What is the treatment for orbital myiasis?

Treatment of Orbital Myiasis

Orbital myiasis requires immediate manual removal of all larvae combined with surgical debridement, with oral ivermectin as an adjunctive therapy to kill remaining larvae, and orbital exenteration reserved for cases with extensive tissue destruction or underlying malignancy. 1, 2, 3

Immediate Management

Primary Treatment: Mechanical Removal

• Manual extraction of all visible larvae using forceps is the cornerstone of treatment and must be performed urgently to prevent rapid progression of tissue destruction 1, 4
• Complete removal is critical as larvae of species like Chrysomya bezziana (Old World screwworm fly) feed on living tissue and can destroy orbital structures within days 1, 5, 4
• Examine for larvae in adjacent structures including nasal cavity and sinuses, as orbital myiasis frequently arises from nasal myiasis 5

Adjunctive Pharmacotherapy

• Oral ivermectin should be administered as a broad-spectrum antiparasitic agent to kill larvae that cannot be mechanically removed, particularly in severe cases 2, 3
• Ivermectin plays an important role in severe orbital myiasis by providing noninvasive treatment of inaccessible larvae 2, 3
• Topical antibiotic ointment should be applied to prevent secondary bacterial infection 5

Diagnostic Imaging

• CT scan of the orbits and paranasal sinuses is essential to determine the extent of larval invasion, assess for bony destruction, and identify involvement of adjacent structures 5
• Imaging guides surgical planning and helps identify intracranial extension risk 4

Definitive Surgical Management

Surgical Debridement

• Aggressive surgical debridement of necrotic tissue is required after larval removal 1, 3
• Debridement must be thorough as Chrysomya bezziana larvae aggressively consume living tissue and pose real risk of intracranial invasion 4

Orbital Exenteration

• Exenteration of the orbit must be seriously considered in massive orbital myiasis and cases associated with underlying malignancies 2
• Extended exenteration followed by reconstructive surgery is indicated when orbital myiasis complicates recurrent basal cell carcinoma or other malignancies 2
• Exenteration is the definitive treatment when orbital tissues are completely destroyed or when malignancy is present 1, 2, 4

High-Risk Populations Requiring Vigilance

• Patients with poor general health or debilitation are at highest risk for rapid progression 1
• Diabetic patients with uncontrolled blood sugar are particularly vulnerable to massive orbital myiasis 5
• Patients with periorbital malignancies (basal cell carcinoma, squamous cell carcinoma) have compromised tissue integrity predisposing to infestation 2
• Previous eyelid surgery or orbital trauma creates entry points for fly larvae 1

Critical Pitfalls to Avoid

• Do not delay treatment—orbital myiasis progresses rapidly and can completely destroy orbital tissues within days, especially in debilitated patients 1
• Do not assume all larvae have been removed with initial mechanical extraction; ivermectin provides coverage for inaccessible larvae 2, 3
• Do not overlook nasal cavity examination, as nasal myiasis is a common source of orbital involvement 5
• Do not underestimate the risk of intracranial invasion with Chrysomya bezziana, which feeds on living tissue 4