eMedicine Specialties > Emergency Medicine > Environmental

Caterpillar Envenomation

Robert L Norris, MD, Associate Professor, Department of Surgery; Chief, Division of Emergency Medicine, Stanford University Medical Center

Updated: Nov 19, 2008

Introduction

Background

More than 165,000 species of caterpillars in the order Lepidoptera (phylum Arthropoda, class Insecta) exist. About 150 are of medical importance. This importance lies in the ability of many species to induce an irritant or toxic dermatitis in humans and in the ability of some species to sting. Caterpillars are the larval forms of moths and butterflies. After hatching from their eggs, caterpillars pass through 4-5 instars (stages between molts) before they pupate in a cocoon. The adult moth or butterfly emerges from the cocoon to reproduce the next generation. More than 50 species in the United States alone are capable of inflicting a painful sting. Seasonal epidemics of dermatitis can occur when caterpillars are numerous.

The most dangerous caterpillar in the United States is the puss caterpillar or asp (Megalopyge opercularis; see Media file 1), the larval form of the flannel moth. It is found throughout the Southeast, from Maryland to Mexico. Stings from this species are common from June through September.

Caterpillar envenomations. Puss caterpillar or asp. Photo courtesy of the Arizona Poison and Drug Information Center.

Pathophysiology

Human disease from caterpillars or moths usually arises from direct contact, exposure to substances or animals that have been infested with caterpillars or their webs, or contact with airborne caterpillar debris.

Diaz classifies the diseases caused by caterpillars into 5 groups: erucism, lepidopterism, dendrolimiasis, ophthalmia nodosa, and consumptive coagulopathy with secondary fibrinolysis.

Erucism (caterpillar dermatitis) is characterized by a localized, pruritic, maculopapular contact dermatitis and urticaria, and follows contact with toxic hairs, spines, or hemolymph, either directly or following aerosolization.

Lepidopterism is a systemic illness that occurs following such contact, and it is typified by diffuse urticaria, upper airway inflammation, nausea, vomiting, headache, and bronchospasm.

Dendrolimiasis is a more chronic illness that follows contact with the Asian Dendorlimus pini caterpillar. Patients with this disorder demonstrate a pruritic maculopapular rash and migratory polyarthritis/polychondritis, which can progress to chronic osteoarthritis. Occasionally, acute scleritis occurs as well.

Ophthalmia nodosa presents with acute conjunctivitis, progressing to panophthalmitis, following penetration of the cornea by urticating hairs.

Consumptive coagulopathy with secondary fibrinolysis occurs most commonly following stings by the South American Lonomia caterpillar whose venom activates factor X and prothrombin. Patients can demonstrate bleeding from almost any anatomic site and may develop acute renal failure.

Caterpillar venoms are produced by glandular cells in the epithelium and are stored in and injected by urticating hairs and spines (setae). Some species produce toxic hemolymph, which can cause human disease.

In some patients, immunoglobulin E (IgE) antibodies are produced following contact, resulting in a hypersensitive state and the production of generalized urticaria on subsequent re-contact. A few caterpillars lacking urticating hairs are capable of inducing a contact dermatitis (type IV hypersensitivity).

Some caterpillars and moths release their toxic hairs into the environment, where the hairs can be inhaled. Pets or contaminated objects also can carry venomous hairs. In any of these situations, contact with the hairs can cause rhinitis or respiratory disease. Seasonal epidemics of respiratory disease have occurred in Latin America because of this phenomenon. The pathologic response leading to erucism or lepidopterism consists of acute inflammation and cellular infiltration around hairs that have penetrated the skin or conjunctiva or have been inhaled into the respiratory tract.

In the skin, diffuse vascular dilatation occurs, with subsequent edema formation in the superficial dermis and ballooning of keratinocytes within the epidermis that can lead to vesiculation. In the eye, hairs have a remarkable penetrating capacity and may work their way into the cornea, anterior chamber, or lens, where an intense inflammatory response occurs secondary to the nature of the foreign material and direct toxic effects.

Caterpillar venom-filled spines, found only in the larval forms (adult moths and butterflies do not sting), are hollow structures with a single basal poison cell that produces toxin. When pressed into the skin, the tip of the spine fractures, and the venom is injected under pressure. Toxicity declines significantly after the creature's death, but irritant or toxic hairs may retain the ability to cause dermatitis for years. Likewise, the toxic hemolymph of some caterpillars retains its potency for prolonged periods after the animal's death.

Caterpillar venoms are poorly studied but may contain peptides, hyaluronidase, phospholipase A, and biogenic amines such as histamine or histamine-releasing substances. Some, such as the South American Lonomia species, contain fibrinolytic proteases and coagulation activators that can stimulate a consumptive coagulopathy and renal failure in victims.

