How To Diagnose And Treat Insect Bites And Stings

Author(s): 
By Gary Dockery, DPM, and Stephen Schroeder, DPM

There are abundant crawling and flying insects that infest, bite and sting humans, particularly on the foot and ankle regions. At this time of the year, people may be particularly susceptible to bites from ants, fleas, ticks and spiders. Other possible problems may include infestations with scabies and stinging insects.
There are various types of ants that can inflict different levels of bites and stings. The three main stinging and biting ants are fire, harvester and pharaoh ants.
The fire ant is common in the southeastern United States and Caribbean islands. Its sting causes immediate pain that quickly resolves and leaves a cluster of cutaneous lesions. Small red wheals form and convert to vesicles within three to four hours. After 24 hours, the lesions typically are pustules with a red rim and will resolve in about 10 days. Multiple ant stings may cause a more serious systemic allergic reaction. Treatment includes cool compresses, antipruritic lotions, oral antihistamines and scrupulous cleansing of the area to prevent secondary bacterial infection.

Harvester ants are found in the southern portion of the U.S. They are large (up to 1 cm long), red-brown and sometimes winged ants. Like fire ants, they are ferocious stingers that swarm in large numbers. The stings can be nasty. They usually sting multiple times and the stings tend to form a linear pattern. Unlike the lesions left by fire ants, the lesions of the harvester ant do not form pustules and they usually clear within a few days. Treatment is symptomatic only.
The pharaoh ant is found in the warm southern states. This small brown ant may inflict a small but painful sting that is considered milder than that of other ants. The area typically stays red for several days before resolving and often resolves with no treatment.

How To Remedy Flea Bites
The flea is a blood-sucking parasite from the order Siphonaptera, which contains two important groups or families: Pulicidae (human, dog, cat and bird fleas) and Tungidae (true sand fleas). Fleas found on beaches on the East Coast of the U.S., in Mexico and in the Caribbean islands are frequently called “sand fleas” but they are almost always of the Pulicidae family rather than the Tungidae family. The Tungidea fleas are more common in South America, Africa and the West Indies.
The human, dog, cat and bird fleas will all feed on humans. Fleas are small, reddish-brown to black, hard-bodied, flat-sided, wingless insects that have the ability to jump about two feet. The adult flea can survive for several months without eating. They live in rugs, furniture, sand, grass and pet sleeping areas.
Human attacks from pet fleas are more often acquired from the furniture or carpet region than from the pet itself. Most pet fleas prefer their host animal but will bite humans in the same house. An increase in flea bites is sometimes noticed when the pet is lost or gone from the living area. Flea bites frequently occur on the lower extremities in irregular clusters because the flea likes to sample several adjacent areas while feeding. Individuals at the beach often get multiple flea bites about the feet and ankles while sitting in the sand.
Fleas also feed in a characteristic linear pattern of three to four bites in a row. These papules may have a hemorrhagic center and be intensely pruritic.

Treatment begins with topical corticosteroids for the pruritus and oral antihistamines for the sensitized individual. In order to eliminate the fleas and larvae from the living environment, one must utilize insecticide sprays and powders for all suspected flea breeding and living grounds.

Understanding The Potential Impact Of Tick Bites
The tick bite is usually inconsequential by itself. However, the tick may act as a carrier of several organisms that cause rickettsial, spirochetal, bacterial and parasitic infections. Some of the more important conditions include Rocky Mountain spotted fever, relapsing fever, Colorado tick fever, Lyme disease, erythema chronicum migrans, tularemia, tick bite paralysis and Western equine encephalitis. Ticks are blood-sucking ectoparasites that typically live in grass, brush and wooded areas. Adults are usually infested on the legs and feet while they are in heavy grass or walking in the woods.
The adult tick can reach 1 cm in length, has eight legs and a large teardrop or oval-shaped body. Soft and hard-bodied ticks comprise the two main families with hard-bodied ticks being the vectors for most tick-borne diseases. Ticks are dark, grayish brown to black, and have a leather-like shell. Hard ticks may remain attached to the victim for up to 10 days while soft ones usually release in a few hours after filling with blood. The tick bite is usually painless and may go unnoticed until a lump, urticarial wheal or pruritus forms around the tick.
Rocky Mountain spotted fever occurs in many parts of the U.S. but is prevalent in Oklahoma, Texas and the South Atlantic states. This condition is caused by Rickettsia rickettsii and is transmitted in the tick bite. The infection is seasonal and corresponds to the increased activity of ticks occurring between early April and late September. The principal vector in the western states is the wood tick, Dermacentor andersoni. In the eastern states, it is the dog tick, Dermacentor variabilis. In the south central states, it is the Lone Star tick, Amblyomma americanum. The tick will transmit the disease after it has been attached for at least six hours. The incubation period ranges from three to 12 days and the onset of early symptoms is abrupt with fever, chills, headache, myalgia, arthralgia and generalized rash.

