Bites and Infestations

West Nile Virus

The mosquito-borne virus that causes West Nile fever. One of the flaviviruses, a family of viruses also responsible for dengue, yellow fever, and tick-borne encephalitis virus. Like the other flaviviruses, the West Nile virus is a positive-strand RNA virus containing three structural proteins and a host-derived lipid bilayer. The West Nile virus is an icosahedral structure of about 500 angstroms in diameter. The overall structure of the West Nile virus most closely resembles that of dengue fever virus but the surface proteins are slightly different, which may give West Nile virus some of its unique features.

Portuguese Man of War Sting

The sting of the Portuguese man-of-war. One of the most painful effects on skin is the consequence of attack by oceanic hydrozoans known as Portuguese men-of-war, which are amazing for their size, brilliant color, and power to induce whealing. They have a small float that buoys them up and from which hang long tentacles. The wrap of these tentacles results in linear stripes, which look like whiplashes, caused not by the force of their swing but from deposition of urticariogenic and irritant substances.

Seabather's Itch

Seabather's itch. Erythematous papules on the unexposed areas of a swimmer.

Swimmer's Itch

This is an acute dermatitis produced by the cercarial forms of schistosomes and primarily occurs in uncovered areas of the body. The eruption may be acquired in fresh water or salt water. Like any intensely pruritic condition, excoriations and secondary infection are complications. Treatment consists of antipruritics and antibiotics when superinfection occurs.

Sea Urhcin Dermatitis

Sea urchin dermatitis. Puncture sites on the plantar surface of an individual who stepped on a sea urchin.

Contact with Sea Urchin

The effect of contact with a sea urchin. Sea urchins are a gastronomic delight when prepared properly, but a cutaneous torture when stepped on unprepared. The echinoids have spines that in some species are several inches long. Driven into skin when one steps or falls on or brushes against the creatures, the hard spines break and lodge in skin. Pain is inevitable, and secondary infection is nearly inevitable if they are left in. Nothing but tedious and meticulous extraction of every one of dozens, possibly scores, of spines is required for relief.

Jellyfish Envenomation

Jellyfish envenomation. Pruritic and painful papules in a linear arrangement on the leg, appearing after contact with jellyfish.

Body Lice

Body lice. Scattered nits seen on the seams of clothing.

Head Lice

Head lice: Pediculus humanus capitis, parasitic insects found on the heads of people. Head lice are most often found on the scalp behind the ears and near the neckline at the back of the neck. The lice hold onto the hair with hook-like claws at the end of each of their six legs. Head lice are rarely found on the body, eyelashes, or eyebrows. These insects lay their sticky, white eggs on the hair shaft close to the root, while hatched lice stay mostly on the scalp. Head lice infection is very common and easily acquired by coming in close contact with someone who has head lice, infested clothing, or infested belongings. Preschool and elementary school children and their families are most often infested. Symptoms include a tickling feeling of something moving in the hair, itching caused by an allergic reaction to the bites, irritability, and sores on the head caused by scratching. Although lice are very small, they can be seen be seen on the scalp when they move. The eggs (nits) are easily seen on hair shafts. Treatment involves a combination of a topical insecticidal medication and manual removal of all nits with a lice comb or the fingers. Both medication and complete nit removal are necessary to prevent reinfestation. All clothing, bedding, and furniture surfaces must also be washed or sprayed with insecticide. Note that pryrethin-based medications such as 1% lindane solution (brand name: Qwell) contain benzine, which can be toxic to the brain and has been linked to childhood leukemia. For this reason, these medications are no longer generally recommended for treatment for head lice.

Flea Bites

Some people are very sensitive to flea bites -- but scratching can cause a wound or infection. The best solution is to get rid of fleas on pets and in your home. Keep pets out of your bed and be sure to vacuum rugs daily. Spray insecticides on infested areas. Consider using a once-a-month insecticide on your pet.

Fire Ant Stings

Fire ant stings. Erythematous macules with central pustule formation 24 hours after bites in the same child.

Fire Ant Bites

The fire ant sting typically causes red hive-like lesions that burn and itch. Painful pus-filled lesions can also occur. Cold packs, pain relievers, and antihistamines can help relieve the discomfort. A large number of stings may trigger a toxic or severe life-threatening allergic reaction. Get emergency care.

Dermatitis From Common Carpet Beetle

The common carpet beetle is not common in modern well-sanitized homes, and even where it is abundant, effects from it are not common. Nevertheless, on occasion, the crawl of the insect on an unwary individual leaves its marks as wheals, papulovesicles, or bullae. This figure shows just such an event in the form of large, flaccid blisters. The three lesions in a line record the walk of a creature and the deposition of its irritant principle.

Brown Recluse Spider Bite

Spiders, timid creatures for all their fierce looks, would rather entertain insects in their parlors than attack humans. The tarantula is more dangerous in fable than in fact. Two spiders can deliver painful bites and serious venenation if frightened or cornered: the black widow spider (Latrodectus mactans) and the brown recluse spider (Loxosceles reclusa). The bite of the latter is illustrated here. It is a hemorrhagic bleb; in time it will become a necrotic ulcer. The patient will be severely sickened.

Brown Recluse Spider Bites

Brown recluse spider bites often go unnoticed initially because they are usually painless bites. Occasionally, some minor burning that feels like a bee is noticed at the time of the bite. Symptoms usually develop 2-8 hours after a bite. Keep in mind that most bites cause little tissue destruction. Initially the bite site is mildly red and upon close inspection may reveal fang marks. Within a few hours, the redness gives way to pallor with a red ring surrounding the area, or a "bull's-eye" appearance. The lesion will often appear to flow downhill over the course of many hours. The center area will then often blister, which over 12-48 hours can sink, turning bluish then black as this area of tissue dies.

