Health & Safety in Mexico
Scorpion stings and snake bites
By Robert H. Page, MD and Curtis P. Page, MD
July 11, 2008 San Miguel de Allende

Of the more than 1,000 species of scorpions worldwide, only 30 carry a toxin that may be fatal in humans. In the US, the rate is very low: one death from a scorpion sting occurs on average every two to three years.

In Mexico, there are a reported 1,000–2,000 deaths per year. Because of their size and ability to travel in shoes and luggage, scorpions are found in many ports all over the world, having arrived as stowaways. Scorpions are nocturnal, typically emerging only at night. They are commonly found in cupboards, closets, in shoes and under beds. Scorpions sting with a poisoned hook on the tail, which is raised prior to an attack.

Being infected by scorpion venom results in a local reaction that, while painful, is easily treated with analgesics, antihistamines, ice, and supportive care. Moderate to severe pain, numbness or tingling is often experienced in the area around the sting. Nausea or vomiting is not uncommon. 

In more serious stings, pain and tingling may be followed by marked changes in blood pressure (high or low), high fever, or difficulty breathing. Symptoms that signify a more serious venom reaction include restlessness, rotary or roving eye movements, involuntary muscle spasms, difficulty swallowing, excessive salivation, or blurred vision. Shock or respiratory arrest may ensue without prompt medical intervention. 

Treatment

Elevate the injured limb at or above the heart. An ice cube may limit pain to the wound. Analgesics such as Tylenol or ibuprofen may be taken for minor pain. Intravenous or intramuscular injections of meperidine (Demerol) or morphine may be used if the pain is severe. Calcium gluconate (10 ml of 10-percent solution) may be given intravenously for muscle spasms. Valium may be given intravenously for anxiety and restlessness. 

Antivenom is available in most Mexican hospitals for more serious stings. There is always the possibility of a severe allergic reaction to the antivenom; thus, it must be administered by a physician in a hospital setting. The antivenom is primarily used for severe reactions to the venom of the Centruoides Exilicauda scorpion, a small, light brown, inch-long creature also known as a “bark scorpion.” This scorpion is found in Mexico and the southwestern US.

Snake bites

With over 320 species in Mexico alone, it is no wonder the snake is stamped on its flag and plays such an important role in the country’s history. Of the different types of snakes, only the rattlesnake (cascabel or crótalo), red coral snake (coralillo), nauyacas and cantiles snakes are venomous. 

The rattlesnake, familiar because of its rattler and triangular head, accounts for 45 percent of snakebites. Masters of disguise, their colors and patterns allow them to blend well with their surroundings, often seeming invisible. The nauyaca snake accounts for 43 percent of snakebites and varies significantly in color and size. The highly venomous red coral snake, recognized by its red-yellow-black or black-red-black rings, accounts for only 4 percent of snakebites. 

In Mexico, 500–700 bites are reported annually. Mortality rates are low (less than one percent) as not all snakes are venomous or are unable to inject their venom and because accurate treatment is administered in a timely manner. Since most snakes strike when a person has accidentally stepped on them, 72 percent of snakebites occur on the feet and ankles and 14 percent on the calves. It is therefore advisable, when hiking in a high-risk region, to wear thick-soled, high boots covering these areas of your body. 

The bite of the snake is usually painless and, but for the fang marks, could go unnoticed. Bruising, bleeding and local swelling are more evident indications. After one hour, possible symptoms include headache, irritability, light sensitivity, nausea, vomiting, abdominal pain, diarrhea, confusion and coagulation abnormalities. If left unattended, limb and respiratory muscle paralysis, respiratory failure, peripheral circulatory failure and eventually death could occur within 8 to 72 hours.

Treatment

If a snake bites you, keep calm and seek immediate medical attention. If the snake has administered its venom, you will require anti-snakebite serum. Until you receive medical attention, minimize your activity and immobilize the area bitten, keeping it below the heart. Do not apply ice to the bite area, do not make any incisions, do not apply a tourniquet and do not administer alcohol or take drugs (especially Demerol, codeine or morphine). If you will be hiking in high-risk areas, be sure to purchase a snakebite kit and booklet.

Copyright© 2008 MedToGo, LLC. Not for unauthorized publication or reproduction without the consent of MedToGo, LLC.

Robert H. Page, MD and Curtis P. Page, MD are authors of MEXICO: Health and Safety Travel Guide and the Healthy Traveler regional series. For more information, visit medtogo.com.