Ivermectin for river blindness (onchocerciasis)

Ejere HOD, Schwartz E, Wormald R, Evans JR

Published Online:

October 7, 2009

Onchocerciasis is caused by tiny worms and is transmitted from person to person by a small biting fly. The fly breeds in fast flowing rivers and streams mainly in West Africa. The disease causes severe itching and thickening of the skin and damages structures at the front and back of the eye. It also affects the nerve that connects the eye with the brain.

Four studies based in west Africa were included in the review; two small studies in Ghana and Liberia and two larger community-based ones in Nigeria and Sierra-Leone. In the smaller studies, people with onchocercal infection were given one dose of ivermectin or placebo and followed up for one year. In the larger studies all individuals in selected communities were treated every six or 12 months with ivermectin or placebo, whether or not they were infected, and followed for two to three years. This review found that ivermectin can prevent damage to the front of the eye but its effectiveness in preventing blindness remains uncertain.

Abstract (click to read)

Background:

It is believed that ivermectin (a microfilaricide) could prevent blindness due to onchocerciasis. However, when given to everyone in communities where onchocerciasis is common, the effects of ivermectin on lesions affecting the eye are uncertain and data on whether the drug prevents visual loss are unclear.

Objectives:

The aim of this review was to assess the effectiveness of ivermectin in preventing visual impairment and visual field loss in onchocercal eye disease. The secondary aim was to assess the effects of ivermectin on lesions affecting the eye in onchocerciasis.

Search strategy:

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Group Trials Register, in The Cochrane Library (Issue 3 2009), MEDLINE (January 1950 to August 2009), EMBASE (January 1980 to August 2009), the WHO International Trials Registry (August 2009), the reference lists of identified trials and the Science Citation Index. We also contacted investigators, experts in the field and pharmaceutical companies to identify additional trials. There were no language or date restrictions in the search for trials. The electronic databases were last searched on 6 August 2009.

Selection criteria:

We included randomised controlled trials with at least one year follow up comparing ivermectin to placebo or no treatment. Participants in the trials were people normally resident in endemic onchocercal communities with or without one or more characteristic signs of ocular onchocerciasis.

Data collection and analysis:

Two authors independently extracted data and assessed trial quality. We contacted study authors for additional information. Trials varied in design and setting so no meta-analysis was performed.

Main results:

The review included four trials: two small studies (n=398) in which people with onchocercal infection were given one dose of ivermectin or placebo and followed up for one year; and two larger community-based studies (n=4941) whereby all individuals in selected communities were treated every six or 12 months with ivermectin or placebo, whether or not they were infected, and followed for two to three years. The studies provide evidence that treating people who have onchocerciasis with ivermectin reduces the number of microfilariae in their skin and eye(s) and reduces the number of punctate opacities. There was weaker evidence that ivermectin reduced the risk of chorioretinitis. The studies were too small and of too short a duration to provide evidence for an effect on sclerosing keratitis, iridocyclitis, optic nerve disease or visual loss. One community-based study in communities mesoendemic for the savannah strain of O.volvulus provided evidence that annual mass treatment with ivermectin reduces the risk of new cases of optic nerve disease and visual field loss. The other community-based study of mass biannual treatment of ivermectin in communities affected by the forest strain of O.volvulus demonstrated reductions in microfilarial load, punctate keratitis and iridocyclitis but not sclerosing keratitis, chorioretinitis, optic atrophy or visual impairment. The study was underpowered to estimate the effect of ivermectin on visual impairment and other less frequent clinical signs. The studies included in this review reported some adverse effects, in particular an increased risk of postural hypotension in people treated with ivermectin.

Authors' conclusions:

The lack of evidence for prevention of visual impairment and blindness should not be interpreted to mean that ivermectin is not effective, however, clearly this is a key question that remains unanswered. The main evidence for a protective effect of mass treatment with ivermectin on visual field loss and optic nerve disease comes from communities mesoendemic for the savannah strain of O.volvulus. Whether these findings can be applied to communities with different endemicity and affected by the forest strain is unclear. Serious adverse effects were rarely reported. None of the studies, however, were conducted in areas where people are infected with Loa loa (loiasis).

This record should be cited as:

Ejere HOD, Schwartz E, Wormald R, Evans JR. Ivermectin for onchocercal eye disease (river blindness). Cochrane Database of Systematic Reviews 2001, Issue 2. Art. No.: CD002219. DOI: 10.1002/14651858.CD002219

Assessed as up to date:

August 6, 2009

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Primary Review Group:

Eyes and Vision Group

Health topics:

Infectious disease > Neglected tropical diseases > Onchocerciasis (river blindness)

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Independent high-quality evidence for health care decision making

Ivermectin for river blindness (onchocerciasis)

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