Frequency

United States

Although no accurate information is available, epidemics of erucism and lepidopterism have been reported. These include school closings, outbreaks of dermatitis and rhinitis in the thousands, and symptoms in more than 500,000 people caused by airborne caterpillar hair dispersion.

International

No accurate information is available, though it appears that the incidence of human disease is increasing.

Mortality/Morbidity

Occasional case reports of death from erucism exist, but death is very rare following stings by most species. Death may be secondary to a hypersensitivity reaction or bleeding diathesis in cases involving caterpillars of the Saturniidae family. In this family, South American Lonomia caterpillars have a high fatality rate (approximately 1.7%) due to the toxicity of their venoms and the fact that many exposures lead to multiple stings due to the communal nature of these species. No deaths have been reported following M opercularis stings.

Reported complications include panophthalmitis, consumptive coagulopathy, intracranial hemorrhage, renal failure, and osteochondritis.

Clinical

History

• While the history of exposure related temporally to the onset of signs and symptoms may be clear, the diagnosis can be challenging. Maintain a high index of suspicion when patients present with unexplained acute dermatitis, rhinitis, conjunctivitis, or wheezing during months when caterpillars are numerous. In some regions of the world, the diagnosis becomes clear when clusters of seemingly unrelated cases start to present.
• Onset of acute dermatitis due to hair exposure may immediately follow exposure or may be delayed 8-12 hours and can be manifested by the following:
  • Intense pruritus, local pain or soreness (less common), and erythematous raised rash, blisters, and bruising at the site may occur. Skin necrosis has occurred following prolonged exposure to toxic hairs. With most toxic caterpillars, systemic symptoms are unusual in the absence of respiratory exposure.
  • Respiratory exposure may precipitate acute rhinitis, tearing, cough, dyspnea, respiratory distress, wheezing, and chest pain. This syndrome may need to be differentiated from the rare case of anaphylaxis.
  • Ocular exposure may initiate an acute conjunctivitis with severe pain, tearing, and redness. Visual acuity can be reduced as inflammation progresses.
  • Stings by venomous caterpillars result in immediate, localized, severe, burning pain, which can radiate proximally and be severe enough to inhibit movement of the extremity (pseudoparalysis). Redness and swelling with slight bruising may occur at the site. Over the first few days, the patient may note the development of small blisters, which can become hemorrhagic. Local findings, including pain, may persist for several days.
  • Systemic complaints may occur within minutes of the sting, although they usually occur within 2 hours. These complaints include headache, dizziness, restlessness, nausea and vomiting, malaise, swollen or tender lymph nodes, muscle spasms, rapid heart rate, and, in exceptional cases, altered mental status. Systemic symptoms usually resolve in 24 hours.
  • Following stings by some of the New World caterpillars in the family Saturniidae, which contain a fibrinolytic component to their venoms, patients may note scattered bruising (onset in 8-72 h) and bleeding from any of a number of sites (eg, gingival bleeding, hematuria). Intracranial bleeding and acute renal failure are possible complications. Coagulopathy can last 2-5 weeks.

Physical

• Local findings include erythematous papules that tend to congregate around the face, neck, trunk, arms, wrists, and hands and may become confluent; vesicles; local purpura; or ecchymosis.
• Systemic signs include a low-grade fever.
• Findings of respiratory exposure include acute rhinitis, tearing, respiratory distress, and wheezing.
• Ocular exposure presents as follows:
  • Findings include acute conjunctivitis.
  • Following penetration of the cornea, findings include keratitis, acute uveitis, and retinochoroiditis.
• Stings present as follows:
  • Local findings include erythema, edema, small petechiae or hemorrhagic papules, vesicles, bullae, and pseudoparalysis of the extremity because of pain. Following M opercularis stings, the site may take on a gridlike pattern matching the distribution of the creature's spines.
  • Systemic findings include restlessness, lymphangitis, lymphadenopathy, muscle spasms, tachycardia, altered mental status (unusual), seizures, and hypotension.

Differential Diagnoses

Other Problems to Be Considered

Phytodermatitis

Workup

Laboratory Studies

Laboratory studies are generally not required for caterpillar stings unless evidence of coagulopathy is present.

• CBC count
• Coagulation studies
  • Prothrombin time (PT)
  • Activated partial thromboplastin time (aPTT)
  • Fibrinogen level
  • Fibrin degradation products
  • D-dimer assay
  • Urine bedside test for blood

Imaging Studies

A chest radiograph is reasonable if the patient has significant respiratory symptoms.

