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Arch Ophthalmol. 1998;116:684.

Human cases of myiasis (infestation by fly larvae) are rarely observed in North America. We report a case of palpebral myiasis that appeared as periorbital cellulitis.

Report of a Case
A 32-year-old man was seen in August 1997 with redness and swelling around his right eye. The patient had noted a "stinging" sensation in his right cheek 2 weeks earlier. Periorbital edema and erythema developed 4 days before presentation in association with a site of serosanguineous drainage in the right medial canthus.

Examination results revealed a track of erythema between the initial stinging site and the site of drainage, in addition to periorbital erythema and edema (Figure 1). Results of the ocular examination were otherwise normal, including normal visual acuity, extraocular motility, and slitlamp and fundus findings. A golden, gelatinous foreign body observed at the site of drainage was removed using forceps and was revealed to be an insect larva measuring 6x2 mm (Figure 2). The larva was identified as that of a botfly (Cuterebra species) based on its size, shape, and pattern of spinous rings. Oral cephalexin was prescribed for possible secondary infection; the cellulitis resolved in 1 week.

View larger version (162K): [in this window] [in a new window] Figure 1. Initial presentation. Note the site of initial "stinging" sensation (black arrow), track of erythema (arrowheads) and site of larval removal (white arrow).

View larger version (63K): [in this window] [in a new window] Figure 2. Cuterebra larva removed from the patient.

Comment
Most reported cases of ocular myiasis have been external to the globe (ophthalmomyiasis externa).¹ Ophthalmomyiasis externa has been associated with larvae of Cuterebra species (rodent or rabbit bots), Oestrus ovis (sheep nasal bot), Hypoderma bovis (cattle grub), and Dermatobia hominis (human bot),¹ and can be differentiated based on larval characteristics and the clinical presentation.² Opthalmomyiasis interna (involvement within the globe) presents with pathognomonic subretinal tracks or an intraocular larva.³

Human infection with Cuterebra larvae, although rare, is the most frequent cause of myiasis in North American patients who have not traveled abroad.² In contrast, patients with myiasis who have recently returned from Latin America typically harbor D hominis.² Rodents and rabbits are natural hosts of Cuterebra larvae. Humans contact the tiny (about 1-mm-long) infective larvae on vegetation or outdoor pets.² Larvae typically enter the host's body through mucous membranes or skin lacerations.^{2, 4} However, a larva may penetrate directly through the skin and develop at this site, or may sometimes migrate to another site.² Once a site is established, the larva cuts a hole through the skin, producing a furuncle-type lesion, through which it obtains oxygen and excretes.⁴ Most patients are seen in August, September, or October² with the typical lesion that does not respond to antibiotic therapy. Treatment involves removal of the larva and the inflammation is generally resolved within 1 week.

The patient in this report lives near a wooded area of North Carolina where Cuterebra is endemic. We believe the patient was infected through the skin at the site of the initial stinging sensation on the cheek, with migration of the larva to the site of presentation. Previously reported cases of ophthalmomyiasis externa have involved primary infection of the ocular surface or adnexa. Our case is unique in that the larva migrated from a distant site to produce periocular involvement simulating preseptal orbital cellulitis.

AUTHOR INFORMATION

Nicholas E. Engelbrecht, MD; R. Patrick Yeatts, MD
Winston-Salem, NC

Frank Slansky, PhD
Gainesville, Fla

Reprints: R. Patrick Yeatts, MD, Wake Forest University Eye Center, Medical Center Boulevard, Winston-Salem, NC 27157-1033 (e-mail: pyeatts{at}bgsm.edu).

REFERENCES
1. Rodrigues MM, Weiss CB, Muncy DW. Opthalmomyiasis of the eyelid caused by Cuterebra larva. Am J Ophthalmol. 1974;78:1024-1026. WEB OF SCIENCE | PUBMED 2. Baird JK, Baird CR, Sabrosky CW. North American cuterebrid myiasis. J Am Acad Dermatol. 1989;21:763-772. WEB OF SCIENCE | PUBMED 3. Slusher MM, Holland WE, Weaver RG, Tyler ME. Ophthalmomyiasis interna posterior: subretinal tracks and intraocular larvae. Arch Ophthalmol. 1979;97:885-887. FREE FULL TEXT 4. Catts EP. Biology of New World bot flies: Cuterebridae. Ann Rev Entomol. 1982;27:313-338. FULL TEXT | WEB OF SCIENCE

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