Originally published in The Ottawa Citizen March 11, 2005

The thrill of the winter sojourn to warmer climes and ocean activities like scuba diving, surfing and snorkeling, among others, can lead many to overlook other notable health and safety precautions.

If you’re heading south for some fun in the surf, remember the ocean is an alien world with creatures that, for all their beauty, can be a literal shock to the system.

What do you do when stung by a jellyfish, step on a sea urchin’s spine, encounter the whip of a stingray’s tail, or eat a poisonous fish?

Certain reef fish like grouper, king mackerel, sturgeon and snapper can ingest microscopic organisms called dinoflagellates either directly or by eating smaller fish. One particular species, gambierdiscus toxicus, produces a toxin that becomes increasingly concentrated as it travels up the food chain.

Thousands of people eating these fish found around Hawaii, Florida, Puerto Rico and the U.S. Virgin Islands can develop Ciguatera (seeg-wha-terra) poisoning. The severity of poisoning depends on the fish size and the number of exposures. The classic symptom found in 80 per cent of patients is a cold sensation reversal, where hot sensations are perceived as cold and vice versa.

Gastrointestinal and neurological symptoms usually begin one to six hours after ingestion and last seven to 14 days, and in some cases months to years. They include nausea, vomiting, watery diarrhea, abdominal pain, numbness, vertigo, severe weakness, muscle aches, slowed heart rate (bradycardia), low blood pressure (hypotension), diffuse pain and decreased vibration and pain sensations.

There is no immediate cure, only symptom relief. Cooking, freezing, salting or smoking the fish does not deactivate the toxin. If these fish are eaten, avoiding eating the fish’s internal organs like the liver because the toxin concentrates in these areas.

Travellers to Hawaii and California who eat tuna or mackerel may develop scombroid. Poor handling and refrigeration of the fish can cause a buildup of histamine and histamine-like substances within the dark meat. The person develops symptoms 30 minutes after ingestion. Symptoms can last about eight hours and include flushing, nausea, vomiting, diarrhea, severe headache, palpitations, abdominal cramping, dizziness, dry mouth, hives, and red eyes.

Treatment includes the use of antihistamines administered by mouth, intravenous or into the muscle, depending on symptom severity.

Encounters with jellyfish are memorable. Their long tentacles have stinging cells, or nematocysts, that sting. Nematocysts found on amputated tentacles and dead jellyfish will sting as well.

Symptom severity depends on the number of stinging nematocysts, the toxicity of the venom and each person’s unique reaction. The poison is destructive; it damages skin, red blood cells, heart tissue and nerves.

The most common symptom is local pain followed (in order or likelihood) by a “pins and needles” feeling (paresthesias), nausea, headache, chills and, rarely, cardiovascular collapse or shock. Symptoms can last up to three days.

Treatment focuses on pain relief and controlling neurologic symptoms. Use gloves or forceps to remove any visible tentacles. Avoid touching towels used to wipe off the nematocysts; they will sting. A 30-minute application of vinegar (five per cent acetic acid) will stop any remaining nematocysts on the skin from releasing their venom. Salt water is a good substitute if vinegar is unavailable. Never use fresh water because it will stimulate venom release.

Scraping the nematocysts off the skin using shaving cream and a razor is another solution. There are reports that cold and hot packs can help sooth the pain.

Stepping on a sea urchins’ toxin-coated spines will cause pain and burning and occasional skin discolouration lasting about 48 hours. The spines will break if you try to remove them by hand. Fragments will remain embedded in the skin and can cause infection. Surgical removal and wound debridement may be necessary.

The stingray’s venomous spine is at the end of its tail. The venom will reduce blood flow to the affected limb causing tissue death and destruction, poor wound healing and infection.

Intense pain is immediate and can be accompanied by salivation, nausea, vomiting, diarrhea, muscle cramps, shortness of breath, seizures, headaches, muscle cramp and cardiac arrhythmias. Fatalities are rare.

Bleeding from the puncture site is controlled by direct pressure to the wound. Hot water soaks will help reduce the pain.

Wound care includes thorough rinsing of the affected area with fresh water. Patients should check for redness and swelling at the site; a sign of infection. Sometimes, part of the spine will remain embedded in the tissue; surgical removal may be necessary.

A tetanus shot may be required for stingray and sea urchin stings. Although fatalities are rare for all these toxic reactions, prompt recognition of the symptoms can lessen the discomfort and morbidity.

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© Dr. Barry Dworkin 2005