselves into steep valleys. Howler monkeys barked from the branches. Animal tracks littered the forest floor. We made our way slowly as early morning temps hit the low 80s. Occasionally, Pompilio would stop to investigate some of the animal tracks. At one point, I worried the location was going to be too easy on the pair of survivalists.

The massive buttressed trees and dense undergrowth choked out the sunlight. The vegetation was so dense that I couldn’t always see my hands in front of me. We were moving vines and constantly tripping, but we couldn’t machete our way through the undergrowth. Cutting a path would have given the couple clues about where to go and offered them an easier path.

At about 11 a.m., the sun started breaking through the canopy and the temperature and humidity began to climb. In no time, the heat was oppressive. Our clothing was drenched with sweat. It felt as though we all had just stepped out of a hot shower. I slurped from my Camelbak and pressed on behind the two guides. The rest of the group strung out behind me in single file.

I scrambled up a five foot fallen tree. I paused, and glanced up ahead at the two guides before looking down to check for anything slithering near my feet. Then I jumped off the trunk.

Bang. It felt like I’d been stabbed in the left foot. I jumped away from the tree and looked back. I saw the writhing brown mottled outline of a snake. It looked maybe five or six feet long and as thick as my wrist. It was right up against the tree. I saw the large, distinct, arrow-shaped head of a pit viper. I knew it was venomous.

“Snake,” I yelled. Pompi and Gerhard thought I’d spotted one. “I’ve been bitten.”

They rushed 40 feet back to me. The whole time I kept my eye on the snake, so I didn’t lose it. It was maybe eight feet away from me.

Within seconds, my heart started racing. I felt a painful burning sensation in my left foot.

One of the guides said, “Terciopelo.”

I looked at Gerhard, confused. “A fer-de-lance,” he said. “We call them terciopelo here.”

Within seconds, my heart started racing. I felt a painful burning sensation in my left foot. I put my weight on my right foot. I suddenly felt weak. The guys grabbed my shoulders and held me up. My knees immediately went to jelly. I was panting like a horse. “Breathe. Breathe slowly—in and out, in and out,” said Derek, a cameraman. “Try not to let the venom spread too quickly.”

“Easy for you to say,” I said.

Someone took off my boot. I dreaded what would be revealed. I tried to think positive. I thought, “Maybe I got lucky. Maybe it was just a warning shot. A hiking boot surely would protect me to some extent?”

Once the boot came off, the sock said everything. A red stain was spreading across the grey fabric covering my instep. “Crap,” I thought. The puncture wounds on the top of my foot were bleeding freely. The venom must have stopped the blood from clotting. There wasn’t a moment to lose. Someone strapped the boot back on. Chris, a line producer, was already on the phone giving our position, organizing a car to meet us, and calling in a chopper. The crew stayed calm, organized, and disciplined. Fear and panic were running around my head. In the midst of that, I just thought, “Keep calm. Keep moving. Keep focused.”

I was full of morphine, so I couldn’t feel much pain, but my lower leg felt heavy and thick. It felt something like a throbbing concrete block.

We started hacking our way back through the undergrowth. After about twenty minutes of hiking with two guys holding onto my shoulders to support me, we hit a trail. The guys built a makeshift stretcher out of branches, backpacks, and ponchos. We still had a long way to go, and I became concerned about the time it would take to get to a hospital. The guys gently helped me onto the stretcher and carried me along two miles of trail. We came to a small house with a tin roof and a round barn near some dirt tracks. A 4 x 4 truck was waiting there to pick us up.

The pain really started to kick in during the truck ride. I felt every bump on the dirt road. Each jostle sent a spike of pain from my foot all the way up to the top of my thigh. Waves of searing heat pulsed through my leg while stabbing pains, like knives shoved into my flesh, added more agony.

After a ten-minute drive, we arrived at the lodge, where a chopper was waiting. Thirty minutes later, I was at a hospital in San Jose. All told, it took two hours to get from the bite site to the hospital.

At Clinica Biblica, the medical team checked out my foot, administered antivenom, and gave me antibiotics and painkillers. Two doctors, Dr. Wu and Dr. Nunoz, checked my condition frequently. I felt safe. I thought, “What a lucky escape.”

