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Image courtesy of Eric R. Eaton.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The kissing bug species Triatoma protracta is shown above. The pictured specimen was found in Colorado in 2017.

With the arrival of summer, the Web is buzzing with reports of dangerous insects and spiders. Although most species are benign, a few of them can inflict painful defensive injuries or are literally out for blood. Moreover, biting bugs can vector a variety of pathogens, and bug-related illnesses are on the rise. According to the US Centers for Disease Control and Prevention (CDC), infections caused by mosquitoes, ticks, and fleas have increased by 300% in the past 12 years, and most states are badly equipped to handle the problem.[1]

However, some insects have an undeservedly bad reputation, including kissing bugs like T protracta. Some members of this subfamily feed on the blood-rich tissues surrounding the mouth or eyes of a sleeping person and can infect the host with Trypanosoma cruzi, a parasite responsible for Chagas disease, a potentially life-threatening condition. However, the incidence of bites from these insects is limited to a few known cases in North America.[2]

Several arthropod bites and stings can be traced back to the bugs causing them. Can you guess the insects or arachnids behind the following clinical presentations?

Image courtesy of BM Drees.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

This patient presents with umbilicated, sterile pustules on a red, edematous base the day after playing in her backyard.

Which of the following is the likely cause?

  1. Mosquito (family Culicidae)
  2. Flea (Pulex irritans)
  3. Bedbug (Cimex lectularius)
  4. Fire ant (Solenopsis invicta)
Image courtesy of Wikimedia Commons | ZeWrestler | (inset) Mike Quinn, TexasEnto.net.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: D. Fire ant (Solenopsis invicta).

The pustules and blisters in the image developed after fire ant envenomation on the leg. Many patients have venom-specific immunoglobulin E (IgE)–mediated wheal-and-flare reactions that develop over hours into pruritic, edematous, indurated, erythematous lesions that persist for up to 72 hours.[3] Anaphylactic reactions may occur, with subcutaneous epinephrine administered and repeated every 10-15 minutes as needed to reverse the symptoms. Stings occurring during the winter months are often less severe and may go unnoticed until a local reaction develops; this reflects the seasonal variation in venom protein concentration.[4] Local reactions can be treated with antihistamines and cool compresses. Topical steroids may be useful. In severe cases, oral prednisone may be used.

Image from Wikimedia Commons | Scott Bauer.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

S invicta is a South American ant that arrived in the United States in the 1930s. The 3- to 6-mm insects have been aggressive colonists, readily settling in North America, China, Australia, and New Zealand. Their venom consists of alkaloids, proteins, and enzymes; the proteinaceous components may account for the anaphylactic reaction.[5] Climate change may significantly expand their current range, but recent research into natural viral enemies of the fire ants may open a promising avenue of counterattack.[6] Additionally, some commonly used food additives and flavor enhancers such as glycine and guanosine monophosphate have been shown to be strongly toxic to fire ants.[7]

Image from Wikimedia Commons | Wilson44691.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

This patient presents with a rash after walking through tall grass near a wetland. Note the raised and fluid-filled centers.

Which of the following is the likely cause?

  1. Deer tick (Ixodes scapularis)
  2. Botfly (Dermatobia hominis)
  3. Chigger (Trombicula alfreddugesi)
  4. Flea (P irritans)
Image from Wikimedia Commons | Slturis.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: C. Chigger (Trombicula alfreddugesi).

Trombiculosis is a rash caused by the larvae of trombiculid mites (chiggers) as they feed on skin cells. (The image in the slide shows a chigger rash 36 hours after exposure.) Once on a host, a chigger feeds through its stylostome, a sclerotized mouth tube that burrows through the epidermis. Mite saliva causes intense irritation, with severe itching and dermatitis, and often produces hard, raised bumps. There is a risk of secondary infection if the bites are scratched open. Itching can be alleviated through the use of over-the-counter topical corticosteroids and antihistamines. More potent, prescription topical steroids may be necessary.

