Crocodile Hunter Had Atypical Stingray Encounter

SAN DIEGO, Sept. 8 -- Fatal encounters with stingrays like the one that killed "Crocodile Hunter" Steve Irwin this week are extremely rare, but minor injuries are common.

In the waters around the United States, as far north as Chesapeake Bay on the east coast, in the summer, and Eureka in northern California, stingrays cause an estimated 1,500 injuries each year, almost all of them minor, according to a recent report in American Family Physician.

Stingrays are passive creatures that attack only if they feel threatened, said Richard Clark, M.D., a toxicologist and emergency room physician at the University of California San Diego Medical Center here.

The usual scenario involves a swimmer who accidentally steps on a stingray concealed on the sandy ocean bottom or an unwary fisherman trying to free one that has accidentally been hooked or netted, Dr. Clark said.

Only one other fatal case has been documented in a medical journal in recent years, he noted. That was a 12-year-old boy who, like Irwin, was pierced in the chest by the stingray's spine. The boy's right ventricle was punctured.

Unlike Irwin, however, the boy did not die immediately but succumbed six days later to cardiac tamponade brought on by venom-induced myocardial necrosis, according to a report in the Medical Journal of Australia.

The 44-year-old Irwin was killed Monday while being filmed for a new TV show off Australia's Great Barrier Reef. Video footage of the incident reportedly shows that as Irwin swam above a stingray, it lashed him with its tail, plunging its spine into his chest. Irwin removed the spine himself, but collapsed and died within minutes.

No formal autopsy report has been announced, but the press reports are consistent with a puncture wound to the heart, Dr. Clark said.

The stingray's venomous defense mechanism includes a sharp, furrowed, serrated cartilaginous spine embedded in the base of its long, whip-like tail. If threatened, the animal may lash out with its tail, thrusting the inches-long spine at a predator or perceived threat and causing a stab-like wound, Dr. Clark said.

The spine is encased by a sheath and attached to a venom gland. On contact with a victim, the sheath ruptures, allowing the venom to flow into the wound. The venom has not been well-characterized, but it is not believed to be deadly. However, it can cause excruciating pain, Dr. Clark said.

"It's a searing, stabbing pain," said Dr. Clark, who was stabbed by a ray once as a boy off of Florida's gulf coast near Pensacola. "It was the worst pain I have ever felt in my life."

The venom is known to cause syncope, hypotension, tachycardia, nausea, diaphoresis, and tissue necrosis. Less frequently, it may cause respiratory distress, cramps, vomiting, and tremors, said Matthew D. Cook, M.D., of the UCSD department of emergency medicine, and colleagues, in The Journal of Emergency Medicine.

For stingray avoidance, it's best to shuffle your feet along the ocean floor rather than walk, Dr. Clark said. That helps avoid stepping on top of a ray, and this "stingray shuffle" alerts the animals to your presence and allows them to move off before you come into contact, he added.

Swimmers should also know that it's safer to swim where there are many people. The human activity frightens stingrays away. While having a sandy beach all to yourself may be inviting, the risk of encountering a ray is higher there, Dr. Clark said.

Shoes or protective clothing won't stop a stingray spine. "Penetration of heavy rubber aprons, rubber and leather boots, and the side of a wooden boat has been reported," said Peter K. Meyer, M.D., of the Columbia Cape Fear Memorial Hospital Emergency Center in Wilmington, N.C., writing in Wilderness and Environmental Medicine.

When treating stingray injuries, the first order of business is usually to relieve the extreme pain, which is normally localized to the wound site. If left untreated, the pain may last up to 48 hours, Dr. Clark said.

Fortunately, pain relief can be accomplished by submerging the affected area in water that is as hot as the patient can tolerate without being scalding. It is believed that the heat denatures some of the heat-sensitive protein components of the venom. Soon-to-be-published case reports indicate that hot water immersion effectively relieves the pain more than 90% of the time, Dr. Clark said.

Dr. Cook and colleagues recommend a water temperature of 105 to 113 degrees Fahrenheit and an immersion time of 30 to 90 minutes. If that does not relieve the pain, regional nerve blocks or infiltration of the skin with Sensorcaine (bupivacaine) may be effective, they said.

Once the pain resolves, it rarely returns, Dr. Clark said.

The next order of business is to explore and irrigate the wound to make sure no part of the stingray spine or sheath has been left behind to cause an infection. Spines often break off and can be found protruding from the wound. If there is a suspicion that a spine or part of a spine is embedded more deeply, an X-ray should detect it as the spines are radiopaque, Dr. Clark said.

Prophylactic antibiotics should be considered if the water the victim was in is known to have a high bacteria content or if the injury is to a high-risk area such as the hands, feet, or joints.

Patients should receive a tetanus shot if they are not up to date, and they should be observed for three to four hours for systemic signs or symptoms before discharge, Dr. Cook said.