In general, biting insects themselves are not dangerous because allergic reactions are rare. However, many insects (like mosquitoes and ticks) can transmit diseases like malaria, Lyme disease, and the West Nile virus to humans.
This is because many insects inject their saliva into the host when they bite. While insect's saliva may aid in digestion, inhibit clotting, increase blood flow to the area bitten or anesthetize (numb) the bite site, it may also contain disease-causing organisms.
The mouthparts of biting insects can be classified into three groups:
piercing and/or sucking, sponging, and biting/chewing. Most insect bites cause minor puncture wounds to the skin.
Deaths associated with insect bites are typically a result of hypersensitivity, either anaphylactic (allergic) or anaphylactoid (non-allergic) or from complications resulting from infection. While the exact incidence rate remains unknown, researchers estimate that between 50 and 150 Americans die each year from insect-provoked anaphylaxis. Mosquito bites cause the greatest number of deaths worldwide because they transmit diseases like malaria and the West Nile virus. Malaria is prevalent in tropical and subtropical areas, such as Africa, Asia, the Middle East, South America, and Central America.
Most insect bites are treated with antihistamines or anti-inflammatories. In some cases, symptoms subside without any treatment. Some insects may transmit diseases that require antibiotic treatment.
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types of insect bites
Overview: Bedbugs are small, brown, flattened insects that feed on the blood of animals and humans. The Cimex lectularius species is most likely to affect humans.
Adult bedbugs are about 1/4 inch long and reddish brown, with flat oval bodies. The nymphs (immature bedbugs) look similar to the adults, but they are smaller and lighter in color. While bedbugs cannot fly, they can crawl quickly.
Female bedbugs lay up to five eggs a day in secluded areas. These whitish-colored eggs are difficult to see without magnification. Bedbugs molt (shed their skin) five times before reaching adulthood. Before each molt, the bugs eat a blood meal.
Bedbugs are able to withstand harsh living conditions. Nymphs can survive months without food, while adults can survive for more than a year without eating. If a home becomes infested with these insects, extermination by a professional is almost always necessary.
The feces of bedbugs will appear as dark spotting and staining. Bloodstains may also appear on bed linens after they feed on the host.
Since bedbugs are active during the night, most bedbug bites occur while people are sleeping. Once the bugs pierce the skin, they become engorged (full) in about 3-10 minutes. Bites are typically painless, and most hosts do not even realize they are being bitten.
Symptoms vary among individuals. Many people develop an itchy red welt or localized swelling, which may develop a day or two after the bite. Others have little or no reaction. Bedbugs feed on any bare skin that is exposed while sleeping. Bedbugs are generally unlikely to transmit diseases to humans, and they are not considered a serious health threat.
Bedbug infestations were common in the United States before World War II. Improvement in hygiene and widespread use of DDT (Dichloro-Diphenyl-Trichloroethane, an insecticide that is no longer available in the United States) during the 1940s and 1950s led to a drastic decline of infestations. However, bed bugs are starting to become more prevalent the United States, especially in apartments, homes, hotels, motels, dormitories, and shelters. The bugs are commonly found in other parts of the world including Africa, Asia, Central and South America, and Europe.
Symptoms: Bedbugs feed on any bare skin that is exposed, including the face, neck, shoulders, feet, arms, and hands. Many people develop an itchy red welt or localized swelling, which may appear a day or two after the bite. Others experience little or no reaction.
Diagnosis: A healthcare provider can diagnose bedbug bites after a physical examination and confirmation of the bugs' presence. Patients should look for specks of blood on bed linens and behind wallpaper. Fecal stains may also be visible. Areas of high infestation may also have an intense sweet odor that is caused by bedbugs' oil secretions.
Treatment: Treatment focuses on alleviating symptoms. Bedbugs will need to be exterminated in order to prevent symptoms from recurring. A professional exterminator should be consulted when there is a bedbug infestation. Bed linens should be washed in hot water to kill the insects. Oral antihistamines like diphenhydramine (Benadryl®) have been used to relieve the itching associated with bedbug bites. Hydrocortisone cream or ointment may also be applied to the skin to relieve itching and irritation.
Black widow spider
Overview: Out of the approximately 20,000 species of spiders found in North, South and Central America, only 60 can bite humans. Black widow spiders are about a half-inch long. The two species that commonly inhabit the United States are the southern black widow and northern black widow. The southern black widow has a shiny, black abdomen with a red hourglass shape on the underside. The northern black widow has red, yellow, or white spots on the upper and underside surface of its abdomen. Some spiders also have red legs.
