Almost all spiders produce toxic venoms, but their fangs are too small and weak to penetrate the skin, the venom is too weak, of the volume of venom is too small to pose a significant threat for humans. The black widow (Latrodectus mactans) is the only spider found in the United States that is capable of routinely producing serious illness by its bite. The "tarantula" native to the U.S. Southwest bites only after extreme provocation. Its weak and ineffective fangs can only penetrate thin skin, such as that on the sides of the fingers; the effects of the bite are no worse than an insect sting.
In other parts of the world are spiders that can cause severe, even fatal poisoning in humans. Other species of Latrodectus produce effects similar to the black widow. The bites of large, hairy tarantulas found in areas such as Brazil or Peru can have similar results. The Sydney funnel web spider, reportedly limited in distribution to the area within 100 miles of Sydney, Australia, is capable of inflicting a bite that can be lethal for healthy young adults.
Some spiders, such as the brown, or violin, spider (Loxoseeles recluse) inflict bites that occasionally cause extensive damage at the site, but usually have less severe generalized effects. The jumping spider (Phidippus) is the most common biting spider in the United States. Bites by this spider, trapdoor spiders, orbweavers, and spiders of the Chiracanthium species, such as the garden spider, commonly produce local reactions that ulcerate and less often produce systemic symptoms. However, individuals with these bites almost never require hospitalization. Spiders usually cling to the site of the bite. (If the spider can not be found, some other arachnid, such as a bedbug, should be suspected.) Anyone who has been bitten should take the spider to be identified.
Rarely, an individual may be bitten repeatedly by a relatively harmless spider or insect and develop an allergy to the toxin produced by that species. Subsequent bites can produce severe, even fatal allergic reactions. Fortunately such events are rare. The treatment for such reactions is identical to the treatment for allergic reactions to Insect stings.
The female black widow typically is coal black and has a prominent, spherical abdomen that may be as large as one-half inch (1.25 cm) in diameter. This appearance is so distinctive that finding the characteristic markings on the undersurface of the abdomen is rarely necessary. The typical markings consist of red or orange figures that usually resemble an hourglass, but may be round, broken into two figures, or have some other configuration. Markings of the same color but in varying patterns are sometimes present on the back, although only the undersurface markings are considered characteristic. In some southwestern states black widow spiders have irregular white patches on their abdomens. Different species of Latrodectus in other countries have a similar appearance. (fbe mate is smaller, has a brown color, and is harmless.)
The black widow weaves a coarse, crudely constructed web in dark corners, both indoors and out. Almost half the black widow bites reported in the medical literature in the first four decades of this century were inflicted on the male genitalia by spiders On the underside of outdoor toilet seats. However, this spider is timid and would rather run than attack an intruder.
Thirty to forty years ago five to ten deaths a year resulted from black widow spider bites, although they were limited almost entirely to small children or elderly individuals in poor health. Recognition and treatment of such bites has improved so much that deaths are rare within the United States. (Bites in children weighing thirty pounds or less would still have a mortality of about fifty percent if untreated.) In healthy adults, black widow spider bites cause painful muscle spasms and prostration for two to four days, but complete recovery essentially always follows. Antivenin treatment is not recommended for adults.
The bite may feel like a pin prick, may produce a mild burning, or may not be noticed at all. Small puncture wounds, slight redness, or no visible marks may be found at the site of the bite. Within about fifteen minutes painful muscle cramps develop at the point of the bite and rapidly spread to involve the entire body. The characteristic pattern of spread is by continuity. From a bite on the forearm the cramps would spread to the upper arm, to the shoulder, and over the chest to involve the rest of the body, including the legs. The abdominal muscles are characteristically rigid and hard, although the abdomen is not tender. Weakness and tremors are also present.
A typical subject is anxious and restless. A feeble pulse and cold, clammy skin suggest shock; labored breathing, slurred speech, impaired coordination, mild stupor, and rare convulsions (in children) suggest disease involving the brain, Bitten individuals are often covered with perspiration; dizziness, nausea, and vomiting are common. If the spider or its bite have not been observed, the signs and symptoms may lead to an erroneous diagnosis of an acute abdominal emergency.
Symptoms typically increase in severity for several hours, occasionally as long as twenty-four hours, and then gradually subside. After two or three days essentially all symptoms disappear, although a few minor residua may persist for weeks or months.
Treatment consists of efforts to relieve the painful muscle spasms and antivenin for small children. No treatment at all should be directed to the site of the bite, with the possible exception of applying an ice cube to relieve pain. Incision and suction is damaging and useless and should not be performed.
Essentially nothing can be done outside a hospital; small children must be hospitalized. Antivenin, produced in the United States by Merck Sharp & Dohme, and the drugs to control spasms are rarely available anywhere else. The antivenin is prepared in horses and should not be given to persons allergic to horse serum. It is usually not administered to healthy adults between the ages of sixteen and sixty, and only to individuals of small body size with severe symptoms who are twelve to fifteen years old. Instructions with the vial of antiserum should be followed.
