Seasonal Care

Be prepared for insect bites and stings

While most common insect bites and stings are minor, when the insect is poisonous or when the patient has an allergic reaction, the situation can be serious. Accurate diagnosis and prompt treatment can save lives and prevent permanent tissue damage.

Encounters with biting and stinging insects are common precipitators of visits to doctor's offices in the warmer months of the year, but the bites of many spiders occur year round.¹ Thriving populations of several species are commonly found indoors, even during the winter months. Most noteworthy is the brown recluse spider whose neurotoxic bite may result in severe systemic and dermatologic manifestations. Here is how to be prepared for patients suffering from bites and stings of both outdoor and indoor insects.

 

Drugs mentioned in this article

Acetaminophen Albuterol (Proventil, Ventolin) Calcium gluconate Cimetidine (Tagamet) Dapsone Diphenhydramine Epinephrine (EpiPen) Glucagon Ibuprofen Nitroglycerin, transdermal Prednisone (Deltasone, Orasone, Meticorten)

HYMENOPTERAN STINGS

The order Hymenoptera contains 3 families of stinging insects. These include the Formicoidea (ants), the Apoidea (honeybees and bumblebees) and the Vespoidea (hornets, wasps, and yellow jackets). The stinging apparatus of these insects is found only in females and is contained within the distal portion of the abdomen. Honeybee stingers contain multiple recurved barbs that prevent the stinger from being withdrawn after use. The insect dies as it attempts to fly away and is separated from its stinger. Honeybees and bumblebees are nonaggressive insects and usually attack only when provoked. The African bumblebee, which was introduced into Brazil in 1956, has gradually migrated north through Central America and Mexico and into the southwest United States. It has spread along the southern United States border from Texas to Arizona and California. The venom of this species is no more toxic than that of the European bumblebee, but unlike its European counterpart, it is highly aggressive, persistent in its attack, and attacks in great numbers.

Because there are fewer barbs on Vespoidea stingers than there are on Apoidea stingers, these stingers can be reused and a single yellow jacket can inflict multiple stings. These insects may dwell in the ground and are likely to sting when stepped on. In the United States yellow jacket stings are the primary cause of allergic reactions. Individuals with known hypersensitivity to hymenopteran venom should always wear shoes when walking outdoors in infested areas.

Hymenopteran venoms have been well-studied. Honeybee venoms contain a number of vasoactive substances including histamine, norepinephrine, dopamine, and peptides that induce mast cell degranulation.² Wasp and hornet venom also contain serotonin. In general, the serotonin concentration in venom is directly related to the amount of pain experienced by the victim.

Sting reactions

The commonest responses to insect stings include localized pain, swelling, erythema, and pruritus (see Table 1). The initial intense stinging sensation usually fades within an hour or so. Severe reactions range from anaphylactic shock and, in some cases, an anaphylactic shocklike state with acute renal failure attributable to muscle breakdown.³ Renal failure results from acute tubular necrosis because of the direct action of venom on the tubular cells and by a deposition of myoglobin and actin in the tubules.⁴ Neurologic complications of insect stings may include optic neuritis and systemic polyneuropathies.^5,6

 

TABLE 1 Common symptoms of hymenopteran stings

Airway obstruction Bronchospasm Erythema Hypotension Pain Pruritus Renal failure Shortness of breath Swelling

Treat local symptoms of insect stings with the application of ice and administration of oral acetaminophen or ibuprofen to relieve pain. Additional treatment includes elevation of the involved extremity and use of a topical corticosteroid (see Table 2). Tetanus vaccination should be updated where indicated.

 

TABLE 2 Treatment for local sting sites

Acetaminophen or ibuprofen Corticosteroids (topical) Diphenhydramine (topical or oral) Elevation of the extremity involved Ice

Hypersensitivity reactions

Insect sting hypersensitivity reactions usually occur within the first 48 hours after the sting and may involve extensive tissue edema (see Figure 1). These sting reactions often superficially resemble cellulitis and are best treated with diphenhydramine, 50 mg q6h po. Antibiotics are not indicated unless the sting site becomes secondarily infected. Individuals who respond to insect stings with large areas of swelling will usually do so with repeated stings but are not likely to develop anaphylaxis, consisting of hypotension, laryngeal spasm, wheezing, and death. Children usually only experience mild sting reactions but may develop hives. They are at little risk for more severe reactions with subsequent stings.⁷ Patients with symptoms of anaphylactic reaction must be rapidly and aggressively treated (see Table 3). Some patients may exhibit a delayed allergic response that can occur up to 2 weeks after the offending sting.⁸

