Page 825 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

784 SECTION | XII Poisonous and Venomous Organisms

VetBooks.ir deliver a potentially life-threatening bite exist in the tropi- TABLE 58.1 Scorpions of Medical Importance: Species
cal regions of South America, Africa, and Australia. Their
and Location
venom contains a neurotoxin; there may also be a necro-
toxin and hemolytic toxin. Following envenomation, mus-
Location Species
cle spasms, edema, hemoglobinuria, jaundice, and
circulatory shock may develop (Mullen, 2002b). India Hottentotta tamulus
Species of tarantula living in the United States are not Mexico and Central America Centruroides spp.
capable of delivering serious envenomation. However,
Middle East Androctonus spp.
many of these species have urticating hairs on their abdo- Buthus spp.
men that possess spines and barbs that can penetrate skin. Hemiscorpion lepturus
When threatened, these tarantulas can stroke their abdo- Leiurus quinquestriatus
men and flick the urticating hairs at their attacker. The Mesobuthus gibbosus
hairs can cause severe inflammation of the skin, eyes, South Africa Parabuthus spp.
mouth, and respiratory tract. The effect is purely mechani- Buthus minax
cal because there is no toxin associated with the hairs. South America Tityus spp.
Urticaria, edema, and vasodilation may occur in the skin. Centruroides gracilis
In the eyes, swelling of the lids and corneal abrasions are United States Centruroides sculpturatus
common (Mullen, 2002b). Dogs or cats attempting to
West Indies (Trinidad) Tityus trinitatis
ingest tarantulas may gag or vomit.
Source: Adapted from Lucas, S.M., Meier, J., 1995a. Biology and
distribution of scorpions of medical importance. In: Meier, J., White, J.
Scorpiones: Scorpions (Eds.), Handbook of Clinical Toxicology of Animal Venoms and Poisons.
CRC Press, Boca Raton, FL, pp. 239 258 and Keegan, H.L., 1980.
Scorpions of Medical Importance. University Press of Mississippi,
Background Jackson, MS.
Scorpions are arachnids with two body divisions: the
combined head and thorax, referred to as the prosoma or
cephalothorax, and the abdomen or opisthosoma. They Stockwell, 2002). The venom consists of a mixture of
possess large paired claws or pincers known as pedipalps low-molecular-weight polypeptides. At least two potent
and four pairs of legs. At the caudal portion of the abdo- neurotoxins have been identified: α-scorpion toxin found
men, scorpions have a tail that terminates in the telson—a in Androctonus, Leiurus,and Buthus spp. and β-scorpion
barbed appendage that houses two venom glands that exit toxin found in Centruroides spp. Both toxins can be
via a stinger at the end of the telson. Scorpions are noc- found in the venom of Tityus spp. These venoms block
turnal hunters; they may spend the day in burrows or hid- voltage-sensitive sodium and potassium channels in
ing under rocks or vegetation. They may also hide in nerves (Mullen and Stockwell, 2002).
blankets, shoes, and clothing, which is a common way for
humans to be exposed to them (Keegan, 1980). Toxicity
There are approximately 1400 species of scorpions
occurring on all continents except Antarctica (Goddard, Scorpion stings cause instant, sharp pain at the site of
2003). Most occur in tropical or temperate regions (Lucas envenomation. Some stings will cause localized pain that
and Meier, 1995a). Table 58.1 lists locations and species of resolves over hours. Localized edema and pruritus are
scorpions capable of inflicting life-threatening envenoma- common. Regional lymph nodes may enlarge, and there
tions in humans. The main genera of scorpions found in may be an allergic reaction characterized by swelling of
North America are the bark scorpions (Centruroides spp.). the eyelids, tongue, and vomiting. Sloughing of the skin
They are found primarily in Central America, Mexico, and at the site of envenomation can also occur (Mullen and
the southern through southwest United States (Mullen and Stockwell, 2002). Signs usually resolve within 24 h
Stockwell, 2002). In the United States, only Centruroides (Keegan, 1980). Systemically, signs generally include
exilicauda (Arizona bark scorpion) is considered capable numbness of face, myalgia, tachycardia or bradycardia,
of inflicting a life-threatening sting (Goddard, 2003). respiratory depression, and seizures; however, there is a
lack of evidence that scorpion envenomation in dogs and
cats is a serious concern (Mullen and Stockwell, 2002).
Mechanism of Action
All scorpions can deliver an envenomating sting
(Keegan, 1980). Scorpion venom components vary Treatment
greatly between genera and may even differ based on In most cases, the treatment of scorpion stings consists of
geographic location within species (Mullen and analgesics and local wound care. Systemic signs are