Bites and stings

Definition

Humans can be injured by the bites or stings of many kinds of insects and animals. These range from the bites from a neighbor's dog or cat to bites from fellow humans and spiders to the stings from bees, wasps, snakes, and marine animals such as jellyfish and stingrays.

Description

Mammals

DOGS With more than 60 million pet dogs in the United States, plus thousands of strays, it is not surprising that an estimated 4.7 million Americans a year are bitten by a dog. Although most dog-bite injuries are minor, about 400,000 children seek medical attention for a dog bite every year, according to the Centers for Disease Control and Prevention. Of those injured, about 386,000 require emergency treatment and about a dozen die from their injuries. However, most of the injuries suffered by children seeking treatment in emergency rooms are of low severity and result in treatment and quick release from the hospital.

Children aged five to nine are most likely to be injured by dog bites. Males are more likely than females to require emergency treatment. About two-thirds of injuries to children aged four years or younger are to the head and neck.

Studies also show that most dog bites are from pets or other dogs known to the child who is bitten. In fact, more than half of the bites seen by emergency departments occur at home. Many of the bites result from attempting to break up fights between animals.

CATS Although cats are found in nearly one third of U.S. households, cat bites are far less common than dog bites. According to one study, cats inflict perhaps 400,000 harmful bites in the United States each year. The tissue damage caused by cat bites is usually limited but carries a high risk of infection. Whereas the infection rate for dog bite injuries is 15 to 20 percent, the infection rate for cat bites is 30 to 40 percent. Cat bites are also more likely to be provoked. A typical person who has been bitten is a young girl playing with a pet.

HUMANS Bites from mammals other than dogs and cats are uncommon, with one exception—human bites. There are approximately 70,000 human bites each year in the United States. Because the human mouth contains a multitude of potentially harmful microorganisms, human bites are more infectious than those of most other mammals.

Arthropods

Arthropods are invertebrates belonging to the phylum Arthropoda , the jointed-leg, spineless creatures of the world. Arthropoda include insects, arachnids (spiders), crustaceans, and other subgroups. There are more than 700,000 species in all. The list of arthropods that bite or sting humans is extensive and includes lice, bedbugs, fleas, mosquitoes, black flies, ants, chiggers, ticks, centipedes, scorpions, and other species. Spiders, ants, bees, and wasps are the four kinds of arthropod that most often bite people.

SPIDERS In the United States, only two kinds of venomous spider are truly dangerous: black widow spiders and brown recluse (violin or fiddle) spiders. The black widow, which is found in every state but Alaska, prefers dark, dry places, such as barns, garages, and outhouses, and also lives under rocks and logs. Disturbing a female black widow or its web may provoke a bite. Brown recluse spiders also prefer sheltered places, including clothing, and may bite if disturbed.

ANTS, BEES, AND WASPS Ants, bees, and wasps will sting to defend their nests or if they are disturbed. Ants sting more than 9.3 million people each year. Other hymenoptera account for more than 1 million stings annually. Species common to the United States include fire ants, honeybees, bumblebees, yellow jackets, bald-faced hornets, brown hornets, and paper wasps. The Africanized bee species, also called "killer bees," is as of 2004 found in the United States.

More than 50 Americans die each year after being stung by a bee or wasp. Almost all of those deaths are the result of allergic reactions to the sting and not of exposure to the venom itself.

Snakes

There are 20 species of venomous snakes in the United States. These snakes are found in every state except Maine, Alaska, and Hawaii. Each year about 8,000 Americans receive a venomous snakebite, but no more than about 15 die, mostly from rattlesnake bites.

The venomous snakes of the United States are divided into two families: the Crotalidae (pit vipers) and the Elapidae. Pit vipers, named after the small heat-sensing pit that lies between each eye and nostril, are responsible for about 99 percent of the venomous snakebites suffered by Americans. Rattlesnakes, copperheads, and cottonmouths (also called water moccasins) are pit vipers. This family of snakes delivers its venom through two long, hinged fangs in the upper jaw. Some pit vipers carry potent venom that can threaten the brain and spinal cord. The venom of others, such as the copperhead, is less harmful.

The Elapidae family includes two kinds of venomous coral snakes indigenous to the southern and western states. Because coral snakes are creatures that come out only at night, they almost never bite humans; they are held responsible for approximately 25 bites a year in the United States. Coral snakes also have short fangs and a small mouth, which lowers the risk of a bite actually forcing venom into the human body. However, their venom is highly poisonous.

