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Last updateMon, 21 Jan 2019 12pm

Warning: Scorpion stings can vary from ‘mild’ to deadly

These last few weeks of the dry season seem to attract far more scorpions than normal into the open, where they can be seen.

The greatly feared scorpions leave their hiding places under rocks and in other dark places to search for water and food. While the prehistoric-looking beasties certainly aren’t the most attractive creatures on earth, it is their sting, not their lack of beauty that creates fear.

A scorpion sting can cause mild to extreme pain, or occasionally, death. The severity of the reaction is determined by the scorpion species, the body mass of the victim, the amount of venom injected, and the person stung.

At lakeside, there are two families of scorpions – Buthidae and Vaejovindae. In Mexico, the genus Buthidae is called Centruroides; northern Mexico has some within this genus that are very dangerous. At Lake Chapala the centruroides infamatus or centruroides elegans are much less dangerous. The other local family of scorpions here is Vaejovindae and its many species of the genus vaejovis.

Most people cannot identify local scorpions. They have more similarities than differences. However, generally the more poisonous scorpions have smaller pincers that have less muscle force, and therefore are given a more venomous toxin in order to kill its prey in the wild. The species of Centruroides have slightly smaller pincers than Vaejovis, and thus a stronger toxin. The good news is that if you are stung here, statistics show it most likely will be by a species of Vaejovis.

How much poison is injected in a scorpion sting depends on the situation. A scorpion needs poison to defend itself and to kill its prey. Using all of it just to sting you is not in its own interest. If you just bump it, it will likely not sting with all its venom. However, if it is trapped in your pant leg or shoe, it will try to save its life and may sting you with all the venom at its disposal. If it has recently stung, it may not have had time to regenerate more toxin, and will not be as dangerous.

Scorpion poison is a neurotoxin, and can work by either retarding inactivation (an α-toxin) or enhancing activation (a ß-toxin). Both conditions lead to spontaneous depolarization of excitable cells (nerves and muscles).

Nerves are “short circuited” to send pain signals of a problem that does not actually exist (there is no real skin burn, just the sensation). In small children, muscles can spontaneously move in limbs, face and eyes from the action of the toxin.

Although the heart could be directly affected, this would be very rare considering the local types of scorpions. Both sympathetic and parasympathetic systems are involved, so the victim could have hypertension or hypotension, hypersalivation, or even priapism in severe cases. In most adults, important symptoms are from nerves controlling the mouth and throat. The most dangerous effects are those that inhibit the ability to breath, either by airway obstruction, or by respiratory failure.

Allergy to the toxin of scorpions is also a possibility, as is allergy to the anti-toxin. Symptoms are usually evident in the first 15 to 45 minutes, although rare atypical symptoms can be delayed as much from five to eight hours. Classic lakeside symptoms are extreme pain at the site of the sting. Clinically important cases will have an unusual sensation in the throat.

There are many home treatments discussed, few work, including grease, garlic, bleach, lime, etc. Pain medications (NSAIDS) are not very effective. Opioids could potentiate vomiting and respiratory depression. Antihistamines (very commonly used) will mask the symptoms. Local injection of anesthesia will resolve some pain, but that’s rarely done.

If the symptoms include an unusual sensation in the throat, an anti-toxin called Faboteropico may be necessary. Faboteropico is a Mexican invention from 1994 which was finally approved by the FDA in 2011. It is a purified and modified antibody treatment that is widely available through the Secretaria de Salud in Mexico. It is available locally at both the Chapala Cruz Roja and the Chapala Municipal Clinic. At this time, the Secretaria de Salud supplies it without charge, but with the cost to supply it in the millions of pesos, it may become necessary for the government to reduce this subsidy. The cost from a private consultorio or clinic can be around 1200 pesos per dose. Some cases can use up to five injections, although the average is just one.

Many people take antihistamines, specifically cloropiramina (Avapena) which can mask but not resolve the symptoms. If you are in the wild, with no doctors, clinics, within the area, try to find a Farmacia Guadalajara, but unless you have uticaria (hives) or signs of a significant allergic reaction, it will do no good. Most people, and many doctors, associate the “closing” of the throat to an allergic reaction, when in reality it is usually caused by altering the control of cranial nerves 9, 10, 11, and 12 that control the mouth and throat. Be aware that if you take an antihistamine and then come to the clinic, you may have done more harm than good. In order to receive Faboteropico, you need to have moderate to severe symptoms. If you mask the symptoms with antihistamines or only have slight symptoms, you may not get the treatment you really need.

There is little you can do to help. Putting covered ice packs on the area will reduce the pain some, as well as very slightly retard the absorption of the toxin (by vasoconstriction).

Scorpions need two things to come into your home – an entrance and food. Screens and door thresholds and seals are important. So is ridding your home of the other insects they are hoping to eat.

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