Chiggers have not been shown to carry diseases in the United States, but in East Asia and Austronesia they can transmit Orientia tsutsugamushi, an obligate intracellular pathogen responsible for scrub typhus (Japanese river disease). Hantavirus-specific RNA, Borrelia-specific DNA, and Ehrlichia-specific DNA have been identified in trombiculid mites in Texas, but there have been no reports of disease transmission to humans.[8] Rising summer temperatures brought an unusual onslaught of these irritating arachnids to north Texas last summer;[9] other areas may be vulnerable to similar outbreaks. Preliminary studies suggest a possible connection between chigger bites and acquired allergy to red meat.[10]

Image from Bal AK, Kairys SW. Kawasaki disease following Rocky Mountain spotted fever: a case report. J Med Case Rep. 2009;3:7320.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

A 16-year-old male presents with complaints of a rash (shown), fever, and joint pain 1 week after a mountain camping trip. Your colleague believes that the patient has Rocky Mountain spotted fever (RMSF).

Which of the following is true concerning this diagnosis?

  1. The rash shown is classic for the disease and is always present
  2. Doxycycline should not be used for treatment in children
  3. Blood/serum testing is usually helpful
  4. A high clinical index of suspicion should be maintained
Image from the CDC.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: D. A high clinical index of suspicion should be maintained.

Ticks transmit a bigger variety of pathogens than any other blood-feeding arthropod and are currently undergoing a considerable range expansion due to climate change.[11] Since 2004, the CDC has identified seven new tickborne diseases,[1] which may have symptoms resembling those of better-known infections. The development of a rash in the setting of recent outdoor activity, usually by day 6, is a major diagnostic sign of RMSF. However, about 10-15% of patients with RMSF never develop a rash.

In the United States, five states (North Carolina, Oklahoma, Arkansas, Tennessee, and Missouri) account for more than 60% of RMSF cases. In the majority of reported cases, the onset of illness occurs during the summer months, peaking in June and July.[12]

Doxycycline is the first-line treatment for RMSF in adults and children. Tetracyclines may also be effective but can cause staining of the tooth enamel when used in children younger than 8 years. Chloramphenicol was previously the drug of choice in pregnant patients but carries the risk of aplastic anemia; the oral formulation is no longer available in the United States, and not all institutions carry IV chloramphenicol. If available, infectious disease consultation should be considered for pregnant patients. If left untreated in the first few days, RMSF can become severe or even fatal (especially in the very young and the elderly). Even in affected regions, however, antibiotic prophylaxis after a tick bite is not currently recommended.

Image from the CDC.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The above 2017 map shows the annual incidence of spotted fever rickettsiosis (the category under which RMSF is now placed, along with Rickettsia parkeri rickettsiosis, Pacific Coast tick fever, and rickettsialpox) in each state per million persons.

RMSF is caused by the bacterium Rickettsia rickettsii, transmitted to humans by the bite of infected ticks. The American dog tick (Dermacentor variabilis) is the most commonly identified source of transmission (though it is found mainly east of the Rocky Mountains). The Rocky Mountain wood tick (D andersoni), found predominantly in the mountain states, can transmit RMSF and tularemia to humans. The brown dog tick (Rhipicephalus sanguineus) has been identified as a source of RMSF in the southwestern United States and along the US-Mexico border, but the disease can be found throughout the country and the world.

Image from the CDC | Billie Ruth Bird.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The above image shows R rickettsii, the cause of RMSF. These organisms live and multiply primarily within cells that line small to medium-sized blood vessels. This results in damage and death to these cells, causing blood to leak through tiny holes in vessel walls and into adjacent tissues and bringing about the rash that is traditionally associated with RMSF. The process also damages organs and other tissues.[12] R rickettsii has been identified as a potential biologic weapon by several international health organizations.[13]

Image courtesy of Medscape.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

A patient presents with the rash shown above, as well as with fever, headache, and fatigue.

Which of the following is the likely diagnosis?

