Making a Case for Onchocerciasis Elimination Mapping: An Interview with Philip Downs and Charles Mackenzie


In 2009 the World Health Organization (WHO) moved its target for onchocerciasis in Africa from control to elimination. Onchocerciasis elimination has proven possible in the Pan-American region, where Colombia, Ecuador, Guatemala, and Mexico have since been verified as free of the disease. However, less progress has been made on the African continent, where 30 out of the 36 onchocerciasis-endemic countries are located. Many factors have posed challenges to elimination programs in Africa, from Loa loa co-endemicity to vector control to the longevity of the parasite. Fortunately, recent developments demonstrating the impact of MDA on transmission have made elimination of onchocerciasis in Africa more feasible, altering the previous paradigm.

However, before ministries of health can launch their elimination strategies, they need to know where to treat. Mapping of areas previously considered free of  blinding  disease – or “hypo-endemic” for onchocerciasis – is critical.

With support from the Bill and Melinda Gates Foundation and working in close coordination with WHO, Sightsavers has launched a pilot project to test a new onchocerciasis elimination mapping protocol based on recommendations by the WHO Onchocerciasis Technical Advisory Subgroup (OTS) to be carried out initially in Ghana and Nigeria. I was able to sit down with the project’s principal investigator, Philip Downs, and technical advisor, Charles Mackenzie, to discuss the origins of the project and their goals for Phase II.


Q: To begin, could you please explain the purpose of onchocerciasis elimination mapping? What is being mapped and how does this approach differ from the earlier control strategy for onchocerciasis?

Charles: The issue with onchocerciasis is that this initial control program left a gap in where to treat. Where are the edges of the endemic area? That’s the big question.

Phil: The African Program for Onchocerciasis Control (APOC) program provided an important baseline to be able to transition to an elimination goal, but this means we now we have to go back to some of the hypo-endemic areas and make that determination of whether there is enough evidence to exclude these areas from interventions. The idea is to try to shrink the map and stay focused on where transmission is actually occurring.

A complementary goal of the pilot is to operationalize a standard that can be scaled up, and to learn in the process from the operational research that other groups are working on to make modifications. Nothing here is written in stone. This is just the first step – a pilot that we can hopefully build upon as new knowledge comes in, but in a standardized way.

We want to be very thoughtful with the way in which we are collecting data – who has ownership over that data and how it will be used. Right now we are looking at onchocerciasis in particular, but the bigger vision is how can we use this knowledge to inform monitoring and evaluation (M&E) for other programs, and other diseases as well. 

Charles: This is something that is still really a work in progress. The rush of getting everything together is difficult. However, by the end of this project in 18 months or so, the techniques will be there – we will have tested them.


Q: What are some of the factors that have enabled this transition from control to elimination?

Charles: Ah, that’s a good question. Why are we transitioning from control to elimination? Well, I won’t go too deep into the historical part. In 2002, there was a meeting here in Atlanta at The Carter Center on the subject, and what was said was that elimination was possible in Latin America, but not yet in Africa.

So then why did we switch – why did we suddenly think we could do it?

Recently we had success stories from Latin America, and in Ecuador in particular. I will admit I’m biased because I happened to work with Ecuador, but success in Ecuador really was significant because of the similarities to what we see in Africa. The vectors are very similar in their ferocity and their ability to keep transmission going. And then the same treatment (carried out by groups like The Carter Center) started seeing successes in Uganda and in Sudan. With all this evidence people started calling on a need to switch from control to elimination.

Phil: We have been seeing successes in meso- and hyper-endemic areas. Programs are demonstrating that higher levels of transmission can be interrupted in these endemic areas, but the problem is that interventions were not happening in the hypo-endemic areas, where transmission was still possibly ongoing. That meant no treatments in certain areas that potentially could sustain transmission and even allow for its spread to other areas.


That led to the question of, “how can we be satisfied with that?” If we’re making progress in meso- and hyper-endemic areas, then we have to do something in these hypo-endemic areas.

There have also been key developments in diagnostics, treatments, and strategy. A few years ago, complications like Loa loa co-endemicity looked like an obstacle we were just never going to be able to overcome. While we have not solved this issue entirely, we have made significant progress. New tools and methodology have been field tested and look promising.

Charles: Yes, we have been working on this in Cameroon. We have been making lots of progress in determining when to treat and also how to treat if you do have Loa loa – with albendazole over ivermectin, and definitely not diethylcarbamazine (DEC).

Phil: There is also more integration of different diseases - where you now have lymphatic filariasis (LF), onchocerciasis, and trachoma initiatives working side by side. When you see the progress being made under LF, I think there is just more of an appetite, more motivation to push for onchocerciasis elimination as well.

Charles: While there is still a long way to go, it’s far better now to talk about elimination – politically and in terms of advocacy. Elimination programs tend to get more interest, the LF program is a perfect example. I look at it as one of those cases where if you shoot for Mars, at least you might be able to make it to the Moon. The time it is going to take between now and elimination – it is going to be a long path.

Phil: I think it’s important – for all donors to recognize that there will be milestones in this effort to eliminate onchocerciasis. For example, the decision to stop treatment is a significant milestone, but the work does not stop there. To demonstrate that transmission has stopped completely, programs have to be very careful. Especially since there is so much about the vector we are still trying to understand, there needs to be a significant surveillance system in place to monitor transmission after the end of mass drug administration (MDA). The support and funding for elimination efforts must be sustained even after the decision to stop treating in a given area.


