|Year : 2021 | Volume
| Issue : 3 | Page : 387-389
Ophthalmomyiasis externa caused by Oestrus ovis
Sangameshwarayya B Salimath, Shruti M Agadi, Brijesh A Patil
Department of Ophthalmology, S Nijalingappa Medical College, HSK Hospital and Research Centre, Bagalkot, Karnataka, India
|Date of Submission||16-Jan-2021|
|Date of Acceptance||21-Jun-2021|
|Date of Web Publication||30-Sep-2021|
Dr. Sangameshwarayya B Salimath
Sector No 62, Plot No-M4, H Road, Navnagar, Bagalkot - 587 103, Karnataka
Source of Support: None, Conflict of Interest: None
External Ophthalmomyiasis caused by Oestrus ovis is the most common cause of human myiasis worldwide. Distinguishing it from other causes is important to prevent sight-threatening complications. Two patients present with pain, redness, and foreign-body sensation in affected eye. Motile larvae were seen on slit-lamp examination later diagnosed as O. ovis infestation on microbiological examination. Larvae were removed and patients were started on topical antibiotics, lubricating eye drops, and systemic antihistaminics and followed up for 3 weeks. Improvement was observed within 1 week of treatment. Early diagnosis will help to know the possibility of internal ophthalmomyiasis.
Keywords: Conjunctivitis, Oestrus ovis, ophthalmomyiasis
|How to cite this article:|
Salimath SB, Agadi SM, Patil BA. Ophthalmomyiasis externa caused by Oestrus ovis. Indian J Health Sci Biomed Res 2021;14:387-9
| Introduction|| |
Ophthalmomyiasis is the infestation of human eye by the larvae of certain flies. The clinical presentation varies from simple irritation to complete destruction of the orbit. Sheep nasal botfly (Oestrus ovis) commonly manifests as ophthalmomyiasis externa when there is conjunctival involvement or rarely as ophthalmomyiasis interna when there is larval penetration into the eyeball.
Ophthalmomyiasis externa and interna in humans have been reported to be caused by many types of dipterous flies, most common being the O. ovis. Other which cause human myiasis are Dermatobia hominis (human botfly) and Cordylobia anthropophaga (tumbu fly).,,
We report two cases of ophthalmomyiasis externa caused by O. ovis infestation
| Case Report|| |
A farmer, male, 22-year-old from a rural area of poor socioeconomic status presented on January 22, 2020 with complaints of foreign-body sensation, redness, and watering in the left eye for 3 days. Symptoms started following the entry of dust particles into the eye while cutting sugarcane in the field 5 days ago. There were no complaints in the right eye. There was no history of any systemic illness. At presentation, his best-corrected visual acuity was 6/6 in both eyes.
The conjunctiva was chemosed. We noticed two motile larvae [Figure 1]. The larvae were photosensitive and tended to move toward the fornix under slit-lamp illumination. AC was quiet, cornea was clear, and fundus was within the normal limits. Examination of the right eye was within the normal limits.
|Figure 1: Slit-lamp photograph showing Oestrus ovis larvae in the lower palpebral conjunctiva near the fornix|
Click here to view
A girl, 7-year-old, from a rural area of poor socioeconomic status presented on March 23, 2020, with pain, watering, redness, and foreign-body sensation in the left eye for 2 days following trauma with cow's tail while playing. There were no complaints in the right eye. She gave a history of fever and running nose for 1 day. At presentation, her best-corrected visual acuity was 6/6 in both eyes.
Left eye slit-lamp examination revealed conjunctival chemosis, petechial hemorrhages on everting the upper eyelid. Two–three larvae were seen crawling toward fornices. The cornea was clear, and fundus examination was within the normal limits. Examination of the right eye was within the normal limits.
Based on findings, unilateral allergic conjunctivitis secondary to parasitic infestation was diagnosed in both the cases.
Removal of larvae
By instilling 4% lignocaine into the eye, larvae were immobilized. Larvae were removed using forceps and collected in a sterile container containing normal saline. Larvae were transferred on a glass slide and observed under a microscope.
Both the patients were started on carboxymethyl cellulose 1% eye drops eight times per day and moxifloxacin eye drops 0.5% for six times a day with systemic antihistaminic drugs (levocetirizine dihydrochloride) 5 mg HS for 5 days.
- Transparent, spindle-shaped organism with a pair of curved mouth hooks connected to a large internal cephalopharyngeal skeleton [Figure 2] and [Figure 3]
- The body was divided into segments and each segment was covered by tufts of numerous brown hooks with spinose tips on the anterior margin.
|Figure 2: Microscopic image of Oestrus ovis larvae showing cephalopharyngeal skeleton with two curved oral hooks|
Click here to view
Morphological features suggested of O. ovis larvae. Both the patients were advised for follow-up next day, after 1 week, and weekly for a month. After 1 week, the affected eye was quiet and visual acuity was 6/6 in both eyes. They were advised to stop all medications and followed up for 3 weeks.
| Discussion|| |
O. ovis is one of the common causes of human myiasis in the reported cases. Three dipteran families Oestridae, Calliphoridae (blowflies), and Sarcophagidae (flesh flies) are considered to be the main cause of myiasis in livestock and also occasionally in humans. O. ovis usually infests the nasal cavity and paranasal sinuses of sheep, goats, cattle, and horses. Flies deposit as many as 500 larvae in the nostrils of sheep. O. ovis is a large, yellowish gray fly about 10–12 mm long. Larvae can become parasites in the host, soon after birth. Humans serve as an accidental host when the botfly deposits a stream of larvae near eyes or nose while it is flying. These larvae cause significant conjunctival eosinophilic infiltrations leading to non-necrotizing granulomatous inflammation and eosinophil degranulation, leading to epithelial cell damage and goblet cell secretion. Organisms grab the conjunctiva firmly using pair of oral hooks and numerous brown hooks on each body segment. O. ovis larvae cannot penetrate the cornea or sclera as they lack cannot secrete proteolytic enzymes.
In humans, larvae cannot survive beyond the first larval stage and die within 10 days if not removed. Ophthalmomyiasis interna is commonly associated with cattle bot fly (Hypoderma bovis), but cases have also been reported due to larvae of O. ovis. Hence, ophthalmomyiasis by O. ovis should not be regarded as a benign condition and must be treated to prevent serious complications of intraocular invasion. The presentation of O. ovis myiasis is similar to viral or allergic conjunctivitis. Awareness of larval conjunctivitis, especially during spring and summer, would lead to a more prompt diagnosis and treatment. Ophthalmomyiasis externa is an underdiagnosed condition and may result in serious complications.,
We, as ophthalmologists, need to rule out ophthalmomyiasis by examining all patients of conjunctivitis with or without a history of insect striking the eye by everting lid. Since the larvae are photophobic, it is necessary to look for them in the fornices and also in discharge.
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Conflicts of interest
There are no conflicts of interest.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understand that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.
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[Figure 1], [Figure 2], [Figure 3]