Black widow spiders are nocturnal (active at night) and they are typically found in dark areas. Only female black widows can bite humans; they only bite when they feel threatened, disturbed, or provoked, according to researchers.
The black widow spider venom affects the victim's nervous system. Some people experience mild symptoms while others may have a severe reaction.
Symptoms: A black widow spider bite is painful. The severity of symptoms after the bite depends on the age and overall health of the victim. Children and elderly individuals are more likely to experience more serious symptoms than healthy adults. Individuals may experience pain at the bite site, which is often followed by severe muscle cramps, weakness, abdominal pain, and tremors. Severe reactions may cause lightheadedness, dizziness, chest pain, difficulty breathing, increased heart rate, increased blood pressure, nausea, and vomiting. Patients who experience severe symptoms should seek medical attention immediately.
Diagnosis: A diagnosis can only be confirmed after a physical examination and medical history. The healthcare provider will also consider the likelihood of a bite, which depends on whether the spider lives in the area of the country where the patient was bitten.
Treatment: Treatment is not generally needed because symptoms will resolve on their own. Severe cases may be treated with narcotics and antivenin (antitoxin to counteract the effects of the spider venom).
The antivenin used to treat black widow spider bites is made from horse serum (clear fluid portion of blood). The antivenin is produced from a horse that has developed antibodies and is immune to the spider's venom.Some experts suggest that antivenin be used in any severe bite because one dose of the antivenin quickly relieves symptoms. However, others only suggest antivenin in children, the elderly, and in those with severe underlying medical conditions.
Patients who receive antivenin may experience allergic reactions to the horse serum. Therefore, patients should be skin-tested for a possible allergy prior to treatment.
Since antivenin may not be readily available at most hospitals, there may be some delay in obtaining it.
Brown recluse spider
Overview: Brown recluse spiders are found in the Midwestern and Southeastern United States.
Brown recluse spiders have a violin pattern on the back of their cephalothoras (body part to which the legs attach). These spiders may range in color from yellowish-tan to dark brown. The name of the genus, Loxosceles, means six eyes. Unlike most other spiders, which have eight eyes, the brown recluse has six.
The spiders live in large numbers, and they are commonly found in dark, warm, dry environments, such as attics, closets, and basements. These spiders only bite humans when they feel threatened, disturbed, or provoked. Bites are most likely to occur during the summer.
The brown recluse venom is more potent than rattlesnake venom. However, the spider's venom causes less severe reactions than a rattlesnake because much smaller quantities are injected into its victims.
The venom is made of enzymes that destroy the tissues of its victims. This allows the spider to suck up and ingest the body parts of the insects it preys on. When the spider bites a human, the venom causes tissue death in the areas immediately surrounding the bite site.
The venom also causes an immune response in humans. The immune system releases inflammatory chemicals such as cytokines, histamines, and interleukins. These chemicals signal white blood cells to flood to the bite site. However, in rare but severe cases, the inflammatory chemicals may cause serious adverse reactions in the human, including the destruction of red blood cells and platelets, blood clots in capillaries, kidney failure, coma, and death. Death has only been reported in children younger than seven years old.
Symptoms: Initially, the bite site becomes red and fang marks might be visible. The bite mark typically has a "bull's-eye" appearance (red ring around the site, which often becomes blistered). Symptoms usually develop two to eight hours after the bite. Some patients may experience a minor burning sensation at the bite site. Patients may experience severe pain at bite site, as well as severe itching, fever, muscle pain, nausea and vomiting. After about 12-48 hours, the blistered bite mark may turn bluish and then black in color, as the skin tissue dies.
Diagnosis: Reliable clinical tests to diagnose a brown recluse spider bite are lacking. A diagnosis can only be confirmed after a physical examination and medical history. The healthcare provider will also consider the likelihood of a bite, which depends on whether the spider lives in the area of the country where the patient was bitten.
Treatment: There is no antivenin available in the United States to treat brown recluse spider bides. Controversial therapies include steroids and the antibiotic dapsone (Avlosulfon®). These therapies are controversial because they have little proven benefit. These are typically reserved for patients with severe systemic diseases (such as certain types of anemia, blood clotting problems, and kidney failure). Most wounds, especially necrotic lesions (dead tissue), will need to be monitored by a healthcare provider every day for at least three to four days. The doctor may remove dead tissue to reduce the likelihood of secondary bacterial infections.
