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Video Report

Ocular Onchocerciasis: Anterior Chamber Microfilariae

Department of Ophthalmology, Wilford Hall Medical Center, San Antonio TX, USA

Correspondence: Dr William J Flynn
Email: william.flynn{at}lackland.af.mil
Tel:210-292-6815
Fax: 210-292-6569

Date of acceptance: 3rd June 2005

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Introduction

Onchocerciasis is a known cause of uveitis, with both anterior and posterior clinical presentations. Glaucoma is a common associated disease with uveitis and from the treatment of uveitis with steroids. We present a patient with uveitic glaucoma that was found to have onchocerciasis.

Case Report

The patient is 26-year-old African-American male who spent his childhood in a small village near a fast moving stream in western Africa. He migrated to the United States as a teenager and at age 22 joined the US Army and was stationed in Texas. At age 22 he complained of blurred vision and was subsequently diagnosed with bilateral uveitis. He was treated with topical steroids periodically and subsequently developed elevated intraocular pressure and secondary glaucoma. He was referred to us for glaucoma surgery.

At that time of referral he was on maximal medical glaucoma therapy and topical steroids twice a day OU. His visual acuities were 20/25 OD and 20/20 OS and intraocular pressures of 35 mmHg OD and 30 mmHg OS with open angles. He had cupping and arcuate scotomas OU. His slit lamp examination showed multiple microfilariae in his anterior chamber OD along with low-grade inflammation OU. There was no evidence of chorioretinitis. He was referred to dermatology and a subcutaneous nodule on the patient�s lower back was excised. An adult nematode worm was identified in the nodule. He was treated with a single dose of ivermectin. His anterior chamber inflammation worsened during this treatment but over a three-month period his uveitis resolved and steroids were gradually discontinued. Six months after ivermectin treatment his IOP was 15 mmHg OU on no medications. He remained free of uveitis recurrences over the next year of follow up.

Discussion

Onchocerciasis is an insect-borne disease caused by the filarial nematode Onchocerciasis volvulus. The transmission of the parasite O. volvulus to humans is by the bite of the Simulium fly. The Simulium fly breeds in rapidly flowing rivers and this where the disease is typically encountered. Because of this Onchocerciasis infections of the eye are often referred to as river blindness. Onchocerciasis is endemic in many countries in Africa and in a few countries in central and South America.[1] In hyperendemic areas almost every person is infected and about half of the population is eventually blinded by onchocerciasis. In one study the prevalence rate of infection was 84% of the general population.[2]

Adult O. volvulus worms are often found in subcutaneous fibrous nodules of infected patients. Adult female worm produces microfilariae and these microfilariae leave the nodule and invade virtually all organs and have a predilection for the eye.[3,4]

It is the world's second leading infectious cause of blindness. It is estimated that anywhere from 300,000 to one million are blind or severely visually disabled people.[1] Blindness is usually due to chorioretinal disease, although optic atrophy and sclerosing keratitis are also causes.[2] Iridocyclitis is another frequent ocular manifestation of the disease and similar to our patient, anterior chamber microfilariae may be found in 29% of those infected.[2,4] The iridocyclitis may present as intermittent low grade, either nongranulomatous or granulomatous anterior uveitis.

Diagnosis can be made by identifying microfilariae in the anterior chamber or by identifying microfilariae or adult worms from subcutaneous tissue. Skin snip testing can readily demonstrate live microfilariae, but numerous skin snips may be required to diagnosis a mild infection. A definitive diagnosis can be achieved by identifying the adult worm from an excised nodule.[5] In our patient the diagnosis was made by a combination of anterior chamber microfilariae and adult worms in a subcutaneous nodule.

Ivermectin, a semisynthetic macrocyclitic lactone, is a very effective agent for treatment of Onchocerciasis and is primarily a microfilaricide.[5] Our patient received a single oral dose of Ivermectin. His anterior uveitis flared after this treatment as is reported to occur following the death of the microfilariae. Although ivermectin may also kill some adult male worms and partially sterilize the female worms, annual retreatments are recommended and that is the plan for our patient.[4,5]

In summary, our patient is 26-year-old male with a four-year history of intermittent uveitic glaucoma that was found on examination to have microfilariae in his anterior chamber. His uveitis and glaucoma resolved following treatment with ivermectin.

References

• Rathinam SR. Cunningham ET Jr. Infectious causes of uveitis in the developing world. International Ophthalmology Clinics. 40(2):137-52, 2000.
• Newland HS. White AT. Greene BM. Murphy RP. Taylor HR. Ocular manifestations of onchocerciasis in a rain forest area of west Africa. British Journal of Ophthalmology. 75(3):163-9, 1991.
• Thylefors B. Onchocerciasis: an overview. International Ophthalmology Clinics. 30(1):21-2, 1990.
• Rowe SG. Durand M. Blackflies and whitewater: onchocerciasis and the eye.
• Sabrosa NA. Zajdenweber M. ematode infections of the eye: toxocariasis, onchocerciasis, diffuse unilateral subacute neuroretinitis, and cysticercosis. Ohthalmology Clinics of North America. 15(3):351-6, 2002.