ONLINE EXCLUSIVE Ecler Ercole Jaqua, MD, DipABLM, FAAFP; Mary How to identify and treat Hanna, MD; Hobart Lee, MD, FAAFP Department of Family common bites and stings Medicine, Loma Linda University Health, CA A thorough history and physical are key to proper [email protected] diagnosis and treatment following a patient’s encounter The authors reported no potential conflict of interest relevant with an insect, arachnid, or other arthropod. to this article. doi: 10.12788/jfp.0111 nsect, arachnid, and other arthropod bites and stings are PRACTICE common patient complaints in a primary care office. A RECOMMENDATIONS thorough history and physical exam can often isolate the ❯ Recommend that patients I specific offender and guide management. In this article, we use an insect repellent, such outline how to identify, diagnose, and treat common bites and as an over-the-counter formulation that contains stings from bees and wasps; centipedes and spiders; fleas; DEET, picaridin, or PMD flies and biting midges; mosquitoes; and ticks, and discuss (a chemical constituent of how high-risk patients should be triaged and referred for ad- Eucalyptus citriodora oil) to ditional testing and treatment, such as venom immunothera- prevent flea bites. C py (VIT). ❯ Prescribe nonsedating oral antihistamines as first-line Insects and arachnids: symptomatic treatment of Background and epidemiology mild-to-moderate pruritus ❚ Insects are arthropods with 3-part exoskeletons: head, tho- secondary to an insect rax, and abdomen. They have 6 jointed legs, compound eyes, bite. C and antennae. There are approximately 91,000 insect species ❯ When indicated, refer in the United States, the most abundant orders being Cole- patients for venom optera (beetles), Diptera (flies), and Hymenoptera (includes immunotherapy, which is ants, bees, wasps, and sawflies).1 approximately 95% effective The reported incidence of insect bites and stings varies in preventing or reducing widely because most people experience mild symptoms and severe systemic reactions therefore do not seek medical care. Best statistics are for Hy- and reduces the risk of menoptera stings, which are more likely to cause a severe re- anaphylaxis and death. A action. In Europe, 56% to 94% of the general population has Strength of recommendation (SOR) reported being bitten or stung by one of the Hymenoptera spe- A Good-quality patient-oriented cies.2 In many areas of Australia, the incidence of jack jumper evidence ant stings is only 2% to 3%3; in the United States, 55% of people B Inconsistent or limited-quality patient-oriented evidence report being stung by nonnative fire ants within 3 weeks of C Consensus, usual practice, moving into an endemic area.4 opinion, disease-oriented evidence, case series ❚ Arachnids are some of the earliest terrestrial organisms, of the class Arachnida, which includes scorpions, ticks, spiders, mites, and daddy longlegs (harvestmen).5 Arachnids are wing- less and characterized by segmented bodies, jointed append- ages, and exoskeletons.6,7 In most, the body is separated into 2 segments (the cephalothorax and abdomen), except for MDEDGE.COM/FAMILYMEDICINE VOL 69, NO 10 | DECEMBER 2020 | THE JOURNAL OF FAMILY PRACTICE E1 FIGURE 1 those stung < 15 times a year than in Large local reaction those stung > 200 times.10 • Patients with an elevated baseline se- rum level of tryptase (reference range, < 11.4 ng/mL), which is part of the allergenic response, or with biopsy- proven systemic mastocytosis are at increased risk of a systemic sting reaction.11 Presentation: Signs and symptoms vary with severity Insect bites and stings usually cause transient local inflammation and, occasionally, a toxic reaction. Allergic hypersensitivity can result in a large local reaction or a generalized sys- temic reaction12: • A small local reaction is transient and mild, develops directly at the site of the Among sting, and can last several days.13 beekeepers, the RESZ, WWW.FLICKR.COM OF DAVID PHOTO COURTESY • A large (or significant) local reaction, A large local reaction is one with an area of swelling risk of a systemic > 10 cm in diameter that lasts > 24 hours. defined as swelling > 10 cm in diam- reaction is eter (FIGURE 1) and lasting > 24 hours, higher in those occurs in 2% to 26% of people who stung < 15 times mites, ticks, and daddy longlegs, in which the have been bitten or stung.14 This is an a year than in entire body comprises a single segment.5 immunoglobulin (Ig) E–mediated late- those stung Arthropod bites are common in the phase reaction that can be accompa- > 200 times. United States; almost one-half are caused by nied by fatigue and nausea.12,13,15 For a spiders.7 Brown recluse (Loxosceles spp) and patient with a large local reaction, the black widow (Latrodectus spp) spider bites risk of a concomitant systemic reac- are the most concerning: