Wiki: Arthropod bites and stings

Many species of arthropods (insects, arachnids, millipedes and centipedes) can bite or sting human beings. These bites and stings generally occur as a defense mechanism or during normal arthropod feeding. While most cases cause self-limited irritation, medically relevant complications include envenomation, Allergy, and transmission of Disease vector.

Signs and symptoms

Most arthropod bites and stings cause self-limited redness, and/or pain around the site. Less commonly (around 10% of Hymenoptera sting reactions), a large local reaction occurs when the area of swelling is greater than . Rarely (1-3% of Hymenoptera sting reactions), Systemic disease reactions can affect multiple organs and pose a medical emergency, as in the case of Anaphylaxis.

(2025). 9780849313875, CRC Press. . ISBN 9780849313875

Defensive and predatory bites and stings

Many arthropods bite or sting in order to immobilize their prey or deter potential predators as a defense mechanism. Stings containing venom are more likely to be painful. Less frequently, venomous spider bites are also associated with Disease and mortality in humans.

Most arthropod stings involve Hymenoptera (ants, wasps, and bees). While the majority of Hymenoptera stings are locally painful, their associated venom rarely cause toxic reactions unless victims receive many stings at once. The low mortality (around 60 deaths per year in the US out of unreported millions of stings nationwide) associated with Hymenoptera is mostly due to anaphylaxis from venom hypersensitivity.

(2019). 9780128140437, Academic Press. ISBN 9780128140437

Most also cause self-limited pain or . Only certain species (from family Buthidae) inject Neurotoxicity venom, responsible for most morbidity and mortality. Severe toxic reactions can occur resulting in progressive Hemodynamics instability, neuromuscular dysfunction, cardiogenic shock, pulmonary edema, multi-organ failure, and death. Although robust epidemiological data is unavailable, global estimates of scorpion stings exceed 1.2 million resulting in more than 3000 deaths annually.

most often cause minor symptoms and resolve without intervention. Medically significant spider bites involve substantial envenomation from only certain species such as Latrodectus and . Symptoms of latrodectism (from widow spiders) may include pain at the bite or involve the chest and abdomen, sweating, muscle cramps and vomiting among others. By comparison, loxoscelism (from recluse spiders) can present with local necrosis of the surrounding skin and widespread Hemolysis. Headaches, vomiting and a mild fever may also occur.

Feeding bites

Feeding bites have characteristic patterns and symptoms that reflect feeding habits of the offending pest and the chemistry of its saliva. Feeding bites are less likely to be felt at the time of the bite, although there are some exceptions. Since feeding requires longer attachment to prey than envenomation, feeding bites are more often associated with vector transmission of disease.Herness J, Snyder MJ, Newman RS. Arthropod bites and stings. American family physician. 2022 Aug;106(2):137-47.

Mosquitoes	exposed appendages	usually not	Low raised welt, itches for several hours.
Midges and no-see-ums	exposed appendages	usually	Itches for several hours.
Fleas	prefer ankles and bare feet	usually	May make red itchy welt; several days. Later bites are less severe.
Biting flies	any exposed skin	painful and immediate	Painful welt, several hours.
Bed bugs	appendages, neck, exposed skin	usually not	Low red itchy welts, usually several together resembling rash, slow to develop and can last weeks.
Hair Lice	pubic area or scalp	usually not	Infested area intensely itchy, with red welts at bite sites. See pediculosis.
Larval ticks	Anywhere on body, but prefer covered skin, crevices.	Usually not; may be scratched off before they are seen.	Intensely itchy red welts lasting over a week.
Adult ticks	covered skin, crevices, entire body	usually not	Itchy welt, several days.
Mites	mainly on the trunk and extremities	usually not	Intensely itchy welts and papules that may last for days. See acariasis.

As vectors of disease

In addition to stings and bites causing discomfort in of themselves, bites can also spread secondary infections if the arthropod is carrying a virus, bacteria, or parasite. The World Health Organization (WHO) estimates that 17% of all infectious diseases worldwide were transmitted by arthropod vectors, resulting in over 700,000 deaths annually.Global vector control response 2017–2030. Geneva: World Health Organization; 2017. License: CC BY-NC-SA 3.0 IGO. The table below lists common arthropod vectors and their associated diseases. The figure below represents endemic areas of common Disease vector.

Mosquitoes ( Culicidae)	Arboviruses (Togavirus, Flavivirus, Bunyavirus) Protozoa ( Plasmodia) Nematode ( Wuchereria bancrofti)	Chikungunya, Zika fever, Yellow fever, Dengue fever, West Nile, California encephalitis, Japanese encephalitis, Equine encephalitis, Rift Valley fever Malaria Lymphatic filariasis	>300 million
Black flies ( Simuliidae)	Nematode ( Onchocerca volvulus)	Onchocerciasis	>10 million
Assassin bug ( Reduviidae)	Protozoa ( Trypanosoma cruzi)	Chagas disease	>6 million
Sand fly ( Phlebotominae)	Protozoa ( Leishmania)	Cutaneous and visceral leishmaniasis	>3 million
Ticks ( Ixodidae)	Arboviruses (Bunyavirus, Flavirus) Bacteria ( Rickettsia, Anaplasma, Ehrlichia, Borrelia burgdorferi, Coxiella burnetti) Protozoa ( Babesia)	Heartland virus, Tick-borne encephalitis, Crimean-Congo hemorrhagic fever Rocky Mountain spotted fever, anaplasmosis, ehrlichiosis, Lyme disease, Q fever Babesiosis	>500,000
Tsetse flies ( Glossinidae)	Protozoa ( Trypanosoma gambiense, T. rhodesesiense)	African sleeping sickness	>10,000
Biting flies ( Tabanidae)	Nematode (Loa Loa)	African eyeworm	NA
Fleas ( Siphonaptera, Pulicidae)	Bacteria ( Yersinia pestis, Bartonella henselae)	Plague, Cat scratch fever	NA
Lice ( Phthiraptera, Pediculidae)	Bacteria ( Borrelia recurrentis, Rickettsia prowazekii, Bartonella quintana)	Lice-borne relapsing fever, Murine typhus, Trench fever	NA

*Estimated global number of cases annually according to WHO in 2017. If a vector transmits multiple diseases, aggregate case numbers are listed. Rough estimates are only meant to provide a sense of scale. Unknown disease burden is listed as NA for not available.