Treatment

Prehospital Care

• The involved skin should be immediately washed with soap and water, and dried without contacting the skin (eg, use a hair dryer).
• Local cooling measures can be applied to reduce pain. This may be enhanced by applying topical isopropyl alcohol or ammonia.
• Following ocular exposure, the eyes should be irrigated immediately with copious water.
• Following dermal exposure to irritant or toxic hairs or setae of caterpillars or moths, sticky tape (especially duct tape) can be applied to the site in an effort to remove retained setae. Alternative effective methods of removal include use of rubber cement, clear fingernail polish, or facial peels (each applied, allowed to dry, then peeled away).
• If acute symptoms follow respiratory exposure, supportive care is in order as necessary, including oxygen, antihistamines, and beta-agonist inhalers, if available.
• Anaphylaxis should be treated in standard fashion.
• Following caterpillar stings, the extremity should be splinted and elevated, and ice should be applied to reduce pain.
• Any potentially constrictive jewelry should be removed before swelling progresses.

Emergency Department Care

• Wash the skin with soap and water as mentioned above if this has not already been done in the field.
• Ensure appropriate tetanus immunization status.
• Treat skin exposure as follows:
  • Apply sticky adhesive tape (especially duct tape) to the site to remove all remaining hairs or spines possible. Other measures of removal as described previously for prehospital care can also be tried.
  • Acute dermatitis can be treated with antihistamines (H1 and/or H2 blockers), although their efficacy is controversial. Additionally, topical steroids may be employed. Systemic steroids may be necessary in patients with severe or persistent cutaneous symptoms. Application of antipruritic products containing menthol may be soothing.
  • Prostaglandin-synthetase inhibitors, such as aspirin or indomethacin, have been reported to reduce associated discomfort, but should be avoided if any evidence of coagulopathy is present.
• Treat respiratory exposure as follows:
  • Symptoms can be managed with antihistamines (H1 and/or H2 blockers) and beta agonist aerosols/inhalers if wheezing is present.
  • If significant symptoms occur, supplemental oxygen administration may be needed, and systemic steroids may be useful.
• Treat ocular exposure as follows:
  • Instill a topical anesthetic and irrigate the eyes immediately with copious saline.
  • Perform a slit lamp examination with fluorescein. The patient should receive close ophthalmologic follow-up care to rule out retained setae or hairs.
  • Eye complications resulting from a retained migrating hair can be severe, and surgical removal may be necessary.
• Treat stings as follows:
  • Management is primarily symptomatic and supportive. Splint and elevate the involved extremity; ice can be applied to reduce pain and swelling. Efforts, as outlined above, should be instituted to remove any retained spines or hairs.
  • Narcotic analgesics may be required for pain relief. Anecdotal reports exist of the successful use of calcium gluconate (eg, 10 mL of a 10% solution by slow intravenous [IV] administration) to relieve muscle pain following M opercularis stings. Antihistamines (H1 and/or H2 blockers) may reduce concomitant pruritus.
• Treat rare cases of caterpillar or moth-related anaphylaxis in standard, aggressive fashion, including airway management, epinephrine, oxygen, antihistamines, steroids, IV fluids, and vasopressors as needed.

Consultations

• Consultations usually are not necessary following most caterpillar contacts.
• Ophthalmology may be needed for prompt consultation if ocular involvement is present.

Medication

Epinephrine and systemic antihistamines (eg, diphenhydramine, cimetidine), topical or systemic steroids, menthol-containing creams, and prostaglandin-synthetase inhibitors, such as aspirin and indomethacin, all may be beneficial in treating dermatitis. Rhinitis resulting from respiratory exposure may respond to antihistamines and systemic steroids. These are also useful for lower respiratory symptoms. Beta-agonist aerosols or inhalers (eg, albuterol) may be beneficial for wheezing. Analgesics may be required for caterpillar stings. The choice of agent should depend on the severity of symptoms. Mild cases may be treated adequately with oral opiates such as hydrocodone or oxycodone, while more severe pain initially may require parenteral agents such as morphine sulfate.

Stings by the South American Lonomia species, which can cause consumptive coagulopathy with hemorrhagic diathesis and acute renal failure, may be treated with antifibrinolytics. If blood products are required, they must be given cautiously to avoid feeding fuel to an on-going consumptive coagulopathy. An antivenom against this species has been produced in Brazil.

Antihistamines

Prevent histamine response in sensory nerve endings and blood vessels. They are more effective in preventing histamine response than in reversing it.

Diphenhydramine (Benadryl, Benylin, Bydramine)

Used for symptomatic relief of allergic symptoms caused by histamine released in response to allergens.

Dosing

Adult

25-50 mg PO q6-8h prn; not to exceed 400 mg/d
10-50 mg IV/IM q6-8h prn; not to exceed 400 mg/d

Pediatric

12.5-25 mg PO tid/qid or 5 mg/kg/d or 150 mg/m²/d divided tid/qid; not to exceed 300 mg/d
5 mg/kg/d or 150 mg/m²/d IV/IM divided qid; not to exceed 300 mg/d

Interactions

Potentiates effect of CNS depressants; due to alcohol content, do not give syrup dosage form to patients taking medications that can cause disulfiramlike reactions

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

May exacerbate angle-closure glaucoma, hyperthyroidism, peptic ulcer, and urinary tract obstruction

Chlorpheniramine maleate (Chlor-Trimeton)

Competes with histamine for H1-receptor sites on effector cells in blood vessels and respiratory tract.

