A 19-year-old male residing in Pittsburgh presented with irritation and watering from his right eye and was diagnosed to have a right subconjunctival nodule. Surgical excision revealed both dead and living worms and histopathological staining of the worms confirmed these to be zoonotic species of
Onchocerciasis is the world’s second-leading infectious cause of blindness and is estimated to account for blindness in half a million people. It is transmitted by the bite of the
A 19-year-old Egyptian male studying and living in Pittsburgh, PA, USA, for 18 months was evaluated for a month-long irritation and watering of the right eye without any visual loss. He had been seen by an ophthalmologist and was prescribed topical steroids for possible allergic conjunctivitis, which did not resolve his irritation.
The patient’s recent travels included a trip to New Delhi, India, and Siwa (an oasis in the West of Egypt) more than a year prior to this presentation. He has never had any pets such as dogs and cats. Review of systems as well as general examination was unremarkable. Ophthalmologic examination revealed a subconjunctival nodule (1.5 cm × 1 cm) in the medial aspect of the right eye. The rest of the eye examination was unremarkable including the retina and the posterior chamber. He underwent surgical exploration of the nodule under local anesthesia, which revealed 12 dead and living worm fragments, each about 1 cm in length and 0.2 to 0.3 mm in thickness. Serology showed a positive IgG4 for filariasis. Complete blood count was normal and peripheral blood smear was negative for eosinophilia or microfilaria. Histopathological examination revealed adult worms that were confirmed to be
Transverse section of the adult worm (H&E stained) showing the internal organs.
Higher magnification of the same worm shows arrangement of the cuticle with external ridges and internal striae. There are two striae for each interridge—one in between two ridges and one striae immediately under each ridge.
Crucial to making this diagnosis is to identify the worm on histopathological examination. Speciation of such worms is often not possible because of improper preservation or a lack of an intact worm structure. We will briefly present the main diagnostic features of the adult worm. A multilayered cuticle forms the outer thick covering of a female adult
Table
Morphologic features of zoonotic
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Identifying characteristics |
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Four striae per interridge |
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Three to four striae per inter-ridge |
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Two internal striae per every inter-ridge |
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Three to four elongated striae per inter-ridge |
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Marked external transverse with no inner striae [ |
Zoonotic Onchocerciasis has been reported to occur from the North American continent as well as from Europe. There have been recent reports of zoonotic Onchocerciasis from the West Coast of the United States [
There are limited pharmacological choices for the management of ocular Onchocerciasis. ivermectin is the recommended treatment for microfilaria but has no effect on the adult worms [
Thus we conclude that zoonotic ocular Onchocerciasis can present with a sub-conjunctival nodule in humans and it should be considered as a differential diagnosis of parasites detected in the ocular structures. The exact mode of transmission is unclear at this time, as is the prevalence of this infestation among cattle or wildlife in this part of the United States. Further information on the epidemiology of the disease among the animals population would be needed before we can understand the risk factors for transmission of the disease to humans.
The authors declare no potential conflict of interests.