The rash usually appears first on the wrist and ankles. The forearm, palms and soles become involved within hours and then the rash becomes generalized. Early in the rash presentation, macules blanch with pressure but this ceases after three to four days when the lesions become petechial in nature. Presentation includes fever, headache, myalgia, arthralgia, cough, nausea, vomiting, abdominal cramps, rash and generalized illness.
Tick-borne relapsing fever occurs worldwide with increasing incidence in the Rocky Mountain regions of the U.S. Many different species of ticks serve as vectors of this acute septicemic process, which is caused by several species of spirochete of the genus Borrelia. As the name suggests, this condition is characterized by recurrent paroxysms of fever with or without a body rash. The onset of fever is abrupt and may reach very high temperatures (> 104o F) with chills, headache, abdominal cramps, nausea, vomiting, myalgia and a dry cough. Treatment of choice is erythromycin or tetracycline and one may reduce toxicity by pretreating with corticosteroids and acetaminophen.

Inside Insights On Recognizing And Treating Lyme Disease
Lyme disease is a multi-system condition that involves the skin, nervous system, joints and heart. The disease is caused by the tick-borne spirochete, Borrelia burgdorferi. It is named after Lyme, Ct., where the disease was first reported in children. Lyme disease is now recognized on six continents, in at least 20 countries, and it affects men, women and children equally. Although many states have reported cases, the highest incidences are from Massachusetts to Maryland in the northeast and in Wisconsin and Minnesota in the upper Midwest. The clinical picture is one of headache, stiff neck, myalgia, arthralgia, fatigue and fever (up to 105oF).
Lyme disease has three primary stages. Stage 1 (sometimes called the flu-like stage) is the early infection phase with erythema chronicum migrans (85 percent of cases) at the bite site followed by minor constitutional complaints and regional lymphadenopathy. Stage 2 (cardiac and neurologic stage) is the disseminated infection phase with characteristic signs and symptoms in the cutaneous system, nervous system and musculoskeletal sites. Stage 3 (chronic arthritis and neurologic syndrome stage) is the late persistent infection phase with severe progressive arthritis, chronic encephalomyelitis, chronic fatigue syndrome, ataxic gait, spastic paresis and polyradiculopathy.
Routine laboratory testing is not helpful in diagnosing Lyme disease. One would frequently make a diagnosis solely on the knowledge that the individual was bitten by a tick and subsequently developed a skin lesion in the general area.

Erythema chronicum migrans (ECM) is the most characteristic finding in Lyme disease. Unfortunately, it does not occur in all cases and may even appear as an isolated case in patients who do not recall any tick bite. The skin lesion begins as a small vesicle or papule at the bite site. It slowly enlarges, forming an erythematous ring with a gradually clearing central area, which may return to normal skin color or may be slightly blue. The erythematous ring blanches on pressure and may be slightly elevated but does not scale or form vesicles. The bite may clear, become indurated or ulcerate.
Treatment for Lyme disease and ECM is early administration of oral tetracycline 250 to 500 mg four times a day or doxycycline 100 mg twice a day for three weeks. For children under 8 years of age and in pregnant or lactating females, amoxicillin 250 to 500 mg three times a day (20 to 40 mg/kg/day) for three weeks is recommended. In patients allergic to the penicillins, prescribing erythromycin 250 mg four times a day (30 mg/kg/day for children) for 30 days is recommended.

