Ongoing transmission of human onchocerciasis in the district of Mont Ngafula 1 in Kinshasa after two decades of uninterrupted onchocerciasis annual mass campaigns using community directed treatment with Ivermectin strategy
Authors: Jean Claude Makenga Bof , Paul Mansiangi , Josué Zanga , Félicien Ilunga , Gilles Adjami Ako Aime , Sounkalo Sanfo Moussa , Bakajika Didier , Yves Coppieters 
Published: May 2023

Background

The district of Mont Ngafula I in Kinshasa, the capital city of the Democratic Republic of Congo (DRC) has been treating for onchocerciasis over the last two decades using community directed treatment with ivermectin strategy (CDTI). This study aimed to determine the transmission of onchocerciasis in blackflies after two decades of uninterrupted annual ivermectin mass campaigns using CDTI.

Material

Blackflies were collected at Kimwenza site in the district of Mont Ngafula 1 along Lukaya river from 1stAugust 2019 to 31stJuly 2020 using human landing catching techniques. Entomological indicators (biting rate, transmission potentials and infectivity rate) were calculated using O-150 Pool screening PCR technique.

Results

A total of 12,217 blackflies ofSimulium squamosumspecies were collected during the study period. Two daily cycles of high biting were identified between 08:00 and 09:00 a.m. and 16:00 and 17:00. Low biting rates were observed between 11:00 a.m. and 13:00. The daily and annual biting rates were 774 and 22,380 bites/person (p = < 0.001). The infectivity rate was 0.09 % (95% CI: 0.04 - 0.17). The calculated annual transmission potential was 21).

Conclusions

The study showed an ongoing transmission of onchocerciasis in the study site despite two decades of uninterrupted ivermectin mass distribution campaigns using community directed treatment with ivermectin. There is an urgent need for alternative treatment strategies to accelerate the interruption of transmission of onchocerciasis.

Author Summary

Human onchocerciasis, also known as river blindness, is a neglected tropical disease targeted for elimination of transmission by the World Health Organization (WHO). Both epidemiological and entomological criteria are highly needed to confirm the interruption and elimination of transmission of onchocerciasis. Following rapid epidemiological mapping of Onchocerciasis conducted in 2001 in Kinshasa, the capital city of the Democratic Republic of Congo, the medical district of Mont Ngafula 1, Nsele and Binza Ozone were found to be mesoendemic for onchocerciasis and were treated using community directed treatment with ivermectin strategy (CDTI) for the last two decades. The aim of this study was to determine the impact of Ivermectin community mass distribution on onchocerciasis transmission in blackflies in the health district of Mont Ngafula 1 after two decades of preventive chemotherapy. A total of 12,217 blackflies were collected from 1stAugust 2019 to 31stJuly 2020 using human landing catching technique. Biting rate and annual potential transmission were calculated and infectivity rate determined using the O-150 PCR technique. The findings confirmed an ongoing transmission of onchocerciasis in blackflies in the health district of Mont Ngafula 1 despite two decades on uninterrupted Ivermectin mass administration. There is an urgent call for alternative treatment strategies to accelerate the interruption of transmission of onchocerciasis in the study site.