Although usually tion is 4% to 10%, typically beginning mild, these bites can be life-threatening but within 30 minutes after envenomation are rarely fatal. In 2013, almost 3500 bites by or, possibly, delayed for several hours black widow and brown recluse spiders were or marked by a biphasic interval.16 reported.8 • Characteristics of a systemic reaction are urticaria, angioedema, broncho- Risk factors spasm, large-airway edema, hypoten- Risk factors for insect, arachnid, and other sion, and other clinical manifestations arthropod bites and stings are primarily en- of anaphylaxis.17 In the United States, vironmental. People who live or work in a systemic sting reaction is reported proximity of biting or stinging insects (eg, to occur in approximately 3% of bite gardeners and beekeepers) are more likely to and sting victims. Mortality among the be affected; so are those who work with ani- general population from a systemic mals or live next to standing water or grassy bite or sting reaction is 0.16 for every or wooded locales. 100,000 people,2 and at least 40 to 100 There are also risk factors for a systemic die every year in the United States sting reaction: from anaphylaxis resulting from an in- • A sting reaction < 2 months earlier in- sect bite or sting.18 creases the risk of a subsequent sys- • The most severe anaphylactic reac- temic sting reaction by ≥ 50%.9 tions involve the cardiovascular and • Among beekeepers, paradoxically, the respiratory systems, commonly in- risk of a systemic reaction is higher in cluding hypotension and symptoms E2 THE JOURNAL OF FAMILY PRACTICE | DECEMBER 2020 | VOL 69, NO 10 BITES AND STINGS of upper- or lower-airway obstruc- FIGURE 2 tion. Laryngeal edema and circulatory Wasp sting failure are the most common mecha- REPRINTED AND DERMNET NZ (WWW.DERMNETNZ.ORG). 19 nisms of anaphylactic death. PHOTO SUPPLIED BY PROFESSOR RAIMO SUHONEN Bees and wasps Hymenoptera stinging insects include the family Apidae (honey bee, bumblebee, and sweat bee) and Vespidae (yellow jacket, yel- low- and white-faced hornets, and paper WITH PERMISSION. wasp). A worker honey bee can sting only once, leaving its barbed stinger in the skin; a wasp, hornet, and yellow jacket can sting 20 multiple times (FIGURE 2). Unlike a bee, a wasp does not deposit its stinger in the Bee and wasp sting allergies are the most skin. common insect venom allergic reactions. FIGURE 3 A bee sting is more likely to lead to a severe allergic reaction than a wasp sting. Allergic Brown recluse spider bite reactions to hornet and bumblebee stings PHOTO SUPPLIED BY DERMNET NZ (WWW.DERMNETNZ.ORG). are less common but can occur in patients already sensitized to wasp and honey bee stings.20,21 ❚ Management. Remove honey bee stingers by scraping the skin with a fingernail or credit card. Ideally, the stinger should be REPRINTED WITH PERMISSION. removed in the first 30 seconds, before the venom sac empties. Otherwise, intense lo- cal inflammation, with possible lymphangitic streaking, can result.22 For guidance on localized symptomatic care of bee and wasp stings and bites and Here, a necrotic ulcer has developed at the site, stings from other sources discussed in this subsequent to an erythematous halo. article, see “Providing relief and advanced care” on page E6. into prey.25 Most spiders found in the United States cannot bite through human skin.26,27 Centipedes and spiders Common exceptions are black widow and ❚ Centipedes are arthropods of the class brown recluse spiders, which each produce Chilopoda, subphylum Myriapoda, that are a distinct toxic venom that can cause signifi- characterized by repeating linear (meta- cant morbidity in humans through a bite, al- meric) segments, each containing 1 pair of though bites are rarely fatal.26,27 legs.23 Centipedes have a pair of poison claws The brown recluse spider is described behind the head that are used to paralyze as having a violin-shaped marking on the prey—usually, small insects.23,24 The bite of a abdomen; the body is yellowish, tan, or dark larger centipede can cause a painful reaction brown. A bite can produce tiny fang marks that generally subsides after a few hours but and cause dull pain at the site of the bite that can last several days. Centipede bites are usu- spreads quickly; myalgia; and pain in the ally nonfatal to humans.23 stomach, back, chest, and legs.28,29 The bite ❚ Spiders belong to the class Arachnida, takes approximately 7 days to resolve. In a order Araneae. They have 8 legs with chelicer- minority of cases, a tender erythematous ae (mouthpiece, or “jaws”) that inject venom halo develops, followed by a severe necrotic MDEDGE.COM/FAMILYMEDICINE VOL 69, NO 10 | DECEMBER 2020 | THE JOURNAL OF FAMILY PRACTICE E3 FIGURE 4 rowing flea infestation—not a secondary in- Flea bites fection for which the flea is a vector.34,35 ❚ Preventive management.