The world is benefiting from years of painstaking work, mainly of villagers and volunteers, to eliminate river blindness (onchocerciasis), a parasitic infection transmitted by repeated bites of the black fly which breeds in fast-flowing waters. Infection with the parasite can result in blindness, impaired vision and skin disease, all of which can be disabling.
An estimated 198 million people live in areas of three WHO regions where the parasite can be transmitted: the African Region, the Region of the Americas and the Eastern Mediterranean Region.
In 2016, almost 133 million people living in areas at risk of onchocerciasis received treatment as compared with 46 million in 2005.
African Region
Despite the progress achieved in the region, elimination requires 100% geographical coverage. Barriers to progress include political instability and a lack of political will in some countries to support the onchocerciasis elimination programmes.
“The number of treatments in the African Region increased from 119 million in 2015 to nearly 133 million in 2016,” said Dr Paul Cantey, Medical Officer for WHO’s global onchocerciasis elimination programme.
Here, the campaign has shifted from prevention to elimination, largely due to the excellent work of previous control programmes. Since 2016, the recently formed Expanded Special Project for the Elimination of Neglected Tropical Diseases (ESPEN) has continued to engage partners, donors and health workers by enhancing the delivery of ivermectin to communities, not only for onchocerciasis elimination but also for combatting the other four neglected tropical diseases1 amenable to preventive treatment. ESPEN’s four priority areas are:
- to achieve full geographical coverage in all endemic districts of Africa;
- to collect disease-specific data to allows mass treatments to stop;
- to strengthen information systems to enhance evidence-based decision-making and measure progress towards elimination; and
- to improve distribution of donated medicines, supply chain management and inventory reporting.
ESPEN continues to support programme evaluations that contribute to the development of the strategy for mapping transmission of onchocerciasis in areas of low transmission and for entomological evaluations to help programmes identify areas that could be prioritized for serological evaluations to determine if MDA can be stopped.
New measures
WHO’s 2016 guidelines2 specify that a key step in eliminating onchocerciasis is to establish country-led expert committees that are independent of the national onchocerciasis programme in order to provide external review of programme data and provide advice to the Ministry of Health.
Country programmes and their partners have been working to develop such committees, recognizing the need for their help in transitioning from the goal of control to that of elimination of transmission.
As of October 2017, 14 countries in the region had a committee that had met at least once; a further 5 countries plan to hold their first meeting in 2018. This represents significant progress, despite 11 countries having yet to plan their first meeting.
“The benefit of the expert committees has extended beyond the borders of the country. More experienced committees have assisted newly established committees to become organized and establish cross-border collaborations necessary for addressing subregional concerns," said Dr Paul Cantey. "Several committees are encouraging programmes to publish evaluation results, and these allow them to share lessons learnt with other countries and advance the evidence that supports particular programme activities.“
Eastern Mediterranean Region
Progress continues to be made in the region, but in Sudan and Yemen programme activities have been challenged by instability. Resources need to be mobilized to conduct elimination mapping and to expand treatment, where appropriate. Despite these difficulties, Yemen has continued to map potential transmission areas and has begun to identify areas outside the traditionally recognized transmission zone.
Region of the Americas
The target date for elimination of onchocerciasis transmission in the Region has been set as 2022. WHO has already verified four countries as having eliminated human onchocerciasis: Colombia (2013), Ecuador (2014), Mexico (2015) and Guatemala (2016). More recently, the north-east focus in the Bolivarian Republic of Venezuela is said to have met the requirements for completion of post-treatment surveillance as described in the WHO 2016 guidelines.
Meanwhile, mass drug administration (MDA) continues in two foci of the cross-border Yanomami area transmission zone, which is shared with Brazil and the Bolivarian Republic of Venezuela. To date, only 30 561 people in the Region of the Americas remain at risk for contracting onchocerciasis.
While significant progress has been made in the African and Eastern Mediterranean regions with the transition to elimination, challenges remain. To overcome the existing challenges, WHO has created a new Onchocerciasis Technical Advisory Subgroup to organize the operational research strategy so that programmes can make evidence-based programmatic decisions.
Entomology is another key issue requiring urgent attention as there is a shortage of trained entomologists.
Despite the many challenges, national and regional onchocerciasis programmes continue to make progress. In the Region of the Americas, four countries have been verified as having eliminated transmission, and several areas in the African Region have demonstrated local interruption of transmission.
There is optimism that interruption of transmission in an entire country in Africa is within reach. Although obstacles remain to be overcome, the programmes and their many partners are tackling them, one at a time.
---------------------------------------
1Lymphatic filariasis, trachoma, schistosomiasis and soil-transmitted helminth infections.
2 Guidelines for stopping mass drug administration and verifying elimination of human onchocerciasis