  1. Tularemia
  2. Ehrlichiosis
  3. Lyme disease
  4. Colorado tick fever
Image courtesy of Medscape.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: C. Lyme disease.

Patients with Lyme disease often present with a characteristic red, expanding rash (erythema migrans), typically on the torso. Multiple lesions of erythema migrans (shown) occur in about 20% of patients; other typical symptoms include fever, headache, and fatigue.[14] A number of antibiotics may be used to treat early Lyme disease;[15] doxycycline is recommended for adults and children aged 8 years or older, whereas young children and pregnant women should be treated with amoxicillin or cefuroxime axetil. If Lyme disease is left untreated, infection can spread to the joints, heart, and nervous system.[14] Some post-Lyme patients also exhibit cognitive impairment.[16] There is some debate as to which longer-term treatments are appropriate for ongoing Lyme-related problems.[17]

Image from the CDC.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Ixodes scapularis (commonly known as the deer tick or black-legged tick, shown) can transmit the spirochete bacterium Borrelia burgdorferi, which causes Lyme disease.[18] Ticks attach themselves by means of a cement secreted by their salivary glands. In most cases, the tick must be attached for at least 36-48 hours before B burgdorferi can be transmitted. Humans are generally infected through the bites of immature ticks, called nymphs. Nymphs are tiny (<2 mm) and difficult to see; they feed during the spring and summer months. Adult ticks can also transmit B burgdorferi, but they are much larger and therefore more likely to be detected and removed before they have time to transmit the bacteria.[14] In May 2016, researchers reported the discovery of a new bacterial pathogen in the northern Midwest that can also cause Lyme disease, B mayonii.[19]

I scapularis is also responsible for the transmission of Powassan virus, a pathogen related to West Nile and Saint Louis encephalitis.[20]

Image from the CDC.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The above map shows the US distribution of reported cases of Lyme disease in 2017. To prevent tick-borne disease, persons exposed to tick-endemic areas should wear long-sleeved, light-colored clothing when outside (with lighter colors allowing easier identification of ticks). Chemical repellents with DEET (N,N-diethyl-3-methylbenzamide) and picaridin are available in numerous over-the-counter skin preparations as sprays or lotions. Permethrin is an acaricide that can be applied to clothing and is used in conjunction with chemical repellents.[14] Vigilant monitoring of tick-prone body regions, such as the armpits, navel, and groin, as well as folds of skin, is also helpful in dealing with tick attacks. Consistent monitoring of companion animals and livestock can also stave off tick complications.

Image courtesy of Medscape.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

This hematoxylin-and-eosin stained section is from a biopsy performed at the periphery of a Lyme disease skin eruption. Note the perivascular lymphocytic infiltrate, a pattern that is not specific for, but is characteristic of, erythema migrans. Ticks prefer warm, moist areas (eg, the belt line, groin, navel, and axilla), though the hairline is a common site for children. Currently, no Lyme disease vaccines are available in the United States. (The manufacturer of the Lyme disease vaccine LYMErix discontinued it in 2002, citing low consumer demand.)[21]

Image courtesy of Darlyne Murawski.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The above photo shows an adult female Amblyomma americanum (lone star tick; upper right) and a nymphal form of the same species (upper left), with a common match (bottom) placed next to them for scale.

Which of the following diseases is associated with the lone star tick?

  1. Lyme disease
  2. Ehrlichiosis
  3. Babesiosis
  4. Colorado tick fever
Image courtesy of Arlo Pelegrin.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: B. Ehrlichiosis.

The mouthparts of the lone star tick (shown) consist of a pair of hooked appendages (pedipalps) that arrange the host's skin into a puncturable mound, along with a hypostome, a blood-absorbing tube covered with overlapping, bladelike scales.

