Reduction in the prevalence and intensity of infection in Onchocerca volvulus microfilariae according to ethnicity and community after 8 years of ivermectin treatment on the island of Bioko, Equatorial Guinea

Abstract

Summary Bioko is the only island known in the world with endemic onchocerciasis. The island's rural communities consist of villages and cocoa plantations inhabited by Bubi and Fang ethnic groups. The aim of this study was to evaluate the impact of 8 years of vertical ivermectin distribution on the prevalence and intensity of Onchocerca volvulus infection in the rural population by means of pre‐ (1989) and post‐long term treatment (1998) epidemiological surveys. In both surveys, the entire population of 12 randomly selected communities (1723 and 1082 individuals) was examined. The mean ivermectin therapeutic coverage for the 8 years was 53.2%. Iliac crest skin snips were used for differential diagnosis between O. volvulus and Mansonella streptocerca. The crude O. volvulus infection prevalence before ivermectin intervention was 74.5% (1284/1723); after the intervention it was 38.4% (415/1082). The Community Microfilarial Load (CMFL) before and after ivermectin intervention was 28.29 microfilariae/snip vs. 2.32 microfilariae/snip. The reduction in prevalence and CMFL after eight annual rounds of ivermectin treatment corroborates the drug microfilaricidal activity and good tolerability. In the pre‐treatment survey, the prevalence was higher in the Bubi group (77.1%, 1126/1461); post‐treatment it was higher among the Fang (51.1%, 92/180). The reduction in prevalence and intensity of O. volvulus infection differed between ethnic groups and communities.

Sustained Clearance of Mansonella ozzardi Infection after Treatment with Ivermectin in the Brazilian Amazon

“…Since 1987, this drug has been used in the treatment of filariae of medical significance such those of Onchocerca volvulus, M. perstans, and M. streptocerca in Africa. [31][32][33][34][35][36][37] However, there are few studies on the specific treatment of M. ozzardi with this drug. 1,18,19,38 This study confirmed the effectiveness of ivermectin in parasitologic blood clearance of previous studies.…”

Arbonematoden - durch Arthropoden übertragbare Nematoden-Infektionen

“…Die einmalige Gabe von Ivermectin pro Jahr führte nach 6 Jahren in Nigeria zu einer Reduktion der MikrofilarienPrävalenz von Onchocerca von 70% zu 40% [28]; in Kamerun und Uganda nach 10 Jahren von 70% auf 7% [29], in Äquato-rialguinea nach 8 Jahren von 75% auf 38%, wobei dort große Unterschiede zwischen zwei Volksstämmen und zwischen einzelnen Gemeinden bestanden [30]. [16].…”

Arbonematodes – Nematode Infections Transmissible by Arthropods

“…A single administration of ivermectin per year led to a reduction in the prevalence of microfilariae of Onchocerca from 70 to 40% in Nigeria after 6 years [28]; in Cameroon and Uganda this figure was reduced from 70 to 7% after 10 years [29], and in Equatorial Guinea from 75 to 38% after 8 years, with significant differences between 2 ethnic tribes and individual communities [30]. Another study from Ghana reported that the prevalence of Onchocerca microfilariae doubled in 2 communities while the general infestation with microfilariae was reduced.…”