Q: Can you describe the pilot project that Sightsavers is taking on? Where will that be rolling out and what do you expect to see from that?

Phil: The original idea was to operationalize the recommendations from the OTS by setting up a platform that can collect and analyze data in a way that can be scaled up in all countries. The goal is for all countries to eventually have access to this kind of a platform that ensures quality data and makes that data more accessible, which will hopefully enable better decision-making around treatment.

We have the support from the Bill & Melinda Gates Foundation and are working very closely with the Expanded Special Project for Elimination of Neglected Tropical Diseases (ESPEN) and national committees to carry out a pilot in two countries: Nigeria and Ghana. From there, we will take the findings from this pilot as well as findings from other studies being done by The Task Force for Global Health to feed into the next OTS meeting. That meeting will give us an opportunity to share with the larger community, discuss experiences and results from the pilot, and make adjustments to the strategy, to inform Phase II. 

That's a big undertaking. It’s easy to say “operationalize this,” but not all diseases are the same, and successes in one are not always replicable with another. We still need a better rapid diagnostic test for the field. Procuring these diagnostics with quality results is something that is going to take time. That’s where all these logistical elements come into play, with supplies and shipping – all these nuances that really need to be worked out. It really is quite complex.

Charles: We don’t yet have an established standard approach. We’re building up a system from the very beginning. It is not like we are implementing established tests and procedures. We are still really just working this out. It will be an iterative process. We will not get it 100% right the first try. The plan is to follow this approach for the first few years as we iron out the issues. Then we can roll it out in a couple more countries while we learn more and change it again, and so on.

Phil: There are also countries that have come up with their own strategies for mapping and onchocerciasis elimination. Uganda, Nigeria, South Sudan all have their own programs underway, and those experiences and their recommendations fed into onchocerciasis elimination mapping protocol. In that way, we are not the trailblazers – they were the real trailblazers and we are learning from them.

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Q: This pilot is rolling out in Nigeria and Ghana. Are there specific reasons you chose those countries?

Phil: We wanted to work with countries that have experience using electronic data capture and that already have pretty robust data available that we can use as a baseline comparison after collecting the pilot data on results and sampling strategy. We are curious to see how well that matches up with the data that has already been collected. We also wanted to pick countries where we were more likely to get an Ov16 signal, bearing in mind that confirmatory ELISA testing might be needed if we don't, and that would require a lot of extra work and time. While we do have partners working with national programs to improve the local lab capacity, there is still has a long way to go.

Charles: Yes, and that brings up the point that this particular project is one part of a greater whole. There are other major activities going on, like the lab capacity piece. This fits into a bigger mosaic of things. It’s like an entire fleet of planes being built. There are many things going on – this is just one of many.


Q: You were both listed as authors on a publication earlier this year about cross-border issues with onchocerciasis elimination. How does that play into elimination mapping?

Charles: Cross-border transmission is a big issue for elimination at large and it mostly comes down to communication between countries.

Phil: Diseases know no borders. Transmission zones will cross over international boundaries, and so having that communication between ministries of health is critical so that they are aware of what their neighbors are doing and how they can assist each other - what resources they have available to them, what tools they have available. This is not equitable across all countries. That’s one of the things we are working on – standardized tools that can be used across all countries that can level the playing field.

Charles: As Phil says, communications is the main piece. There are some places where this is going to be a bigger problem. If you’ve got two districts bordering on each other, they need to coordinate things like MDA. Where mapping can come in is identifying where the disease exists, and therefore where this coordination must take place.

Where I’ve seen this work is the Tanzanian National Onchocerciasis Elimination Program has learned how to run their national program by looking at their neighbors and coordinating with them.

Phil: Another example I like is Uganda, which has had a lot of success in stopping transmission. That program is mostly concerned with the border with the Democratic Republic of Congo (DRC), which is a very porous border with a lot of movement. The Ugandan ministry has been collaborating with their local counterparts in DRC to assist in fly capture, looking at infection. Their point is that if transmission ends on their side of the border and Uganda stops treatment or MDA, who’s to say that people from deeper within the DRC – where transmission may still be occurring – will not come over? Similarly, they are concerned with vectors that can travel – it’s not just humans, vectors can also transport disease across borders.

The key to all this is collaboration, how we partner together – implementing partners, donors, national programs, communities – that’s what makes it successful. We could have the best tools available, but if there is no coordination, if there is fighting between partners, then nothing gets accomplished. That is what we are hoping to demonstrate with this project. We are working very hard to communicate in an effective way so that each of our partners feels engaged and no one feels left out. 

We still have a long way to go together. The path is still very long for oncho, but maybe this project can help shorten that path just a little.


UPDATE: Since this interview, a dialogue has begun between the Ministry of Health in Mozambique and the onchocerciasis elimination mapping team. Mozambique will now also join Nigeria and Ghana in pilot mapping project. 



 To learn more about Sightsavers' project, visit their website and read the most recent project updates.




Photos (Credit: Sightsavers)

Top: Mahmoud Alene from Asubende in Ghana who has been badly affected by river blindness

Middle: Community drug distributors distribute treatments for onchocerciasis and lymphatic filariasis as part of a mass drug administration in Kaduna, Nigeria

Bottom: Mahmoud Alenle from Asubende in Ghana is led by a young family member