Emergency Department Care
Occlusion/suffocation approaches
This noninvasive approach includes placing petroleum jelly, liquid paraffin, beeswax or heavy oil, or bacon strips over the central punctum and has been used to coax the larvae to emerge spontaneously head-first over the course of several hours, at which time, tweezers (or forceps) aid in the capture. Enlarging the punctum beforehand may make it easier to remove the larvae later as it emerges and is usually needed for botflies. [17] Anecdotal evidence has shown the larvae to emerge within 3-24 hours after application of suffocating material. [18, 19]
These approaches take advantage of the larva's oxygen requirements, encouraging it to exit on its own. However, the covering should not be restrictive (eg, nail polish) because this may asphyxiate the larva without causing it to migrate out of the skin. If the larva does asphyxiate, then surgical removal is necessary.
Surgical removal with local anesthesia
The skin lesion is locally anesthetized with lidocaine and excised surgically followed by primary wound closure. Alternatively, lidocaine can be injected forcibly into the base of the lesion in an attempt to create enough fluid pressure to extrude the larvae out of the punctum. [20] The larvae are anchored deeply to the subcutaneous by anterior hooklets and it is important to remove all parts from the site to prevent a foreign body reaction. [2] Another surgical approach would be to perform a 4- to 5-mm punch excision of the overlying punctum and surrounding skin to gain better access to and visibility of the larva. The larva can then be removed carefully using toothed forceps (experience of B.B. Wilson, MD).
The larva should not be forcibly removed through the central punctum because its tapered shape with rows of spines and hooks prevents simple extrusion.
Furthermore, care should be taken to avoid lacerating the larva because retained larval parts may precipitate foreign body reaction. After removal of the larvae, antiseptic dressings, thorough cleansing, and debridement are indicated, as well as antibiotics if secondary infection is present.
Systemic/topical ivermectin
An alternative treatment for all types of myiasis is oral ivermectin or topical ivermectin (1% solution), proven especially helpful with oral and orbital myiasis.
Wound myiasis
Wound myiasis requires debridement with irrigation to eliminate the larvae from the wound or surgical removal. Application of chloroform, chloroform in light vegetable oil, or ether, with removal of the larvae under local anesthesia, has been advocated for wound myiasis. [1, 20]
Surgical removal is not required unless requested by the patient, as the larvae are naturally sloughed within 5-7 weeks.
Consultations
Depending on the location of the larval infestation, dermatologists (wound and furuncular myiasis), ophthalmologists (ophthalmomyiasis), or otorhinolaryngologists (oral, facial, nasal myiasis) may need to be consulted.
Complications
Care must be taken to extract the larva whole, otherwise a considerable foreign body reaction may ensue. Also, in the case of secondary pyogenic infection, appropriate antibiotics should be administered.
Myiasis can be a portal of entry for Clostridium tetani; therefore, vaccination should be considered in affected individuals. [1]
Prevention
Individuals traveling to rural endemic areas should be covered at all times with long-sleeved shirts, pants, and hats. At night, sleeping on raised beds, in screened rooms, or under a mosquito net is appropriate. Insect repellents are also recommended. Clothing should be hot-ironed and dried appropriately to remove any residual eggs in areas endemic to tumbu flies. [2]
To prevent wound myiasis, simple antisepsis is usually adequate. Wounds should be cleaned and irrigated intermittently, and proper dressings should be applied. Patients with any type of wound should not be permitted to sleep outside and, if in an indoor or hospital environment, the windows should never be opened, unless properly screened. [20]
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Mature larva of the Dermatobia hominis fly; rows of hooks apparent on its tapered body. Image courtesy of Kenneth E Greer.
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Boil-like lesion on toe of a patient with botfly myiasis; the central punctum is apparent. Image courtesy of Kenneth E Greer.
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Boil-like lesions on a patient with botfly myiasis; the central punctum is apparent. Image courtesy of Kenneth E Greer.