Key Tips To Share With Patients On Tick Bites
People can best prevent tick bites by wearing protective socks and boots with pant cuffs tucked into the socks. Additionally, patients should inspect all skin areas regularly and apply repellents such as permethrin to outer clothing. Treatment involves the immediate removal of the tick following identification. Removal requires care and patients should perform this with the fingers because of the danger of contracting a rickettsial infection. The hard-bodied ticks are more difficult to remove because they cement their mouth parts into the skin.
The proper technique for tick removal is to attach forceps, tweezers or thread as close to the skin surface as possible while pulling upward with steady even pressure for several minutes until one has removed the tick. Avoid squeezing the tick’s body because infectious fluids can enter the skin. Do not rotate or twist the tweezers during the removal process as this may allow the forepart to break off within the skin, possibly producing a nodule known as a tick bite granuloma. If the mouth parts do not come away or portions are left in the skin, one may remove them with a small punch biopsy. After removing the tick, cleanse the area well with warm water and soap, and disinfect it with isopropyl alcohol.

Applying hot packs, handling ticks with bare hands, twisting the tick off, cutting or puncturing the tick’s body, applying hot items to the tick’s body (which induces regurgitation of infected fluids into the skin) or giving the patient sulfonamides are contraindicated as they appear to enhance rickettsial infections.

What You Should Know About Brown Recluse Spiders
Two species of spiders of the class Arachnida have venom strong enough to produce significant toxic and cutaneous effects in humans while others produce lesions to a lesser degree. The two main genera are Loxosceles and Latrodectus. Five different species of Loxosceles have been associated with cutaneous loxoscelism, a morbid condition following the spider bite that begins with a painful erythematous vesicle and progresses to a gangrenous slough of the affected area. The most frequent offender appears to be Loxosceles recluse or the brown recluse spider. The brown recluse spider hibernates during the winter months. Most bites occur during the spring and summer, and occasionally during the early fall.
This spider’s web is small and haphazard. This spider may be found in old buildings, storage sheds, garages or woodpiles. It will move into occupied homes to nest in closets, behind hanging pictures, in stored clothing areas, under beds and in basements. This makes the spider relatively more accessible to human encounters than other spiders. The brown recluse spider is 5 to 25 mm long, yellow-tan to dark brown in color and has a characteristic, dark violin-shaped design on its back.
The bites of the brown recluse spider usually occur when a person is working around storage areas or cleaning out the garage. Other scenarios include putting on boots, coveralls or jackets that have been hanging in storage closets or basements for some time. Bites typically occur on the hands, arms, feet, legs and buttocks. One may not notice the actual bite or there may be minor stinging or burning to an instantaneous sharp pain similar to a bee sting. The variability of the bite may be due to the amount of venom injected, the age of the victim or the victim’s overall medical status.

