Bites are wounds caused by the teeth of a wild or domestic animal or human. In addition to mammals, many insects, spiders, marine animals, and reptiles can bite or sting humans. A person's reaction to a bite or sting depends on the type of wound; whether venom is injected during the bite; whether the person is allergic to the venom; and whether the biting animal is carrying a disease-causing agent.
Animal bites can range from mild to life threatening. When the skin is not broken, bites usually are not dangerous. Bites can be very serious, however, if the skin, muscles, or tendons are torn; bones are crushed; a deep hole (puncture) is made; the animal injects venom into the wound; or the wound becomes infected by germs in the animal's saliva.
Between 80 and 90 percent of all bite wounds that receive emergency room medical treatment in the United States are caused by dogs, about 316,000 in an average year. Of these, about 1 percent are serious enough to require hospitalization. Cats are responsible for 5 to 15 percent of all bites. About 6 percent of cat bites require hospitalization. Other reported bites are caused by such animals as rats, mice, bats, raccoons, rabbits, ferrets, snakes, farm animals, and zoo animals, and vary in severity. Children between the ages of 5 and 14 are the most likely to be bitten, and very young children are the most likely to die from a bite. Between 20 and 35 people die of dog bites each year in the United States. In developing countries where rabies * is poorly controlled, the death rate from dog bites can be quite high.
Dog bites usually occur on the hands, face, or legs. About 1 million people per year seek medical care for dog bites in the United States, and many more bites are unreported. Sixty percent of those bitten are children, so dog bites are a major health problem for children. Dog bites can become infected, particularly in the elderly and people with weakened immune systems, but rabies in dogs is rare in the developed world. On average, 20 to 35 people, mostly young children, die each year from dog bites in the United States.
Most dogs do not bite unless provoked or teased, so most dog bites can be prevented by following simple guidelines that include:
Cat bites and scratches are also very common, and they are more likely than dog bites to become infected and require hospitalization. The reason why cat bites are more likely than dog bites to become infected is the shape of a cat's teeth. While dog teeth are shaped to crush food, cat teeth are longer and adapted to pierce food. This difference means that a cat bite can drive disease organisms much deeper into human skin than a dog bite. In addition, most cat bites occur on a person's hands or feet. These parts of the human body contain many small compartments below the skin that can easily become infected by the bacteria in the cat's saliva.
Cat bites most often involve the hands, followed by the legs, face, and torso. While men are more likely than women to be bitten by dogs, women are more likely to be bitten by cats. The most common situation that provokes a cat to bite is having its tail accidentally stepped on, although lengthy teasing can also provoke a cat to bite. Warning signs that a cat may bite include hissing, growling, flattening of the body against the ground, and ears flattened against the head. Rabies is rare in cats, but it is more common in cats than in dogs in the United States. One infection caused by cat bites or cat scratches is cat scratch disease (CSD), which causes enlargement of the lymph nodes * but usually goes away by itself after about three weeks.
Human bites are the third-most-common bite in the United States after dog and cat bites. They are dangerous because the human mouth contains bacteria * and viruses that can cause a serious infection. Human bites have been shown to transmit hepatitis B, hepatitis C, syphilis, tuberculosis, and tetanus.
Twenty-five species of poisonous snake live in the United States, and every state except Maine, Alaska, and Hawaii has at least one type. Pit vipers, which include rattlesnakes, copperheads, and cottonmouths, cause 99 percent of poisonous snakebites in the United States. Coral snakes cause the other 1 percent. Worldwide, about 15 percent of the 3,000 known snake species are poisonous to humans.
Venoms of different snake species range in toxicity, and a poisonous snake does not always release venom when it bites. The poisons in some species are mild, whereas others are neurotoxins (noor-o-TOK-sins; poisons that destroy nerve cells) that may cause damage to the brain or spinal cord or cause people to stop breathing.
