Impact of long-term treatment of onchocerciasis with ivermectin in Kaduna State, Nigeria: first evidence of the potential for elimination in the operational area of the African Programme for Onchocerciasis Control

Abstract

BackgroundOnchocerciasis can be effectively controlled as a public health problem by annual mass drug administration of ivermectin, but it was not known if ivermectin treatment in the long term would be able to achieve elimination of onchocerciasis infection and interruption of transmission in endemic areas in Africa. A recent study in Mali and Senegal has provided the first evidence of elimination after 15-17 years of treatment. Following this finding, the African Programme for Onchocerciasis Control (APOC) has started a systematic evaluation of the long-term impact of ivermectin treatment projects and the feasibility of elimination in APOC supported countries. This paper reports the first results for two onchocerciasis foci in Kaduna, Nigeria.MethodsIn 2008, an epidemiological evaluation using skin snip parasitological diagnostic method was carried out in two onchocerciasis foci, in Birnin Gwari Local Government Area (LGA), and in the Kauru and Lere LGAs of Kaduna State, Nigeria. The survey was undertaken in 26 villages and examined 3,703 people above the age of one year. The result was compared with the baseline survey undertaken in 1987.ResultsThe communities had received 15 to 17 years of ivermectin treatment with more than 75% reported coverage. For each surveyed community, comparable baseline data were available. Before treatment, the community prevalence of O. volvulus microfilaria in the skin ranged from 23.1% to 84.9%, with a median prevalence of 52.0%. After 15 to 17 years of treatment, the prevalence had fallen to 0% in all communities and all 3,703 examined individuals were skin snip negative.ConclusionsThe results of the surveys confirm the finding in Senegal and Mali that ivermectin treatment alone can eliminate onchocerciasis infection and probably disease transmission in endemic foci in Africa. It is the first of such evidence for the APOC operational area.

The contribution of mass drug administration to global health: past, present and future

“…Following cessation of IVM treatment in five to eight villages per focus, evaluation after 16-22 months showed that no infected individuals were found and vector infectivity was less than 0.2 per 1000 blackflies, suggesting that transmission has been interrupted. Similar results have been obtained from studies in several African Programme for Oncocerciasis Control (APOC) project areas throughout Africa [20]. These results suggest that MDA with IVM alone can, if given at coverage of at least 70%, impact onchocerciasis transmission even without concurrent vector control interventions.…”

Interruption of Onchocerca volvulus Transmission in the Abu Hamed Focus, Sudan

“…14,15 An additional report from Nigeria showed absence of mf in skin after years of annual treatment but provided no entomological data as required by the WHO criteria. 38 The Abu Hamed focus in Sudan and the Wadelai focus in Uganda 26 are the first endemic regions reporting interruption of O. volvulus transmission using ivermectin alone in East Africa. However, interruption of the disease transmission in Wadelai might have been partially or completely because of the disappearance of the vector resulting from environmental change.…”

Factors affecting onchocerciasis transmission: lessons for infection control

“…Tekle et al [48] reported successful elimination after using ivermectin for 15 to 17 years in the Birnin Gwari Local Government Area (LGA) and in the Kauru and Lere LGAs of Kaduna State. The median initial prevalence was 52% and was reduced to zero in a sample of 3703 patients following the APOC-led CDTI programme.…”