How To Diagnose And Treat Insect Bites And Stings

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Continuing Education Course #142 — June 2006

I am pleased to introduce the latest article, “How To Diagnose And Treat Insect Bites And Stings,” in our CE series. This series, brought to you by the North American Center for Continuing Medical Education (NACCME), consists of regular CE activities that qualify for one continuing education contact hour (.1 CEU). Readers will not be required to pay a processing fee for this course.

Podiatrists will invariably see an increase in patients with insect bites and stings on the lower extremity as more people participate in outdoor activities. With that in mind, Gary Dockery, DPM, and Stephen Schroeder, DPM, discuss the diagnosis of bites and stings inflicted by ants, ticks, spiders and bees. They also offer pertinent insights on appropriate treatment.

At the end of this article, you’ll find a 10-question exam. Please mark your responses on the enclosed postcard and return it to NACCME. This course will be posted on Podiatry Today’s Web site ( roughly one month after the publication date. I hope this CE series contributes to your clinical skills.


Jeff A. Hall
Executive Editor
Podiatry Today

INSTRUCTIONS: Physicians may receive one continuing education contact hour (.1 CEU) by reading the article on pg. 91 and successfully answering the questions on pg. 98. Use the enclosed card provided to submit your answers or log on to and respond via fax to (610) 560-0502.
ACCREDITATION: NACCME is approved by the Council on Podiatric Medical Education as a sponsor of continuing education in podiatric medicine.
DESIGNATION: This activity is approved for 1 continuing education contact hour or .1 CEU.
DISCLOSURE POLICY: All faculty participating in Continuing Education programs sponsored by NACCME are expected to disclose to the audience any real or apparent conflicts of interest related to the content of their presentation.
DISCLOSURE STATEMENTS: Drs. Dockery and Schroeder have disclosed that they have no significant financial relationship with any organization that could be perceived as a real or apparent conflict of interest in the context of the subject of their presentation.
GRADING: Answers to the CE exam will be graded by NACCME. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam.
EXPIRATION DATE: June 30, 2007
LEARNING OBJECTIVES: At the conclusion of this activity, participants should be able to:
• discuss and contrast the clinical presentation of stings from fire ants, harvester ants and pharaoh ants;
• review the early clinical presentation of patients who have Rocky Mountain spotted fever transmitted by ticks;
• discuss the primary stages of Lyme disease;
• review the proper technique for tick removal;
• diagnose bites inflicted by brown recluse and black widow spiders; and
• discuss appropriate treatment for bee stings in allergic and non-allergic patients.

Sponsored by the North American Center for Continuing Medical Education.

Here are fire ant bites on the dorsum of the foot. Note the typical circle of stings with two tiny red dots in the center where the jaws were attached.
Harvester ant stings are typically very red and may form a linear pattern.
Here one can see multiple small flea bites on the ankle after a trip to the beach.
A patient noticed an embedded tick on the dorsal surface of the foot after an outing. There was no pain but mild pruritus was present.
Here one can see a brown recluse spider, Loxosceles reclusa, with characteristic fiddle-shaped markings on the cephalothorax.
A close-up view of a brown recluse spider bite shows that the center of the necrotic plaque has sunken below the normal skin (‘sinking infarct’). The ulcerated lesion has a firmly attached, thick black eschar with a ragged edge.
The above photo reveals a bumblebee sting on the lower leg with local reaction and blister formation, and a surrounding wheal in a non-allergic individual.
The above photo reveals a bumblebee sting on the lower leg with local reaction and blister formation, and a surrounding wheal in a non-allergic individual.
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.

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