Any snakebite should receive emergency medical care because many people do not know what species of snake bit them, and even nonpoisonous snakes can cause infection or an allergic reaction. Each year, between 4,000 and 7,000 people are treated for snakebite in emergency rooms in the United States, with bites most often reported in North Carolina. Men are bitten about nine times more often than women, with 50 percent of bites occurring in young adults between the ages of 18 and 28. Between 2004 and 2015, only 11 deaths in the United States were caused by snakebites.
Mice, rats, guinea pigs, and hamsters sometimes bite, as do such exotic pets as ferrets, lizards, monkeys, snakes, snapping turtles, and birds. Horses, mules, sheep, pigs, and goats can also bite. Such wild animals as skunks, raccoons, bats, sharks, and Gila monsters cause bite injuries each year. Bites from wild animals are especially dangerous because these animals sometimes have rabies.
Wild or wounded animals should never be approached. If a wild animal that usually avoids people starts to approach them or to seem friendly, it may be sick. Skunks and raccoons are nocturnal, and if they are seen walking around in midday, they should be considered to be ill, perhaps rabid. A law officer, park ranger, or animal control officer with training in handling sick or injured animals should be notified promptly about any sick animal or animal that is acting abnormally.
All bites should be cleaned as soon as possible. If the skin is broken but not torn or bleeding, the wound should be washed with soap and water and treated with antibiotic cream to prevent infection. When any of the following situations occur, the person who has been bitten should get medical care promptly.
Many doctors agree that ice packs, tourniquets * , and incisions should not be used. Bites should be washed with soap and water, and the bitten area should be kept still and lower than the heart. Walking and other movement should be limited to only what is absolutely necessary, and a doctor should be seen as soon as possible. Suction devices from snakebite kits if used immediately, or tourniquet wrapped snugly 2 to 4 inches (5 to 10 centimeters) above the bite might slow the spread of venom until professional medical help arrives. Bites of poisonous snakes are treated with antivenin to neutralize the toxin (poison). Although death is rare, poisonous snakebites usually require 12 to 24 hours of observation in the emergency room. Pain and swelling can last for several weeks.
Rabies is a viral disease that affects the nervous system and is fatal if left untreated. In humans, symptoms can develop between five days and several years after a person has been bitten by a rabid animal, although the average incubation time is 20 to 90 days. A rabid animal whose saliva contains the rabies virus usually infects other animals or individuals by biting them. All mammals * can get rabies, but the disease is extremely rare among pets or domestic animals in the United States because they are vaccinated against it. Bat bites are the most common source of rabies infections in humans in the United States; less than 5 percent of cases involve dogs. More than nine out of ten cases of rabies occur in wild animals, particularly skunks, raccoons, bats, and foxes. Small rodents including rats and mice are almost never rabid because they die from the rabies virus before they can transmit it to larger animals or humans. In the developing world, rabies is common in dogs. The World Health Organization estimates that at least 35,000 people worldwide die from being bitten by a rabid dog each year, almost all of them in developing countries where routine veterinary vaccinations rarely occur.
Rabies is rarely transmitted to people in the United States. Between 1995 and 2011 only 51 cases of human rabies were reported: however, only 3 of those persons survived. Nevertheless, a person who has been bitten or scratched by a suspected rabid animal needs immediate medical treatment. Once the virus takes hold in humans, rabies almost always results in death. Every year, more than 15 million people worldwide receive a postexposure rabies vaccination * to prevent the disease. The vaccine is given in multiple doses, beginning as soon as possible after exposure. It is no more painful to receive than any other routine vaccination. Early treatment with the rabies vaccine is essential if the person is to survive.
Animal stings occur when an animal, often an insect, breaks a human's skin and injects saliva into the body. The saliva may contain venom or a substance that causes an allergic reaction. Depending on the type of venom, a person can experience pain, itching, hives (red bumps), nerve damage, or in rare cases, death. Bites from mosquitoes and ticks can be dangerous in places where those insects are vectors * (carriers) for diseases caused by bacteria, viruses, or parasites.
Various insects and spiders sting or bite. The best way to prevent being bitten or stung is to avoid areas where these insects or spiders live, or to wear protective clothing in areas where a person might encounter them.