Marine animals

Several varieties of marine animal may bite or sting. Jellyfish and stingrays are two kinds that pose a threat to people who live or vacation in coastal communities.

Causes and symptoms

Mammals

DOGS A typical dog bite results in a laceration, tear, puncture, or crush injury. Bites from large, powerful dogs may even cause fractures and dangerous internal injuries. Also, dogs trained to attack may bite repeatedly during a single episode. Infected bites usually cause pain , inflammation of the connective tissues, and a pusfilled discharge at the wound site within eight to 24 hours. Most infections are confined to the wound site, but many of the microorganisms in the mouths of dogs can cause systemic and possibly life-threatening infections. Examples are bacteremia and meningitis , especially severe in children with health conditions that increase their susceptibility to infection. Rabies is rare among pet dogs in the United States, most of which have been vaccinated against the disease. Tetanus is also rare but can be transmitted by a dog bite if the victim is not immunized.

CATS The mouths of cats and dogs contain many of the same microorganisms. Cat scratches and bites are also capable of transmitting the Bartonella henselae bacterium, which can lead to cat-scratch disease , an unpleasant but usually not life-threatening illness.

Cat bites are mostly found on the arms and hands. Sharp cat teeth typically leave behind a deep puncture wound that can reach muscles, tendons, and bones, which are vulnerable to infection because of their comparatively poor blood supply. This is why cat bites are much more likely to become infected than dog bites. Also, people are less inclined to view cat bites as dangerous enough to require immediate attention. The risk that infection has set in by the time a medical professional is consulted is, therefore, greater.

HUMANS Humans bites result from fights, sexual activity, medical and dental treatment, and seizures. Bites also may be sign of child abuse . Children often bite other children, but those bites are hardly ever severe. Human bites are capable of transmitting a wide range of dangerous diseases, including hepatitis B , syphilis, and tuberculosis .

Human bites fall into two categories: occlusional bites and clenched-fist injuries. Occlusional bites result from an actual bite and present a lower risk of infection. The clenched-fist injury happens when a fist hits a mouth during a fight and may lead to an infected hand.

Arthropods

SPIDERS As a rule, children rarely see a black widow bite them, nor do they feel the bite when it happens. The first (and possibly only) evidence that a child has been bitten may be a mild swelling of the injured area and two red puncture marks. Within a short time, however, some victims begin to experience severe muscle cramps and rigidity of the abdominal muscles. Other possible symptoms include excessive sweating, nausea , vomiting , headaches, and vertigo, as well as breathing, vision, and speech problems.

A brown recluse spider's bite can lead to necrotic arachnidism, in which the tissue in an area of up to several inches around the bite becomes necrotic (dies), producing an open sore that can take months or years to disappear. In most cases, however, the bite simply produces a hard, painful, itchy, and discolored area that heals without treatment in two to three days. The bite may also be accompanied by fever , chills, edema (an accumulation of excess tissue fluid), nausea and vomiting , dizziness , muscle and joint pain, and a rash.

BEES, WASPS AND ANTS The familiar symptoms of bee, wasp, and ant stings include pain, redness, swelling, and itchiness in the area of the sting. Multiple stings can have much more severe consequences, such as anaphylaxis , a life-threatening allergic reaction that occurs in children who are hypersensitive to the venom.

The fire ant sting usually produces immediate pain followed by a red, swollen area that disappears within 45 minutes. A blister or a red, swollen, itchy patch then develops. The blister may rupture and become infected.

Snakes

Venomous pit viper bites usually begin to swell within ten minutes and sometimes are painful. Other symptoms include skin blisters and discoloration, weakness, sweating, nausea, faintness, dizziness, bruising, and tender lymph nodes. Severe poisoning can also lead to tingling in the scalp, fingers, and toes, muscle contractions, an elevated heart rate, rapid breathing, large drops in body temperature and blood pressure, vomiting of blood, and coma.

Many pit viper and coral snake bites (20%) fail to poison their victim or introduce only a small amount of venom into the victim's body. The wounds , however, can still become infected by the harmful microorganisms that snakes carry in their mouths.

Coral snake bites are painful but may be hard to see. One to seven hours after the bite, the victim begins to experience the effects of the venom, which include tingling at the wound site, weakness, nausea, vomiting, excessive salivation, and irrational behavior. Major nerves of the body can become paralyzed for six to 14 days, causing double vision, difficulty swallowing and speaking, respiratory failure, and other problems. Six to eight weeks may be needed before normal muscular strength is regained.