Black Widow Spider Bites

The black widow spider produces a protein venom that affects the victim's nervous system. Some people are slightly affected by the venom, but others may have a severe response. The first symptom is acute pain at the site of the bite though there may only be a minimal local reaction. The local pain may be followed by localized or generalized severe muscle cramps, abdominal pain, weakness, and tremor. In severe cases, nausea, vomiting, faintness, dizziness, chest pain, and respiratory difficulties may follow. The severity of the reaction can depend on the age and physical condition of the person bitten. Children and the elderly are more seriously affected than young adults. Read more about the symptoms and treatments for black widow spider bites.

Bee, Wasp, Hornet, Yellow Jacket Stings

Although many different types of insects in the United States are able to inflict a poisonous bite or sting (meaning they are venomous), the insects most likely to cause medical problems are bees (including the domestic honey bee, its Africanized "killer bee" race, and the bumble bee), wasps (including paper wasps, hornets, and yellow jackets), and ants (including the fire ant). These insects are all in the Hymenoptera family, and thus stings from them are occasionally called Hymenoptera stings. Because many of these species live in colonies, if one stings you, you may be stung by many. Although most stings cause only minor medical problems, some stings may cause serious medical problems and even death. Read more about bee, wasp, hornet, and yellow jacket stings.

Rickettsialpox (Tâche Noire)

Rickettsialpox: tâche noire. A crusted, ulcerated papule (eschar) with a red halo resembling a cigarette burn at the site of a tick bite.

Tick Bite Granuloma

Sometimes at the site of a tick bite, a persistent firm papulonodular lesion may develop. A common site for this reaction to develop is in the scalp. This area may be very pruritic and with excoriation may result in secondary infection. Topical or intralesional corticosteroids may alleviate the pruritus and inflammation, but sometimes these nodules persist for many months and may require biopsy for confirmatory diagnosis and treatment.

Lyme Disease (Erythema-Migrans)

Lyme disease is caused by the spirochete Borrelia burgdorferi and is transmitted by the pinhead-sized Ixodes ticks. The illness is endemic in large areas of the continental United States. The early cutaneous manifestation, termed erythema migrans, is pictured here. It consists of an expanding annular lesion around the original tick bite. Satellite areas of involvement may also be present. Pruritus or burning may be present at the site of the lesion, and the rash may be accompanied by fever, malaise, and regional lymphadenopathy. The systemic manifestations of Lyme disease include neurologic dysfunction (e.g., Bell's palsy), cardiac conduction abnormalities, and arthritis. Early antibiotic therapy for the typical skin lesion will often prevent the development of the more serious ]and long-lasting systemic illness. Serologic testing is of some value in diagnosis but results may be negative early on, especially in the absence of neurologic or joint symptoms.

Lyme Disease

Lyme disease is transmitted through a bite from a specific type of tick. The animals that most often carry these insects are white-footed field mice, deer, raccoons, opossums, skunks, weasels, foxes, shrews, moles, chipmunks, squirrels and horses. The majority of these ticks have been found in New York, Connecticut, New Jersey, Minnesota and Wisconsin. In the early stages of Lyme disease, you may experience flu-like symptoms that can include a stiff neck, chills, fever, swollen lymph nodes, headaches, fatigue, muscle aches and joint pain. You also may experience a large, expanding skin rash around the area of the tick bite. Joint and muscle pain are other early signs of Lyme disease. In more advanced disease, nerve problems and arthritis, especially in the knees may occur.

Bedbug Bites

The first sign of bedbugs may be red, itchy bites on the skin, usually on the arms or shoulders. Bedbugs tend to leave straight rows of bites, unlike some other insects that leave bites here and there. Bedbugs do not seem to spread disease to people. But itching from the bites can be so bad that some people will scratch enough to cause breaks in the skin that get infected easily. The bites can also cause an allergic reaction in some people. Read more about bedbug bites - symptoms, treatments and prevention.

Bedbugs

Adult bed bugs are wingless insects about one-quarter of an inch long and oval in shape. Their color is nearly white after molting, then ranges from tan to burnt orange. After a blood meal, they'll appear dark red or black. Their flat bodies enable them to hide in dark, cozy cracks and crevices in beds, baseboards, sofas, and drawers, and even behind wallpaper and electrical switchplates. That's where they nest during the day, typically not far from where they'll find their host -- that's you -- at night.

Scabies 3

This figure illustrates burrows that are diagnostic of scabies. Burrows are represented by slightly raised white to light-brown linear lesions. The superficial part of the burrow has a scaly appearance, and at the distal end there may be a tiny black dot representing the mite, eggs, and/or fecal material (scybala) in a small vesicle.

Scabies 2

Inflammatory nodular lesions involving the axillae and the diaper area are particularly typical of scabies in the very young child. These lesions may coexist with burrows, papules, vesicles, pustules, and areas of crusting. The nodules may persist for quite some time after the infestation is treated and do not reflect a persistent infestation.

Scabies 1

Scabies: Infestation of the skin by the human itch mite, Sarcaptes scabies. The initial symptom of scabies are red, raised bumps that are intensely itchy. A magnifying glass will reveal short, wavy lines of red skin, which are the burrows made by the mites. Treatment is with any of several scabicide medications.

Scabies

Scabies: Infestation of the skin by the human itch mite, Sarcaptes scabies. The initial symptom of scabies are red, raised bumps that are intensely itchy. A magnifying glass will reveal short, wavy lines of red skin, which are the burrows made by the mites. Treatment is with any of several scabicide medications.

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