In many parts of the United States, mosquitoes are a summertime annoyance. Only female mosquitoes bite. When they bite, they inject saliva into the skin in the process of taking a blood meal. The red itchy bump that appears at the site of the bite is an allergic reaction to the saliva. Mosquito bites go away on their own after several days. Mosquito repellent sprays help deter mosquitoes from biting, and calamine lotion or hydrocortisone cream may help ease the itching caused by bites.
Chiggers, also called redbugs, are the larvae (immature stage) of red mites. They live in woods, pastures, and areas with high grass and weeds, in the United States, most often in the South and Midwest. Chiggers attach to a person's clothing and then move to bare skin around the tops of socks, in armpits, or at waistbands. There they bite the skin, inject a fluid that dissolves cells, and suck up the liquefied tissue. Chiggers cause extremely itchy bumps that can keep itching for days after the larvae are removed. Bathing and scrubbing after exposure to chiggers will kill or dislodge them, and rubbing alcohol followed by calamine lotion is said to help relieve the itching. A doctor should be consulted if the chigger bites become infected after scratching.
In the United States, fire ants come in a variety of types: imported (from South America) or native, red or black. Different types live in different geographic regions, but they are most common in the southeastern states. Fire ants usually build mounds in soft soil, but sometimes they nest in the walls of buildings.
Fire ants are very aggressive and territorial. When a person or animal disturbs their nest, they swarm. Thus, many ants can sting a person at once. The venom causes a painful burning sensation, hence the name “fire” ant, followed by tiny, itchy white blisters. Fire ant stings can be fatal, but only to the small number of people who are allergic to their venom.
Ticks live in woods and fields all over the United States. Their flat dark bodies are about the size of a match head. Ticks bite humans and other animals because they need blood to survive. Usually, a tick bite causes only minor itching or irritation, but ticks also spread a number of diseases with their bites, including Rocky Mountain spotted fever and Lyme disease * , both of which can be very serious illnesses. If a tick is seen on the skin, tweezers should be used to pull the tick up and out of the skin. The bite should be washed with soap and water and watched for signs of infection.
Almost all spiders have glands that contain venom, but only 20 to 30 of the 30,000 species of spider in the world are potentially dangerous to humans. Spider bites can cause pain, nausea, fever, and cramps, but the majority of bites are minor and cause only swelling, a blister, and temporary pain. The brown recluse and the black widow spiders are the most dangerous spiders found in the United States. Tarantulas also bite, but their bite usually is no worse than a bee sting.
The brown recluse spider is mostly found in the south-central United States, in dark places such as woodpiles, sheds, and barns. With legs extended, this spider can be as large as a half-dollar. Males and females look alike and vary in color from orange to brown. They are covered with short hairs and have a violin-shaped marking on their back. Brown recluse bites usually are not fatal, but the spider's venom can cause serious illness, especially for children and the elderly.
Following a bite by a brown recluse spider, the skin around the bite may quickly become warm and swollen. Within about 15 minutes the bitten person may become dizzy and sick to the stomach. Other symptoms include fever, chills, weakness, convulsions *
Black widow spiders live in all parts of the United States but are most common in the warmer regions. They live in the same types of places as brown recluse spiders. Black widows are about one-half-inch long (not including the legs), and they can be identified by the reddish-orange hourglass shape on the belly of their black bodies.
Scorpions are about as long as an index finger. They have eight legs and a curled tail with a stinger on the end. There are 30 different kinds of scorpions in the United States, and they can be found all over the country. The stings of two species, both of which live in the southwestern states, can be fatal.
Scorpion venom causes a burning feeling in the skin, followed by swelling and discoloration. About a day later, the affected person's face, mouth, and jaw muscles become hard to control. Other symptoms include nausea, vomiting, drooling, convulsions, and difficulty breathing. Scorpion bites are treated with antivenins and other medications to control muscle spasms and convulsions. In 99 percent of cases, complete recovery occurs after three days. However, if a person is particularly sensitive to the venom, and if muscle spasms begin immediately after the sting, then the person may die.