Marine animals

JELLYFISH Jellyfish venom is delivered by barbs called nematocysts, which are located on the creature's tentacles and penetrate the skin of people who brush up against them. Instantly painful and itchy red lesions usually result. The pain can continue up to 48 hours. Severe cases may lead to skin necrosis, muscle spasms and cramps , vomiting, nausea, diarrhea , headaches, excessive sweating, and other symptoms. In rare instances, cardiorespiratory (heart/lung) failure may also occur.

STINGRAYS Tail spines are the delivery mechanism for stingray venom. Deep puncture wounds result that can cause an infection if pieces of spine become embedded in the wound. A typical stingray injury scenario involves a person who inadvertently steps on a resting stingray and is lashed in the ankle by its tail. Stingray venom produces immediate, excruciating pain that lasts several hours. Sometimes the victim suffers a severe reaction, including vomiting, diarrhea, hemorrhage (bleeding), a drop in blood pressure, and cardiac arrhythmia (disordered heart beat).

Diagnosis

Mammals

DOGS Gathering information on the circumstances of a dog attack is a crucial part of treatment. Medical professionals need to know:

• when the attack occurred (The chances of infection increase dramatically if the wound has been left untreated for more than eight hours.)
• what led to the attack (Unprovoked attacks are more likely to be associated with rabies.)
• the child's general health, including tetanus immunization history and information about allergies to medication and pre-existing health problems that may increase the risk of infection

A physical examination requires careful scrutiny of the wound, with special attention to possible bone, joint, ligament, muscle, tendon, nerve, or blood-vessel damage caused by deep punctures or severe crush injuries. Serious hand injuries should be evaluated by a specialized surgeon. Most of the time, laboratory tests for identifying the microorganisms in bite wounds are performed if infection is present. X rays and other diagnostic procedures may also be necessary.

CATS The diagnostic procedures used for dog bites also apply to cat bites.

HUMAN Testing the blood of a person who has been bitten for immunity to hepatitis B and other diseases is always necessary after a human bite. Ideally, the biter should be tested as well for the presence of transmissible disease. Physicians can advise if this is necessary if the biter is another small child. Medical professionals will also look for indications of child abuse when evaluating human bites.

Arthropods

SPIDERS Because bites from widow spiders and brown spiders require different treatment, capturing and identifying the spider helps to establish diagnosis.

Snakes

Diagnosis relies on a physical examination of the victim, information about the circumstances of the bite, and a look at the snake itself (if it can safely be killed and brought in for identification). Blood tests and urinalysis supply important data on the victim's condition. Chest x rays and electrocardiography (a procedure for measuring heart activity) may also be necessary.

Treatment

Mammals

DOGS Minor dog bites can be treated at home. The American Academy of Family Physicians recommends gently washing the wound with soap and water and then applying pressure to the injured area with a clean towel to stop the bleeding. The next step is to apply antibiotic ointment and a sterile bandage to the wound. To reduce swelling and fend off infection, ice should be applied and the injured area kept elevated above the level of the heart. The wound should be cleaned and covered with ointment twice a day until it heals.

Any dog bite that does not stop bleeding after 15 minutes of pressure must be seen by a medical professional. The same is true for bites that are deep or gaping; for bites to the head, hands, or feet; and for bites that may have broken a bone, damaged nerves, or caused a major injury of another kind. Bite victims must also watch for infection. A fever is a sign of infection, as are redness, swelling, warmth, increased tenderness, and pus at the wound site. Children with diabetes or cancer who have not had a tetanus shot in five years or who have a medical problem that can increase susceptibility to infection should seek medical treatment no matter how minor the bite appears.

Medical treatment of dog bites involves washing the wound with an anti-infective solution. Removal of dead and damaged tissue (under local, regional, or general anesthetic) may be required after the wound has been washed, and any child whose tetanus shots are not up-to-date should receive a booster injection. Some wounds are left open and allowed to heal on their own, while others require stitches (stitching may be delayed a few days if infection is a concern). Many emergency departments prescribe antibiotics for all people with dog bites, but some researchers suggest that antibiotics are usually unnecessary and should be limited to those whose injuries or other health problems make them likely candidates for infection. A follow-up visit after one or two days is generally required for anyone who has received bite treatment.

CATS Because of the high risk of infection, parents of children who are bitten by a cat should always call the child's doctor. Most cat scratches do not require professional medical treatment unless the wound appears infected or the scratched person has a weakened immune system.

Medical treatment for cat bites generally follows the procedures used for dog bites. Experts advise, however, that cat-bite wounds should always be left open to prevent infection. Persons who have been bitten by cats generally receive antibiotics as a preventive measure.