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TABLE 3 Common symptoms of hypersensitivity reactions

Abdominal cramps Airway obstruction Bronchoconstriction Bronchospasm Hypotension Pruritus Tachycardia Urticaria

Treatment of anaphylaxis

Anaphylaxis is appropriately treated with epinephrine SC (see Table 4). H₁-receptor stimulation is responsible for the majority of the symptoms of anaphylaxis. The treatment of anaphylaxis—induced hypotension in adult patients—may also utilize H₁ antihistamines such as diphenhydramine. Children having an anaphylactic reaction are treated with diphenhydramine either IM or IV, 5 mg/kg/d in 4 divided doses.

 

TABLE 4 Anaphylaxis treatment

Epinephrine, 1:1000 (0.3 mL SC, adults; 0.01 mL/kg SC, children) Diphenhydramine, 50 mg po; 10-50 mg IV not to exceed a rate of 25 mg/min; or 50 mg deep IM Cimetidine, 300 mg IV, slow push over 5 min* Trendelenburg maneuver Airway maintenance: oral airway, endotracheal tube prn Supplemental oxygen IV fluids (normal saline) *Unlabeled use.

H₂-receptor stimulation can also contribute to extremely low BP. H₂ antihistamines, such as cimetidine,* may help correct hypotension that persists after administration of epinephrine and diphenhydramine. Other modalities for treating hypotension include the Trendelenburg maneuver and administering normal saline IV. Hypotension that does not respond to these measures may be treated with IV glucagon, 1 mg in 1000 mL D5W. Bronchospasm should be treated with beta-agonists such as albuterol. Airway edema is treated with inhaled epinephrine. Oxygen may be given through nasal cannulae, mask, or through a ventilator. A patient who is in severe respiratory distress may need mechanical ventilation.

*Unlabeled use.

Venom immunotherapy

The diagnosis of venom allergy is based on the history and physical examination, skin tests, and demonstration of serum IgE antibodies to venom. Immunotherapy utilizes the same venom as is used in the skin testing procedure. Approximately 98% of patients allergic to yellow jacket venom and 75% to 80% of patients allergic to bee venom are protected after a 3-year course of treatment.⁹ Initiate therapy in patients who experience sting-induced anaphylaxis or other systemic IgE-mediated reactions. Individuals allergic to the venom of both yellow jackets and hornets may be treated with a combination of their venoms.² Serum sickness, which may occur within 7 to 10 days after a sting and is accompanied by fever, arthralgia, and an urticarial rash, should also be treated with venom immunotherapy.

RED FIRE ANT STINGS

The red fire ant (Solenopsis invicta) is a wingless member of Hymenoptera that is found in the southeastern and south central United States. This ant was first introduced into this country during the 1930s with South American produce that was unloaded in the port of Mobile, Alabama. In addition to S invicta, the most commonly encountered fire ant, 4 other species are recognized. All exhibit venom cross-reactivity. The venom of fire ants is unique: it consists primarily of piperidine alkaloids and less than 1% of protein allergen.¹⁰ These alkaloids have been implicated in the induction of both toxin and IgE-mediated hypersensitivity in humans.¹¹

Red fire ants build their nests in sunny areas in lawns and along roadways. Nests containing a single queen may contain up to 240,000 worker ants while multiple queen nests may contain double that number. Mound density may be as great as 800 per acre.¹² Cold or wet weather induces fire ants to move indoors into areas of human habitation.

Fire ants sting their victims in a unique manner—they bite their prey then pivot along their long axis while repeatedly stinging. This results in a number of stings arranged in a semicircle. Stings produce an immediate, painful, burning sensation generally followed by self-limited, small, sterile pustules, which form within 4 to 24 hours (see Figure 2). Fire ant stings may also result in hypersensitivity reactions characterized by pain, erythema, and swelling that can rapidly involve the entire extremity. These reactions usually occur within 2 days of the sting but they can occur several days later and can be confused with cellulitis. Local allergic reactions as well as neurologic complications leading to seizures and stroke also occasionally occur.

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In rare cases, a single sting can result in anaphylaxis. Most human deaths from fire ant stings, however, result from the simultaneous stings of hundreds of ants that have attacked patients such as those who are bed bound and demented. Deaths due to fire ant envenomation have been reported in the medical literature.^13-15

The treatment of fire ant stings should include a thorough cleansing of the site while carefully avoiding tissue excoriation. Administer a tetanus vaccination. Place a cold compress or ice pack over the affected area. Involved extremities should be elevated and analgesics given. Antibiotics are only indicated in cases of secondary infection.