Bee, wasp, hornet, and yellow jacket stings are common injuries in the United States, particularly in warmer weather. Honeybees and bumblebees are fat and round, and when they sting they leave their stinger in the skin. Wasps and yellow jackets are long and thin, and when they sting they keep their stinger and they can sting again. All of these insects inject venom into the skin, which causes pain, itching, swelling, and redness. For most people, bee stings are painful but not dangerous. However, some people are severely allergic to bee venom; for these people, bee stings can be fatal unless they are given medication right away. Africanized bees, also often called killer bees, are dangerous because they swarm, and many bees can sting a person at once. Even nonallergic people can be killed by killer bees, but this occurrence is very rare.
After a sting, the stinger should be scraped off the skin, as pulling it out may squeeze more venom into the bite. Ice or cold compresses may help reduce pain and swelling.
The oceans are home to many types of animals that bite or sting. The most familiar of these is the jellyfish. All types of jellyfish have stinging tentacles that can cause a burning welt on a person's skin. In Australia, the sting of the box jellyfish can be fatal, but most jellyfish stings are only painful. Jellyfish like the Portuguese man-of-war and sea nettles are common in warm coastal waters in the United States near the Atlantic Ocean. Avoiding contact with jellyfish while swimming can sometimes be difficult, especially when there are many of them in the water. Vinegar, calamine lotion, and antihistamines may help relieve the pain of stings.
The CDC recommends the following steps to lower people's risk of animal bites and stings:
See also Allergies • Cat Scratch Disease • Elephantiasis • Filariasis • Hives • Lyme Disease • Malaria • Parasitic Diseases: Overview • Rabies • Rickettsial Infections • Rocky Mountain Spotted Fever • Skin Parasites: Overview • Tetanus (Lockjaw) • Tick-Borne Illnesses: Overview • TravelRelated Infections: Overview • Vaccines and Immunization • Yellow Fever • Zoonoses: Overview •
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* rabies is a viral infection of the central nervous system that is usually transmitted to humans by the bite of an infected animal.
* lymph nodes (LIMF) are small bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
* bacteria (bak-TEER-ee-uh) are single-celled microorganisms that typically reproduce by cell division. Some, but not all, types of bacteria can cause disease in humans. Many types can live in the body without causing harm.
* diabetes (dye-uh-BEE-teez) is a condition in which the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood.
* AIDS or acquired immunodeficiency (ih-myoo-no-dih-FIH-shensee) syndrome, is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).
* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.
* tetanus (TET-nus) is a serious bacterial infection that affects the body's central nervous system.
* tourniquet (tour-nih-KET) is a device, often a bandage twisted tight around an arm or a leg, used to stop blood flow or hemorrhage.
* mammals are warm-blooded animals with backbones, who usually have fur or hair. Female mammals secrete milk from mammary glands to feed their young. Humans are mammals.
* vaccination (vak-sih-NAY-shun) is giving, usually by an injection, a preparation of killed or weakened germs, or a part of a germ or product it produces, to prevent or lessen the severity of the disease caused by that germ. Also called immunization.
* vectors (VEK-tors) are animals or insects that carry diseases and transfer them from one host to another.
* malaria (mah-LAIR-e-uh) is a disease spread to humans by the bite of an infected mosquito.
* elephantiasis (eh-luh-fan-TIE-uhsis) is the significant enlargement and thickening of body tissues caused by an infestation of parasites known as filaria.
* Lyme disease (LIME) is a bacterial infection that is spread to humans by the bite of an infected tick. It begins with a distinctive rash and/or flulike symptoms; and in some cases can progress to a more serious disease with complications affecting other body organs.
* convulsions (kon-VUL-shuns), also called seizures, are involuntary muscle contractions caused by electrical discharges within the brain, and are usually accompanied by changes in consciousness.
* antivenin is an antibody (protein) capable of neutralizing a specific venom.