Indian Journal of Ophthalmology

: 1991  |  Volume : 39  |  Issue : 4  |  Page : 176--178

Incidence of ocular myiasis due to infection with the larva of oestrus ovis (Oestridae Diptera)

S Narayanan1, K Jayaprakash2,  
1 Sangereswari Eye Hospital, Gobichettipalayam 683, India
2 Lecturer in Zoology, Sri Vasavi College, Erode-638 316, India

Correspondence Address:
S Narayanan
Sangereswari Eye Hospital, Dhamu Complex. Modachur Road, Gobichettipalayam-638 452, Tamil Nadu


The present paper is the result of the study of frequent occurrences of ocular myiasis due to the infection by the insect larva in 14 patients. The collected larvae were identified as first stage larva of oestrus ovis. The results of the examinations of the infected eyes show swollen conjunctiva, redness and watering of the eyes. These symptoms may be mistaken for mucopurulent conjunctivitis. The above results are discussed with earlier literature.

How to cite this article:
Narayanan S, Jayaprakash K. Incidence of ocular myiasis due to infection with the larva of oestrus ovis (Oestridae Diptera).Indian J Ophthalmol 1991;39:176-178

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Narayanan S, Jayaprakash K. Incidence of ocular myiasis due to infection with the larva of oestrus ovis (Oestridae Diptera). Indian J Ophthalmol [serial online] 1991 [cited 2023 Sep 30 ];39:176-178
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Myiasis is the infestation of the body with maggots or bots of certain flies. The infection is either specific or facultative. Although myiasis in man is generally rare, members of cyclorhabid mainly the genus of Sarcophaga and Oestridae Diptera may produce myiasis [1],[2],[3], in countries where the standard of hygiene is low and flies abound. The larva of these flies with long hairs are said to be capable of living either in the tissue or internal cavities such as head-sinuses, throat or intestine of higher mammals. They do not invade the flesh but cause irritation by their curved mandibular barbs and body spines. Infection occurs when the adult female fly strikes the body tissues [4],[5].

The Oestrus ovis, the common sheep bot fly 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. It takes a year to complete its life-cycle feeding on mucous substances. It is veri interesting to note that the adult flies do not feed [5].

We have been observing a high incidence of ocular myiasis due to infection with the first stage larva of Oestrus ovis in our vicinity. The present paper is the result of the study of frequent occurrences of ophthalmo-myiasis due to the infection by the larva described above in fourteen patients.


The study took place over a period of four years from 1986 to 1990. The patients were treated as out patients. The infected eyes were seen through the slit lamp. The movements of the parasites were also observed. The removal of the pathogen was done after immobilizing the larva by applying 4% xylocaine and grasping with the help of forceps. Patients were followed up for 4 or 5 days. Routine antibiotics and antiinflammatory drops and tablets were given as treatment.

The collected larva were preserved in 75% alcohol, processed for microslide preparation and were iden�tified.


[Table 1] shows the summary of the 14 ocular myiasis subjects under this study over the four year period. There were four acute cases; four persons of high and six individuals of medium ophthalmo-myiasis. It can also be noted that the number of larvae under investigation also varied with the nature of myiasis observed.

The above data show that the occurrence of ocular myiasis is due to the infection of Oestrus ovis larva in this study region (Gobichettipalayam-638 452, Periyar District, Tamil Nadu, India) where the said flies abound. It is also be assumed that being viviparous the fly O. ovis constantly deposits larvae in the human eye.

The results of the examinations of infected eyes show swollen conjunctiva, redness and watering of the eye. There were also signs of conjunctival irritation such as itching, photophobia and sometimes oedema of the lids [Figure 1][Figure 2]. Mucous discharge from the conjunctiva was present. These symptoms mimic an acute mucopurulant conjunctivitis.

Observations on the larva show that the parasites are less than 2 mm in size, robust, of worm like structure bearing bands or rows of chitinous spines or teeth, a pair of sharp curved mandibular hooks at the anterior end and a pair of spiracles at the posterior end. They are capable of living in eye fluid, freely crawling on the eye balls with the help of anterior hooks. They are able to attach themselves to the conjunctiva and erode the mucous membrane of the eye [Figure 3].

In the light of the above results it would be reasonable to suggest that incidence of ocular myiasis due to the infection of sheep bot fly is common. It is also to be presumed that the gravid Oestrus fly frequently deposits larvae in the conjunctival sac of human eye and causes ocular myiasis externa.


The results of the present study and the observations of 14 patients document the high incidence of ocular myiasis due to the infestation of the larva Oestrus ovis. The Indian knowledge on ocular myiasis with the larva of O. ovis is very scanty. The survey of literature shows the earlier works were orbital based case reports with the maggots of Chrysomyia bez�ziana (screw worm) either from the wound or patients predisposed with diseases [6],[7],[8],[9],[10],[11].

Our present account, in the occurrence of ocu!ar myiasis due to the fly Oestrus ovis from the Indian sub tropical continent, may be the first of this kind.

It is also to be noted that infestation of this zoonotic ocular myiasis externa occurs frequently where the flies abound and in poor hygiene. Man is slowly becoming a host and not a non-compromised host as suggested by earlier workers [3],[11].

The main relevance of this medically important ec�toparasitic bot larva on ophthalmological interest is this type of infection may be mistaken for acute mucopurulant conjunctivitis.


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