HUMANS Human bites should always be examined by a doctor. Such bites are usually treated with antibiotics and left open because of the high risk of infection. A person who has been bitten may also require immunization against hepatitis B and other diseases. This is usually not necessary if the biter is a child.

Arthropods

SPIDERS No spider bite should be ignored. The antidote for severe widow spider bites is a substance called antivenin, which contains antibodies taken from the blood serum of horses injected with spider venom. Doctors exercise caution in using antivenin, however, because it can trigger anaphylactic shock, a potentially deadly (though treatable) allergic reaction, and serum sickness, an inflammatory response that can give rise to joint pain, a fever, rashes , and other unpleasant, though rarely serious, consequences.

An antivenin for brown spider bites exists as well, but it is not readily available in the United States. The drug dapsone, used to treat leprosy, can sometimes stop the tissue death associated with a brown spider bite. Necrotic areas (areas of dead tissue) may need debridement (removal of dead and damaged tissue) and skin grafts. Pain medications, antihistamines , antibiotics, and tetanus shots are a few of the other treatments that are sometimes necessary after a bite from a brown spider or widow spider.

BEES, WASPS, AND ANTS Most stings can be treated at home. A stinger that is stuck in the skin can be scraped off with a blade, fingernail, credit card, or piece of paper (using tweezers may push more venom out of the venom sac and into the wound). The area should be cleaned and covered with an ice pack. Aspirin and other pain medications, oral antihistamines, and calamine lotion are good for treating minor symptoms. Putting meat tenderizer on the wound has no effect.

Persons who have been stung and experience an allergic reaction or who are at risk due to their medical history require immediate medical attention. The danger signs, which usually begin ten minutes after an individual is stung (though possibly not for several hours) include nausea, faintness, chest pain, abdominal cramps, diarrhea, and difficulty swallowing or breathing.

Snakes

Although most snakes are not venomous, any snakebite should immediately be examined at a hospital. While waiting for emergency help to arrive, the victim should wash the wound site with soap and water and then keep the injured area still and at a level lower than the heart. Ice should never be used on the wound site nor should attempts be made to suck out the venom. Making a cut at the wound site is also dangerous. It is important to stay calm and wait for emergency medical aid if it can arrive quickly. Otherwise, the child should proceed directly to a hospital.

When the child arrives at a hospital, the medical staff must determine whether the bite was inflicted by a venomous snake and, if so, whether envenomation (venom is injected into the victim) occurred and how much venom the person has received. Patients may develop low blood pressure, abnormal blood clotting, or severe pain, all of which require aggressive treatment. Fortunately, the effects of some snake bites can be counteracted with antivenin. Minor rattlesnake envenomations can be successfully treated without antivenin, as can copperhead and watermoccasin bites. However, coral snake envenomations and the more dangerous rattlesnake envenomations require antivenin, sometimes in large amounts. Other treatment measures include antibiotics to prevent infection and a tetanus booster injection.

Marine animals

JELLYFISH Vinegar and other acidic substances are used to neutralize jellyfish nematocysts still clinging to the skin, which are then scraped off. Anesthetic ointments, antihistamine creams, and steroid lotions applied to the skin are sometimes beneficial. Other measures may be necessary to counter the many harmful effects of jellyfish stings, which, if severe, require emergency medical care.

STINGRAYS Stingray wounds should be washed with saltwater and then soaked in very hot water for 30 to 90 minutes to neutralize the venom. Afterwards, the wound should be examined by a doctor to ensure that no pieces of spine remain.

Prognosis

Mammals

Prompt treatment and recognizing that even apparently minor bites can have serious consequences are the keys to a good outcome after a mammal bite. Infected bites can be fatal if neglected. Surgery and hospitalization may be needed for severe bites.

Arthropods

SPIDERS Even without treatment, most children recover from black widow bites after two to three days. In the case of brown spider bites, the risk of death is greatest for children, though rare.

BEES, WASPS, AND ANTS The pain and other symptoms of a bee or wasp sting normally fade away after a few hours. Children who are allergic to such stings, however, can experience severe and occasionally fatal anaphylaxis (life-threatening allergic reaction to bites and stings).

Snakes

A snakebite victim's chances of survival are excellent if medical aid is obtained in time. Some bites, however, can result in amputation, permanent deformity, or loss of function in the injured area, although this is rare.

Marine animals

STINGRAYS Stingray venom kills its human victims on rare occasions.

