Work on Onchocerciasis

Onchocerciasis (river blindness) is a vector-borne disease caused by the parasite Onchocerca volvulus. It manifests as severe itching, visual impairment and irreversible blindness. It is common and widespread in Cameroon. The current control strategy is mass drug administration (MDA) with ivermectin; a drug that kills the immature, transmissible form of the parasite in skin, but leaves adult worms alive. The WHO recommends annual MDA for 15-17 years with high population coverage, as this should be sufficient to interrupt transmission in most settings.

MDA has been delivered in South West Cameroon for 12 years using Community-Directed Treatment with ivermectin (CDTi), yet higher than expected prevalence and intensity of onchocerciasis persists. The geographic overlap between L. loa and O. volvulus provides a possible explanation for the lower than expected benefit from CDTi: lack of adherence to treatment due to fear of adverse reactions and poor perception of the treatment in general. The World Health Organization (WHO) recommends either doxycycline or vector control as alternative strategies in L. loa co-endemic areas, yet implementation research on the integration of these interventions has been lacking.

There was an urgent need exists to validate and implement such alternative strategies. The overall aim of the Cameroonian onchocerciasis work was to implement a test-and-treat strategy for onchocerciasis control using the WHO-endorsed macrofilaricidal treatment, doxycycline, in tandem with focal vector control, to reduce the blackfly biting rate. Doxycycline differs from ivermectin as it acts directly on adult worms; permanently sterilising them, thus preventing the production of skin infecting micofilariae, and significantly reducing adult worm lifespan. Offering an alternative treatment to ivermectin will help counter the poor community perception of the current strategy. Biological monitoring will be undertaken to determine the impact of this alternative strategy on the prevalence of onchocerciasis microfilariae in the skin, using traditional parasitological techniques. The focal vector control aspect of the study consisted of adapting tools used with huge success on a large scale in the onchocerciasis control programme (OCP) for use in small targeted areas. Rather than applying larviciding chemicals from the air, as was done during the OCP, larvicides were applied from the riverside to local tributaries and rivers within the vector control area.

Social science approaches were used to help identify risk factors for the poor efficacy of the current CDTi strategy, alongside the capture of societal and health economic data to assess the acceptability and feasibility of the test and treat and vector control strategies.

Mass Drug Administration (MDA) of Schistosomiasis (SCH) and Soil-transmitted Helminthiasis (STH) requires rapid scale-up to achieve the 2020 target. COUNTDOWN has been evaluating how to deliver equitable drug delivery to currently excluded populations, in Cameroon and Ghana. 


The main aim of the project was to develop innovative strategies for expanded access of treatment and improved diagnostic tools for schistosomiasis (SCH) and Soil-Transmitted Helminths (STH) in Cameroon and Ghana.

The specific objectives were:

1. To conduct targeted baseline parasitological and epidemiological surveys to describe infection levels of schistosomiasis and STH, and associated morbidity indicators

2. To assess expanded annual community treatment in reducing prevalence of schistosomiasis and STH

3. To assess community understanding of the current MDA programme and its strengths and weaknesses and economic aspects of whole community treatment.

4. To assess the acceptability and feasibility of introducing an alternative treatment strategy to the current treatment regimen from different perspectives

5. To investigate different levels of access and factors influencing scale-up to PZQ and ALB treatment in areas with limited treatment coverage

The studies were conducted in communities that were endemic for SCH/STH in Cameroon in low and high-transmission settings. Social science research outputs and impact on parasitological and general health indicators were monitored at baseline and follow-up timepoints.  The data generated by the community screening was fed back into the Ministry of Health and helped inform mass drug administration, continuous community surveys are monitoring the success of the intervention.