Onchocerciasis continues to be a major cause of
blindness, particularly in those sub-Saharan African countries which are outside the area of West Africa monitored by the
Onchocerciasis Control Programme (OCP). Onchocercal ocular disease and
blindness develop as a result of long exposure to onchocercal
infection. Until 1987,
suramin and
diethylcarbamazine were the only drugs available for the treatment of
onchocerciasis and they could not be used for community
therapy because of their toxicity and the dosage schedules required. The registration of
Mectizan (
ivermectin, MSD) for treatment of human
onchocerciasis in 1987, and the donation of this
drug by Merck & Co. for as long as it is needed, provided a new opportunity for the safe treatment and control of the disease. The data available on the impact of repeated doses of
Mectizan on ocular onchocercal disease indicate a significant reduction of ocular microfilarial loads and regression of early lesions of the anterior segment, including
iridocyclitis and sclerosing
keratitis. Such improvements are seen more rapidly when
Mectizan is used than when
onchocerciasis is limited by vector control alone.
Mectizan treatment also has a beneficial effect on onchocercal
optic-nerve disease and visual-field loss. Long-term maintenance of
Mectizan therapy should lead to a reduction in the prevalence of
blindness in endemic communities.