Muscle spasms may be relieved by periodic injections of 10 cc of a ten percent calcium gluconate solution or 10 cc of methocarbamol, but these are rarely available outside a hospital. A tranquilizer (diazepam) may help relieve less severe muscle spasms; hot baths are occasionally helpful. Strong analgesics are helpful but rarely provide complete pain relief.
The brown, or violin, spider (Loxosceles recluse) more recently labeled the "brown recluse spider," has received attention as the cause of "necrotic arachnidism." Following the bite of this spider, a blister appears, and is surrounded by an area of intense inflammation about one-half inch (1.25 cm) in diameter. Pain is mild at first but may become quite severe within about eight hours. Over the next ten to fourteen days the blister ruptures and the involved skin turns dark brown or black. Eventually the dead, black tissue drops away, leaving a crater that heals with scarring.
A few individuals have large skin losses that require grafts to cover the defect. Some children have lost considerable portions of the face. Such events have attracted great notoriety for this spider, even though much smaller wounds are far more typical. Bites are attributed to Loxosceles recluse (incorrectly) well outside of its habitat, which is limited to the southeastern and south-central portion of the United States and ends at the Texas-New Mexico border.
Generalized symptoms that may appear within thirty-six hours of the bite include chills and fever, nausea and vomiting, joint pain, and a skin rash or hives. With severe reactions, red blood cells are broken down (hemolysis) and platelets are destroyed (thrombocytopenia), which can result in a significant anemia and bleeding tendency. Rare fatalities have occurred, mostly in children.
Essentially nothing can be done for such bites in a wilderness situation unless appropriate injectable medications are carried along. If the person can be hospitalized within less than eight hours, the site of the bite can be surgically excised. Such therapy should be reserved for bites from spiders clearly identifiable as L. recluse, so the spider must be captured (intact if possible) and brought to the hospital to be identified. After eight hours the area involved may be too large to be excised. Corticosteroids may also be administered. One recommended program is 4 mg of dexamethasone, administered intramuscularly every six hours until the reaction starts to subside, and then in tapered doses. Others include injection of hydrocortisone beneath the bite and the administration of dapsone. Nothing is very satisfactory.
Scorpions are found throughout most of the United States, but the species lethal for man, Centruroides, are limited to Arizona, New Mexico, Texas, southern California, and northern Mexico. In these areas scorpions are a significant problem. Sixty-nine deaths resulted from scorpion stings in Arizona between 1929 and 1954. During the same period, only twenty deaths resulted from poisonous snake bites. With improved medical management of the complications of scorpion stings, no deaths have occurred in Arizona for twenty years.
Scorpions are eight-legged arachnids that range in length from three to eight inches (7.5 to 20 cm) and have a rather plump body, thin tail, and large pinchers. They are found in dry climates under rocks and logs, buried in the sand, in accumulations of lumber, bricks, or brush, and in the attics, walls, or understructures of houses or deserted buildings, The problems with scorpions in Arizona are clearly related to their tendency to live in the vicinity of human habitation where children are frequently playing.
Stings can be avoided by exercising care when picking up stones, logs, or similar objects under which scorpions hide during the day. Since scorpions are nocturnal, walking barefoot after dark is inadvisable. Shoes and clothing should be shaken vigorously before dressing in the morning, particularly when camping outdoors.
The lethal species of scorpions are often found under loose bark or around old tree stumps. They have a yellow to greenish yellow color and can be distinguished from other species by a small, knoblike projection at the base of their stingers. Adults measure three inches (7.5 cm) in length and three-eighths inch (I cm) in width. One subspecies has two irregular dark stripes down its back.
The sting of a nonlethal scorpion has been described as similar to that of a wasp or hornet, although usually somewhat more severe, and should be treated in an identical manner. (Scorpion venom is not identical to insect venom, and individuals allergic to insect stings usually are not allergic to scorpion stings.) Lethal scorpion stings are more painful, but fatalities have been limited almost entirely to small children.
Initially the sting of a scorpion of one of the lethal species produces only a pricking sensation and may not be noticed. Nothing can be seen at the site of the sting. (Swelling and red or purple discoloration are indications that the sting has been inflicted by a nonlethal species.) Pain follows in five to sixty minutes and may be quite severe. The sting site is quite sensitive to touch and is the last part of the body to recover. Tapping the site produces a painful tingling or burning sensation that travels up the extremity toward the body. (Apparently stings by other species of scorpions can occasionally produce a similar sensation.) Sensitivity may persistas long as ten days, although other symptoms usually disappear within ten hours.
Individuals who have been stung typically are extremely restless and jittery. Young children writhe, jerk, or flail about in a bizarre manner that suggests a convulsion. Their movements are completely involuntary. However, in spite of their constantly moving bodies, the children can talk. Although they appear to be writhing in pain, they usually state that they do not hurt. Convulsions have been described, but the true nature of these events is questionable. Visual disturbances such as roving eye movements or a fluttering type of movement known as nystagmus are common. Occasionally a child complains that he can not see, but nothing abnormal can be found when examining his eyes, and sight returns spontaneously in a few minutes. Children under six years of age may develop respiratory problems such as wheezing and stridor, and a few may need assisted respiration.
