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Image from Wikimedia Commons | Correogsk.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Lesions from bedbug (Cimex lectularius) feeding sites are seen above.

Insect bites and stings can cause symptoms ranging from skin irritation to life-threatening disease. The World Health Organization states that globally, vector-borne diseases, including those transmitted by insects, result in 700,000 deaths per year.[1] According to the US Centers for Disease Control and Prevention (CDC), infections caused by mosquitoes, ticks, and fleas increased by 300% between 2004 and 2016.[2] New vector-borne diseases have emerged, and previously identified diseases have begun to reemerge, facilitated by a number of changing factors.[3]

Image from the CDC | James Gathany.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Lice

Pictured above, a female body louse (Pediculus humanus corporis) feeds on a human host.

Lice are parasitic insects from the suborder Phthiraptera. The three types of louse that feed on humans are Pediculus humanus capitis (head louse), Pediculus humanus corporis, and Pthirus pubis (pubic louse; also called the "crab" louse).[4] Only body lice are known to spread disease,[4] being vectors for three major bacterial disorders: typhus, trench fever, and relapsing fever. Additionally, irritation from bites can lead to excoriation and secondary bacterial infections.[5]

Body louse infestation correlates with poor hygiene, overcrowding, and cold or damp conditions, as experienced by homeless people, refugees, and prisoners.[5] Recent developments in pediculicide chemistry may enable more efficient treatment.[6]

Image from Wikimedia Commons | ZeWrestler | (inset) Mike Quinn, TexasEnto.net.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Fire Ants

The above-pictured pustules and blisters developed after multiple red imported fire ant (Solenopsis invicta) stings. S invicta's venom contains alkaloids, proteins, and enzymes; the proteinaceous components may account for the anaphylactic reaction that can occur.[7] Many patients have venom-specific immunoglobulin E–mediated wheal-and-flare reactions, which develop into pruritic, edematous, indurated, erythematous lesions that persist for up to 72 hours.[8]

When anaphylactic reactions arise, epinephrine is administered and repeated every 10-15 minutes to reverse the symptoms. Local reactions can be treated with antihistamines and cool compresses. Topical steroids may be useful, and in severe cases, oral prednisone may be employed. Venom immunotherapy can be used to decrease the risk of systemic reactions.[9]

Image from Wikimedia Commons | Slturis.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Mites

Many mite species feed on humans, but the larvae of trombiculid mites (chiggers) cause trombiculosis, a painful rash, as they feed on skin cells. (The above image shows a chigger rash 36 hours post exposure.) Mite saliva gives rise to 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.

Although transmission is largely confined to East Asia and Austronesia, chiggers have been associated with transmission of 31 bacterial pathogens, including Orientia tsutsugamushi, the organism responsible for scrub typhus.[10] New developments in the field of videodermatoscopy allow for rapid, noninvasive diagnosis of trombiculosis and other skin lesion disorders.[11]

Image from the CDC.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Ticks

The above-pictured rash is associated with Rocky Mountain spotted fever (RMSF), a tick-borne disease. Ticks collectively transmit more varieties of disease than any other group of blood-feeding arthropods.[12] They are known vectors for bacteria, protozoa, viruses, and nematodes.[13]

Rocky Mountain spotted fever

RMSF is caused by the bacterium Rickettsia rickettsii, which is transmitted to humans by infected ticks. The development of a rash in the setting of recent outdoor activity, usually by day 6, is a major diagnostic sign of RMSF. Doxycycline is the first-line treatment for RMSF in adults and children.

The American dog tick (Dermacentor variabilis), found east of the Rocky Mountains and in California,[14] is the most commonly identified source of RMSF transmission.

Image from Medscape.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Lyme disease

Erythema migrans, a rash caused by Lyme disease, is shown above.

