What Is Coming Out of This Wound?

A 63-year-old male patient presented with multiple, oozing nodules on the lower extremities after noticing moving organisms on his right leg (Figure 1). The patient had a history of lymphedema with chronic peripheral venous insufficiency. He denied associated fever, weakness, weight loss, or night sweats. On physical examination, there was bilateral lymphedema and verrucous, pink, cobblestone-like nodules on the lower extremities. There was associated serous drainage and 3 organisms protruding from the right leg.

What Is The Diagnosis?

Keep scrolling for the answer!

Cutaneous Myiasis

Originally coined by Frederick William Hope in 1840, the term myiasis refers to the parasitic infestation of live humans or animals with dipterous larvae (maggots).^1,2 The nomenclature originates from the Greek word for fly, “myia.”³ There are multiple ways to classify myiasis, including anatomical, ecological, and parasitological categorization. Parasitological classification is subdivided into obligatory, wherein the parasite cannot survive without living tissue, or facultative or accidental, in which the larvae are free-living and infection is considered opportunistic.² Clinically, it is more beneficial to use classifications related to the area of the body that is infested, such as cutaneous, ophthalmic, nasopharyngeal, auricular, oral, and urogenital.¹ Although many organs can be infested with maggots, flies are commonly attracted to open wounds, thus rendering cutaneous myiasis as the most common form.³ Cutaneous myiasis can further be subdivided by the type of larvae into furuncular, migratory (creeping), and wound myiasis (eTable 1).^3,4

Human myiasis is seen worldwide, with higher incidence in tropical and subtropical regions of poor socioeconomic status.² It is the fourth most common travel-associated skin disease in countries where myiasis is not endemic.² Wound myiasis is often a result of flies laying eggs into open lesions, especially when necrotic, hemorrhagic, or filled with pus.² In the presence of an open wound, a lack of hygiene and wound care are the most important predisposing factors for myiasis.² Risk factors also include homelessness, advanced age, psychiatric illness, alcoholism, diabetes, vascular occlusive disease, and physical disability.^1,2 Multiple dermatologic manifestations have been associated with the risk of wound myiasis, including ulcers, hyperkeratosis, psoriasis, seborrheic keratosis, onychomycosis, lipedema, herpes zoster infection, leprosy, and impetigo.² Basal cell carcinoma and cutaneous B lymphoma are among the most common skin cancers at risk for larvae infestation.²

Patients typically present after noticing maggots at the wound site. There may be associated erythema, pus, or serosanguinous fluid with the presence of secondary infection. Clinical manifestations of cutaneous myiasis may vary between furuncular, migratory (creeping), and wound myiasis.

Histopathology can be used to distinguish the species of larvae found, determine how the patient was infested, and guide treatment measures. Following immersion in hot water for 30 seconds, the maggots should be preserved in 75% to 90% ethanol to maintain morphology.² Identification is usually performed by an entomologist, taking into account the larvae shape, papillae, posterior and anterior spiracles, spines, skeleton, and pigmentation.² Biopsy of lesions will demonstrate a largely eosinophilic, inflammatory infiltrate with some lymphocytes and histiocytes, and possible necrotic material.^5,6 If granuloma formation is present, giant cells can be identified microscopically.⁶

Cutaneous myiasis is a clinical diagnosis following inspection. Differential diagnoses include abscess, bacterial furunculosis, pyoderma gangrenosum, arthropod bites, and epidermal inclusion cysts (eTable 2).^6-10

Adequate treatment for myiasis consists of complete removal of the maggots in conjunction with antimicrobial therapy. The type of larvae identified and the lifecycle stage can be used to guide the mechanism of removal and antimicrobial regimens.¹¹ Because larvae and fly eggs are allergenic, care must be taken to remove all larvae and larvae fragments from a wound.¹² Chloroform 15% in either oil or ether can assist in removal by immobilizing the larvae.¹² The literature has cited the use of bacon and pork fat, beeswax, petroleum jelly, and mineral oils over the infected area to encourage the larvae to exit the wound.^11,13 If necrotic tissue is present, wound debridement is necessary.¹²

Conversely, maggots, specifically Lucilia cuprina and Lucilia sericata, can be used for treatment purposes to debride wounds and stimulate wound healing.¹² Maggots have been shown to increase granulation tissue formation in open, wet wound beds, although the mechanism is not completely understood.¹⁴ One theory proposes that maggots lead to an increased migration of fibroblasts via serine and metalloproteinases, whereas another cites increased levels of interferon-gamma and IL-10 from maggot excretions.¹⁴ In addition, the ammonia excreted by maggots causes an alkaline environment, which inhibits bacterial growth and helps prevent subsequent infection.¹⁴

