Excision of furuncular myiasis larvae using a punch: a simple,practical and aesthetic method*
Abstract
INTRODUCTION
Myiasis refers to Diptera larvae infesting vertebrate animals. It affects mainlydeveloping countries and is the fourth most common travel-related disease in placeswhere it is not endemic.1 There aretwo forms of myiasis: primary and secondary. In primary myiasis, fly larvae invadeand develop in healthy tissue. They are thus obligate parasites at this stage. Insecondary myiasis, flies lay their eggs in cutaneous or mucous ulcerations, and thelarvae develop in tissue necrosis products. In these cases they are occasionalparasites.2 The diseasecauses feelings of disgust and discomfort to the patient, and the extraction of thelarvae presents a technical difficulty to health professionals. The risk factors formyiasis include low economic status and precarious hygiene standards.3 Pruritus, pain, and movementsensation are the most commonly reported symptoms, followed by serous output fromsmall orifices.4 Furuncular myiasis(boil-like myiasis) - the form analyzed in this article - is the most common type ofprimary myiasis, and its causative agent in the Americas is Dermatobiahominis (D. hominis). In Brazil, it is known as"berne".5 Diagnosis isbased on history, especially in endemic regions. In case of doubt, dermoscopy,ultrasound and MRI can help make the diagnosis.6 Treatment for furuncular myiasis consists of threetechniques: application of toxic substances to the eggs and larvae; methodsproducing localized hypoxia to force emergence of the larvae; and mechanical orsurgical debridement.7,8 We propose here a new technique for treating furuncular myiasisusing a skin trephine ("punch"). This technique might facilitate the surgicalprocedure and constitute a virtually painless and aesthetic option for thepatient.
CASE REPORT
We describe two cases of furuncular myiasis. Our patients were both female and intheir third decade of life. One lived in the rural area of Muriaé, MG,and the other had a history of travel to the same rural area two weeks before theonset of symptoms. Both patients complained of having pain in the nodular lesion,serous drainage and movement sensation in the left breast and in the left mandibularregion, respectively, for about two weeks. The diagnosis of furuncular myiasis inboth cases was based on clinical and epidemiological data. We performed antisepsisof the surgical site, local anesthesia with lidocaine (infiltrating the periphery ofthe lesion in order to prevent puncturing the larvae) and created an orifice usingpunch 4 (Figure 1A). Detachment of the incisedskin fragment was not carried out, in order to keep the pedicle intact and avoidtissue necrosis (Figure 1B). Next, we lightlycompressed the skin and the larva came out of the orifice in its entirety. Theincised skin fragment was then relocated and an occlusive dressing was applied tothe wound in order to permit proper healing and obtain an aesthetic result (Figures 1C, 1D, 2A, 2B and 2C).
DISCUSSION
Myiasis is the invasion of dead or necrotic body tissues by Diptera larvae. Thefuruncular form of the disease presents as a pruriginous, erythematous nodule,similar to an insect bite, which drains serous fluid from a central orifice, and isassociated with pain and a movement sensation. In the life cycle of D. hominis, thefemale deposits her eggs onto mosquitoes that feed on mammalian blood. The larvathen penetrates the skin and reaches the subcutaneous tissue, where it remains forabout 100 days. The maggot exits the host through the central orifice, falls to theground, and pupates during the next 2-3 weeks. D. hominis emerges as an adult andlives for 8-9 days, during which time it lays eggs on mosquitoes, completing thecycle.9 Although it onlyremains in the host for 100 days, the majority of affected persons choose to havethe larva removed as soon as the disease is diagnosed. There are several extractiontechniques, but the ideal technique is the one that is practical, less painful andleads to less risk of secondary infection. The currently most widely used techniquesfor myiasis treatment are manual compression, larva asphyxiation by occlusion, andsurgical removal with a scalpel. They all have some drawback: technical difficulty,pain, rupture of the larva or unaesthetic scars. Compression causes discomfort andpain to the patient, and is difficult to perform in areas with little folding suchas the scalp or in individuals in certain age groups such as children or olderadults. Furthermore, the circumference of the larva and its spikes, which anchorinto the skin, hinder removal by lateral compression. Occlusion has been reportedusing mineral oil, petroleum jelly, bacon, adhesive tapes, enamel, glue and chewinggum.10 These alternatives,however, may be unsuccessful and elicit foreign body granulomatous reactions if thelarva remains in the subcutaneous tissue instead of exiting through the orifice.Surgical removal with a scalpel is an often unnecessary invasive technique.Moreover, it is contraindicated in cases with cellulitis and often lacerates thelarva, causing local inflammation. The punch is an instrument composed of a circularcutting blade attached to a rod. The use of punch to create an orifice that allowsthe extraction of the larva makes (delicate) lateral compression possible withoutcausing major trauma to the skin. The larva is removed in its entirety, therebyminimizing the potential of an inflammatory response caused by its fragmentation.Besides, it is a less painful procedure, because it is performed with localanesthesia. Furthermore, this surgical extraction method does not remove the skinfragment cut by the punch, as it is used to cover the cavity created by it. Thisallows for a more aesthetic and almost imperceptible healing of delicate body areassuch as the face, because there is no need for suturing of the incision. Treatmentof furuncular myiasis with punch excision of the larvae is a simple and practicaltechnique, and, in addition to generating excellent cosmetic results, causes lessdiscomfort to the patient.
Footnotes
*Study conducted at the Center for Research in Dermatology - University Hospital,Federal University of Juiz de Fora (Nupede-HU-CAS-UFJF) - Juiz de Fora (MG),Brazil.
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