After suffering the brown recluse spider bite, people may have two general types of reactions. There is the localized cutaneous injury (loxoscelism) and there is the systemic reaction with intravascular hemolysis, acute vasculitis, platelet thrombi and leukocyte infiltrates. Severe nausea, vomiting, fever, malaise, arthralgias and generalized weakness may all occur. A severe reaction is rarely fatal and most frequently occurs in children and debilitated patients. Most bites result in local cutaneous reactions that have a benign course.
The local cutaneous reaction may be minor. Patients may present with mild to moderate pruritus and an urticarial plaque, or a very small area of necrosis. In many of these cases, the patient will rub or excoriate the area due to the itching and burning, making the clinical diagnosis more difficult. Increased swelling, erythema and pain occur in more involved cases.
With a greater amount of venom, the tissue reaction is more intense and cutaneous loxoscelism occurs. The process starts with the development and expansion of a blue-gray, macular halo around the bite site. A cyanotic vesicle or bulla may appear and the superficial skin may be rapidly infarcted. Pain may be severe at this point. The violaceous macule with a blue center may widen. It may extend into adjacent tissue and start to indent in the center. The depth of the necrotic tissue may extend deeply into muscle. The dead tissue sloughs and leaves a very deep, indolent ulcer.
A closer evaluation of the ulcer shows that it has a necrotic, thick, black eschar with ragged edges. There is usually a surrounding zone of erythema, which becomes violaceous. Lymphangitis or lymphadenopathy may also be present. In a few cases, usually involving children, the tissue reaction is much more severe with extensive tissue necrosis and subsequent generalized systemic symptoms. Rarely, the systemic reaction progresses with peripheral edema, significant discoloration and generalized ecchymosis. Within 12 to 24 hours, the patients frequently complain of fever, chills, nausea, vomiting, muscle cramps, joint pain, generalized weakness and, in some cases, urticaria or hives.
One would make a specific diagnosis via visual identification of the spider. In many cases, no spider is actually seen or captured. However, clinicians may make a presumptive diagnosis by combining the patient’s clinical presentation with the patient’s description of activities immediately before the incident.
Treatment of the brown recluse spider bite is symptomatic in lesser involved cases with rest, cold packs, control of pain and antibiotics to prevent infection. In more severe cases, emphasizing limb elevation, antihistamines for the pruritus and dapsone may be required. One would prescribe dapsone, a leukocyte inhibitor, orally at 50 to 100 mg/day doses. The medication may be helpful in preventing severe necrosis. Dapsone may also prevent severe perivasculitis with polymorphonuclear leukocyte infiltration in viscerocutaneous loxoscelism.
There are treatments and activities that should be avoided in these cases. Clinicians and patients should avoid hot compresses, early incision or excision of the lesion, and localized compression. Patients should avoid strenuous exercise. Once a lesion has passed through all phases of conversion to a dry, necrotic lesion and all of the secondary and systemic symptoms have resolved, clinicians may perform surgical excision of the area with skin grafting for larger (> 1 cm) lesions.

When A Black Widow Spider Bites
The black widow spider, Latrodectus mactans, is one of the most feared of the spider family. However, the fatality rate of those bitten is less than 1 percent. The black widow spider is shiny black and usually has a red or orange double triangle or “hourglass” design on the ventral surface of the abdomen. The female is larger (up to 4 cm in total length) than the male.
The venom of the black widow is a neurotoxin, which produces symptoms of general toxemia after about 10 to 15 minutes. The patient may not feel the actual bite or the bite may produce an immediate, sharp or burning pain that disappears promptly. The black widow injects venom into its victim through its fangs and if one examines the bite area immediately, one may see the two small red fang marks. In most reported cases, there are no local puncture sites noticed. Local tissue reaction is negligible but may include mild erythema or edema.
After the latency period, characteristic symptoms appear. These symptoms include: muscle spasms and cramps, especially of the legs and abdomen; numbness gradually spreading from the inoculation site to involve the entire torso; marked abdominal rigidity; headache; sweating; increased salivation; eyelid edema; a diffuse macular rash; increased deep tendon reflexes; nausea and vomiting. This series of symptoms is collectively termed “latrodectism.” The acute symptoms last for up to 48 hours and gradually decrease in two or three days. In some cases, residual symptoms last for several weeks or months after the acute stage.
Treatment for the black widow spider bite includes: cool compresses; ice packs; analgesics (aspirin for mild pain, morphine for severe pain); muscle relaxants (methocarbamol or diazepam); intravenous calcium gluconate (10 ml of 10% solution); and, in very severe cases or in the young or debilitated patient, antivenom 2.5 ml intramuscularly. The antivenom is prepared from horse serum. A 1 ml vial of normal horse serum for eye sensitivity testing is supplied.
In regard to treatments that are not recommended for these bites, one should avoid applying hot packs to the bite site; performing lancing or suction of the injection area; applying a tourniquet proximal to the site; or performing surgical incision or excision of tissue.