Oral antihistamines like diphenhydramine (Benadryl®) may be used to decrease the histamine reaction. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Motrin® or Advil®), may be used to decrease the pain and inflammation at the bite site.
Overview: Chiggers are the parasitic larvae of the harvest mite. While the adults are harmless to humans, the larvae are parasites to many animals, including birds, livestock, reptiles, and humans. Chigger bites only occur during the late summer and early autumn because this is when the larvae are active.
Chiggers are found in many parts of the world, including the southern United States. Chiggers typically live in brush and grassy areas. Females lay up to 400 eggs in damp areas on the ground.
Once the eggs have developed into larvae (chiggers), they move to the tips of grasses. When a potential host, such as a rodent or human passes by, the chigger latches on. The chiggers then move to protected areas on the host, such as under socks or under belts.
Chiggers pierce the skin, especially near hair follicles. When they pierce the skin, they secrete digestive enzymes from their saliva and then they suck up and ingest the liquefied host tissues. The rash and intense itching that develops after a chigger bite is an allergic reaction to their salivary secretions. Once the larva is fully fed, it drops off the host.
These insects generally do not transmit diseases, but they are known to carry "scrub typhus" in certain parts of Asia.
Symptoms: After a chigger is fully fed, it will drop off the individual. Three to six hours after a bite, patients develop a red, itchy welt that has a white center. The welt may develop into dermatitis (dry, itchy, flaky skin). Some patients may also experience fever and swelling. Depending on the sensitivity of the patient, symptoms may last for weeks. Patients should not scratch the bite mark because it may break the skin and potentially lead to secondary infections.
Diagnosis: A qualified healthcare provider can diagnose chigger bites after examining the patient's rash. Chiggers cause a distinctive red welt, with a hard central area on the skin that itches.
Treatment: Hydrocortisone cream has been applied to the affected area to temporarily relieve itching. Hydrocortisone 1% cream, which is available over-the-counter, has anti-inflammatory effects, and relieves swelling and redness in addition to itching. Antipruritic agents like calamine lotion (Calamox®) have been applied to the skin to relieve itching.
Overview: Mosquitoes have long, slender bodies, and long, thin legs. The males, and occasionally, the females, eat nectar and other plant juices. However, the females of most mosquito species need to have a blood meal to mature their eggs, which are laid on the surface of water.
The female mosquito inserts a thin proboscis (tubular, feeding, and sucking organ) into the victim's skin. The mosquito injects saliva into the host. This prevents the victim's blood from clotting as it is sucked into the insect's abdomen. Mosquitoes feed until they are full or brushed away by the victim.
The mosquito's saliva causes an allergic reaction in humans that causes the bite site to itch and swell.
Mosquitoes are potentially dangerous because they can carry diseases such as malaria and the West Nile Virus (WNV). The Anopheles mosquito can transmit malaria. Malaria is an infectious disease of the red blood cells. The disease is most common in tropical and subtropical areas, such as Africa, Asia, the Middle East, South America, and Central America.
The WNV causes a viral infection of the brain called encephalitis. The infection is considered a seasonal epidemic in Northern America. Outbreaks typically occur during the summer and fall months.
Eastern equine encephalitis (EEE) is a virus found in freshwater swamp birds and mosquitoes. It is occasionally transmitted to horses, and very rarely, to people. EEE affects the brain and central nervous system. The risk of contracting EEE is highest in mid to late summer.
Symptoms: Mosquito bites usually cause swelling, itching, and burning at the bite site. A bite may take several days to heal and stop itching.
Symptoms of malaria include cycles of chills, fever, and sweating every one, two, or three days if the infection is not treated. Some individuals may also experience diarrhea, jaundice (yellowing of the skin and eyes), coughing, nausea, and vomiting.
According to the U.S. Centers for Disease Control and Prevention (CDC), an estimated 80% of patients who are infected with WNV experience no symptoms. If symptoms do develop, they typically occur three to 14 days after being bitten by an infected mosquito. Mild symptoms may include fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach, and/or back. Mild symptoms can last anywhere from a few days to several weeks. Severe symptoms may include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis. Severe symptoms may last several weeks and neurological effects may be permanent.
Symptoms of EEE include fever, stiff neck, and headache starting between two and 10 days after infection. Encephalitis followed by coma is possible. Patients who survive suffer mild to severe neurological complications.
