Clinical Pathology: Nasal Myiasis (Peenash)
High-Yield Revision Notes for NEET PG / NEXT
Nasal myiasis is a parasitic infestation of the nasal cavities by the larval stage (maggots) of dipterous flies, heavily associated with poor hygiene and conditions causing a putrid odor.
Etiology & Pathogenesis
- Primary Causative Vector: The gravid female fly of Chrysomya bezziana (Old World screwworm fly).
- The Destructive Mechanism: Larvae possess sharp oral hooks and secrete proteolytic enzymes (including collagenases) to liquefy and devour living or necrotic tissue.
- Classic Risk Profiles: Uncontrolled Atrophic Rhinitis (Ozaena) due to its foul odor, neglected leprosy, advanced midfacial malignancies, or comatose patients.
Clinical Progression & Complications
Initial phase presents with irritation, a crawling sensation, and sneezing. This rapidly escalates into a foul-smelling, blood-tinged serosanguinous discharge with profound facial edema.
Endoscopic exam reveals motile, whitish-creamy maggots burrowed deep into inflamed, necrotic tissue.
| Pathological Defect | Anatomical Route & Secondary Sequelae |
|---|---|
| Meningoencephalitis | Larvae eat superiorly through the cribriform plate of the ethmoid bone. This grants direct access to the anterior cranial fossa, triggering purulent meningitis or localized brain abscesses. |
| Orbital Invasion | Erosion through the thin lamina papyracea of the ethmoid bone, allowing larvae to enter the orbit and causing proptosis or absolute blindness. |
Management Protocol
- Larval Immobilization: Instillation of a Chloroform and Turpentine oil mixture (traditionally in a 1:4 ratio) into the nasal cavity. Chloroform paralyzes the maggots, while the turpentine oil forces them to release their grip and surface.
- Mechanical Extraction: Meticulous extraction of maggots one by one using Tilley’s forceps or under direct nasal endoscopy.
- Systemic Antiparasitic Therapy: Oral or intravenous Ivermectin (200 µg/kg as a single dose) serves as a gold-standard systemic therapy to arrest larval development in deep or inaccessible sinus tracts.