My leg continued to swell for the next five or six days. My left foot blistered as the pain from the bite subsided. The trouble was, every time I stood up, the pain from the swelling took hold. I remember It felt like every muscle fiber in my leg was full of pressure and about to explode. Picture a bubbling sausage on a grill about to burst. That pressure was more painful than the pain immediately after the bite. I’d never felt anything like it. I remember leaning on my fiancé, Jackie, to use the toilet as tears just poured down my face.

By April Fool’s Day, one week after the initial bite, the blisters popped and the resulting wounds began festering. “To be expected,” said the doctors. Then Dr. Wu sniffed my foot and frowned. “We better get you to the OR,” he said.

The flesh in my foot was rotting. Nurses put me on a gurney. As they wheeled me away, I watched my foot drip a trail of pus and blood onto the hospital clean floor.

They performed an eight-hour operation that included taking a chunk of flesh from my left thigh and grafting it onto my foot.

The surgeons opened up my foot and removed the infected, liquefied flesh. They cut away any extra bits of tissue that were beginning to go bad and dressed the ankle and foot with a vacuum bag—a big polythene sack that they wrapped around my lower leg and attached to a pump. I was full of morphine, so I couldn’t feel much pain, but my lower leg felt heavy and thick. It felt something like a throbbing concrete block.

They couldn’t say that the spread of dead tissue had been completely arrested. I wondered if I was going to keep my foot.

The people in Costa Rica knew their stuff about treating snakebites. A lot of people at work said it was best to deal with the snakebite in Costa Rica because they dealt with so many. But the reconstructive surgery I needed would be better in the U.S, especially where I’m from—Hollywood.

After one more cleaning operation on my foot, Clinica Biblica released me on April 5. I left San Jose around midnight on a Lear Jet kitted out like a mobile ICU. In Los Angeles, an ambulance drove me to Cedars Sinai Medical Center, where a team of new doctors took a look at me every few minutes. They performed an eight-hour operation that included taking a chunk of flesh from my left thigh and grafting it onto my foot.

On my birthday, April 11, Jackie brought me cupcakes, cards, and gifts. It cheered me up. A woman played happy birthday for me on a flute. After she stopped, I noticed the sound of my arterial and venous pulses on the Doppler probe. Over the next four days, I listened for changes in the strength or rhythm of the beeping. It got stronger. Before I was released on April 17, I thought, “I will be fine.” More than fine, I thought, “I will be able to walk Jackie down the aisle.”

Expert Opinion

The snake bit him in defense. “Agressive” is a misnomer for snake behavior toward humans; “defensive” is more accurate. When he stepped into the snake's strike range, the snake felt threatened and instinctively struck him. I am not surprised that he did not see the snake before he stepped near it. The fer-de-lance, Bothrops atrox, is cryptically colored so that it blends almost invisibly against the rainforest floor.

It is common for a large fer-de-lance bite to lead to this sort of reaction. These snakes have a very sophisticated venom-delivery apparatus that seldom delivers a "dry bite." More than 90 percent of those struck receive a significant dose of venom.

The biggest lesson from this story is that getting to an appropriate hospital and antivenom as quickly and safely as possible, as was done in this case, can save your life.

The primary purpose of viper venom in nature is predatory. As soon as it is delivered, it begins to pre-digest tissue. This is so that an animal with no means to break prey down into smaller pieces can efficiently digest it: from the inside out at first strike, then from the outside in when the snake swallows it. The venom also causes the victim to bleed abnormally. Bleeding prey loses blood and blood pressure so that it cannot perfuse its muscles and brain, which causes it to stop running at a distance that is not too far for the snake to recover. Now the snake can track the prey at the snake's own pace while the prey starts to digest.

When human tissue gets digested and bleeds abnormally, the result is tissue death. Dead tissue necroses, or rots. The biggest lesson from this story is that getting to an appropriate hospital and antivenom as quickly and safely as possible, as was done in this case, can save your life.

—Sean P. Bush, MD