Pertinent Pearls For Treating Bee Stings
The bumblebee, honeybee, wasp, hornet and yellow jacket are the more prominent members of the order Hymenoptera. The stinger unit and venom sac is a modified ovipositor apparatus and only the honeybee leaves its barbed stinger and venom sac in the wound. The stingers of the other bees in this group are not barbed and may be used multiple times. Hymenoptera venoms contain histamines and other vasoactive agents, which are both hemolytic and neurotoxic.

Lower extremity stings usually occur in the spring and summer. Patients are frequently in shorts or shoeless while mowing the grass or working in the garden. The clinical picture after a sting in a non-allergic individual includes moderate to severe pain, a localized wheal, erythema, pruritus and edema. The reactions are greatly exaggerated among people who are allergic to Hymenoptera stings.
Since the honeybee will leave behind a stinger attached to a venom sac, one should try to remove it as quickly as possible. One way is to scrape it out gently with a blunt-edged object such as a credit card or a dull knife. Avoid using forceps and tweezers since the venom sac will compress and inject additional venom into the skin, causing a more severe sting. In some patients, a more extensive local reaction may occur and is marked by severe pain, prolonged edema and intense erythema. These symptoms usually last for greater than two days and may extend for as long as a week. Systemic allergic reactions range from mild or moderate to severe in nature. The moderate reactions include malaise, nausea, vomiting, dizziness and wheezing. The most severe hypersensitivity reactions are anaphylactic and involve hypotension, bronchospasm and laryngeal edema.
One should treat localized stings in non-allergic individuals by emphasizing cool compresses or ice, elevation of the affected part, and a topical lotion composed of equal parts of water and meat tenderizer. Treat localized reactions in allergic patients in the same manner but give patients antihistamines to reduce the inflammatory component of the reaction. In delayed local reactions that appear after 24 hours, utilizing a short course of systemic corticosteroids may be very effective.
For more severe allergic manifestations in adults, one must administer subcutaneous injections of aqueous epinephrine 1:1000 in a dosage of 0.3 to 0.5 ml. Repeat this injection in 20-minute intervals for three injections. Pre-packaged bee sting kits with epinephrine (1:1000) loaded syringes, tourniquets and antihistamine tablets are available. Advise people with known sensitivity to keep one of these kits available at home and during travel to prevent serious anaphylactic episodes.

Dr. Dockery is a Fellow of the American Society of Podiatric Dermatology and a Fellow of the American College of Foot and Ankle Surgeons. He is board certified in foot and ankle surgery. He is the Chairman of the Board and Director of Scientific Affairs for Northwest Podiatric Foundation for Education and Research. Dr. Dockery is the author of Cutaneous Disorders of the Lower Extremity and Lower Extremity Soft Tissue and Cutaneous Plastic Surgery (Elsevier Science).
Dr. Schroeder is a Fellow of the American College of Foot and Ankle Surgeons, and is board certified in foot and ankle surgery. He is the Chief of Podiatric Surgery at Southwest Washington Medical Center. Dr. Schroeder has a private practice in Vancouver, Wash.

