Development of a New Rapid Diagnostic Test to Support Onchocerciasis Elimination

Onchocerciasis, also known as river blindness, stands as the second leading cause of infectious blindness worldwide. According to estimates by the World Health Organization (WHO), approximately 25 million people are infected globally, with another 90 million at risk. Over 99% of these cases occur in Africa, and vision loss affects around 1.15 million individuals. The primary strategy for combating onchocerciasis currently is Community Directed Treatment with Ivermectin (CDTI), requiring a minimum of 80% therapeutic coverage for 10 -15 years.

Areas of West and Central Africa endemic for loiasis and mansonellasis, where ivermectin may trigger severe side effects, pose a significant challenge in the battle against onchocerciasis. Existing diagnostic tools for onchocerciasis have limitations that make mapping, epidemiological assessments and verification of elimination of onchocerciasis difficult. This situation underscores the importance of improving the specificity of onchocerciasis diagnosis to reduce cross-reactivity and false results due to other parasitic helminths in co-endemic regions. It is in this context that WHO, in its 2021-2030 roadmap for onchocerciasis, has identified the development of new diagnostic tests, or the improvement of existing diagnostic tests, as a critical condition for achieving the goal of eliminating onchocerciasis transmission.

To this end, a series of cross-sectional studies will be carried out to build up a bank of well-characterized biological samples for the development and evaluation of a new rapid diagnostic test for onchocerciasis. These studies will take place in the Centre, Littoral, West and South regions of Cameroon over a one year period. The study will target individuals aged 18 and over, mono-infected with one of the filarial species Onchocerca volvulus, Loa loa or Mansonella perstans; and non-infected. The study will begin with a screening phase during which potential participants will be diagnosed for the different filariasis. Following this screening phase, individuals meeting the inclusion criteria will be selected. Once consent has been obtained, blood samples will be taken for test development and validation of the onchocerciasis RDT. In fact, venous blood sample (in a tube containing EDTA) will be taken for each participant, by venipuncture. After collection, the tube(s) containing the blood will be stored in a cooler containing ice and transported to the laboratory within 6 hours of collection. Once at the laboratory, the plasma will be immediately prepared, then aliquoted and stored at -80ºC until transfer to BIOASTER for development and evaluation of the new diagnostic test for onchocerciasis.

At the end of this study, data on the endemicity of onchocerciasis, loiasis and mansonellosis in the selected communities will be updated. More importantly, a new rapid diagnostic test will be developed, which can then be used to monitor the activities of onchocerciasis control programs.

Inclusion criteria

• Subjects informed of the objectives of the study and who signed a consent form
• Subjects without filariasis (for control subjects), or
• Subjects mono-infected with Onchocerca volvulus, or
• Subjects mono-infected with Loa loa, or
• Subjects mono-infected with Mansonella perstans or alternatively co-infected with Mansonella perstans and Loa loa

Exclusion criteria

• Pregnant or breast-feeding women
• Subjects having taken antihelminthic treatment less than 6 months before the inclusion date