Facts about Killer Scorpion: Facts and Pictures

Facts of the Killer Arthropods

Scorpions are venomous arthropods of the class Arachnida and they are considered relatives of the spider, mite, tick and harvestmen. There are approximately 1,300 species of scorpions worldwide, and everyone of them is characterized by an elongated body and a segmented tail tipped with a venomous stinger. Scorpions are usually thought of as desert animals, but in fact they occur in many other habitats as well including: grasslands, savannahs, deciduous forests, montane pine forests, rain forest and caves. Scorpions have been found under snow-covered rocks at elevations of over 12,000 feet in the Andes Mountains of South America and the Himalayas of Asia. About 90 species of scorpions occur in the U.S., and all but four of them are naturally occurring West of the Mississippi River. Living scorpions reflect ultraviolet light and can glow with an eerie greenish colour when exposed to UV light, no matter what colour they appear under normal lighting conditions.

Androctonus is widespread in the Middle East and North Africa. Countries where Androctonus species live include: Mauritania, Algeria, Tunisia, Libya, Israel, Egypt, Jordan, Saudi Arabia, Yemen, United Arab Emirates, Kuwait, Iraq, Iran, Pakistan, South Eastern Africa.

Fattail scorpion or fat-tailed scorpion is the common name given to scorpions of the genus Androctonus, which is one of the most dangerous groups of scorpion species in the world. They are found throughout the semi-arid and arid regions of the Middle-East and Africa. They are a moderate sized scorpion, attaining lengths of 10 cm (just under 4 in). Their name is derived from their distinctly fat metasoma, or tail. Their venom contains powerful neurotoxins and is especially potent. Stings from AndroctonusGermanantivenin for treatment of Androctonus and two closely related genera, Buthus, and Leiurus, envenomations. species are known to cause several human deaths each year. The pharmaceutical company Twyford manufactures an

Dangerous Scorpions

Most potentially lethal scorpions belong to the Family Buthidae which primarily is distributed in Africa and Southeast Asia. However, all scorpion stings, regardless of geographic location should be treated as potentially dangerous unless the scorpion can be positively identified. For example, several species of Centruroides distributed from Mexico southward in the Americas have stings with serious medical consequences but other species in this genus only produce painful encounters. Among the most dangerous scorpions in the world are Centroides sufussus in Mexico, Tityus serrulatus in Brazil, and the infamous yellow scorpion of the Middle East, Leiurus quinquestriatus. Of the 86 species of scorpions known from India, only two species Mesobuthus tamulus, the common red scorpion, and Palamneits swammerdami, are potentially lethal. Indeed, the common red scorpion has killed many people with a historic mortality rate around 30%. In the western Cape of Africa, Parabuthus granulatus is the most important venomous species while Androctonus australis and Buthus occitanus in northern Africa are regularly implicated in stinging humans with serious consequences. Opistophthalmus glabrifrons, Family Scorpionidae, is widespread in southern Africa, and is able to produce a variety of dangerous systemic symptoms, but no deaths have yet been attributed to this species. Androctonus crassicauda and Buthus occitanus generally are considered to be the two most dangerous scorpions in Jordan. Similarly, A. crassicauda is the second most frequent source of scorpion sting in southwest Iran where it is considered to be a significant social hazard. This species is responsible for many deaths annually, mostly among children. Of 2,534 patients in one study in southwest Iran, three scorpion species accounted for nearly all of the stings, i.e., Androctonus crassicauda (41%) and Mesobuthus eupeus (45%) (Family Buthidae), and Hemiscorpion lepturus (13%) (Family Scorpionidae). In the United States, the only scorpion capable of inflicting a fatal sting is Centruroides exilicauda (=C. sculpturatus, C. gertschi) which is distributed in Arizona, California, Utah, and western Mexico. However, no deaths in the United States have been attributed to this species since 1968.