Ixodes scapularis (commonly known as the deer tick or black-legged tick) can transmit the spirochete bacterium Borrelia burgdorferi, which causes Lyme disease.[15]

Patients with Lyme disease often present with a characteristic red, expanding rash (the above-mentioned erythema migrans), typically on the torso. Multiple lesions of erythema migrans occur in about 20% of patients; other typical symptoms include fever, headache, and fatigue.[16] A number of antibiotics may be used to treat early Lyme disease.[17] If the disorder is left untreated, infection can spread to the joints, heart, and nervous system.[16] Some post-Lyme patients also exhibit cognitive impairment.[18] However, individuals who are infected with B burgdorferi can be asymptomatic.[19]

Image from the CDC.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Ticks are large, blood-feeding mites that attach themselves to their host by means of a cement secreted from their salivary glands. Female ticks are the primary blood feeders, but males can often be found in the vicinity of attached females. In most cases, I scapularis (shown) must be attached for at least 36-48 hours before B burgdorferi can be transmitted. In 2016, researchers reported the discovery of a new bacterial pathogen in the northern Midwest that can cause Lyme disease, B mayonii.[20] Lyme disease is the most commonly reported vector-borne disease in the United States.[21]

Image courtesy of Arlo Pelegrin.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Monocytic ehrlichiosis

The mouthparts of the lone star tick (Amblyomma americanum, shown) include 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 principal vector for monocytic ehrlichiosis, which occurs in the south-central and southeastern United States.[22] Although the bacteria Ehrlichia chaffeensis and E ewingii both cause disease in humans, most documented cases of ehrlichiosis have been attributed to E chaffeensis. Doxycycline is the treatment drug of choice for all age groups, and administration should be initiated immediately whenever ehrlichiosis is suspected.[23] Ehrlichiosis can also be transmitted via organ donation.[24]

Image from the CDC | James Gathany.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Mosquitoes

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.[25] Also called breakbone fever, because of the associated joint and muscle pain, it often presents in a nonspecific manner. Signs and symptoms may include severe headache, eye pain, mild bleeding, and leukopenia.[26] Many patients experience a prodrome of chills, erythematous mottling of the skin, and facial flushing. About 5% of patients with dengue develop severe signs, including plasma leakage, shock, hemorrhage, and acute cholecystitis.[27]

A novel vaccine is available to a limited set of people.[28] The incidence of dengue fever continues to rise, particularly in tropical countries.[29]

Image from Froeschl G, Huber K, von Sonnenburg F, et al. BMC Infect Dis. 2017 Jan 10;17(1):55. [PMID: 28068904]

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Zika

The above image demonstrates a diffuse, macular rash in a 41-year-old man infected with the Zika virus.

According to the CDC, Zika transmission in the United States has dropped to zero since 2018.[30] In 2021, there was one case acquired abroad and detected in the country.[31]

Like dengue fever, Zika is transmitted by mosquitoes of the genus Aedes. It can also be passed on through sexual contact.

Early indicators of Zika infection include conjunctivitis, as well as fever, maculopapular rash, and joint pain. Zika has been linked to Guillain-Barré syndrome, an autoimmune disorder,[32] whereas antenatal Zika infections are known to be capable of causing devastating birth defects (eg, microcephaly).[33] Range expansion of competent Zika vector species may be exacerbated by global warming.[34]

Image from Feldmeier H. Trop Med Health. 2014 Jun;42(2 Suppl):15-20. [PMID: 25425946]

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Burrowing Fleas

Fleas (order Siphonaptera) have been a constant menace throughout human history. The scanning electron micrograph above shows the terminal abdominal segments of a female chigoe flea (Tunga penetrans) protruding from its host's skin.

Tungiasis is an infection caused by the burrowing fleas T penetrans and T trimamillata.[35,36] Adult females embed themselves in the host's skin and cause itching or irritation as they become engorged on host blood. These insects can also infect pets and other domestic animals.[37]

Treatment of tungiasis is usually highly successful if proper sterile methods are followed for flea extraction. Additionally, occlusive agents such as dimeticones and coconut oil have shown promise in addressing the disease.[38,39]

Image from the CDC | Piotr Naskrecki.

7 Bug Bites You Need to Know

Bo Burns, DO, FACEP, FAAEM | June 23, 2023 | Contributor Information

Bedbugs

Common bedbugs (Cimex lectularius; 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 tend to aggregate in spots where feeding has been successful.[40] Using a stylet-tipped feeding tube, they inject their host with a self-dispersing saliva that digests cells; C lectularius then sucks up the liquefied slurry.

The most commonly reported host response is the development of 2- to 5-mm pruritic, maculopapular, erythematous lesions at bedbug feeding sites.[41]

Although their bites are a nuisance, bedbugs have not yet been shown to transmit disease to humans.[42] In laboratory tests, however, C lectularius was identified as a competent vector for Borrelia recurrentis, which causes louse-borne relapsing fever.[43]

Like C lectularius, another Cimex species, C hemipterus, the tropical bedbug, also strongly prefers human hosts.[44]

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