Dosing

Adult

10-20 mg IV/IM/SC as a single dose; not to exceed 40 mg/d
4 mg PO q4-6h; not to exceed 24 mg/d
Sustained release: 8-12 mg PO q8-12h; not to exceed 24 g/d

Pediatric

2-6 years: 1 mg q4-6h IV/IM/SC in equally divided doses; not to exceed 6 mg/d
6-12 years: 2 mg PO q4-6h; not to exceed 12 mg/d PO
Sustained release: 8 mg PO hs

Interactions

CNS toxicity increases with coadministration of other CNS depressants, TCAs, MAOIs, and phenothiazines

Contraindications

Documented hypersensitivity; acute asthma attacks; narrow-angle glaucoma; bladder neck obstruction; symptomatic prostate hypertrophy; stenosing peptic ulcer

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

May cause significant confusional symptoms; not for administration to premature or full-term neonates

Cimetidine (Tagamet)

H2 antagonist that, when combined with an H1 type, may be useful in treating itching and flushing in anaphylaxis, pruritus, urticaria, and contact dermatitis that do not respond to H1-receptor antagonists alone. Use in addition to H1 antihistamines.

Dosing

Adult

Patients with persistent symptoms: 300 mg IV followed by PO administration as outpatient q6h for 2 d or for as long as clinically indicated

Pediatric

25-30 mg/kg/d IV in 6 divided doses

Interactions

Can increase blood levels of theophylline, warfarin, TCAs, triamterene, phenytoin, quinidine, propranolol, metronidazole, procainamide, and lidocaine

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Elderly patients may experience confusional states; may cause impotence and gynecomastia in young males; may increase levels of many drugs; adjust dose or discontinue treatment if changes in renal function occur

Corticosteroids

Onset of action is approximately 4-6 h, and they have limited benefit in the initial acute treatment of rapidly deteriorating anaphylactic patients. However, corticosteroids may benefit patients with persistent bronchospasm or hypotension.

Topical steroids can help reduce cutaneous inflammatory response in caterpillar-induced dermatitis.

Methylprednisolone sodium succinate (Solu-Medrol)

Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.

Dosing

Adult

Loading dose: 125-250 mg IV, followed by 0.5-1 mg/kg/dose q6h for up to 5 d

Pediatric

Loading dose: 2 mg/kg IV, followed by 0.5-1 mg/kg/dose q6h for up to 5 d

Interactions

Coadministration with digoxin may increase digitalis toxicity secondary to hypokalemia; estrogens may increase levels; phenobarbital, phenytoin, and rifampin may decrease levels (adjust dose); monitor patients for hypokalemia when taking medication concurrently with diuretics

Contraindications

Documented hypersensitivity; viral, fungal, or tubercular skin infections

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Hyperglycemia, edema, osteonecrosis, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, growth suppression, myopathy, and infections are possible complications of glucocorticoid use

Prednisone (Deltasone, Orasone, Meticorten)

Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.

Dosing

Adult

1-2 mg/kg PO qd or divided bid until symptom resolution, followed by a 1-wk taper

Pediatric

Administer as in adults

Interactions

Coadministration with estrogens may decrease prednisone clearance; concurrent use with digoxin may cause digitalis toxicity secondary to hypokalemia; phenobarbital, phenytoin, and rifampin may increase metabolism of glucocorticoids (consider increasing maintenance dose); monitor for hypokalemia with coadministration of diuretics

Contraindications

Documented hypersensitivity; viral, fungal, or tubercular infections

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Abrupt discontinuation may cause adrenal crisis; hyperglycemia, edema, osteonecrosis, myopathy, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, myasthenia gravis, growth suppression, and infections may occur

Topical hydrocortisone (Westcort, Dermacort, Cortaid)

DOC for reducing cutaneous inflammatory response in caterpillar-induced dermatitis. Adrenocorticosteroid derivative suitable for application to skin or external mucous membranes. Has mineralocorticoid and glucocorticoid effects resulting in anti-inflammatory activity.

Dosing

Adult

Apply sparingly to affected areas bid/qid

Pediatric

Administer as in adults

Interactions

None reported

Contraindications

Documented hypersensitivity; viral, fungal, and bacterial skin infections

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Prolonged use, applying over large surface areas, application of potent steroids, and occlusive dressings may increase systemic absorption of corticosteroids and may cause Cushing syndrome, reversible HPA axis suppression, hyperglycemia, and glycosuria

Bronchodilators

Via combined alpha-adrenergic and beta-adrenergic agonist action, sympathomimetics are effective in reversing acute bronchospasm of allergic or irritant origin.