Most dangerously venomous scorpions have long and slender pedipalps (“claws”) in comparison to those of less venomous species which tend to have more robust pedipalps. This has led to the simple, although not universal, rule that scorpions with thin claws and thick tails tend to be more venomous than those with stout pedipalps and thinner tails. The toxicity of the venom is therefore associated with the ability of the scorpion to subdue prey with the pedipalps. In southern Africa, thick clawed scorpions belonging to the families Scorpionidae, Bothriuridae and Ischnuridae, and are generally assumed to be harmless. However, 0pistophtalmus glabrifrons is an exception to the rule. Opistophthalmus species are burrowing scorpions, and probably never leave their burrows except when coming out to mate. This probably accounts for the timing and relative rarity of their stings.

Effects of scorpion venom

The effects of scorpion venom on people are highly variable with severity ranging from localized, self-resolving pain to death. For all scorpion stings, every effort should be made to establish the species responsible because the relative seriousness of envenomation is species dependent and varies widely. Additionally, the response to scorpion envenomation may vary with the general health and age of the victim, their physiology and genetics, and emotional condition. Further variability may be attributed to the site and depth of sting penetration, quantity of the injected venom, and the proportion of the venom reaching the circulatory system. The severity of complications often seen in children likely is due to the higher concentration of venom per unit volume of blood. Although individual play a key role in determining the reaction of stinging victims, other factors also may be involved.

Scorpion venom contains both hemolytic and neurotoxic components of which the former produces the pain and swelling associated with stings. The local and systemic responses associated with envenomation often are quite different and variable. The venom of some species may produce severe swelling and discoloration at the site of the sting while that of other species causes pronounced swelling, inflammation and pain. Although the general initial response to a scorpion sting is immediate local burning pain, some species with potentially lethal venom often cause little initial pain and produce minimal or no swelling, inflammation, and discoloration. However, the sting site may become painful to the touch and have a "woody" feeling. Some patients develop dark blue skin patches usually surrounded by a red halo within the first hour following a sting. These areas may gradually become hardened and inflamed followed by necrosis and subsequent sloughing of the skin. Large blisters may develop around the sting site, and extensive ulceration may follow. In cases of severe envenomation, the hemolytic components of venom can destroy red blood cells, disrupt the blood ability of blood to clot, and other cardiovascular complications can occur. Onset of acute kidney failure following scorpion envenomation can result within 24 hours to a few days following the sting and is sometimes typified by the presence of blood in the urine, and associated anemia and jaundice from destroyed blood cells. Some patients may require kidney dialysis. Although most patients have difficulty producing urine, other patients may start secreting abnormal amounts of urine between 6 and 21 days after a sting.

The neurotoxic fraction of the venom, depending on the species involved, can produce a broad range of dangerous and potentially fatal reactions when present in sufficient quantity. This fraction of the venom contains a variety of polypeptides that interfere with ionic balance and channel activity in the nervous system. The primary and initial effects are on the peripheral nervous system which causes intense pain, altered heart activity, and numbness. Other symptoms associated with the neurotoxic component of the venom include muscle twitching, crying, salivation, profuse sweating, respiratory distress, urinary urgency, nausea, paresthesia of the tongue, restlessness, stiffness of the joints, convulsions, and increased muscle activity around the eyes. For the stings of some species, pain can be negligible initially, but patients may seek medical treatment hours to days later when they have already developed swelling and inflammation with gradually increasing local pain. Another common response in children is an extreme form of restlessness characterized by excessive neuromuscular activity (jerking and spasms). Typically, blood pressure, body temperature, and tendon reflexes often increase while motor skills become impaired. Other striking features include the inability to write or manipulate small objects, difficulty articulating speech, and varying degrees of loss of pharyngeal reflexes. Heightened sensitivity to touch, cold or heat, muscle pain and cramps also occur in many patients. Systemic symptoms and signs usually develop within 4 hours of the sting, and anaphylaxis and death from cardiac or respiratory failure can occur within 24 hours. However, despite the seriousness of such symptoms in victims, death from scorpion stings has become less common due to the availability of antivenom in some areas where highly venomous species occur. Recovery often is complicated by varying degrees of respiratory dysfunction which tend to be more serious in children.

