Arthropod bites and stings | |
---|---|
Other names | Bug bite |
Tick bite | |
Symptoms | Swelling, itching, pain |
Complications | Anaphylaxis, envenomation, disease transmission |
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, allergic reactions, and transmission of vector-borne diseases. [1]
Most arthropod bites and stings cause self-limited redness, itchiness 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 10 centimetres (4 in). Rarely (1-3% of Hymenoptera sting reactions), systemic reactions can affect multiple organs and pose a medical emergency, as in the case of anaphylactic shock. [2] [3]
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 morbidity 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. [4]
Most scorpion stings also cause self-limited pain or paresthesias. Only certain species (from family Buthidae ) inject neurotoxic venom, responsible for most morbidity and mortality. Severe toxic reactions can occur resulting in progressive hemodynamic 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. [5]
Spider bites most often cause minor symptoms and resolve without intervention. Medically significant spider bites involve substantial envenomation from only certain species such as widow spiders and recluse spiders. 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 breakdown of red blood cells. Headaches, vomiting and a mild fever may also occur. [6]
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. [7]
Pest | Preferred body part | Felt at time of bite | Reaction |
---|---|---|---|
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. |
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. [8] 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. [9] The table below lists common arthropod vectors and their associated diseases. The figure below represents endemic areas of common vector-borne diseases.
Vector | Pathogen class | Disease | Annual disease burden* |
---|---|---|---|
Mosquitoes (Culicidae) | Arboviruses (Togavirus, Flavivirus, Bunyavirus)
Nematode (Wuchereriabancrofti) | Chikugunya, Zika, Yellow fever, Dengue, West Nile, California encephalitis, Japanese encephalitis, Equine encephalitis, Rift Valley fever | >300 million |
Black flies (Simuliidae) | Nematode (Onchocercavolvulus) | River blindness | >10 million |
Assassin bug (Reduviidae) | Protozoa (Trypanosomacruzi) | Chagas disease | >6 million |
Sand fly (Phlebotominae) | Protozoa (Leishmania) | Cutaneous and visceral leishmaniasis | >3 million |
Ticks (Ixodidae) | Arboviruses (Bunyavirus, Flavirus)
Protozoa (Babesia) | Heartland virus, Tick-borne encephalitis, Crimean-Congo hemorrhagic fever
| >500,000 |
Tsetse flies (Glossinidae) | Protozoa (Trypanosomagambiense, 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, endemic typhus, Trench fever | NA |
*Estimated global number of cases annually according to WHO in 2017. [9] 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.
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, dermoscopic findings of bitten or stung skin rarely aid in diagnosis. [11] 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.
Skin biopsies are not indicated for bites or stings, since the histomorphologic appearance is non-specific. Bites and stings as well as other conditions (e.g. drug reactions, urticarial reactions, and early bullous pemphigoid) can cause microscopic changes such as a wedge-shaped superficial dermal perivascular infiltrate consisting of abundant lymphocytes and scattered eosinophils, as shown in the adjacent figure: [12]
Prevention strategies against arthropod bites and stings comprise measures for personal protection, travel advisories, public health and environmental concerns.
Travelers should seek to minimize outdoor activity during peak activity times and avoid high risk areas such as regions with known outbreaks or epidemics. 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 repellants such as N,N-diethyl-m-toluamide (DEET) is supported by a large body of evidence. [7]
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. [13]
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 IgE to venom allergens. VIT can help prevent future severe systemic reactions in select patients. [2]
International organizations such as WHO aim to reduce disease burdens of neglected tropical diseases, many of which are vector borne. [14] Such campaigns must incorporate multipronged approaches to consider global inequality, access to resources, and climate change.
Most arthropod bites and stings require only supportive care. However, complications such as envenomation and severe allergic reactions can present as medical emergencies.
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 antihistamines, calamine lotion, topical corticosteroids 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 glucocorticoids are sometimes prescribed, although limited evidence supports their effectiveness. There are limited data to support one treatment over another. [15]
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. [2]
Toxic reactions to envenomation are similarly managed with medical stabilization and symptomatic treatment. Tetanus prophylaxis 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. [15]
Several vector-borne diseases can present emergently.