Diagnosis: Mosquito bites are harmless, unless the insect transmitted a disease such as malaria or WNV.
Patients who have traveled to areas of the world where malaria is common and who experience symptoms of malaria should consult their qualified healthcare providers. A diagnosis of malaria can be confirmed after a blood test. Since malaria is a cyclic virus, two samples taken at six- and 12-hour intervals can confirm the presence of malaria.
A diagnosis of WNV or EEE can be made after the virus is identified. A sample of blood and spinal fluid is analyzed for the viral DNA.
Treatment: Antipruritic agents like calamine lotion (Calamox®) have been used to relieve itching. Oral antihistamines like diphenhydramine (Benadryl®) are also commonly used to relieve the itching associated with mosquito bites.
Malaria is treated with one or more antimalarials including: chloroquine (Aralen®), quinine (Quinamm® or Quiphile®), hydroxychloroquine (Plaquenil®), Mefloquine (Lariam®), doxycycline (Doryx®, Vibramycin®), a combination of sulfadoxine and pyrimethamine (Fansidar®), or a combination of atovaquone and proguanil (Malarone®).
There is currently no cure for WNV. However, since most patients experience no symptoms, treatment is not usually necessary. Patients who experience severe symptoms may need to be hospitalized and receive intravenous (IV) fluids. Some patients may also need to have breathing tubes inserted into their airways to help them breathe.
There is currently no cure for the EEE virus in humans. Medical treatment focuses on treating symptoms of the infection. Treatment options may include antibiotics to treat secondary infections, anticonvulsants to treat seizures, a respirator for assisted breathing, and corticosteroids to reduce swelling in the brain.
Overview: Ticks are external parasites that feed on the blood of animals and humans. These arachnids (invertebrates that have four pairs of legs and simple eyes) are usually found in tall grasses or bushes. There are two main types of ticks: hard ticks and soft ticks. Hard ticks, such as the common dog tick and the deer tick, have a hard shell just behind the mouthparts, while soft ticks do not. Soft ticks rarely affect humans because they prefer to feed on birds or bats.
Once the tick has reached its host, it will attach firmly and draw blood until full (engorged), and then it will drop off.
In general, ticks do not cause serious health problems, unless they carry a disease. However, in rare cases, the tick itself can cause temporary paralysis in some patients. Symptoms include numbness, tingling, weakness, lack of coordination, and spreading paralysis. Once the tick is removed, symptoms will disappear.
Internationally, there are more 30 major tick-borne diseases. The most common disease transmitted by ticks is Lyme disease, which is a bacterial infection that that may lead to arthritis, as well as neurological and heart-related problems.
Symptoms: Some people may have a mild allergic reaction and experience symptoms such as swelling, itching, and reddening at the bite site. In rare cases, a severe and potentially life threatening allergic reaction called anaphylaxis may occur. Another rare symptom is temporary paralysis, which may occur in sensitive patients. Symptoms of tick-induced paralysis include numbness, tingling, weakness, lack of coordination, and spreading paralysis. Once the tick is removed, symptoms will subside and the patient will fully recover.
In the United States, Lyme disease is caused by the bacteria called Borrelia burgdorferi,which is carried by deer ticks. These ticks are brown and usually about the size of the head of a pin. Patients who have Lyme disease typically develop a rash with a bull's eye appearance at the bite site (red ring around the bite mark). Symptoms may also include flu-like symptoms, joint pain and swelling, inflammation of the meninges surrounding the brain, Bell's palsy (temporary paralysis on one side of the face), numbness or weakness in the limbs, poor muscle movement, and memory loss. Some patients may develop heart-related problems, such as irregular heartbeat, several weeks after infection. These symptoms typically only last a few days or weeks. Other less common symptoms include eye inflammation, severe fatigue, and hepatitis (inflamed liver).
Diagnosis: If Lyme disease is suspected, a qualified healthcare provider may conduct an enzyme-linked immunosorbent assay (ELISA) and a Western blot test to determine whether the patient has the disease. An ELISA test is used to determine whether the patient has developed antibodies to B. burgdorferi. During the procedure, a sample of the patient's blood is sent to a laboratory for testing. If antibodies to the B. burgdorferi are present in the patient's blood sample, the test solution will have an intense color reaction generated by the attached enzyme. If results are positive, a Western blot test is performed to confirm a diagnosis because ELISA may produce false-positive results.