excertps from

^{Field Guide to Venomous and Medically Important Invertebrates Affecting Military Operations:}

^{Identification, Biology, Symptoms, Treatment}

^{http://www.afpmb.org}

^{courtesy from : Sean P Bush}

Envenomation from most scorpions results in a simple, painful, local reaction that can be treated with analgesics, antihistamines, and symptomatic/supportive care. This article focuses on scorpions that generally are considered more dangerous to humans. All of the potentially lethal scorpions belong to the family Buthidae, with the exception of one genus, Hemiscorpius, which belongs to the family Scorpionidae (ie, Ischnuridae). A triangular sternal plate helps distinguish Buthidae from other scorpion families in which the sternal plate is more pentagonal (see Image 3). Scorpions of medical significance include the following genera in the given distributions:

• Centruroides - Southern United States, Mexico, Central America, and the Caribbean (Centruroides exilicauda is found in Mexico and Centruroides sculpturatus is found in the southwestern United States, primarily Arizona and small parts of Texas, New Mexico, Nevada, and California.) The accepted taxonomy of the bark scorpion has changed over time. Either C exilicauda or C sculpturatus have been accepted at various times. However, recent evidence from biochemical, genetic and physiologic characterization of their venom suggests that they are two different species as listed above.
• Tityus - Central America, South America, and the Caribbean
• Buthus - Across the Mediterranean area, from Spain to the Middle East
• Mesobuthus - Throughout Asia
• Parabuthus - Western and southern Africa
• Buthotus (ie, Hottentotta) - Across southern Africa to southeast Asia
• Leiurus - Across northern Africa and the Middle East
• Androctonus - Northern Africa to southeast Asia

Note that scorpions may be found outside their natural range of distribution when inadvertently transported with items such as luggage.

Pathophysiology

Scorpions grasp prey with pincers, arch their tails over their bodies, and deliver venom with the stinger. They inject venom from glands located lateral to the tip of the stinger.

Scorpion venom may contain multiple toxins and other compounds. Venom composition is complex, and detailed discussion of its pharmacological effects is beyond the scope of this article. The most important clinical effects of envenomation are neuromuscular, neuroautonomic, or local tissue effects. The primary targets of scorpion venom are voltage-dependent ion channels, of which sodium channels are the best studied. Venom toxins alter these channels, leading to prolonged neuronal activity. Many end-organ effects are secondary to this excessive excitation. Autonomic excitation leads to cardiopulmonary effects observed after some scorpion envenomations. Somatic and cranial nerve hyperactivity results from neuromuscular overstimulation. Additionally, serotonin may be found in scorpion venom and is thought to contribute to the pain associated with scorpion envenomation.

Frequency

United States

In 2004, a total of 14,950 scorpion envenomations were reported to the American Association of Poison Control Centers. However, because of underreporting, this is probably an underestimation of the true number of stings.

International

Reliable statistics on scorpion envenomation are not available. Many potentially dangerous scorpions inhabit the underdeveloped or developing world. Consequently, numerous envenomations go unreported, and true incidence is unknown.

Mortality/Morbidity

Accurate worldwide data do not exist. The highest reported mortality rate is recorded in data from Mexico, with estimates as high as 1000 deaths in one year. In the United States, 4 deaths were reported in an 11-year period according to one source (Langley, 1997). However, no deaths were reported to the American Association of Poison Control Centers from 1983 to 1999. Only one death from the Arizona bark scorpion (C sculpturatus) has been reported since 1964 (Boyer, 2001). Ironically, the highest and lowest mortality estimates are associated with different species within the same genus of scorpion (Centruroides).

• Children and elderly persons have an increased risk of mortality.
• In terms of venom lethality, the venom of Androctonus australis and Leiurus quinquestriatus are the most toxic. C sculpturatus venom is low in toxicity compared with most scorpions of medical importance.