After confirmation of diagnosis, antimicrobials are prescribed according to standard of care.
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 anticoagulants, as in insects and arachnids which feed from blood. Feeding bites may also contain anaesthetic, to prevent the bite from being felt. Feeding bites may also contain digestive enzymes, as in spiders; spider bites have primarily evolved to paralyse and then digest prey. A sting comes from the abdomen; in most insects (which are all largely hymenopterans), the stinger is a modified ovipositor, [16] 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. [17] In ants 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 scorpions), the stinger is not a modified ovipositor, but instead a metasoma that bears a telson. [18] (Scorpions lack an ovipositor entirely and give birth to live young.)
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved venom apparatus, such as fangs or a stinger, in a process called envenomation. Venom is often distinguished from poison, which is a toxin that is passively delivered by being ingested, inhaled, or absorbed through the skin, and toxungen, which is actively transferred to the external surface of another animal via a physical delivery mechanism.
The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typically its form is adapted to functions such as preparing a place for the egg, transmitting the egg, and then placing it properly. For most insects, the organ is used merely to attach the egg to some surface, but for many parasitic species, it is a piercing organ as well.
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionary strategies within parasitism, distinguished by the fatal prognosis for the host, which makes the strategy close to predation.
Velvet ants (Mutillidae) are a family of more than 7,000 species of wasps whose wingless females resemble large, hairy ants. Their common name velvet ant refers to their resemblance to an ant, and their dense pile of hair, which most often is bright scarlet or orange, but may also be black, white, silver, or gold. Their bright colors serve as aposematic signals. They are known for their extremely painful stings,, and has resulted in the common name "cow killer" or "cow ant" being applied to the species Dasymutilla occidentalis. However, mutillids are not aggressive and sting only in defense. In addition, the actual toxicity of their venom is much lower than that of honey bees or harvester ants. Unlike true ants, they are solitary, and lack complex social systems.
Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" (petiole) formed between the first two segments of the actual abdomen; the first abdominal segment is fused to the thorax, and is called the propodeum. Therefore, it is general practice, when discussing the body of an apocritan in a technical sense, to refer to the mesosoma and metasoma rather than the "thorax" and "abdomen", respectively. The evolution of a constricted waist was an important adaption for the parasitoid lifestyle of the ancestral apocritan, allowing more maneuverability of the female's ovipositor. The ovipositor either extends freely or is retracted, and may be developed into a stinger for both defense and paralyzing prey. Larvae are legless and blind, and either feed inside a host or in a nest cell provisioned by their mothers.
The Ichneumonidae, also known as ichneumon wasps, ichneumonid wasps, ichneumonids, or Darwin wasps, are a family of parasitoid wasps of the insect order Hymenoptera. They are one of the most diverse groups within the Hymenoptera with roughly 25,000 species described as of 2016. However, this likely represents less than a quarter of their true richness as reliable estimates are lacking, along with much of the most basic knowledge about their ecology, distribution, and evolution. It is estimated that there are more species in this family than there are species of birds and mammals combined. Ichneumonid wasps, with very few exceptions, attack the immature stages of holometabolous insects and spiders, eventually killing their hosts. They thus fulfill an important role as regulators of insect populations, both in natural and semi-natural systems, making them promising agents for biological control.
A tarantula hawk is a spider wasp (Pompilidae) that preys on tarantulas. Tarantula hawks belong to any of the many species in the genera Pepsis and Hemipepsis. They are one of the largest parasitoid wasps, using their sting to paralyze their prey before dragging it to a brood nest as living food; a single egg is laid on the prey, hatching to a larva which eats the still-living host. They are found on all continents other than Europe and Antarctica.
A stinger is a sharp organ found in various animals capable of injecting venom, usually by piercing the epidermis of another animal.
The jack jumper ant, also known as the jack jumper, jumping jack, hopper ant, or jumper ant, is a species of venomous ant native to Australia. Most frequently found in Tasmania and southeast mainland Australia, it is a member of the genus Myrmecia, subfamily Myrmeciinae, and was formally described and named by British entomologist Frederick Smith in 1858. This species is known for its ability to jump long distances. These ants are large; workers and males are about the same size: 12 to 14 mm for workers, and 11 to 12 mm for males. The queen measures roughly 14 to 16 mm long and is similar in appearance to workers, whereas males are identifiable by their perceptibly smaller mandibles.