An additional option in the management of persistent bronchospasm is via anticholinergics. These agents block the action of acetylcholine at parasympathetic sites in bronchial smooth muscle, causing bronchodilation.

Albuterol sulfate (Ventolin, Proventil)

Beta-agonist useful in treatment of bronchospasm refractory to epinephrine. Relaxes bronchial smooth muscle by acting on beta2 receptors with little effect on heart rate.

Dosing

Adult

2-4 mg/dose PO divided tid/qid; not to exceed 32 mg/d
Inhalant: 1-2 inhalations q4-6h; not to exceed 12 inhalations/d
Nebulizer: 0.5 mL (2.5 mg) of 0.5% inhalation solution diluted in 1-2.5 mL of normal saline q4-6h; higher frequency may be used for intensive care patients

Pediatric

2-6 years: 0.1-0.2 mg/kg/dose PO divided tid; not to exceed 12 mg/d
6-12 years: 2 mg/dose PO divided tid/qid; not to exceed 24 mg/d
>12 years: Administer as in adults
Inhalant dose:
<12 years: Using a tube spacer, give 1-2 inhalations qid
>12 years: Administer as in adults
Nebulizer dose:
<5 years: 0.25-0.5 mL (1.25-2.5 mg) of 0.5% inhalation solution diluted in 1-2.5 mL of normal saline q4-6h in equally divided doses
>5 years: Administer as in adults

Interactions

Beta-adrenergic blockers antagonize effects; inhaled ipratropium may increase duration of bronchodilatation by albuterol; cardiovascular effects may increase with MAOIs, inhaled anesthetics, TCAs, and sympathomimetic agents

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Caution in hyperthyroidism, diabetes mellitus, and cardiovascular disorders

Epinephrine (Adrenalin, EpiPen)

Alpha-agonist effects increase peripheral vascular resistance and reverse peripheral vasodilatation, vascular permeability, and systemic hypotension. Conversely, beta-agonist effects produce bronchodilatation, cause positive inotropic and chronotropic cardiac activity, and result in an increased production of intracellular cAMP.

Dosing

Adult

Initial dose: 0.01 mL/kg IM/SC of 1:1000 solution, not to exceed 0.5 mL of 1:1000 solution (0.5 mg); if accessible, administer fraction of total dose (0.1-0.2 mL) at site of antigenic exposure
Severe anaphylaxis (laryngeal edema, respiratory failure, shock): 10 mL of 1:100,000 dilution of aqueous epinephrine IV over 10 min; if no improvement is seen, establish continuous infusion in which 1 mcg/min of a 4-mcg/mL concentration is started and increased to 4 mcg/min prn

Pediatric

Infuse 0.1 mcg/kg/min IV with increasing increments of 0.1 mcg/kg/min; not to exceed 1.5 mcg/kg/min

Interactions

Increases toxicity of beta-blocking and alpha-blocking agents and that of halogenated inhalational anesthetics

Contraindications

Documented hypersensitivity; cardiac arrhythmias or angle-closure glaucoma; local anesthesia in areas such as fingers or toes because vasoconstriction may produce sloughing of tissue; do not use during labor (may delay second stage of labor)

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Caution in elderly patients, prostatic hypertrophy, hypertension, cardiovascular disease, diabetes mellitus, hyperthyroidism, and cerebrovascular insufficiency; rapid IV infusions may cause death from cerebrovascular hemorrhage or cardiac arrhythmias

Ipratropium bromide (Atrovent)

Synthetic quaternary anticholinergic ammonium compound chemically related to atropine; has antisecretory properties; when applied locally, inhibits secretions from serous and seromucous glands lining nasal mucosa.

Dosing

Adult

Nebulizer: 1 U dose vial (500 mcg) tid/qid with doses 6-8 h apart
Metered dose inhaler: 2 inhalations q4-6h qid; not to exceed 12 inhalations in 24 h

Pediatric

Nebulizer: 250 mcg tid
Metered dose inhaler: 1-2 inhalations tid; not to exceed 6 inhalations in 24 h

Interactions

Drugs with anticholinergic properties, such as dronabinol, may increase toxicity; albuterol increases effects

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Caution in narrow-angle glaucoma, prostatic hypertrophy, and bladder neck obstruction

Analgesics

Pain control is essential to quality patient care. Most analgesics have sedating properties, which may be beneficial for patients who have sustained severe caterpillar stings.

Aspirin (Anacin, Ascriptin, Bayer Aspirin, Bufferin)

Used for treatment of mild to moderate pain and headache.