SPIDER BITES

The bites of approximately 60 species of spiders have been involved in human injury in the United States. All spiders are poisonous, but the bites of members of 2 genera, including the brown recluse spider (Loxosceles reclusa) and the black widow spider (Lactrodectus mactans), cause intense pain and local tissue destruction.

Brown recluse spider bites

Although there are 13 species of brown recluse spiders (brown spiders, fiddleback spiders) in the United States, the venom of only 5 of these species have been reported to cause systemic problems in bitten patients. Human encounters with this spider, especially in the colder latitudes, are often due to the spider's habit of moving indoors and seeking shelter in nooks and crannies. Brown recluse venom has been found to contain al-kaline phosphatase, hyaluronidase, lipase, hemolysins, levarterenol, sphingomyelinase D, and protease. Collectively, these venom components break down the endothelial lining and induce platelet aggregation and thrombi formation in small capillaries resulting in tissue necrosis and ulcer formation. The hyaluronidase component has been implicated in the spread of venom throughout the tissue.

Brown recluse spiders are secretive and often take refuge in clothing that has been placed on the floor; they bite when pressed between the patient's clothing and skin. Bites may instantly result in severe pain, but more often victims experience a slight burning pain that resolves only to reoccur more severely several hours later. The area around the bite generally turns reddish blue during the immediate 24 hours after the bite (see Figure 3). A small blister often forms at the center of the bite. This blister may develop into an eschar over several days. Sloughing of the eschar can result in a large necrotic ulcer (necrotic arachnidism). Ulcers may enlarge up to 30 to 40 cm in diameter although most are less than 1 cm in diameter. Systemic symptoms of the bite of the brown recluse spider, often referred to as loxoscelism, may include fever up to 105°F (40.5°C), chills, arthralgia, myalgia, hemolysis, rash, disseminated intravascular coagulation, and death. A recent study indicates that most patients are women between the ages of 18 and 65 with nonserious bites to the extremities.¹⁶

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Treating brown recluse spider bites

Dapsone is commonly utilized in the treatment of brown recluse spider bites (see Table 5).* Patients may develop a dosage-related hemolysis resulting in aplastic anemia, agranulocytosis, and methemoglobinemia. Treatment plans may include wound curettage and surgical excision of bitten tissue. Wound curettage is generally performed directly after the bite in an effort to remove as much venom as possible. Surgical excision of the bite site is generally undertaken after the bite site has stopped expanding. Prednisone, 100 mg/d, may be given to decrease the inflammation associated with the bite. Transdermal nitroglycerin, 0.1 mg/h, at the bite site may also decrease the morbidity associated with brown recluse spider bites.¹⁷ Brown recluse spider antivenom is the most effective treatment modality for these bites, but it must be used within 24 hours of the bite.

*Unlabeled use.

 

TABLE 5 Treatment for brown recluse spider bites

Dapsone, 50-100 mg/d* Nitroglycerin, transdermal, 0.1 mg/h Prednisone, 100 mg/d Surgical excision Wound curettage *Unlabeled use.

Black widow spider bites

The black widow spider is shy and unassuming and produces irregularly shaped webs in outhouses, under rocks and debris, and along embankments. This spider is found in tropical and temperate regions worldwide and is indigenous to the contiguous 48 United States. It is glossy black in color and possesses a large red hourglass on the underside of a globular abdomen. Several other species are contained within the genus. Considerable interspecies variation in coloration is a natural occurrence. The Florida spotted black widow (Latrodectus bishopi) has a red-spotted, black abdomen but is otherwise entirely orange. It is found in the pine and palmetto thickets of central Florida. Females may reach a body size of approximately 15 mm and an extended leg length of up to 40 mm. Although male spiders are poisonous, they are half the size of the female. Their smaller size precludes human envenomation.

Black widow venom contains alpha-latrotoxin, a potent neurotoxin that ultimately results in muscle depolarization (see Figure 4). A targetlike lesion, or halo lesion is often seen surrounding 2 small fang marks after envenomation. Most black widow envenomations occur on extremities. Upper extremity bites often result in chest or arm tightness or cramps. Patients suffering from lower extremity envenomation may experience severe abdominal cramps. These patients may exhibit a boardlike rigidity of the abdominal muscles.