Delayed diagnosis can prove hazardous to maggot-infected tissues, causing further tissue destruction and a possible risk of amputation.¹² There is an increased risk of granuloma formation with incomplete maggot removal.¹¹ Untreated eye myiasis can lead to serious complications, including retinal detachment and blindness.¹³ Immunosuppression is linked with increasing complications in patients with maggots.¹³

Our patient was referred following maggot removal by forceps and povidone soak. On inspection, there was verrucous thickening of the bilateral lower extremities. No new maggots were observed. The patient was advised to treat the wound with metronidazole 500 mg mixed in a half gallon of water and applied directly to the affected area. Metronidazole cream was also prescribed for application to the legs daily. He was recommended for follow up with the wound care center as needed and for consideration of a lymphedema pump.

The term myiasis refers to the parasitic infestation of live humans or animals with dipterous larvae (maggots). Cutaneous myiasis can be subdivided into furuncular, migratory (creeping), and wound myiasis. Furuncular myiasis is most commonly caused by Dermatobia hominis and presents with a boil-like nodule that enlarges over time, with associated pain and/or itching. Gasterophilus intestinalis and Hypoderma spp. burrow subcutaneously, causing linear lesions characteristic of migratory myiasis. Wound myiasis is associated with Cochliomyia hominivorax, Chrysomya bezziana, and Wolfhartia magnifica infesting open wounds, mucous membranes, and body cavity openings. Treatment for all variations consists of complete larvae removal and antimicrobial therapy. Risks associated with maggots include tissue destruction, amputation, and granuloma formation.

1. McGraw TA, Turiansky GW. Cutaneous myiasis. J Am Acad Dermatol. 2008;58(6):907-926; quiz 927-929. doi:10.1016/j.jaad.2008.03.014

2. Francesconi F, Lupi O. Myiasis. Clin Microbiol Rev. 2012;25(1):79-105. doi:10.1128/ CMR.00010-11

3. Solomon M, Lachish T, Schwartz E. Cutaneous myiasis. Curr Infect Dis Rep. 2016;18(9):28. doi:10.1007/s11908-016-0537-6

4. Weekes M, Matheson N, Coggle S, Gkrania-Klotsas E. Furuncular myiasis. BMJ Case Rep. 2009;2009:bcr06.2009.2026. doi:10.1136/bcr.06.2009.2026

5. Rodríguez-Cerdeira C, Gregorio MC, Guzman RA. Dermatobia Hominis infestation misdiagnosed as abscesses in a traveler to Spain. Acta Dermatovenerol Croat. 2018;26(3):267-269.

6. Toberer F, Hanner S, Haus G, Haenssle HA. Furuncular myiasis of the lower leg. Acta Dermatovenerol Croat. 2019;27(3):190-191.

7. Baiu I, Melendez E. Skin abscess. JAMA. 2018;319(13):1405. doi:10.1001/ jama.2018.1355

8. Ibler KS, Kromann CB. Recurrent furunculosis—challenges and management: a review. Clin Cosmet Investig Dermatol. 2014;7:59-64. doi:10.2147/CCID.S35302

9. Brooklyn T, Dunnill G, Probert C. Diagnosis and treatment of pyoderma gangrenosum. BMJ. 2006;333(7560):181-184. doi:10.1136/bmj.333.7560.181

10. Weir CB, St.Hilaire NJ. Epidermal inclusion cyst. In: StatPearls [Internet].

StatPearls Publishing; 2021. https://www.ncbi.nlm.nih.gov/books/NBK532310

11. Robbins K, Khachemoune A. Cutaneous myiasis: a review of the common types of myiasis. Int J Dermatol. 2010;49(10):1092-1098. doi:10.1111/j.1365- 4632.2010.04577.x

12. Demir SÖ, Soysal A, Akkoç G, et al. Myiasis of the toe as a complication of a neglected wound: a case report. Wounds. 2016;28(11):E44-E46.

13. Millikan LE. Myiasis. Clin Dermatol. 1999;17(2):191-195; discussion 105-106. doi:10.1016/s0738-081x(99)00011-5

14. Marineau ML, Herrington MT, Swenor KM, Eron LJ. Maggot debridement therapy in the treatment of complex diabetic wounds. Hawaii Med J. 2011;70(6):121-124.