The lone star tick is the principle vector for monocytic ehrlichiosis, which occurs in the south-central and southeastern United States.[22] Although Ehrlichia chaffeensis and E ewingii both cause disease in humans, most documented cases of ehrlichiosis have been attributed to E chaffeensis. Ehrlichiosis has a wide spectrum of manifestations, ranging from subclinical to a severe febrile illness with seizures, coma, and cardiac, renal, and respiratory failure.[23] Doxycycline is the drug of choice for all age groups, and administration should be initiated immediately whenever ehrlichiosis is suspected.[24] Lone star ticks can also carry the potentially fatal heartland virus.[25]

Image from Wikimedia Commons | Katja Schulz.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

In addition to spreading pathogens, the bite of a lone star tick (shown) can induce an allergy to red meat.[26] Unlike with most food allergies, response is delayed by several hours. Symptoms can include hives, intestinal distress, swelling, and anaphylaxis.[27] There is no known treatment.

Ticks and insects are also thought likely to spread Bourbon virus (Thogotovirus), which has been found in the midwestern and southern United States.[28] The symptoms of this rare, potentially fatal infection are not yet completely clear, though fever, fatigue, rash, headache, body aches, and vomiting have occurred in persons diagnosed with Bourbon virus, along with low white blood cell and platelet counts. The virus, for which there is currently no treatment, has been isolated from ticks of the genus Ornithodoros.

Image from Wikimedia Commons | Evanherk at Dutch Wikipedia.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Ticks attach to their hosts by secreting a cone of cement from their salivary glands and then drilling into blood vessels with their serrated mouthparts. To remove a tick, use clean tweezers and grasp the tick as close to the skin surface as possible, taking care to avoid squeezing the body of the tick. Pull upward with steady, even pressure until the cement cone breaks and the tick comes free. Do not twist or jerk the tick; doing so can cause the mouth to break off and remain in the skin. If this happens, remove the mouth with tweezers. If you are unable to remove the mouth easily with tweezers, leave it alone and let the skin heal. After the tick has been removed, clean the area with soap and water or alcohol. In Australia, patients who have experienced anaphylaxis when attempting to remove the tick are instructed to freeze the tick with some wart-freezing spray or ether-containing Aerostart aerosol spray and then promptly go to an emergency department, where the tick can be safely removed.[29, 30]

Seven new tick-borne illnesses have been discovered in the United States since 2004.[1] Additionally, new populations of the invasive East Asian longhorn tick (Haemaphysalis longicornis) have become established in New Jersey; these ticks also carry Ehrlichia, as well as other pathogens.[31,32]

Image courtesy of Duane Gubler, PhD.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

A patient presents with a rash (shown) and flulike symptoms, including arthralgia, after a trip to Australia.

Which of the following is the likely diagnosis?

  1. West Nile encephalitis
  2. Zika
  3. Dengue fever
  4. Leptospirosis
Image from the CDC | James Gathany.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: C. Dengue fever.

Dengue fever is transmitted by mosquitoes of the genus Aedes (above), which are widely distributed in subtropical and tropical areas of the world.[33] Dengue fever (also called breakbone fever, because of the associated joint and muscle pain) often presents in a nonspecific manner, though many individuals develop a characteristic rash. Other symptoms may include severe headache, eye pain, mild bleeding, and leukopenia.[34] Many patients experience a prodrome of chills, erythematous mottling of the skin, and facial flushing, which is a sensitive and specific indicator of dengue fever.

A sharp increase in new cases of dengue has been occurring in 2019 in the tropical western Pacific region, including in Australia, Singapore, China, the Philippines, and Lao People's Democratic Republic.[35]

Image from Wikimedia Commons | CDC.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The rash associated with dengue fever is variable and may be maculopapular or macular. The rash typically begins on day 3 and persists for 2-3 days. Petechiae and purpura may develop as hemorrhagic manifestations. Islands of sparing are characteristic of dengue. A tourniquet test is often positive for dengue fever (shown). This test is performed by inflating a blood pressure cuff on the upper arm to midway between diastolic and systolic blood pressure for 5 minutes. The results are considered to be positive if more than 20 petechiae per square inch are observed on the skin in the area that was under pressure. Other hemorrhagic manifestations of dengue include nasal or gingival bleeding and melena. Dengue fever is usually a self-limited illness, and no specific antiviral treatment is currently available for it. Supportive care that includes analgesics, fluid replacement, and bed rest is usually sufficient.

