Myiasis Clinical Presentation
- Author: Adam B Blechman, MD; Chief Editor: Joe Alcock, MD, MS more...
Often, a history of traveling to a tropical country or existence of a previous wound is noted. In one study, the average time from exposure to diagnosis was 1.5 months.
Patients complain of boil-like lesions usually on exposed areas of the body, like the scalp, face, forearms, and legs.
Lesions can be painful, pruritic, and tender, and patients often have the sense of something moving under the skin. Sometimes, patients also complain of fever or swollen glands.
In the cases of ophthalmomyiasis, patients complain of severe eye irritation, redness, foreign body sensation, pain, lacrimation, and swelling of the eyelids.
In the cases of nasal myiasis, patients present with epistaxis, foul smell, passage of worms, facial pain, nasal obstruction, nasal discharge, headache, dysphagia, and sensation of foreign body in the nose.[11, 12]
This type of myiasis , caused by both the human botfly and the tumbu fly, causes nonhealing boil-like lesions (see images below). Whereas myiasis from the tumbu fly occurs on the trunk, thigh, and buttocks, botfly lesions are on the exposed areas of the body, including the scalp, face, forearms, and legs. A pruritic erythematous papule develops within 24 hours of penetration, enlarging to 1-3 cm in diameter and almost 1 cm in height. These lesions can be painful and tender. Each has a central punctum (see images below) from which serosanguineous fluid may be discharged. Lesions may become purulent and crusted; the movement of the larva may be noticed by the patient. The tip of the larva may protrude from the central opening (punctum), or bubbles produced by its respiration may be seen. The inflammatory reaction around the lesions may be accompanied by lymphangitis and regional lymphadenopathy.
In wound myiasis , the larvae are deposited in a suppurating wound or on decomposing flesh. The diagnosis is obvious when larvae are visible on the surface within or around the wound and more difficult when they have burrowed beneath the surface.
Creeping cutaneous myiasis
Creeping (or migratory) cutaneous myiasis may be caused when there is exposure to infested cattle or in those who work with horses. This form of myiasis resembles cutaneous larva migrans, with an apparent tortuous, thread-like red line that ends in a terminal vesicle marking the passage of the larva through the skin. The larva lies ahead of the vesicle in apparently normal skin.
Ophthalmomyiasis externa, caused by Oestrus ovis, is characterized by conjunctivitis, lid edema, and superficial punctate keratopathy in response to movement of larvae across the external surface of the globe. Larvae may appear within the cornea, lens, anterior chamber, or vitreous body but rarely undergo development once the globe has been entered.
Patients who are victims of facial trauma or extensive scalp injury can develop extensive intracranial maggot infestation causing meningitis and encephalitis if not properly managed within a reasonable period of time.
In nasal myiasis, examination of the nose (rhinoscopy) reveals an edematous, ulcerated mucous membrane filled with necrotic material and crawling maggots. Patients may have septal perforation or palatal perforation or both. Erosion of the bridge of the nose and adjacent area of the face can also be seen as well as orbital cellulitis and diffuse cellulitis of the face. In a smaller number of patients, examination reveals extensive ulceration of the tonsils and the posterior pharyngeal wall due to maggots.
As mentioned above, the cause for myiasis is the infestation of humans with the larvae of the Diptera order of fly species. More than a hundred species of Diptera have been reported to cause human myiasis. Some of the most common are as follows:
Dermatobia hominis (human botfly) causes furuncular myiasis.
Cordylobia anthropophaga (tumbu fly) also causes furuncular myiasis.
Cochliomyia hominivorax (America) and Chrysomyia bezziana (Africa, Australia, Asia) both cause wound myiasis.
Hypoderma bovis (infested cattle) and Gasterophilus intestinalis (infested horses) both cause creeping (migratory) myiasis.
Oestrus ovis (sheep botfly) causes ophthalmomyiasis.
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