Alternative treatment strategies for accelerating onchocerciasis elimination

Main Objectives

• To evaluate the impact of alternative treatment strategies in accelerating onchocerciasis elimination in an area of persistent transmission in the West Region of Cameroon

Summary

Onchocerciasis is a potentially blinding disease caused by an infection with the Onchocerca volvulus (OV) parasite, transmitted by the bite of the blackfly. Epidemiological and entomological surveys conducted in 2015 and 2016 in the West Region of Cameroon showed evidence of an ongoing transmission of OV infection in the Massangam health district, despite 18 years of uninterrupted annual mass distribution of ivermectin.

Previous research by Sightsavers investigated why this area is struggling to reach elimination targets and identified a focus of high ongoing transmission that requires a new strategic approach if elimination is to be achieved.

In collaboration with the Ministry of Health, alternative treatment strategies (ATS) were implemented consisting of: testing individuals for onchocerciasis infection and treating those positive with doxycycline in the focus of high transmission area; targeting the blackfly population by larviciding their breeding sites; providing ivermectin twice a year (currently it is only once a year) to and communities outside this focus of high transmission which are closer to elimination but still require intervention.

The impact of this intervention to accelerate progress towards onchocerciasis elimination in this area was evaluated after two years, and lessons were learned for potential scale-up of this approach to other problematic areas where elimination is proving difficult.

Key findings

1. Reduction in OV prevalence and intensity of infection: the alternative treatment strategy significantly reduced both the prevalence and intensity of infection after two years of implementation.

2. Higher reduction with alternative treatment strategies compared to ivermectin over time: there was a reduction of microfilaria prevalence by 23.2% following the two years of alternative treatment strategies. This is compared to a 20.3% reduction over 15 years of treatment with IVM in Massangam.

3. Increased population coverage with multiple rounds: Additional rounds of test and treat and ivermectin mass drug administration ensured that a greater percentage of population were reached with at least one drug.

Implications for policy and practice

ATS – CDTi, ground larviciding and test and treat with doxycycline implemented is feasible and has achieved its objective as a proof of principle in using alternative strategies to accelerate elimination in problematic areas.

However, challenges noted during implementation may limit programmatic implementation. Thus, there is need for proper documentations of these challenges and lessons learned for subsequent implementation in similar settings.  

Resources

• Read our from the field article: How our research is finding new ways to treat river blindness
• Read the PLOS journal article: Factors associated with ivermectin non-compliance and its potential role in sustaining Onchocerca volvulus transmission in the West Region of Cameroon
• Read the PLOS journal article: On-going transmission of human onchocerciasis in the Massangam health district in the West Region of Cameroon