The release of tetracycline-dependent male mosquitoes decimated the rate of new dengue infections during field trials in Brazil. These mosquitoes mate with females and soon die, with their tetracycline dependence passed on to the larvae, which also soon die.[36]

Image from Wikimedia Commons | FRED.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

A botanist presents with conjunctivitis, a rash (shown), and joint pains after a scientific expedition to Panama.

Which of the following is the likely diagnosis?

  1. West Nile encephalitis
  2. Zika
  3. Dengue fever
  4. Leptospirosis
Image from the CDC.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: B. Zika.

The provisional data in the above map reflect laboratory-confirmed US cases of Zika virus reported to ArboNET (a national arboviral surveillance system) as of May 1, 2019. Zika virus was first detected in 1947, in Ugandan primates; since then, it has been moving steadily eastward. Central and South American and Caribbean outbreaks began in 2015, but the disease appears to be diminishing, with no current outbreaks worldwide.[37] Like dengue fever, Zika is transmitted by mosquitoes in the genus Aedes, which are widely distributed in subtropical and tropical areas of the world. It can also be transmitted by sexual contact.

Image from Wikimedia Commons | Joyhill09.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Early indicators of Zika infection include conjunctivitis (shown), as well as fever, maculopapular rash, and joint pain. Many people in affected areas who contract Zika report only mild symptoms or none at all. The viral infection typically manifests as mild denguelike symptoms that quickly resolve. However, it has been linked to Guillain-Barré syndrome, an autoimmune disorder,[38] and antenatal Zika infections are known to be capable of causing devastating birth defects (eg, microcephaly).[39]

Many new medical countermeasures are currently in development. Research suggests that mosquitoes carrying the intracellular bacterium Wolbachia have a lower chance of acquiring and transmitting Zika.[40] A variety of promising vaccines are in development,[41] and there appears to be a correlation between acquired immunity to dengue fever and lowered susceptibility to Zika.[42] Additionally, plant-produced Zika proteins have been found to confer immunity to the virus in mice.[43]

Image from Wikimedia Commons | Beethoven.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

In the United States, most mosquito bites (shown) cause local irritation and itching rather than serious illness. Worldwide, however, an estimated 700 million cases of mosquito-transmitted disease occur each year, resulting in nearly 1 million deaths.[44] In addition to dengue fever and Zika, mosquitoes can transmit diseases such as malaria, yellow fever, chikungunya, and West Nile encephalitis, as well as other viral encephalitides.

Image from Ugbomoiko US, Ariza L, Ofoezie IE, Heukelbach J. PLoS Negl Trop Dis. 2007 Dec 5;1(3):e87. [PMID: 18160986]

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

A patient presents with the lesion shown, as well as pruritus, after a vacation in Jamaica.

Which of the following is the likely cause?

  1. Tick (Ixodes spp.)
  2. Botfly (D hominis)
  3. Hookworm (Ancylostoma duodenale)
  4. Chigoe flea (Tunga penetrans)
Image from Feldmeier H. Trop Med Health. 2014 Jun;42(2 Suppl):15-20. [PMID: 25425946]

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: D. Chigoe flea (Tunga penetrans).

The scanning electron micrograph above shows a female chigoe flea's last abdominal segments protruding from its host's skin.

Tungiasis is an infestation by the burrowing flea T penetrans or one of various related species, often called chigger fleas, sand fleas, or jiggers.[45] At 1 mm in size, the unattached fleas are difficult to spot. The female flea embeds herself in the host's cuticle until only her terminal abdominal segments protrude (shown), giving the lesion its characteristic black dot. As she feeds, the flea begins to swell to a width of up to 1 cm. The female also produces eggs, which are expelled from the exposed abdomen. The flea dies about 25 days after the initial infection.[46]

Treatment of tungiasis usually is highly successful if proper sterile methods are followed for the extraction of fleas.