References
1. Berger BW: Erythema chronicum migrans of Lyme disease. Arch. Dermatol., 120:1017-1021, 1984.
2. Black JR, Fenske NA: Cutaneous Infestations. In, McCarthy DJ, Montgomery R (eds): Podiatric Dermatology, Williams & Wilkins, Baltimore, Ch. 12, pp.165-177, 1986.
3. Cangialosi CP, Schnall SJ: Pedal spider bite (arachnidism) - report of two similar cases. J Am Pod Assoc., 71: 1981.
4. Caselli MA: Recognizing and treating insect bites and stings in athletes. Podiatry Today 17(8):84-90, 2004.
5. Dockery GL: Infestations, Stings and Bites, In: Dockery GL (ed): Cutaneous Disorders of the Lower Extremity, WB Saunders, Ch. 8, pp 84-100, 1997.
6. Dockery GL: Infestations, Parasites, and Bites. In: Dockery GL and Crawford ME (eds): Color Atlas of Foot & Ankle Dermatology, Ch. 11, pp 191-206, 1999.
7. Fishman TD: How to Treat Bite Injuries, Podiatry Today 16(5):32–36, 2003.
8. Goldenberg E: Soft Tissue Injuries of the Lower Extremities. In, Levy LA, Hetherington VJ (eds): Principles and Practice of Podiatric Medicine, Ch. 40, Churchill Livingstone, New York, 1990, pp. 967-977.
9. Gutowicz M, Fritz RA, Sonoga AL: Brown recluse spider bite: A literature review and case report. J Am Podiat Med Assoc., 79:142-146, 1989.
10. Istell R, Bodmer EJ, Bodmer E: Black widow spider (latrodectus mactans) bite of the foot. J Am Pod Assoc., 69: 562-563, 1979.
11. Marcinko DE, Rappaport MJ: Cutaneous necrotic arachnidism - a case report. J Am Pod Med Assoc., 76:105108, 1986.
12. Needham GR: Evaluation of five popular methods for tick removal. Pediatrics, 75:997-1002, 1985.
13. Pardo RJ, Kerdel FA: Parasites, Arthropods, and Hazardous Animals of Dermatologic Significance. In, Moschella SL, Hurley HJ (eds): Dermatology, Ch. 72, W.B. Saunders Co., Philadelphia, 1992, pp.1923-2003.
14. Steere AC, Malawista SE, Snydman DR: Lyme arthritis: An epidemic of oligoarticular arthritis in children and adults in three Connecticut communities. Arthritis Rheum., 20:7-17, 1977.
15. Woodward TE: Rocky Mountain spotted fever: epidemiology and early clinical signs are key to treatment and reduced mortality. J Infect Dis., 150:465-468, 1984.
16. Wongs RC, Hughes SE, Voorhess JJ: Spider bites: review in depth. Arch Derm, 123:98-105, 1987.
For related articles, please visit the archives at www.podiatrytoday.com.




References:

CE Exam #142

Choose the single best response to each question listed below.

1. In regard to fire ant stings, which of the following statements is true?
a) Small red wheals form but resolve within three to four hours.
b) One should avoid using cold compresses in treatment.
c) They cause immediate pain that quickly resolves and leaves a cluster of cutaneous lesions.
d) None of the above

2. “Sand fleas” are found …
a) on West Coast beaches and the Caribbean islands
b) on East Coast beaches, in Mexico and in the Caribbean islands
c) in Mexico and Europe
d) none of the above

3. When it comes to bites from pet fleas …
a) they occur in a characteristic linear pattern
b) the papules from the bites have a hemorrhagic center
c) the papules from the bites can be intensely pruritic
d) all of the above

4. In regard to Rocky Mountain spotted fever …
a) a rash usually appears first on the wrists and ankles
b) a rash usually appears on the soles of the feet
c) the incubation period ranges from 15 to 30 days
d) none of the above

5. Stage 1 of Lyme disease is marked by …
a) severe progressive arthritis and chronic fatigue syndrome among other symptoms
b) the disseminated infection phase with characteristic signs and symptoms in the cutaneous system
c) erythema chronicum migrans at the tick bite site in 85 percent of cases
d) all of the above

6. What should one do when removing a tick?
a) Squeeze the tick’s body with tweezers
b) Twist the tweezers when hard-body ticks are particularly difficult to remove
c) Utilize a small punch biopsy if the tick’s mouth parts or other portions are left in the skin after removal
d) none of the above

7. Which of the following is true about brown recluse spider bites?
a) Most bites result in local cutaneous reactions that have a benign course.
b) Patients present with severe necrosis in approximately 30 percent of reported cases.
c) When the bite involves a greater amount of venom, there won’t be much of a tissue reaction and cutaneous loxoscelism is rare.
d) None of the above

8. How long can acute symptoms of black widow spider bites last?
a) Six hours
b) 12 hours
c) 24 hours
d) 48 hours

9. Non-allergic individuals who suffer a bee sting may present with …
a) pruritus
b) headache
c) muscle spasms
d) all of the above

10. When people have a delayed local reaction 24 hours after being stung by a bee, what additional treatment step “may be very effective” according to the authors?
a) Topical lotions
b) Antihistamines to reduce the inflammatory component
c) A short course of systemic corticosteroids
d) None of the above

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