Persons who have been stung typically have an elevated blood pressure, which may be an important diagnostic sign since hypertension is rare in children. The blood pressure usually returns to normal within four to six hours and becomes life-threatening only in infants.
Elderly individuals with preexisting health problems and small children stung by one of the lethal scorpion species should be taken to a hospital. Only a medical facility of that sophistication has the equipment and supplies necessary to monitor these individuals and deal with any complications that may arise. An ice cube applied to the site of the sting may help reduce pain, but no other therapy is possible outside a hospital. In locations such as the Grand Canyon, where prompt evacuation is not possible, diazepam can be given to children for control of the involuntary movements.
Other countries have species of lethal scorpions much more deadly than those in the Southwestern United States. Mexico reportedly has had as many as 76,000 scorpion stings resulting in 1,500 deaths in a single year. The stings of such scorpions must be treated with antivenin, which is rarely obtainable outside a hospital, particularly by someone who does not speak the country's language. Death from the stings of such scorpions is usually the result of sudden, very severe high blood pressure. Adrenergic blocking agents such as propranolol may be an effective method for treating such stings and probably should be carried by visitors to the countries where such lethal species of scorpions exist.
Between fifty and one hundred deaths result annually from allergic reactions to Hymenoptera stings (bees, wasps, hornets, and fire ants) in the United States, more than the deaths from rabies, poisonous snakes, spiders, and scorpions combined. Approximately one of every two hundred people in the United States has experienced a severe reaction to such stings. Potentially fatal reactions can be prevented or successfully treated in individuals known to have such allergies, but many deaths still occur in persons whose allergic status had not been previously recognized. The problem of allergies and the severe, potentially lethal allergic reactions known as "anaphylactic shock" are discussed in Chapter Twenty, "Allergies."
An individual allergic to insect stings usually experiences milder allergic reactions before having a potentially fatal reaction. Two types of nonlethal reactions occur: local reactions and systemic reactions.
Local reactions are characterized b severe swelling limited to the limb or portion of the limb that is the site of the insect sting. Almost all insect stings are associated with some swelling, but the area of swelling is usually three inches (7.5 cm) or less in diameter. With severe local reactions, a major portion of an extremity, such as the entire forearm, is swollen, and may be painful, associated with itching, or mildly discolored.
Systemic reactions occur in areas of the body some distance from the site of the Sting. Most typical are hives, which may be scattered over much of the body. Generalized itching or reddening of the skin may also occur. Persons with more severe reactions may have hypotension (low blood pressure) and difficulty breathing. (Clearly, the last two reactions could be fatal if severe.)
Investigators of insect hypersensitivity reactions have recommended that individuals who have had a systemic reaction to an insect sting undergo skin testing with Hymenoptera venoms. (If the results of skin tests are inconclusive, more sophisticated measurement of venom-specific IgE antibodies by the radioallergosorbent procedure can be carried out.) About half of the people who have had a systemic reaction and also have a positive skin test would be expected to have a severe, possibly fatal reaction if stung again. Desensitization with purified insect venoms-not whole-body extracts-is recommend for these individuals. (In one recent study of children who had experienced an anaphylactic reaction following a sting, only nine percent of subsequent accidental stings led to severe reactions. None of the reactions were more severe than the original reactions, which led to the conclusion that immunotherapy was unnecessary for such individuals.)
Desensitization can be a drawn-out, uncomfortable procedure but also can be life-saving. Starting with very small quantities, increasingly larger amounts of the insect venoms are injected subcutaneously until the allergic reaction is "neutralized." The individual is still allergic to the Hymenoptera venoms, but the antibod'ble for producing the allergic reactions are "used up" by the repeated les response I injections of the material with which they react. Generally, even after successful desensitization, injections must be continued at approximately monthly intervals for years or indefinitely. If the desensitization injections are stopped, the former allergic condition often reappears.
Desensitization must be carried out under the close supervision of a physician experienced with the procedure. Severe, life-threatening allergic reactions to the desensitization injections may occur, and a physician must be on hand to deal with them. However, a physician who is standing by watching for a reaction can treat it effectively. Allergic reactions to insect stings in a wilderness environment without a physician in attendance are a far greater threat.
Desensitization, or even skin testing, is not recommended for individuals who have large local reactions because these are rarely followed by systemic reactions. However, carrying epinephrine (adrenaline) is recommended for individuals who have had either type of reaction.
For individuals experiencing an anaphylactic reaction, 0.3 cc of a 1:1,000 solution of epinephrine should be injected subcutaneously as soon as symptoms are detected. Second (and sometimes third) injections are often needed at intervals of twelve to fifteen minutes.
Rock climbers and some other wilderness users who have systemic allergic reactions to insect stings have a unique risk of fatal reactions because they are subject to stings in locations, such as rock walls, where they can not be immediately treated by others and only with difficulty by themselves. Such persons should seriously consider desensitization now that purified venom preparations, which make that procedure so much more reliable, are available. They also must be prepared to treat an anaphylactic reaction at any time.