Prevention

Mammals

DOGS The risk of a dog-bite injury can be reduced by avoiding sick or stray dogs, staying away from dogfights (children can get bitten when they try to separate the animals), and not behaving in ways that might provoke or upset dogs, such as wrestling with them or bothering them while they are sleeping, eating, or looking after their puppies. Infants and young children must never be left alone with a dog. Pit bulls, rottweilers, and German shepherds (responsible for nearly half of all fatal dog attacks in the United States in 2000) are potentially dangerous pets in households where children live or visit. For all breeds of dog, obedience training as well as spaying or neutering lessen the chances of aggressive behavior .

CATS Prevention involves warning children to stay away from strange cats and to avoid rough play and other behavior that can anger cats and cause them to bite.

Arthropods

SPIDERS Common-sense precautions include clearing webs out of garages, out buildings, and other places favored by venomous spiders; teaching children to keep their hands away from places where spiders may be lurking; and, when camping or vacationing, checking clothing, shoes, and sleeping areas.

BEES, WASPS, AND ANTS Children should avoid the nests of bees, wasps, and ants. When playing outside in an area where these insects are found, children also should avoid eating sweet food or wearing bright clothing, perfumes, or cosmetics that attract bees, wasps, and ants.

Emergency medical kits containing self-administrable epinephrine to counter anaphylactic shock are

available for allergic children and should be carried by them at all times. Children who are suspected of being allergic should consult an allergist about shots that can reduce reactions to bee and wasp venom (venom immunotherapy). Venom immunotherapy in children leads to a significantly lower risk of reaction to stings up to ten to 20 years after treatment is stopped.

Snakes

Snakes should not be kept as pets. Measures such as mowing the lawn, keeping hedges trimmed, and removing brush from the yard also discourages snakes from living close to human dwellings. Tongs should be used to move brush, lumber, and firewood, to avoid exposing one's hands to snakes that might be lying underneath. Children should be prevented from playing in weedy, vacant lots and other places where snakes may live. Leather boots and long pants offer hikers and campers some protection from bites. Approaching a snake, even a dead one, can be dangerous since the venom of recently killed snakes may still be active.

Marine animals

JELLYFISH Prevention of jellyfish stings includes obeying posted warning signs at the beach. Also, jellyfish tentacles may be transparent and up to 120 feet (36.5 m) long; therefore, great caution must be exercised whenever a jellyfish is sighted nearby.

STINGRAYS Kicking the sand while walking through shallow areas that may be inhabited by stingrays will disturb the water, causing the animal to move before it can be stepped on.

Parental concerns

Children frequently play in areas where they can be exposed to stings and bites. Children who are sensitive to certain stings and bites are at risk for serious anaphylactic reactions.

See also Insect sting allergy .

Resources

BOOKS

Holve, Steve. "Envenomations." In Cecil Textbook of Medicine , 21st ed. Edited by Lee Goldman and J. Claude Bennett. Philadelphia: W.B. Saunders, 2000, pp. 2174–78.

"Overview of the 2002 Household Pet Survey." In U.S. Pet Ownership and Demographics Sourcebook . Schaumburg, IL: American Veterinary Medical Association, 2002.

Nagami, Pamela. Bitten: True Medical Stories of Bites and Stings. London: St. Martin's Press, 2004.

Royston, Angela. Stings and Bites. Oxford, UK: Heinemann Library, 2004.

Siverstein, Alvin, et al. Bites and Stings. Danbury, CT: Scholastic Library Publishing, 2002.

PERIODICALS

Graudins, A., et al. "Red-back spider (Latrodectus hasselti) antivenom prevents the toxicity of widow spider venoms." Annals of Emergency Medicine 37 (2001): 154–60.

Jarvis, R. M., et al. "Brown recluse spider bite to the eyelid." Ophthalmology 107 (2000): 1492–96.

Metry, D. W., and A. A. Hebert. "Insect and arachnid stings, bites, infestations, and repellents." Pediatric Annals 29 (2000): 39–48.

Sams, H. H. "Nineteen documented cases of Loxosceles reclusa envenomation." Journal of the American Academy of Dermatology 44 (2001): 603–08.

Sams, H. H., et al. "Necrotic arachnidism." Journal of the American Academy of Dermatology 44 (2001): 561–73.

ORGANIZATIONS

American Academy of Emergency Medicine. 611 East Wells Street, Milwaukee, WI 53202. Web site: http://www.aaem.org.

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211–2672. Web site: http://www.aafp.org.

American Medical Association. 515 N. State Street, Chicago, IL 60610. Web site: http://www.ama-assn.org.

Christine Kuehn Kelly