Conjunctival Myiais caused by Oestrus ovis in a medical college student which responded to Ivermectin


Ophthalmomyiasis can present as external, internal or orbital infestation. Oestrus ovis is the commonest cause of conjunctival myiasis. Myiasis is a disease usually caused due to poor hygiene and responds to removal of the larvae. We are reporting a case of conjunctival myiasis caused by Oestrus larvae in a medical college student with persistent symptoms after removal of the larvae. The symptoms resolved with ivermectin.

Keywords: Ivermectin, Oestrus ovis, ophthalmomyiasis

How to cite this article:
Kumar M A, Joseph NM, Srikanth K, Stephen S. Conjunctival Myiais caused by Oestrus ovis in a medical college student which responded to Ivermectin. Ann Trop Med Public Health 2013;6:315-6
How to cite this URL:
Kumar M A, Joseph NM, Srikanth K, Stephen S. Conjunctival Myiais caused by Oestrus ovis in a medical college student which responded to Ivermectin. Ann Trop Med Public Health [serial online] 2013 [cited 2017 Nov 14];6:315-6. Available from:

Myiasis, the infestation of live human or vertebrate animals by dipterous larvae, can be cutaneous, ocular, nasopharyngeal, intestinal or urogenital with cutaneous form being the commonest presentation. Human infestation is very rare and is usually seen with low standard of hygiene. The commonest human infestation is by Oestrus ovis (sheep botfly). [1] Ocular infestation can lead to external or internal ophthalmomyiasis. We are reporting a case of conjunctival myiasis in a medical college student.

 Case Report

A 20 year old male undergraduate student of medical college, presented with severe foreign body sensation and redness of right eye after waking up. He gave history of sleeping overnight in the playground after a cultural festival. On examination he had congestion of the lower fornix of right eye. Slit lamp examination revealed multiple larvae which started moving on increasing the illumination. [Figure 1] There was no evidence of corneal or intra-ocular involvement. The left eye was normal. The larvae were immobilized with 4% lignocaine and 7% larvae were removed and sent for microbiological evaluation. They were identified as first instar larva of Oestrus ovis based on their spindle shape and the presence of a pair of sharply curved mouth-hooks.[Figure 2] The patient was started on topical antibiotic-steroid combination (0.3% ofloxacin and 0.1% dexamethasone eye drops). He had persistent irritation and foreign body sensation after 2 days of topical medication. Repeated examination, including double eversion of the upper eyelid did not show any larvae. He was started on oral ivermectin 12 mg single dose. The symptoms started resolving within 24 hours and he was completely asymptomatic after 5 days.

Figure 1: Severe conjunctival congestion of lower fornix with the larvae

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Figure 2: First instar larva of Oestrus ovis showing the presence of a pair of sharply curved mouth-hooks at the anterior end

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Oestrus ovis breeds in the nasal cavity and sinuses of sheep. The fly enters the nostril and deposits larva. The larva crawls into the nose and attach to the mucous membrane with the help of oral hooks. When they mature, they fall out from the nasal passage to pupate in the ground. [1]

Human myiasis is an accidental infection rather than a facultative or obligatory one. [2] Oestrus ovis typically causes external ophthalmomyiasis because the larvae do not usually invade the tissue but cause significant irritation by their curved mandibular barbs and body spines. [1] External ophthalmomyiasis can present acute mucopurulent conjunctivitis, sub-conjunctival nodule or periocular skin lesion. [1],[2] In a recent report from India, pseudo-membrane formation and keratitis have been observed secondary to Oestrus ovis infestation. [3] Internal ophthalmomyiasis due to Oestrus ovis is rare. [4] Orbital ophthalmomyiasis occurs usually in debilitated individuals with nasopharyngeal or ethmoidal sinus tumors. Myiasis has also been reported as a possible risk factor for prion disease. [5]

The typical conjunctival involvement presents as redness, itching, photophobia, discharge, swollen conjunctiva and eyelids mimicking acute mucopurulent conjunctivitis. Under magnification using a slit lamp we can see the larvae freely crawling on the eye balls and moving away from light. Management consists of immobilizing the larvae with 4% lignocaine eye drops and removing with forceps. Mostly the symptoms resolve after removal of the larvae. [1]

Macdonald et al., reported 3 cases of ophthalmomyiasis where the patients developed symptoms of nasal myiasis, after removal of the larvae from the eyes, which cleared with ivermectin. [6] In the present case being reported the patient had persistent ocular symptoms after removal of the larvae and the prompt response to ivermectin suggests a possible sub-conjunctival migration of the larva.

The case is being highlighted because external ophthalmomyiasis should be considered as a differential diagnosis for acute conjunctivitis especially in patients from areas where the fly is endemic [1] and also for the rapid resolution of the symptoms with single dose of ivermectin. Mostly the problem is associated with poor hygiene but the case being reported has occurred in a medical college student because of sleeping in an open area.

1. Narayanan S, Jayaprakash K. Incidence of ocular myiasis due to infection with the larva of oestrus ovis (Oestridae Diptera). Indian J Ophthalmol 1991;39:176-8.
2. Jun BK, Shin JC, Woog JJ. Palpebral myiasis. Korean J Ophthalmol 1999;13:138-40.
3. Sreejith RS, Reddy AK, Ganeshpuri SS, Garg P. Oestrus ovis ophthalmomyiasis with keratitis. Indian J Med Microbiol 2010;28:399-402.
4. Parikh V, Biswas J, Vaijayanthi K, Das D, Raval V. Bilateral ocular myiasis interna caused by botfly (Oestrus ovis): a case report. Ocul Immunol Inflamm 2011;19:444-7.
5. Lupi O. Myiasis as a risk factor for prion diseases in humans. J Eur Acad Dermatol Venereol 2006;20:1037-45.
6. Macdonald PJ, Chan C, Dickson J, Jean-Louis F, Heath A. Ophthalmomyiasis and nasal myiasis in New Zealand: a case series. N Z Med J 1999;112:445-7.

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1755-6783.121027


[Figure 1], [Figure 2]

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