A bee sting is the wound and pain caused by the stinger of a female bee puncturing skin. Bee stings differ from insect bites, with the venom of stinging insects having considerable chemical variation. The reaction of a person to a bee sting may vary according to the bee species. While bee stinger venom is slightly acidic and causes only mild pain in most people, allergic reactions may occur in people with allergies to venom components.
Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causing the death of these hosts. Different species specialise in hosts from different insect orders, most often Lepidoptera, though some select beetles, flies, or bugs; the spider wasps (Pompilidae) exclusively attack spiders.
Aculeata is a subclade of Hymenoptera containing ants, bees, and stinging wasps. The name is a reference to the defining feature of the group, which is the modification of the ovipositor into a stinger. However, many members of the group cannot sting, either retaining the ovipositor, or having lost it altogether. A large part of the clade is parasitic.
Insect sting allergy is the term commonly given to the allergic response of an animal in response to the bite or sting of an insect. Typically, insects which generate allergic responses are either stinging insects or biting insects. Stinging insects inject venom into their victims, whilst biting insects normally introduce anti-coagulants into their victims.
The discipline of medical entomology, or public health entomology, and also veterinary entomology is focused upon insects and arthropods that impact human health. Veterinary entomology is included in this category, because many animal diseases can "jump species" and become a human health threat, for example, bovine encephalitis. Medical entomology also includes scientific research on the behavior, ecology, and epidemiology of arthropod disease vectors, and involves a tremendous outreach to the public, including local and state officials and other stake holders in the interest of public safety.
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. The wasps do not constitute a clade, a complete natural group with a single ancestor, as bees and ants are deeply nested within the wasps, having evolved from wasp ancestors. Wasps that are members of the clade Aculeata can sting their prey.
A scorpion sting is an injury caused by the stinger of a scorpion resulting in the medical condition known as scorpionism, which may vary in severity. The anatomical part of the scorpion that delivers the sting is called a "telson". In typical cases, scorpion stings usually result in pain, paresthesia, and variable swelling. In serious cases, scorpion stings may involve the envenomation of humans by toxic scorpions, which may result in extreme pain, serious illness, or even death depending on the toxicity of the venom.
Biting is an action involving a set of teeth closing down on an object. It is a common zoological behavior, being found in toothed animals such as mammals, reptiles, amphibians, fish, and arthropods. Biting is also an action humans participate in, most commonly when chewing food. Myocytic contraction of the muscles of mastication is responsible for generating the force that initiates the preparatory jaw abduction (opening), then rapidly adducts (closes) the jaw and moves the top and bottom teeth towards each other, resulting in the forceful action of a bite. Biting is one of the main functions in the lives of larger organisms, providing them the ability to forage, hunt, eat, build, play, fight, protect, and much more. Biting may be a form of physical aggression due to predatory or territorial intentions. In animals, biting can also be a normal activity, being used for eating, scratching, carrying objects, preparing food for young, removing ectoparasites or irritating foreign objects, and social grooming. Humans can have the tendency to bite each other whether they are children or adults.
Leiurus abdullahbayrami is a species of scorpion in the family Buthidae. Its venom is highly toxic to humans, but can be used in medical development.
Hemiscorpius lepturus is a species of scorpion in the family Hemiscorpiidae. It is found in deserts of the Middle East, especially in southern Iraq and Iran, where it is sometimes referred to as the "Gadim scorpion". These scorpions have long, thin tails and wide bodies and grow to 8 cm (3.1 in) in males and 5.5 cm (2.2 in) in females, allowing them to live in tight rock crevices. They are fairly solitary creatures. H. lepturus has mainly been studied to discover the components and effects of its venom, which is highly lethal and is responsible for most deaths due to scorpion sting in the Iran area. H. lepturus is the only scorpion not in the family Buthidae that is potentially lethal to humans; the Buthidae family is the largest and most abundant family of scorpions, containing many highly venomous species.