May 1996
BROOKLYN, N.Y. — It's that time of year when people crawl into the attic for boxes of spring clothes, sort through the storage shed for bikes and basketballs, and spend more time outdoors. All of these activities put your patients at risk for spider bites.
"Most spider bites are merely a nuisance; however, some may be dangerous, especially in children," said Audrey Echt, MD, an assistant clinical instructor of dermatology at the State University of New York at Brooklyn.
In the United States, the two major offenders are the black widow and the brown recluse spiders, which come out of hibernation in April.
These spiders can be found in all areas of the country, indoors as well as out, so physicians must have a high index of suspicion.
"They cannot be complacent and say, 'This is New York; we do not have [poisonous] spiders,''' said Teresita A. Laude, MD, director of the division of pediatric dermatology, State University of New York at Brooklyn.
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If a child presents four to five days after being bitten and the lesion is just a papule or a slightly red area with no other symptoms, this is probably a nuisance bite.
On the other hand, if a symptomatic local reaction occurs within 12 hours after the bite, it may be more serious. Normally, the child with a serious spider bite will present with a solitary skin lesion on an exposed part of the body, such as an arm or leg. The local reaction will involve swelling, redness, pain, itching or tingling.
"It may be difficult to say for sure that this [reaction] is from a spider bite," said Laude, who is also an associate professor of pediatrics and dermatology. The diagnosis is presumptive in most instances because there is no laboratory test to confirm it.
"Even if you do a skin biopsy, the changes are not specific. So you must look at the history, the nature of the local reaction, and the presence of systemic signs and symptoms to come up with the diagnosis," she said.
During the examination, physicians should determine whether the child remembers being bitten, whether the child has been in areas where spiders live, and whether the child has ever been bitten before.
"It is important to ask about previous spider bites because the effects of these bites are cumulative," Laude said. "Each recurrence will be worse than the previous one."
The brown recluse spider is 1 mm to 5 mm long and comes in various shades of brown. It has no fur, and its defining characteristic is a violin-shaped mark on the cephalothorax. These spiders like corners and warm, dark places; they are commonly found, for example, inside closets and in storage boxes in the attic or garage.
The brown recluse spider is indigenous in the South Central states (such as Arkansas, Missouri, Kansas and Tennessee), but it can be found anywhere.
The most helpful thing in diagnosing a brown recluse spider bite is the progression of the local reaction. Several hours after the bite, the skin lesion may become painful and pruritic.
"A helpful sign may appear, called the 'flag sign' because it is red, white and blue," Laude explained. The wound is pale in the center, surrounded by a dusky purple and then by an area of erythema.
There is usually an eschar, a dark, almost black crust in the center of the bite, which helps to distinguish this from insect bites.
The brown recluse spider produces an enzyme called sphingomyelinase, which may produce systemic reactions. Because of this toxin, necrosis of the wound is common. Depending on the severity of the envenomization and the location of the bite, the necrosis may be rapid and extensive. For example, if the person is bitten on the thigh, the necrosis may be so severe as to involve the entire thigh. When the bite is in a fleshy, fatty area like the abdomen, thigh, or buttock, necrosis is more common and more rapid. In severe reactions, the necrotic skin may ulcerate.
"It is not a whole body involvement," Laude said. "So this would not be the same as a systemic reaction, like a severe drug eruption, but it may be mistaken for other conditions like ecthyma gangrenosum or an infection with Pseudomonas aeruginosa."
The systemic signs of brown recluse bites are nonspecific. They may include nausea, vomiting, malaise, fever and chills. The most serious systemic reactions, such as severe hemolysis and renal failure, are rare, occurring in fewer than 1% of the patients. "These can be avoided if the bite is caught early," Laude noted.
To identify the black widow spider, the most helpful marking is a red hourglass shape on the abdomen. This spider is about the size of a quarter, and is most common in the Southwest and West Coast regions, although it can be found throughout the United States.
"In black widow spider bites, the lesion is generic looking; it is hard to distinguish from other bites that become secondarily infected," Laude said.
The patient may experience profuse sweating, nausea, vomiting and headache. The young child may present with nothing more than unexplained persistent crying.
The black widow produces a neurotoxic poison. This toxin can lead to severe systemic reactions such as paralysis and even death in rare cases.
Severe systemic signs include pain, cramping and rigidity of muscle groups. If the child was bitten in the lower extremity, he or she may complain of severe abdominal pain. The abdomen may be rigid, and the physician may think this is appendicitis.
"In the presence of a skin lesion, however, a black widow local and systemic reaction is probable," she said.
Sometimes muscles go into spasms, so the black widow bite may be mistaken for tetanus or drug withdrawal.
In treating serious spider bites, the local area must be cleaned, rested, elevated and kept relatively motionless. Cold compresses help to slow the spread of the venom. "It seems that the poison works best if the area is warm," Laude said.
If the local reaction involves a large area, with severe swelling and inflammation, a local injection of steroid may help as an anti-inflammatory. Severe necrosis may require débridement and, in the worst cases, skin grafting.
To alleviate the muscle pain and cramping caused by black widow envenomization, muscle relaxants and systemic drugs, such as morphine, meperidine hydrochloride (Demerol, Sanofi Winthrop) or diazepam (Valium, Roche Products), are used.
An antivenom is available for black widow bites, but the probability of a reaction to the antidote is high.
"Sometimes it can result in death from anaphylactic reaction," Laude cautioned. "This should be used only in the worst cases as a last resort."
Infants, children, the elderly and those with previous bites are at higher risk of severe reactions and should be treated more aggressively. Anyone with an underlying medical problem should be admitted to a hospital, even with a mild local reaction.
"Don't wait for the onset of the systemic symptoms," Laude advised.
In brown recluse bites, the necrotic skin reaction may take six to eight weeks to heal. If there is hemolysis, thrombocytopenia or anemia, the child should be followed until the laboratory results return to normal, which may take weeks depending on the severity of the envenomization.
Even the mild to moderate systemic symptoms of black widow spider bites may last two to three weeks; the child must be followed until all symptoms disappear.
Laude pointed out that the best treatment is prevention. All pediatricians must educate parents to keep their children away from places where there might be spiders — closets, attics, basements, storage sheds. If they remove clothes or shoes from storage, they must carefully check for spiders.
"These spiders are shy; they are not aggressive," Laude said. "They usually bite when they are trapped."
Doctors also should find out about the dangerous spiders in their region. These two spiders have many relatives; for example, there are red and brown widow spiders. Physicians can call their state department of epidemiology and the poison control center for more information.
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