|Year : 2021 | Volume
| Issue : 1 | Page : 60-61
A case report of conjunctival ophthalmomyiasis by oestrus ovis with insights into its morphology, life cycle, and clinical presentation
Vishnu Teja Gonugunta1, Datta Dipankar2, Chinmayee Pabolu3
1 Department of Cornea and Refractive Surgery Services, Aravind Eye Hospital, Madurai, Tamil Nadu, India
2 Chief Medical Officer, Aravind Eye Hospital, Theni, Tamil Nadu, India
3 Department of Glaucoma Services, Aravind Eye Hospital, Madurai, Tamil Nadu, India
|Date of Submission||03-Jun-2021|
|Date of Decision||17-Jul-2021|
|Date of Acceptance||19-Jul-2021|
|Date of Web Publication||01-Nov-2021|
Dr. Vishnu Teja Gonugunta
Department of Cornea and Refractive Surgery Services, Aravind Eye Hospital, Madurai - 625 020, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Conjunctival ophthalmomyiasis is an infestation of larvae on the conjunctiva. The larvae of sheep botfly (Oestrus ovis) can be the cause of ocular irritation in occupationally predisposed individuals like shepherds. External (conjunctival) ophthalmomyiasis can progress to severe form of internal ophthalmomyiasis. We report the presence of live motile larvae of sheep botfly on the conjunctiva of a patient, shepherd by occupation presenting with irritation in the eye. Diffuse ocular examination was normal until everted lid examination revealed two white larvae with black dots at their head end crawling fast on the tarsal conjunctiva. Removal of the larvae is the only treatment, and treatment of the cattle as well, is essential to prevent recurrence and also to increase the cattle yield.
Keywords: Conjunctiva, larvae, Oestrus ovis, ophthalmomyiasis, sheep botfly
|How to cite this article:|
Gonugunta VT, Dipankar D, Pabolu C. A case report of conjunctival ophthalmomyiasis by oestrus ovis with insights into its morphology, life cycle, and clinical presentation. J Ophthalmol Clin Res 2021;1:60-1
|How to cite this URL:|
Gonugunta VT, Dipankar D, Pabolu C. A case report of conjunctival ophthalmomyiasis by oestrus ovis with insights into its morphology, life cycle, and clinical presentation. J Ophthalmol Clin Res [serial online] 2021 [cited 2022 Jan 22];1:60-1. Available from: http://www.jocr.in/text.asp?2021/1/1/60/329780
| Introduction|| |
Conjunctival ophthalmomyiasis is an infestation of larvae on the conjunctiva. The larvae of sheep botfly (Oestrus ovis) can be a common cause of ocular irritation in predisposed individuals like shepherds. External (conjunctival) ophthalmomyiasis can be the cause of ocular irritation in such individuals. We report such a case here.
| Case Report|| |
A 32-year-old female patient, who rears sheep and goat by occupation, presented to our outpatient department in September 2020 with complaints of irritation in her left eye. Two white larvae measuring 1–2 mm in length were seen crawling fast – one on the upper tarsal conjunctiva seen after everting the upper lid and one in the lower fornix [Figure 1]. The eye was immediately anesthetized with 0.5% proparacaine and forceps was used to remove the larva on the conjunctiva and placed on a wet mount for light microscopy and it was then identified as the larva of sheep botfly (Oestrus ovis) from its characteristic appearance [Figure 2]. The patient's symptoms improved following its removal. Gatifloxacin (0.3%)–loteprednol (0.5%) combination eye drop was advised four times a day for 1 week. There was no recurrence in the follow-up period.
|Figure 1: Live larvae of the sheep botfly causing conjunctival inflammation – (a) on the upper tarsal conjunctiva (white arrow). (b) Near the lower lid margin (black arrow). Transparent-to-white body with black dots corresponding to oral hooks is seen at the headend of the larvae|
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|Figure 2: Microscopic appearance (×40) of the first instar stage larva L1 demonstrating the 11 body segments, well-defined black oral hooks at its headend (left side of the image). Contents of the body are partially leaked out due to the trauma inflicted with forceps while holding it|
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| Discussion|| |
Most of the treating ophthalmologists do not necessitate the understanding of the source of the larva, mode of its transmission, and the life cycle of the adult fly, as it does not alter the treatment to the patient. However, the concern arises, when the same patient or others from the same community are repeatedly infected. Thus, knowledge of the life cycle of the sheep botfly is required to address the infestation source in the cattle.
The sheep botfly needs the sheep nasal passages and sinuses to complete its life cycle. Affected sheep can be identified with having nasal discharge, frequent sneezing due to irritation caused by the crawling larvae within their nasal cavities, and decrease in their yield.
Female sheep botflies are known to larviposit. This means the eggs are hatched while still remained inside the female fly, and she will deposit a droplet containing approximately 500 live first instar larvae, L1 stage, into the nose of sheep. The larvae transform into L2 instar in the nasal cavities of sheep and then into L3 instar in the sinuses of sheep, when they are expelled out by the sheep by sneezing and reach the soil. In the soil, the larva transforms into pupa stage within 24 h and finally becomes the adult botfly by 1 month.,
The larvae in the first instar stage, L1, may be deposited into the human eyes directly by the sheep botfly or by direct contact with the sheep., The first instar stage larva which gets deposited on the human ocular surface, cannot grow into the next instars, and moves erratically on the ocular surface. The larva has a small white body tapered at its head and tail ends and measures 1–2 mm with two black oral hooks at its headend. The hooks help them in acquiring food and moving on the surface, especially useful in the nasal cavity of sheep. It has 11 segments on the body and 4 rows of black spines on the posterior surface of its body. The larva crawls with significant speed on the ocular surface, where in a second, they may creep and hide into the fornices as they are photophobic. Complete mechanical removal of the larvae is the only treatment, and a combination of antibiotic-mild steroid drops can be advised after removal to promote faster recovery. If untreated, progression to serious complications like internal ophthalmomyiasis, where the larvae penetrate the globe through the sclera, can occur.
| Conclusion|| |
An everted lid examination is a must in patients with complaints of irritation. Mechanical removal of the larvae is the only treatment. Light microscopy of the larvae can easily be done and helps in identifying the larva, thus its source. Cattle of the patient should be treated by a veterinary doctor to improve their symptoms, yield, and to prevent further infection to humans and community.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
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Cameron JA, Shoukrey NM, Al-Garni AA. Conjunctival ophthalmomyiasis caused by the sheep nasal botfly (Oestrus ovis) Am J Ophthalmol 1991;112:331-4.
Wong D. External ophthalmomyiasis caused by the sheep bot Oestrus ovis L. Br J Ophthalmol 1982;66:786-7.
[Figure 1], [Figure 2]