Dosing

Adult

325-650 mg PO q4-6h; not to exceed 4 g/d

Pediatric

10-15 mg/kg/dose PO q4-6h; not to exceed 60-80 mg/kg/d

Interactions

Effects may decrease with antacids and urinary alkalinizers; corticosteroids decrease salicylate serum levels; additive hypoprothrombinemic effects and increased bleeding time may occur with coadministration of anticoagulants; may antagonize uricosuric effects of probenecid and increase toxicity of phenytoin and valproic acid; doses >2 g/d may potentiate glucose-lowering effect of sulfonylurea drugs

Contraindications

Documented hypersensitivity; liver damage; hypoprothrombinemia; vitamin K deficiency; bleeding disorders; asthma; because of association of aspirin with Reye syndrome, do not use in children (<16 y) with flu

Precautions

Pregnancy

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

May cause transient decrease in renal function and aggravate chronic kidney disease; extreme caution in patients with severe anemia, with history of blood coagulation defects, or who are taking anticoagulants

Morphine sulfate (Duramorph, Astramorph, MS Contin)

Parenteral opiates may be necessary to manage extreme pain in patients with severe stings.

Dosing

Adult

0.1 mg/kg in 2-4 mg increments IV; titrate to desired effect

Pediatric

0.1 mg/kg IV; titrate to desired effect

Interactions

TCAs, MAOIs, and other CNS depressants may potentiate adverse effects

Contraindications

Documented hypersensitivity; hypotension; potentially compromised airway with uncertain rapid airway control; nausea; emesis; constipation; urinary retention

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Avoid in hypotension, respiratory depression, nausea, emesis, constipation, and urinary retention; caution in atrial flutter and other supraventricular tachycardias; has vagolytic action and may increase ventricular response rate

Hydrocodone and acetaminophen (Vicodin)

Drug combination indicated for relief of moderate to severe pain.

Dosing

Adult

1-2 tab or cap PO q4-6h prn pain

Pediatric

Single dose not to exceed 10 mg of hydrocodone bitartrate or 2.6 g/d of acetaminophen
<12 years: Administer based on acetaminophen dose of 10-15 mg/kg/dose PO q4-6h prn
>12 years: Administer based on acetaminophen dose of 750 mg PO q4h
Not to exceed 5 doses in 24 h

Interactions

Coadministration with phenothiazines may decrease analgesic effects; toxicity increases with CNS depressants or TCAs

Contraindications

Documented hypersensitivity; elevated ICP

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Tablets contain metabisulfite, which may cause hypersensitivity; caution in patients dependent on opiates since this substitution may result in acute opiate-withdrawal symptoms upon discontinuation; caution in severe renal or hepatic dysfunction

Nonsteroidal anti-inflammatory agents (NSAIDs)

NSAIDs can be effective in reducing discomfort associated with caterpillar-induced dermatitis.

Indomethacin (Indocin, Indochron ER)

Commonly prescribed NSAID used for reducing inflammatory responses. Rapidly absorbed; metabolism occurs in liver by demethylation, deacetylation, and glucuronide conjugation; inhibits prostaglandin synthesis.

Dosing

Adult

25-50 mg PO bid/tid
75 mg SR PO bid; not to exceed 200 mg/d

Pediatric

1-2 mg/kg/d divided PO bid/qid; not to exceed 4 mg/kg/d or 150-200 mg/d

Interactions

Coadministration with aspirin increases risk of inducing serious NSAID-related adverse effects; probenecid may increase concentrations and, possibly, toxicity of NSAIDs; may decrease effect of hydralazine, captopril, and beta-blockers; may decrease diuretic effects of furosemide and thiazides; may increase PT when taking anticoagulants (instruct patients to watch for signs of bleeding); may increase risk of methotrexate toxicity; phenytoin levels may be increased when administered concurrently

Contraindications

Documented hypersensitivity; GI bleeding or renal insufficiency; coagulopathy

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Acute renal insufficiency, hyperkalemia, hyponatremia, interstitial nephritis, and renal papillary necrosis may occur; increases risk of acute renal failure in patients with preexisting renal disease or compromised renal perfusion; reversible leukopenia may occur (discontinue if persistent leukopenia, granulocytopenia, or thrombocytopenia)

Cardiovascular agents

These agents may be used to support organ perfusion in hypotensive patients unresponsive to intravenous volume expansion.

Dopamine (Intropin)

May be required to support BP in the face of hypotension caused by anaphylactic/anaphylactoid reaction that is unresponsive to fluids and epinephrine.

Dosing

Adult

5-20 mcg/kg/min IV; titrate to effect

Pediatric

Administer as in adults

Interactions

Phenytoin, alpha-adrenergic and beta-adrenergic blockers, general anesthesia, and MAOIs increase and prolong effects

Contraindications

Documented hypersensitivity; patients diagnosed with pheochromocytoma or ventricular fibrillation

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Closely monitor urine flow, cardiac output, pulmonary wedge pressure, and BP during infusion; prior to infusion, correct hypovolemia with either whole blood or plasma, as indicated; monitoring central venous pressure or left ventricular filling pressure may be helpful in detecting and treating hypovolemia

Toxoid

Used for tetanus immunization. A booster injection in previously immunized individuals is recommended to prevent this potentially lethal syndrome.

