Taking the sting out of scorpion venom

Although only as long as a finger, the Arizona bark scorpion delivers a neurotoxin that can make a child critically ill. An antivenom used in Mexico has passed a U.S. test.

APDIC/R. Wagner

About as long as a human finger, the Arizona bark scorpion is small enough that most people probably don’t even notice it. Unless they happen to step on one — and that’s a different story. The scorpion’s sting contains a poison so powerful that it can seriously harm or even kill a child. Every year, more than 200 children in Arizona and New Mexico become seriously ill from the sting of this scorpion. Many more get stung but have milder effects.

There is no government-approved cure for treatment of this scorpion’s sting in the United States. But now there is hope for an antivenom, and it comes from Mexico. A team of scientists in Arizona recently studied a remedy that is given to stung children in Mexico. The scientists found that the drug works quickly to reduce the harm caused by the venom.

The scorpion’s venom is a type of neurotoxin. “Neuro” means nervous system and “toxin” means poison, so a neurotoxin is a poison that attacks the nervous system. A child who gets stung may start thrashing about, or moving violently, and have trouble breathing. At the hospital, the victim is given a sedative, or a drug that calms. The poison’s effects may take hours or days to wear off. An adult who gets stung usually feels a lot of pain, but the symptoms are less severe.

Leslie Boyer of the University of Arizona in Tucson is a pediatrician who helped test the antivenom that is given in Mexico. In 2004 and 2005, she and her team of scientists conducted a study on 15 children who had been stung by the scorpion. Each child, when admitted to the hospital, was given either the antivenom from Mexico or a placebo.

A placebo is a common tool used by researchers who want to test how well a medication works. A placebo looks like medicine, but it is neutral — which means it has no chemical effect on the person. Researchers use a placebo so that people who participate in a study don’t know if they’ve received the experimental medicine. In fact, typically even the doctors who give the medicine don’t know if they’re giving a placebo or the real medicine.

At the end of a study, since all the participants receive a similar-looking treatment, the researchers can see if the people who got the medication did better or worse than those who got the placebo.

In the Arizona bark scorpion study, eight children were given the antivenom. After only one hour, all signs of the scorpion venom were gone from their bodies. They all recovered completely within four hours of treatment. Of the seven children who received the placebo, only one recovered in four hours. That child was the oldest and heaviest participant in the study. The rest of the children required more time and more sedatives. All eventually recovered, and none of the children died.

This study suggests the antivenom used in Mexico could make life easier for kids in the United States who get stung by this scorpion — if the drug is approved for use north of the border. Meanwhile, Boyer and her team are now expanding their research to all of Arizona, so that they may reach more scorpion victims. The antivenom may be useful in rural areas, where children who get stung are far from large hospitals.

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Power words:

Venom: A poisonous secretion of an animal, such as a snake, spider or scorpion, usually transmitted by a bite or sting.

Sedative: An agent or a drug having a soothing, calming or tranquilizing effect.

Nervous system: The system of cells, tissues, and organs that regulates the body’s responses to internal and external stimuli. In vertebrates it consists of the brain, spinal cord, nerves, ganglia and parts of other organs.

Neurotoxin: A toxin that damages or destroys nerve tissue.

Pediatrician: A doctor who specializes in the care of infants and children.

Placebo: An inactive substance or preparation used as a control in an experiment or test to determine the effectiveness of a medicinal drug.

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