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Other symptoms include headache, nausea and vomiting, diaphoresis, and edema of the face, eyelids, and hands. Cyanosis, erythema, urticaria, and vesiculation may surround the bite site. Rashes of varying form, including scarlatiniform, papular, vesicular, and morbilliform may be associated with the bite. Although muscle pain and soreness usually resolve within a few days, some patients experience persistent fatigue and myalgia. A 13-year-old male experienced shortness of breath, facial edema, spasmodic muscle contraction and visual hallucinations shortly after suffering a black widow spider bite.¹⁸

Treating black widow spider bites

The treatment of black widow spider bites generally utilizes 10% calcium gluconate IV for muscle pain. Dosages up to 10 mL may be administered with careful monitoring of cardiac status. Repeated doses may be required to completely alleviate the patient's discomfort. Some studies, however, have found calcium gluconate to be ineffective in relieving muscle cramps secondary to black widow envenomation.¹⁹ Black widow antivenom is available but it is not commonly utilized in the United States. Extremely ill patients, or those in whom the potential benefit from treatment with antivenom clearly outweighs the risk of anaphylaxis can certainly be selected for antivenom treatment. Patients who receive antivenom should be pretreated with diphenhydramine IV, 1 mg/kg up to 50 mg. These patients should also be pretreated with epinephrine 1:1000, 0.25 mL SC.

PRODUCED BY DEBORAH KAPLAN

REFERENCES

1. Bischof RO Seasonal incidence of insect stings: autumn "yellow jacket delirium." J Fam Pract. 1996;43:271-3.

2. Reisman RA. Insect stings. N Engl J Med. 1994;331:523-527.

3. Nittner-Marszalska M, Malolepszy J, Mlynarczewski A, et al. A toxic reaction induced by Hymenoptera stings. Pol Arch Med Wewn. 1998;100:252-256.

4. Dos Reis MA, Costa RS, Coimbra TM, et al. Acute renal failure in experimental envenomation with Africanized bee venom. Ren Fail. 1998;20:39-51.

5. Maltzman JS, Lee AG, Miller NR. Optic neuropathy occurring after bee and wasp sting. Ophthalmology. 2000;107:193-195.

6. Creange A, Saint-Val C, Guillevin L, et al. Peripheral neuropathies after arthropod stings not due to Lyme disease: a report of 5 cases and review of the literature. Neurology. 1993;43:1483-1488.

7. Valentine MD, Schuberth KC, Kagey-Sobotka A, et al. The value of immunotherapy with venom in children with allergy to insect stings. N Engl J Med. 1990;323:1601-1603.

8. Reisman RA, Livingston A. Late-onset allergic reactions, including serum sickness, after insect stings. J Allergy Clin Immunol. 1989;84: 331-337.

9. Knulst AC, de Maat-Bleeker F, Bruijnzeel-Koomen CA. Wasp and bee venom allergy. Ned Tijdschr Geneeskd. 1998;18:889-892.

10. Sher MR, Bloom FL. Stinging insect allergy in Florida. J Fla Med Assoc. 1996;83:398-400.

11. Lockey RF. The imported fire ant: immunopathologic significance. Hosp Pract. 1990;25:115-124.

12. deShazo RD, Williams DF. Multiple fire ant stings indoors. South Med J. 1995;88:712-715.

13. deShazo RD, Williams DF, Moak ES. Fire ant attacks on residents in health care facilities: a report of two cases. Ann Intern Med. 1999;131: 424-429.

14. Prahlow JA, Bernard JT. Fatal anaphylaxis due to fire ant stings. Am J Forensic Med Pathol. 1998;19:137-142.

15. deShazo. Imported fire ants—from medical nuisance to medical menace: new concerns for medical facilities in endemic areas. South Med J. 1995;88:1181.

16. Cacy J, Mold J. The clinical characteristics of brown recluse spider bites treated by family physicians: an OKPRN study. Oklahoma Physicians Research Network. J Fam Pract. 1999;48:536-542.

17. Burton KG. Nitroglycerin patches for brown recluse spider bites. Am Fam Physician. 1995;51:1401.

18. Casha P, Criscelli J, Fanton Y, et al. Latrodectism in a child. Arch Pediatr. 1998;5:510-512.

19. Clark R F, Wethern-Kestner S, Vance M V, et al. Clinical presentation and treatment of black widow spider envenomation: a review of 163 cases. Ann Emerg Med. 1992;21:782 787.

ARTICLE CONSULTANT

THOMAS P. FORKS, DO, PhD, Assistant Professor of Family Medicine, University of Mississippi School of Medicine, Jackson.

 

Seasonal Care: Be prepared for insect bites and stings. Patient Care 2002;8:33-47.