Re-assessment of the prevalence of onchocerciasis in Adamawa State, Nigeria after more than twenty years of mass drug administration with ivermectin

Onchocerciasis is an eye and skin infection caused by a filarial worm (Onchocerca volvulus) transmitted by haematophagous female Simulium blackfly. The study was carried in four Local Government Area (LGA) of Adamawa State. Toungo, Yola-South, Song and Hong LGAs to assess the prevalence of onchocerciasis after more than twenty years of mass drug administration with Ivermectin drug. The technique employed was the use of Ov16 Rapid Diagnostic Test. 1311 blood samples were collected and examined for onchocerciasis from eight sentinel sites across four LGAs. 81 of those examined were positive for onchocerciasis giving prevalence of 6.18 %. The result showed higher prevalence in Bolki Community of Song LGA (8.77 %) and lowest in Ganzamanu in Toungo LGA (3.66 %). The prevalence in relation to sex was statistically not significant (p>0.05), though prevalence was higher among the males (6.80 %), compared to female (5.42 %). Infection was statistically significant (p<0.05) in relation to age with highest prevalence (27.84 %) observed in age group >60 years, while zero (0.00 %) prevalence was observed in age groups 5 – 20 years. Assessment of interruption of transmission among 486 children between the ages 5 – 9 years showed zero (0.00 %) prevalence in all the children in the sentinel communities. The continuous use of the microfilaricide drug over the years has interrupted the transmission of onchocerciasis. This implies that continuous distribution of the drugs will lead to elimination of the parasite and eventually the disease in Adamawa State, hence, distribution should be sustained.