Furuncular myiasis should be considered in a patient who has traveled recently to a botfly-endemic area and who has a furuncular lesion.
A 31 -year-old male, presented to the out patient department with a 2 week history of a gradually enlarging painful boil on right arm. He gave a history of occasional serosanguinous discharge from the lesion. He was systemically well, and had no recollection of an insect bite. He had no history of any topical or systemic treatment. He gave history of recent travel to Africa.
Examination revealed a 2.5cm furuncle (fig 1A & B) with a central pore. When the lesion was manipulated to extract the discharge/pus to send for further examination, a whitish soft tube like projection was seen extending through the central pore. On close examination it seemed like a breathing tube and body of an insect larva.
The protruding larva was grasped immediately with forceps and completely extracted with gentle, continuous tension together with manual pressure exerted on the sides of the nodule. Complete extraction of the larva was possible (fig 2 A & B).
The area was cleaned, and the patient was started on oral antibiotics to prevent any secondary bacterial infection. Oral as well as topical ivermectin was also given along with the antibiotics.
We referred the patient for an ultrasound examination to rule out possibility of multiple larvae. The examination did not reveal any further larvae. Myiasis is the infestation of human tissue by fly larvae. Forms of infestation include wound myiasis, furuncular myiasis, plaque myiasis, creeping dermal myiasis, and body cavity myiasis.1
The human botfly, Dermatobia hominis, is a common cause of furuncular myiasis in the neotropical regions of the New World. The female glues its eggs to the body of a mosquito, stablefly, or tick. When the unwitting vector punctures the skin by biting, the larva emerges from the egg and enters the skin through the puncture wound. Over several days, a painful furuncle develops in which the larva is present.2
Removal of the maggots of furuncular myiasis can be accomplished by injection of a local anesthetic into the skin, which causes the larva to bulge outward. The opening of the furuncle can also be occluded with hair gel, surgical lubricant, lard, petrolatum, or bacon, causing the larva to migrate outward.2 Removal of the intact larva is curative, although infestation may be complicated by secondary bacterial infection.3
A close examination of all furuncular lesions is a must so that the diagnosis is not missed. Furuncular myiasis should be considered in a patient who has traveled recently to a botfly-endemic area and who has a furuncular lesion. The furuncle has a central pore that intermittently exudes a serosanguinous discharge (the feces of the larva), and protrusion of the breathing tube of the larva frequently can be observed with the aid of a hand lens.4
1. Andrew’s diseases of skin. Parasitic infestations, stings, and bites. :Dermatology.12th edition. Elsevier,2016: 441-42.
2.Fydryszewski NA: Myiasis: diagnosis, treatment and medical use of maggots. Clin Lab Sci 2013; 26(2):76–81.
3.Mandell GL, Bennett JE, Dolin R.Myiasis and tungiasis.: Principles and practice of infectious diseases. 6th edn Vol 2. Philadelphia: Churchill Livingstone, 2004: 3307–10.
4. Ramnath B, David PJ and Photini S.: Furuncular myiasis caused by dermatobia hominis in a returning traveler. Am J Trop Med Hyg. 2007 Mar; 76(3): 598–599.