
7 Bug Bites You Need to Know
Lesions from bedbug (Cimex lectularius) feeding sites are seen above.
Insect bites can give rise to signs and symptoms ranging from skin irritation to life-threatening disease. The World Health Organization (WHO) states that globally, vector-borne diseases, including those transmitted by insects, result in 700,000 deaths per year,[1] while 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]
7 Bug Bites You Need to Know
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).[3] Only body lice are known to spread disease,[3] 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.[4]
Body louse infestation correlates with poor hygiene, overcrowding, and cold or damp conditions. People who are homeless, incarcerated, or refugees are at higher risk for hosting lice and contracting louse-borne diseases.[4]
7 Bug Bites You Need to Know
Fire Ants
The above-pictured pustules and blisters developed after red imported fire ant (Solenopsis invicta) envenomation of the leg. S invicta's venom contains alkaloids, proteins, and enzymes; the proteinaceous components may account for the anaphylactic reaction that can occur.[5] 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.[6]
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.[7]
7 Bug Bites You Need to Know
Mites
Trombiculosis is a rash caused by the larvae of trombiculid mites (chiggers) 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.
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). New developments in the field of videodermatoscopy allow for rapid, noninvasive diagnosis of trombiculosis and other skin lesion disorders.[8]
7 Bug Bites You Need to Know
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.[9]
Rocky Mountain spotted fever
RMSF is caused by the bacterium Rickettsia rickettsii, which is transmitted to humans by the bite of 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. However, about 10-15% of patients with RMSF never develop a rash. 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,[10] is the most commonly identified source of RMSF transmission.
7 Bug Bites You Need to Know
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.[11]
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.[12] A number of antibiotics may be used to treat early Lyme disease.[13] If the disorder is left untreated, infection can spread to the joints, heart, and nervous system.[12] Some post-Lyme patients also exhibit cognitive impairment.[14] However, individuals who are infected with B burgdorferi can be asymptomatic.[15]
7 Bug Bites You Need to Know
Ticks 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 May 2016, researchers reported the discovery of a new bacterial pathogen in the northern Midwest that can cause Lyme disease, B mayonii.[16]
7 Bug Bites You Need to Know
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.[17] 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.[18] Ehrlichiosis can also be transmitted via organ donation.[19]
7 Bug Bites You Need to Know
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.[20] Dengue fever (also called breakbone fever, because of the associated joint and muscle pain) often presents in a nonspecific manner, although a number of individuals develop a characteristic rash. Other signs and symptoms may include severe headache, eye pain, mild bleeding, and leukopenia.[21] Many patients experience a prodrome of chills, erythematous mottling of the skin, and facial flushing. About 5% of dengue patients develop severe signs, including plasma leakage, shock, hemorrhage, and acute cholecystitis.[22]
Patients with a history of Zika virus infection have a higher risk of developing serious symptoms from a novel dengue infection.[23]
7 Bug Bites You Need to Know
Zika
The above image demonstrates a diffuse, macular rash in a 41-year-old male patient infected with the Zika virus.
According to the CDC, Zika transmission in the United States has dropped to zero since 2018.[24] In 2021, there was one case acquired abroad and detected in the country.[25]
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,[26] while antenatal Zika infections are known to be capable of causing devastating birth defects (eg, microcephaly).[27] As of mid-2022, no specific treatment for Zika virus existed.[28]
7 Bug Bites You Need to Know
Burrowing Fleas
The scanning electron micrograph above shows the last 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.[29,30] 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.[31]
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.[32,33]
7 Bug Bites You Need to Know
Bedbugs
Common bedbugs (C 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.[34] 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.[35]
While their bites are a nuisance, bedbugs have not yet been shown to transmit disease to humans.[36] In laboratory tests, however, C lectularius was identified as a competent vector for Borrelia recurrentis, which causes louse-borne relapsing fever.[37]
Like C lectularius, another Cimex species, C hemipterus, the tropical bedbug, also strongly prefers human hosts.[38]
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