Diagnosis

Most arthropod bites and stings do not require a specific diagnosis since they typically improve with supportive management alone. Certain bites and stings present with characteristic appearances and distributions. In general, however, Dermatoscopy findings of bitten or stung skin rarely aid in diagnosis. Rather, patient history (recent travel to endemic areas, outdoor activities, and other risk factors) primarily guides the diagnostic approach, which can raise clinical suspicion for more serious complications like vector-borne diseases.

Microscopic appearance

Skin Biopsy are not indicated for bites or stings, since the Histomorphology appearance is non-specific. Bites and stings as well as other conditions (e.g. drug reactions, Hives, and early bullous pemphigoid) can cause microscopic changes such as a wedge-shaped superficial Dermis perivascular infiltrate consisting of abundant Lymphocyte and scattered Eosinophil, as shown in the adjacent figure:

Prevention

Prevention strategies against arthropod bites and stings comprise measures for personal protection, travel advisories, public health and environmental concerns.

Personal protection

Travelers should seek to minimize outdoor activity during peak activity times and avoid high risk areas such as regions with known outbreaks or . Standing water and dense vegetation also commonly attract arthropods. Clothes covering most exposed skin can also provide a measure of physical protection, which may be augmented when the fabric is treated with pesticides such as Permethrin. Topical Insect repellent such as N,N-diethyl-m-toluamide (DEET) is supported by a large body of evidence.

Vaccines may also help prevent vector-borne diseases for eligible patients. For example, Japanese encephalitis, Yellow fever, and Dengue fever have FDA-approved vaccines available. Since they are relatively new vaccines, however, they are not standard of care as of 2023. Additionally, patients traveling to Malaria endemic regions are routinely prescribed Malaria chemoprophylaxis.

Patients with a history of venom hypersensitivity may benefit from venom immunotherapy (VIT). Patients eligibile for VIT include those with a prior anaphylactic reaction to a venomous sting and who have Immunoglobulin E to venom allergens. VIT can help prevent future severe systemic reactions in select patients.

Global health

International organizations such as WHO aim to reduce of neglected tropical diseases, many of which are vector borne.Global report on neglected tropical diseases 2023. Geneva: World Health Organization; 2023. Licence: CC BY-NC-SA 3.0 IGO. Such campaigns must incorporate multipronged approaches to consider global inequality, access to resources, and climate change.

Management

Most arthropod bites and stings require only supportive care. However, complications such as envenomation and severe allergic reactions can present as medical emergencies.

Supportive care

Local reactions to bites and stings are treated symptomatically. If a stinger is still embedded, manual removal can reduce further irritation. Washing the affected area with soap and water can help reduce risk of contamination. Oral , calamine lotion, topical and cold compresses are common over the counter remedies to reduce itchiness and local inflammation. In more severe cases, such as large local reactions, systemic are sometimes prescribed, although limited evidence supports their effectiveness. There are limited data to support one treatment over another.

Medical emergencies

Systemic reactions from venom hypersensitivity can rapidly progress to a medical emergency. The mainstay of anaphylactic shock management is intramuscularly injected epinephrine. The patient should be stabilized and transferred to an intensive care unit.

Toxic reactions to envenomation are similarly managed with medical stabilization and symptomatic treatment. Tetanus vaccine should be up to date but antibiotics are typically unnecessary unless a bacterial superinfection is suspected. Antivenom drugs have been created for certain species such as Centruroides scorpion stings, but these drugs are not yet widely available and so typically reserved for severe systemic toxicity.

Several vector-borne diseases can present emergently.

Treatment of vector-borne diseases

After confirmation of diagnosis, antimicrobials are prescribed according to standard of care.

Biting and stinging arthropods

'', the yellow fever mosquito, biting. Female mosquitoes feed on blood. This species is known for also transmitting yellow fever.]] A bite is defined as coming from the mouthparts of the arthropod. The bite consists of both the bite wound and the saliva. The saliva of the arthropod may contain , as in insects and arachnids which feed from blood. Feeding bites may also contain Anesthetic, to prevent the bite from being felt. Feeding bites may also contain , as in ; spider bites have primarily evolved to paralyse and then digest prey. A sting comes from the abdomen; in most insects (which are all largely ), the stinger is a modified ovipositor,

(2025). 9780128114100, Elsevier. ISBN 9780128114100

which protrudes from the abdomen. The sting consists of an insertion wound, and venom. The venom is evolved to cause pain to a predator, paralyse a prey item, or both. Because insect stingers evolved from ovipositors, in most hymenopterans only the female can sting. However, there are a few orders of wasp where the male has evolved a "pseudo sting" - the male genitalia has evolved two sharp protrusions which can deliver an insertion wound. However, they do not contain venom, so they are not considered a true sting. In that bite instead of sting, such as the Formicinae, the bite causes the wound, but during the bite the abdomen bends forward to spray formic acid into the wound, causing additional pain. In arachnids that sting (all largely Scorpion), the stinger is not a modified ovipositor, but instead a metasoma that bears a telson. (Scorpions lack an ovipositor entirely and give birth to Viviparity.)

Insects

Diptera (True flies)