Image from Criado PR, Landman G, Reis VM, Belda W Jr. An Bras Dermatol. 2013 Jul-Aug;88(4):649-51. [PMID: 24068146]

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The histopathologic image above shows T penetrans embedded in the excised skin of its host, with eggs visible in the flea's abdomen. After surgical extraction of the flea, the remaining crater should be thoroughly cleansed and covered with a topical antibiotic cream to prevent secondary infection.

Image from the CDC.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The above patient, a healthcare worker in a hospital, presents complaining of a spider bite received during sleep. He confirms having seen spiders occasionally around the house. He is diabetic and has not had any recent outdoor activities. He did not see what bit him. The lesion (shown) is painful and started with a pustule.

Which of the following is the likely agent?

  1. Brown recluse spider (Loxosceles reclusa)
  2. Black widow (Latrodectus mactans)
  3. Flea (P irritans)
  4. None of the above; this lesion is not a bug bite
Image from the CDC | Gregory Moran, MD.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: D. None of the above; this lesion is not a bug bite.

A history of a "bug bite" or "spider bite" is often given by patients as the explanation for skin lesions and is typically spurious. Nearly every reported case occurs while the patient is unconscious and unable to witness a spider actually biting him or her. This patient's lesion is typical of a staphylococcal skin infection, presenting as a purulent cellulitis. Treatment consists of drainage of an abscess if present and an antibiotic for cellulitis with activity against both methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S aureus (MRSA). Consider a wound culture. Nonpurulent cellulitis is usually due to Streptococcus, and the first-choice antibiotic is dicloxacillin or cephalexin. Diabetes is a risk factor for skin infection, and working in a healthcare setting is a risk factor for MRSA infection.

Image from Wikimedia Commons | James Heilman.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

This patient, a college-age male, has intensely itchy, red bumps on his back and around his ankles. The ones on his back (shown) are in a row subparallel to his spine. He recently spent the night on his grandmother's couch.

Which of the following is the probable cause of the bumps?

  1. Mosquito
  2. Spider
  3. Bedbug (Cimex lectularius)
  4. Flea (P irritans)
Image from the CDC | Piotr Naskrecki.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

Answer: C. Bedbug (Cimex lectularius).

Bedbugs (shown) conceal themselves in cracks, margins, and folds around areas used by humans for sleeping. They are attracted to the smell of their own species' urine and thus will tend to aggregate in spots where feeding has been successful.[47] Using a feeding tube, they inject their host with a self-dispersing saliva that digests cells and then suck up the liquefied slurry.

Image courtesy of Arlo Pelegrin.

9 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 4, 2019 | Contributor Information

The above image shows the underside of a bedbug, with its feeding tube dangling between its eyes.

Because bedbugs are gregarious diners, bites are usually arranged in rows or clusters. Although some people have no reaction at all to the bites, the most commonly reported response is the development of 2- to 5-mm pruritic, maculopapular, erythematous lesions at bug feeding sites.[48] Compounds in the bugs' saliva induce different skin reactions, such as erythema, wheals, vesicles, and hemorrhagic nodules. If untreated, the condition usually disappears within a week. However, the itching can be so severe that patients scratch the bites open and facilitate secondary infections. Bedbugs are not known to transmit disease. Research has shown that bedbugs can acquire and transmit Trypanosoma cruzi, the pathogen that causes Chagas disease, but so far, this finding has been confined to the laboratory.[49]

Removal of bedbug colonies has become more difficult in the past few years because some bedbugs have evolved resistance to common pesticides.[50]

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Foreign Bodies: Curious Findings

Common, curious, and often challenging, foreign bodies carry a unique set of presentations, risks, and treatment options.Slideshows, May 2019
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Lyme Disease

Lyme disease is a multisystem illness caused by infection with the spirochete Borrelia burgdorferi and the body's immune response to the infection. The disease is transmitted to humans via tick bites, from infected ticks of the genus Ixodes.Diseases/Conditions, May 2019
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References