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

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 1st August 2019 to 31st July 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 of Simulium squamosum species 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 1st August 2019 to 31st July 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Republique Democratique du Congo, Universite de Kinshasa, Ecole de Sante Publique, Comite d'Ethique, numero d'approbation ESP/CE/139/2019 I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript * ABR : annual biting rate APOC : African Programme for Onchocerciasis Control ATP : annual transmission potential CDTI : Community Directed Treatment with Ivermectin DBR : daily biting rate DRC : Democratic Republic of Congo DTT : dichlorodiphenyltrichloroethane ESPEN : Expanded Special Project for Elimination of Neglected Tropical Diseases ESPK : Ecole de Santé Publique de Kinshasa HLC : Human Landing Catch ISTM : Institut Supérieur des Techniques Médicales MBR : monthly biting rate MDA : mass drug administration MTP : monthly transmission potential NPOC : National Program for Onchocerciasis Control NS : Non-significant NTDs : neglected tropical diseases PNLMTN-CP : National Programme for Neglected Tropical Diseases Control REMO : Rapid Epidemiological Mapping of Onchocerciasis SD : Standard deviation ULB : Université Libre de Bruxelles UNIKIN : Université de Kinshasa WHO : World Health Organization