Effect of repeated ivermectin treatments on ocular onchocerciasis: evaluation after six to eight dosings

Abstract

In 26 villages (1987 population 12,302), hyperendemic for savanna onchocerciasis in North Cameroon, ivermectin was distributed annually between 1987/89 and 1995. Each year until 1992, ophthalmologic examinations were performed before treatment. A final examination was made in 1995. The effects of ivermectin on ocular onchocerciasis were assessed by following (a) the ophthalmologic indices in three cohorts of males recruited before treatment in 1987, 1988 and 1989, who were treated and examined annually, and (b) the indices recorded yearly in the cross-section of males aged 15-19 years. The indices in 1995 from patients who had received up to eight doses were compared with those calculated before treatment in individuals of similar age. In the cohorts, the prevalences of microfilariae in the anterior chamber (MFAC) and of punctate keratitis (PK) recorded in 1995 were markedly reduced; there was a non-significant decrease in sclerosing keratitis (SK), and a significant worsening in the fundus indices in the cohorts. The cross-sectional analysis showed significant decreases in the prevalences of MFAC, PK and SK, and a significant increase in the mean visual acuity; there was no significant change in any fundus index. The findings suggest that repeated ivermectin treatment does not prevent the appearance of initial retinal lesions or the worsening of existing retinal lesions.

Seventeen Years of Annual Distribution of Ivermectin Has Not Interrupted Onchocerciasis Transmission in North Region, Cameroon

“…North Region, Cameroon, is part of a large area with a severe, blinding strain of onchocerciasis. 12 The presence of mf in the anterior chamber (5.5%) and in the cornea (3.6%) indicated that low rates of recent (acute) onchocercal eye disease were still present after years of ivermectin treatment. From the entomological side, previous studies have shown that ATPs above 100 were associated with a risk of onchocercal-associated eye lesions and blindness.…”

B-Cell Deficiency Suppresses Vaccine-Induced Protection against Murine Filariasis but Does Not Increase the Recovery Rate for Primary Infection

“…Despite new chemotherapy protocols (30), filariae are still a major cause of serious tropical diseases (9,35); therefore, it is worthwhile to consider a vaccination approach as a complementary measure. We now have a particularly relevant experimental model at our disposal with the rodent filaria Litomosoides sigmodontis.…”

Sustainable Control of Onchocerciasis: Ocular Pathology in Onchocerciasis Patients Treated Annually with Ivermectin for 23 Years: A Cohort Study

“…The regression of punctate keratitis, early-stage iridocyclitis and chorioretinitis and to some extent scelorosing keratitis confirm ivermectin as an effective long term control means against ocular pathology in human O. volvulus infection [9], [10], [19], and the efficacy of annually repeated treatments extends to disease prevention, as it may halt migration of MF of O. volvulus into the eye and evolution of onchocerciasis-related ocular lesions. Previous studies accomplished in Africa have similarly observed that annual treatments for 2 to 8 years strongly reduced prevalence of ocular MF [10], [20], [21], [22], [23]. In the Americas, a complete reduction of disease of the anterior eye segment has been achieved with semi annual ivermectin dosing for 14 years [24], [25].…”

“…In the Americas, a complete reduction of disease of the anterior eye segment has been achieved with semi annual ivermectin dosing for 14 years [24], [25]. In African onchocerciasis cohorts, ivermectin therapy applied bi-annually or annually for up to eight years lessened the number of ocular MF and significantly improved anterior eye segment lesions, despite persisting skin MF [22], [23].…”