Introduction
Myiasis is infestation of human and animals with larva (maggots) of certain flies.1 Skin is the most common organ of infestation, but maggots have been reported to have been removed from eyes, ears, nose, intestine and urogenital tract.2 Opthalmomyiasis was first reported by Keyt in the year 1910.1 In India it was first described by Elliot as quoted by Subramanyam et al. Very few cases have been documented in Odisha. We here in report a case of opthalmomyiasis reported in southern Odisha (Berhampur) in a 10yr old child.
Case History
A 10 year old male child of a farmer presented to Opthalmology OPD with acute onset of redness of right eye associated with profuse watery discharge, irritation and foreign body sesation and photophobia. There was no history of trauma to the right eye nor any medical history of any allergic conditions that was elicited. There was no hisory of sheep rearing. Opthalmological examination revealed conjunctival erythema, chemosis and haemorrage. Examination of bulbar conjunctiva showed multiple small transluscent organisms with dark head were found to crawl over the bulbar conjunctiva. It avoided the light beam in slit lamp examination. The occular position was normal and movements were full. The cornea, anterior chamber, nostrils and ears were normal. Internal opthalmoscopy was normal without any inflammation. Management started with profuse saline irrigation of right eye. Lachrymal swab was send to our lab for cytological study. After applying 4% lignocaine to paralyse them 6 flies were removed in total from the bulbar conjunctiva. They were fixed with formalin, dehydrated with alcohol, cleared with xylene to make a DPX mount. Microscopy revealed larvae ranging from 0.5 to 1 .5 mm size with a spindle shaped segmented cephalopharyngeal skeleton, one pair of oral hooks and tuft of brown hooks arising from each body segment. Laryngeal swab cytology revealed few benign mature squamous cells and sparse inflammatory cells. Topical antibiotics and antihistaminics were advocated and follow up was done. He was relieved of his symptoms. Based on clinical findings and microscopic identification of sheep botfly larva (oestus ovis) a diagnosis of opthalmomyiasis externa was rendered.
Discussion
Myiasis is an infestation of human by dipterous fly larva. 1 Opthalmomyiasis accounts for less than 5% of total myiasis cases 3, 4. Most common myiatic flies are botfly, blowfly and screwfly. Ocular myiasis is generally caused by 3 species- Oesttridae, calliphoridae and sacrophagidae. It is classified accordingly to part of host involved as dermal, subdermal, nasopharyngeal, occular, auricular, intestinal and urogenital. 2, 4, 5 Invasion through skin is the most common route. 4
The sheep botfly larva is an obligate parasite of sheep and cattle. Man becomes an accidental host when the fly disharges a stream of larva near the conjunctiva, 4, 5 that is similar in our case. Larva cannot survive in human eye for more than 10 days, hence the condition is self limiting.6 Depending on the severity and site of infestation myiasis can be categorised into externa, interna and orbital involving conjunctiva, globe and orbit respectively. 4 External ocular Myiasis refers to the superficial infestation of the ocular tissues including conjunctiva. Most common clinical symptoms includes redness of eye, excessive lacrimation, photobia, itching and foreign body sensation. Conjunctival myiasis if neglected leads to destructive myiasis with penetration of larvae into sclera and subretinal space resulting in iridocyclitis, endopthalmitis (Opthalmomyiasis interna), invasion of orbit sometimes even leading to blindness.3, 6 Opthalmomyiasis normally occurs in the spring and summer seasons of the year. Our case was also detected this year March 2022. Khurana et al stated that ulcerated, diseased and immunocompromised hosts are more prone to the disease.3 Other Predisposing factors include diabetes mellitus, leprosy, open wounds and psychiatric illness.
Myiasis is often underdiagnosed due to its rare occurrence and similarity of clinical presentation as that of allergic and viral conjunctivitis 5 which is one the closest differential of red eye. Larvae may be at times missed during slit lamp examination, hence double eversion of eyelid is essential to locate them in fornices.3 Larva is also not found in lachrymal secretions as it anchors with conjunctiva by means of body hooks. Sometimes profuse irrigation with normal saline may fail to dislodge the larvae.4 The key diagnostic feature thus rests on manual removal of larva and positive identification of larva by microscopic examination. Care must be taken to prevent laceration of larvae as left out portion may evoke an inflammtaory response or secondary bacterial infection.3 Topical application of antibiotics needs to be given. Anti parasitic drugs like ivermectin seems promising in the treatment aspect and may be used in the dosage of 200µg/kg. Besides manual removal and surgical debridement other treatment options described in literatures includes the use of turpentine oil, liquid paraffin and betadine for removal of maggots.7 Follow up examination is prudent to ensure total clearance of the larvae. Our patient is asymptomatic as of now and is on follow up since past two months.
Conclusion
We report this case to draw attention that larval conjunctivitis may be a cause of red eye in spring and summer season and should be included in differential diagnosis of allergic conjunctivitis. Practise of improved sanitation, hand hygiene preventive measure may be emphasised for people involved in sheep rearing as suggested by Seema Bose.6 An early prompt diagnosis by taking proper history, examination and immediate management thus reduces the duration of discomfort, morbidity and potential complications like endopthalmitis and orbital Opthalmomyiasis.
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