Tetanus toxoid

Used to induce active immunity against tetanus in selected patients. Immunizing agents of choice for most adults and children >7 y are tetanus and diphtheria toxoids. Necessary to administer booster doses to maintain tetanus immunity throughout life.
Pregnant patients should receive only tetanus toxoid, not a diphtheria antigen-containing product.
In children and adults, may administer into deltoid or midlateral thigh muscles. In infants, preferred site of administration is mid thigh laterally.

Dosing

Adult

Primary immunization: 0.5 mL IM; give 2 injections 4-8 wk apart and a third dose 6-12 mo after second injection
Booster dose: 0.5 mL q10y

Pediatric

Administer as in adults

Interactions

Patients receiving immunosuppressants, including corticosteroids or radiation therapy, may remain susceptible despite immunization due to poor immune response; cimetidine may enhance or augment delayed-hypersensitivity responses to skin-test antigens; avoid concurrent use with systemic chloramphenicol since it may impair amnestic response to tetanus toxoid; concurrent use of tetanus immune globulin may delay development of active immunity by several days (interaction is nevertheless clinically insignificant and does not preclude concurrent use)

Contraindications

Documented hypersensitivity; a history of any type of neurologic symptoms or signs following administration of this product; FDA recommends that elective tetanus immunization be deferred during any outbreak of poliomyelitis because tetanus toxoid injections are an important cause of provocative poliomyelitis

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Do not use to treat actual tetanus infections or for immediate prophylaxis of unimmunized individuals (use instead tetanus antitoxin, preferably human tetanus immune globulin); diminished antibody response to active immunization may be seen in patients receiving immunosuppressive therapy; better to defer primary diphtheria immunization until immunosuppressive therapy discontinued; routine immunization of symptomatic and asymptomatic HIV-infected persons is recommended

Follow-up

Further Inpatient Care

• The vast majority of victims of erucism or lepidopterism are treated as outpatients. The rare patient with significant anaphylaxis following exposure should be admitted to the hospital for further standard monitoring and management.
• Victims of stings by the South American Lonomia caterpillars should be admitted to the hospital and observed for development of coagulopathy.

Further Outpatient Care

• Victims of caterpillar stings can be observed for 2 hours in the ED to ensure that they do not develop significant systemic toxicity.
• Although uncommon, secondary infection can occur following erucism or lepidopterism. Instruct patients to follow up immediately if any signs or symptoms of infection occur. Patients with particularly severe exposures should have scheduled follow-up care to exclude infection or necrosis.
• All patients with ocular exposures to caterpillar or moth hairs or setae should receive early ophthalmologic follow-up care to exclude retained fragments, which can lead to catastrophic complications.
• Following caterpillar stings, local findings, including pain, may persist for several days. Systemic symptoms usually resolve in 24 hours.
• Patients who experience a significant allergic reaction to caterpillar exposure (eg, hypotension, bronchospasm) should receive a prescription for an epinephrine self-administration device prior to discharge from the hospital and should be instructed in its use. They also should consider obtaining and carrying medical alert identification of this history. Unlike therapy for hymenoptera-induced anaphylaxis, there is no desensitization therapy for patients highly allergic to caterpillars.

Deterrence/Prevention

• All caterpillars should be considered potentially toxic, and contact should be avoided. Children particularly should be warned in this regard. When working outdoors during peak caterpillar seasons, individuals should wear long-sleeved shirts, long pants with the cuffs tucked into their socks, and work gloves. Collars should be close fitting to avoid having a caterpillar fall into one's shirt. When working in an area where airborne caterpillar debris is a problem, a tight-fitting face mask and eye protection should be used. Laundered clothing should not be hung outdoors to dry as it may collect airborne caterpillar debris.
• Insecticides can be used to control caterpillar populations. A professional pest specialist or entomologist should be consulted before applying such agents because many caterpillar species are beneficial to agricultural and ornamental plants.
• If a caterpillar is found on one's body, it should be gently lifted off with a stick to avoid contact with potentially toxic hairs, setae, or hemolymph.

Complications

• The wounds or dermatitis that follow exposures to irritant or toxic caterpillars and moths can become secondarily infected, which can lead to scarring and permanent dysfunction. The risk is increased when hairs or spines are retained or in patients with severe pruritus that leads to excessive scratching. In rare cases, necrosis can result from prolonged exposure to caterpillar or moth setae.
• Ocular exposures can cause development of keratitis, acute uveitis, retinochoroiditis, endophthalmitis, and ophthalmia nodosa in the setting of retained hairs that tend to migrate into the eye. The ultimate outcome may be permanent blindness.
• An uncommon but very concerning complication following caterpillar or moth exposures is the development of anaphylaxis in sensitized individuals.