Treatment: Patients should remove ticks promptly with tweezers after they are discovered. If the tick is difficult to remove, rub a petroleum jelly (Vaseline®) or paint nail polish over the tick. These products will kill the tick. Patients should consult their healthcare providers if they are unable to remove the tick. Once the tick is removed, patients should thoroughly wash the bite site and their hands with soap and water. Patients should observe the bite site for the next several days. If a bull's eye rash develops around the bite site, a qualified healthcare provider should be consulted immediately.
Oral antihistamines like diphenhydramine (Benadryl®) are usually taken to decrease the histamine reaction in the body.
Patients who have Lyme disease usually receive oral antibiotic treatment with doxycycline (Vibramycin®) for adults and children who are at least eight years old. Younger children typically receive treatment with amoxicillin (Amoxil®, Prevpac®, Trimox®) or cefuroxime axetil (Ceftin®). Treatment generally lasts 14-21 days.
Patients who have late-stage Lyme disease typically receive intravenous antibiotics like ceftriaxone (Rocephin®) for 14 to 28 days. Symptoms of late-stage Lyme disease include chronic joint inflammation, Bell's palsy, memory loss, and irregular heartbeat. Side effects of treatment may include low white blood cell count, gallstones, and mild to severe diarrhea.
According to the U.S. Food and Drug Administration (FDA), bismacine, also known as chromacine, should not be used to treat Lyme disease. Alternative medicine practitioners sometimes prescribe bismacine for the treatment of Lyme disease. Bismacine contains high amounts of bismuth, a heavy metal that is used in some medications taken by mouth to treat Helicobacter pylori (a bacteria that can cause stomach ulcers). Although bismuth is considered safe when used in some oral medications to treat stomach ulcers, it is not approved as an intravenous medication or to treat Lyme disease. Bismacine can cause bismuth poisoning, which may lead to heart and kidney failure. In March 2005, one patient was hospitalized after receiving a bismacine treatment and in 2006, one person died after treatment, according to the FDA.
General: Many types of insect repellents are available in the United States. The U.S. Centers for Disease Control and Prevention (CDC) recommends the use of products containing active ingredients like DEET (N, N-diethyl-meta-toluamide), picaridin, permethrin, and oil of lemon eucalyptus that have been registered with the U.S. Environmental Protection Agency (EPA) for use as repellents applied to skin and clothing.
DEET: DEET (N, N-diethyl-meta-toluamide) is the active ingredient in many insect repellent products. According to the EPA, insect repellents containing DEET are not a health concern, as long as consumers follow the label directions and take necessary precautions.
DEET is used to repel biting insects like mosquitoes and ticks. On average, about one-third of Americans use DEET each year, according to the EPA. Products containing DEET are currently available to the public in many different types of liquids, lotions, sprays, and impregnated materials (such as wrist bands). DEET-containing products that are applied to the skin are made with 4-30% DEET. If used as directed (as a personal insect repellant), DEET is not likely to adversely affect aquatic or terrestrial wildlife, according to the EPA.
Picaridin: Picaridin, which is nearly odorless, offers protection against insect bites equal to DEET at similar concentrations. In addition, picaridin prevents mosquitoes from locating individuals who have applied the repellant.
Permethrin: Permethrin is primarily used to treat lice and permethrin-containing products are highly effective as insecticides and repellents, according to the EPA. Insect repellants that contain permethrin (like Permanone®) may be applied to clothing, shoes, and camping equipment to help reduce the risk of insect bites. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods (like spiders). Permethrin treated clothing is still effective after repeated washings.
Oil of lemon eucalyptus: Oil of lemon eucalyptus is a plant-based chemical. This ingredient, according to the EPA, may offer protection that is comparable to low concentrations of DEET.
Others: Shorter-acting repellents, such as the oil of geranium, lemon grass, cedar, soy, or citronella, may offer limited protection against insect bites.
EPA safety recommendations: Repellents should only be applied to exposed skin and/or clothing. These products should not be used under clothing. Do not apply to eyes or mouth, or to cuts, open wounds, or irritated skin. Apply sparingly around ears. Do not spray repellents directly onto the face. Instead, spray the repellant onto the hands and gently rub onto the face. Heavy application is not needed for effectiveness. After returning indoors, wash treated skin with soap and water. Patients who experience side effects or allergic reactions after exposure should wash the repellent off with mild soap and water and call a local poison control center and physician's office for further instructions. Keep repellants out of reach of children.