Two individuals presented to the Aga Khan
University Opthalmology service with foreign-body sensa-
tion, pain and redness in one of their eyes. Slit-lamp biomi-
croscopy revealed tiny larvae crawling around the conjunc-
tival sac. They were mechanically removed under topical
anaesthesia and preserved for light microscopy and photog-
raphy. Comprehensive liaison was established with the
Australian Centre for International Agriculture Research for
identification of these larvae. Their morphology character-
ized them as members of fruit-fly, Oestridae family. At least
one of them was positively identified as first instar larva of
Oestrus ovis. This report describes the first instance of such
infections in Southern Pakistan, as concluded after a
A 49 year old woman from rural Sindh, Pakistan,
presented to us at the Aga Khan University Ophthalmology
service with unilateral redeye, itching and mild photophobia
for the preceding two weeks in late summer of 2001. There
was no ocular discharge or acute visual impairment.
Examination revealed left inferior follicular conjunctivitis
with hyperemia and mild visual loss consistent with bilater-
al moderate nuclear sclerosis. The cornea was clear; with
multiple linear corneal epithelial defects appreciated with
fluorescein staining. The anterior chamber was deep and
quiet. Twelve white, mobile larvae, less than a millimeter in
length, were counted on the surfaces of both the fornices.
Under topical anaesthesia, all the larvae were removed with
fine forceps and preserved in formaldehyde. The symptoms
resolved within two weeks after instilling drops of mild
steroid and topical antibiotic ointment. The larva, after care-
ful light microscopic examination, remained unidentified,
but the overt characteristics of the head of the larva classi-
fied it as belonging to the Oestridae family (Figure 1).
A 19 year old boy presented with unilateral redeye
and foreign body sensation for the previous couple of days.
He had spent the preceding week at his family's farms in
rural Sindh and distinctly remembered a fly hitting his eye
in the fields a day prior to his return. There were no com-
plaints of pain or discharge from the eye or any acute visu-
al impairment. Slit-lamp biomicroscopy revealed a clear
cornea without any infiltrates or edema. The anterior cham-
ber was deep and quiet. Four white larvae, about a millime-
ter in length, were counted moving around the surfaces of
both the conjunctival cul-de-sacs and cornea. Under topical
anaesthesia, all the larvae were removed with fine forceps
and placed in Balanced Salt Solution (BSS). During
removal, the larvae seemed to be attached to the conjuncti-
va at one of their ends. The conjunctiva was then rinsed with
saline. No local therapy was applied and symptoms sub-
sided after the procedure. The larvae were observed under
light microscope. According to the characteristics of their
head and tail, they were identified as first instar (youngest
stage) larvae of the sheep and goat nose botfly (Oestrus
ovis) (Figure 2).
Larval identification is aided by the dark mouth
claws and the active vermiform movements of its body
against the congested and edematous conjunctiva. The only
way to be certain of the species of a larva is to have it pupate
and grow into an adult fly.
The sheep nasal botfly (Oestrus ovis) is the most
common cause of ophthalmomyiasis externa.1Other mem-
bers of the Diptera family may also cause ophthalmomyia-
sis.2Internal ophthalmomyiasis may present as endoph-
thalmitis, complicating a penetrating injury with an intraoc-
ular foreign body.3The adult flies hover in front of the nos-
trils of animals and squirt a stream of very tiny larvae into
them. These larvae develop in the nasopharyngeal cavities
and frontal sinuses of livestock. In the occasional case of a
human infection, the larvae never fully develop but may
cause ophthalmomyiasis externa and/or interna. Vector of
the Oestrus ovis larvae is most prevalent in warm climates
and there is data to suggest increased prevalence of infesta-
tion with O. ovis in early summer and autumn.4
Narayan et al. and Mathai et al. have described sim-
ilar O. ovis cases in India.5,6Other reports from India have
also highlightened the potentially vision threatening seque-
lae of ophthalmomyiasis.7There are several case reports
from both the western and eastern hemispheres.8-10English
language Medline search for reports of ophthalmomyiasis in
Pakistan has been unfruitful.
First Report of Ophthalmomyaisis Externa in Pakistan
Azam Ali1, Agha Hassan Feroze2, Paul Ferrar3, Asad Abbas4, Mohammad Asim Beg5
Departments of Ophthalmology, Aga Khan University Hospital, Karachi, Pakistan1, Military Hospital, Rawalpindi, Pakistan2, Australian Centre for
International Agriculture Resarch (ACIAR), Canberra, Australia3, Department of Ophthalmology Southeast Texas Medical Associates, Beaumont, Texas,
USA4, Department of Microbiology, Aga Khan University Hospital, Karachi, Pakistan5.
86 J Pak Med Assoc
References Download full-text
1.Risco JM, Al-Dosari F, Millar l. Sheep nasal botfly (Oestrus ovis) larvae infes-
tation of the conjunctiva. Arch Ophthalmol 1995;113:529-30.
2.Denion E, Dalens PH, Couppie P, Aznar C, Sainte-Marie D, Carme B, et al.
External ophthalmomyiasis caused by Dermatobia hominis. A retrospective
study of nine cases and a review of the literature. Acta Ophthalmol Scand
3. Gozum N, Kir N, Ovali T. Internal ophthalmomyiasis presenting as endoph-
thalmitis associated with an intraocular foreign body. Ophthalmic Surg Lasers
4. Amr ZS, Amr BA, Abo-Shehada MN. Ophthalmomyiasis externa caused by
Oestrus ovis L. in the Ajloun area of Northern Jordon. Ann Trop Med Parasitol
Narayan S, Jayaprakash K. Incidence of ocular myiasis due to infection with
the larva of Oestrus ovis (Oestridae Diptera). Indian J Ophthalmol
Mathai E, George JA, Lalitha MK, Raju R. Ophthalmomyiasis externa caused
by Oestrus ovis - a case report from South India. Indian J Pathol Microbiol
Balasubramanya R, Pushker N, Bajaj MS, Rani A. Massive orbital and ocular
invasion in ophthalmomyiasis. Can J Ophthalmol 2003;38:297-8.
Verstrynge K, Foets B. External ophthalmomyiasis - a case report. Bull Soc
Belge Ophthalmol 2004;294:67-71.
Gregory AR, Schatz S, Laubach H. Ophthalmomyiasis caused by the sheep
bot-fly Oestrus ovis in Northern Iraq. Optom Vis Sci 2004;81:586-90.
Victor R, Bhargva K. Ophthalmomyiasis in Oman - a case report and com-
ments. Wilderness Environ Med 1998;9:32-5.
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