Prognosis

• The prognosis is generally excellent.

Miscellaneous

Medicolegal Pitfalls

• Since secondary infection or necrosis following erucism or lepidopterism is possible, wound care instructions and follow-up care are necessary.
• The risk of major complications following retained, fine setae in the eye dictates that all patients with ocular exposure to caterpillar or moth hairs be referred to an ophthalmologist for further examination and follow-up care.
• Patients who have experienced an anaphylactic reaction following any form of arthropod sting or exposure should receive an appropriate field epinephrine kit and instruction in its use at the time of discharge.

Multimedia

Media file 1: Caterpillar envenomations. Puss caterpillar or asp. Photo courtesy of the Arizona Poison and Drug Information Center.

References

1. Balit CR, Geary MJ, Russell RC, Isbister GK. Prospective study of definite caterpillar exposures. Toxicon. Nov 2003;42(6):657-62. [Medline].

2. Carrijo-Carvalho LC, Chudzinski-Tavassi AM. The venom of the Lonomia caterpillar: an overview. Toxicon. May 2007;49(6):741-57. [Medline].

3. Hare T. Poisonous dwellers of the desert. Presented at: Southwest Parks & Monuments Association. 1995:1-32.

4. Henwood BP, MacDonald DM. Caterpillar dermatitis. Clin Exp Dermatol. Jan 1983;8(1):77-93. [Medline].

5. Horng CT, Chou PI, Liang JB. Caterpillar setae in the deep cornea and anterior chamber. Am J Ophthalmol. Mar 2000;129(3):384-5. [Medline].

6. Peters S. A Colour Atlas of Arthropods in Clinical Medicine. Wolfe Publishing Ltd; 1992:1-304.

7. Pinson RT, Morgan JA. Envenomation by the puss caterpillar (Megalopyge opercularis). Ann Emerg Med. May 1991;20(5):562-4. [Medline].

8. Seibert CS, Shinohara EM, Sano-Martins IS. In vitro hemolytic activity of Lonomia obliqua caterpillar bristle extract on human and Wistar rat erythrocytes. Toxicon. Jun 2003;41(7):831-9. [Medline].

9. Shama SK, Etkind PH, Odell TM, et al. Gypsy-moth-caterpillar dermatitis. N Engl J Med. May 27 1982;306(21):1300-1. [Medline].

10. Sridhar MS, Ramakrishnan M. Ocular lesions caused by caterpillar hairs. Eye. May 2004;18(5):540-3. [Medline].

11. Steele C, Lucas DR, Ridgway AE. Endophthalmitis due to caterpillar setae: surgical removal and electron microscopic appearances of the setae. Br J Ophthalmol. Apr 1984;68(4):284-8. [Medline].

12. Stipetic ME, Rosen PB, Borys DJ. A retrospective analysis of 96 "asp" (Megalopyge opercularis) envenomations in Central Texas during 1996. J Toxicol Clin Toxicol. 1999;37(4):457-62. [Medline].

Keywords

caterpillar envenomations, caterpillar bite, caterpillar sting, Megalopyge opercularis, M opercularis, caterpillar dermatitis, erucism, dermatitis, lepidopterism, Lepidoptera, Arthropoda, Insecta, puss caterpillar, asp, Lonomia

Contributor Information and Disclosures

Author

Robert L Norris, MD, Associate Professor, Department of Surgery; Chief, Division of Emergency Medicine, Stanford University Medical Center
Robert L Norris, MD is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, California Medical Association, International Society of Toxinology, Society for Academic Emergency Medicine, and Wilderness Medical Society
Disclosure: Nothing to disclose.

Medical Editor

Samuel M Keim, MD, Associate Professor, Department of Emergency Medicine, University of Arizona College of Medicine
Samuel M Keim, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Public Health Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

John T VanDeVoort, PharmD, Regional Director of Pharmacy, Sacred Heart & St. Joseph's Hospitals
John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists
Disclosure: Nothing to disclose.

Managing Editor

Gino A Farina, MD, Program Director, Associate Professor of Clinical Emergency Medicine, Department of Emergency Medicine, Long Island Jewish Medical Center, Albert Einstein College of Medicine
Gino A Farina, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Scott H Plantz, MD, FAAEM, Associate Clinical Professor of Emergency Medicine, Rosalind Franklin University of Medicine and Science, Chicago Medical School; Medical Director, WeCare Med, Inc
Scott H Plantz, MD, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine
Disclosure: Nothing to disclose.

© 1994- by Medscape.
All Rights Reserved
(http://www.medscape.com/public/copyright)