Continuing medical education
Cutaneous myiasis

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Myiasis is the infestation of living tissue by the larvae of flies in the order Diptera. Cutaneous involvement is the most common type of myiasis. Cutaneous myiasis can be subdivided into furuncular, migratory, and wound myiasis. Each subtype is reviewed with discussion of the larvae involved, presenting signs and symptoms, clinical differential diagnoses, and treatment. Preventive measures are also described.

Learning objectives

At the conclusion of this learning activity, participants should be familiar with the causal agents, clinical manifestations, and treatment of human cutaneous myiasis.

Section snippets

Key points

  • The larvae that commonly cause human furuncular myiasis are Dermatobia hominis, Cordylobia anthropophaga, Cuterebra spp., Wohlfahrtia vigil, and W opaca.

  • D hominis is the most common agent of both cutaneous myiasis and furuncular myiasis diagnosed in North America.

  • D hominis is found in Central and South America and uses a carrier insect to transport its eggs to the host.

  • C anthropophaga is found in tropical Africa and causes furuncular myiasis through human contact with egg-infested soil or

Key points

  • The two most common agents of human migratory myiasis are Gasterophilus intestinalis and Hypoderma spp.

  • The burrowing G intestinalis larva is located in the lower layers of the epidermis; the Hypoderma larva burrows subcutaneously and forms a less distinct, erythematous, linear lesion.

  • The G intestinalis larva can be seen with the aid of mineral oil and magnification.

  • Hypoderma myiasis is usually self-limited but can cause a number of serious complications.

  • The larvae that cause migratory myiasis

Key points

  • Cochliomyia hominivorax, Chrysomya bezziana, and W magnifica are the most common flies worldwide that cause human wound myiasis.

  • Predisposing factors for human wound myiasis include open wounds, poor social conditions, poor hygiene, advanced age, psychiatric illness, alcoholism, diabetes, vascular occlusive disease, and the inability to discourage flies from depositing eggs or larvae on the skin because of a physical handicap.

  • Mucous membranes and body cavity openings can also be affected in

Key points

  • One or more treatment regimens, including occlusion, the manual removal of the larva, and larvicides, may be used.

  • Occlusion deprives the larva of oxygen and either kills the larva or induces it to move upward in search of air.

  • Manually squeezing out the larva is a therapeutic option in all forms of furuncular myiasis.

  • Wound myiasis may be treated with occlusion, irrigation, the manual removal of the larvae, and/or larvicides.

Removal of the larvae is curative in all types of myiasis, and all

Preservation and identification of larvae

Identification of dipterous larvae is highly specialized and requires the skill of an experienced pathologist, entomologist, or parasitologist. State health departments and state universities with entomology, parasitology, and veterinary pathology departments can be contacted for assistance in larval identification. Selected additional resource laboratories are listed in Table II. Because the recommendations for killing and preservation of larvae may vary slightly between laboratories,

Conclusion

Human cutaneous myiasis is found year-round in the tropics and typically in the summer months in temperate zones. Because of an increase in international travel, “adventure” travel, and ecotourism, physicians are more likely to encounter myiasis today and in the future than in the past. Obtaining a thorough travel history and having a high index of suspicion is key to the proper diagnosis and, ultimately, the treatment of cutaneous myiasis.

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    Funding sources: None.

    Conflicts of interest: None declared.

    The views expressed in this article are those of the authors and do not reflect the official policy of the Department of the Army, Department of the Air Force, Department of Defense, or the United States Government.

    Reprints not available from the authors.

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