African Herders Help Eradicate Deadly Livestock Disease

interview

Photo: Stevie Mann/ILRI
Rinderpest, known as "cattle plague" in English, is thought to have had its origin in the dense cattleherds of Central Eurasia more than two millennia ago.

The last known case of rinderpest, a lethal livestock disease, was confirmed 10 years ago in a buffalo wandering Kenya's Mount Meru National Park. In May 2011 the disease was declared officially eradicated - aside from smallpox, no other pestilence has ever been wiped out. Now scientists have published their analysis of the decades-long battle to eradicate a disease that has plagued herders for more than two millennia.

In the journal Science on Thursday, researchers examines their decision to use a time-tested vaccine despite industry and funder pressure to try novel approaches, as well as highlighting the role of African herders in helping to eradicate the disease.

Lead author Jeffrey Mariner told AllAfrica's Lauren Everitt that he tweaked a proven rinderpest vaccine to make it temperature stable so it could survive transport in Africa's extreme temperatures - a critical development. However, the scientist credits the eradication achievement to his team's results-oriented focus, reliance on tried-and-true science and willingness to forge partnerships with local communities. He said he is taking the lessons learned from rinderpest and applying them to his newest challenge - tackling a disease killing off goats and sheep across Africa.

Most of us have heard of smallpox, the only other disease to be completely eradicated, but few people are as familiar with rinderpest. Could you describe the disease and why it was selected for eradication as opposed to foot-and-mouth disease, for example?

It's a German term so "rinder" is cattle and "pest" means plague, which translates to "cattle plague" in English. And it's a highly fatal diarrheal disease so animals that were infected would generally die within a week ... up to a 90 percent fatality rate. Foot-and-mouth disease rarely kills - it's much more of a disease of trade and production that lowers production. It doesn't have the catastrophic effect that rinderpest did.

Losing a cow is a clearly a big deal for a smallholder farmer, but could you address the larger socio-economic costs of a disease like rinderpest in Africa?

At the time we started there were not good economic studies on the impact of rinderpest. But there are two sides to the equation: the impact of rinderpest and the continuous process of trying to control rinderpest. A major activity in veterinary services in the developing world was vaccination against rinderpest and that's where they would spend most of their budgets.

It was the kind of thing where, back in the 60s and 70s, it was sort of a no brainer because when you have a disease that can kill 90 percent of the cattle population, you don't need a detailed analysis to know that should probably be your largest priority.

This is only the second disease in history to be completely eliminated, and the first ever livestock disease. Why was your team successful where others have failed?

As far as animal diseases, I think it's the one that's received the most concerted effort over the years. Also rinderpest was well chosen for eradication because, besides being a very important disease, there were certain attributes that made it easier to control.

There's no reservoir for rinderpest, it depends on continuous transmission. If an animal gets sick, it has to transmit the disease or the disease dies out because it doesn't have a reservoir. So it's a lot like measles in children in that sense. Capitalizing on that and the fact that there were good vaccines, we could effectively vaccinate out the disease.

With a lot of other diseases it's not that simple - the vaccine is not as effective or they have reservoirs in nature, or they exist in the soil as well as in animals, and so to eradicate them is much more challenging.

So rinderpest was a good choice in that it had a lot of characteristics that lent it toward eradication. The changes that really proved effective, if we want to take some credit for anything, were moving from the traditional approach of mass vaccination where we just tried to vaccinate everything.

We're getting much smarter in two senses: One was how we delivered vaccines. We started to work through the community and local health workers. The other sense was about targeting our approach, thinking about the key populations for the transmission of rinderpest and then focusing our resources on those. What we found was that those are often the most difficult populations to reach; often they're in these remote areas. So it was this combination of getting the community animal health workers involved to vaccinate in remote areas, but also convincing governments to focus on those areas because they were the sources of infection.

So revising our strategy to be epidemiologically targeted, but also changing the institutional setup of the way that different actors were doing vaccination work - those are the kinds of changes that allowed us to complete the eradication.

I think for a lot control programs, that's what they struggle with. It's all very nice and well to eradicate a disease in France, but that's different from working in Afghanistan. If you do want to do global eradication, you have to do the hard places as well as the easy places.

And having solutions for the most challenging places is the crux of eradication.

The first vaccine created for rinderpest worked, but it had to be refrigerated - making transport to rural African areas nearly impossible. What other false starts and challenges did you have to contend with?

The vaccine we started with was an amazing vaccine, and actually Walter Plowright, who developed it, won the World Food Prize for that work, which is a major achievement. It's one of the finest vaccines ever developed in human or veterinary medicine because it's effective against all forms of rinderpest with no adverse reactions, and it generates lifelong immunity with a single vaccination. So in many ways it was an ideal vaccine - it just had to be kept cold.

Our idea was to take that vaccine and to just change the way it was freeze dried, effectively repackaging the vaccine. So we didn't have to go through lengthy field trials to show that the vaccine was effective, because we didn't make any substantial changes to it. That was one of the cruxes of the approach - that in two years we could actually have a vaccine that we could go into the field with and start work, rather that going through the normal process, which can amount to 10 years of testing and rigorous registration processes. Because we didn't change Plowright's original vaccine, the virus and so forth, we didn't have all those problems.

The challenge for us was that the idea was so simple. For example, we published in Veterinary Microbiology, which is a smaller journal, but there were other vaccines published in Science. Those vaccines had no practical impact - they were never used. But we actually had trouble generating attention for what we were doing. We had this solution to the problem but it wasn't the kind of thing that got you in Science because it wasn't some bizarre, novel approach. It was just a good, basic approach using an existing product and very focused on a solution.

And when we moved to the field, we also had to explain how this thing worked. One of the questions I got in 1990 was why were we using such old technology, why weren't we doing something like genetic engineering? That was what the paper that ran in Science used. And the thing was that we knew we could solve the problem with our approach, and we knew that in two years we could be in the field with the vaccine.

So in the long run, that was the vaccine that eradicated rinderpest. They never used the GMOs for rinderpest because their advantages didn't outweigh the risks of introducing them into the field. I guess the disadvantage for us was that it was such a simple approach that it's hard to generate the kind of excitement you would otherwise.

I'm applying the same approach to peste des petits ruminants (PPR), which is a disease that affects sheep and goats with the same issues as rinderpest, such as high mortality rates. I've taken that vaccine and used the same approach, and I got the same questions when applying for funding: Why are you using this old technology? If this was really going to work, wouldn't someone have already done it by now? And I gave them the answer that I was told the same thing years ago and we eradicated rinderpest. We're still waiting for the promise of these GMOs to take over the place of this, but it hasn't happened yet. Maybe it will someday.

The issue that comes out for me is that science is a bit screwed up. They don't want solutions - it's not about actually solving the problems. You get rewarded for publishing in certain journals, and you get rewarded for being novel. But you don't necessarily get rewarded for solving the problem. So scientists, of course, do what they get rewarded for in their jobs to draw attention to their work. It's actually a problem with scientific research.

From the article it's clear that scientists relied on nomadic herders to help in eradicating rinderpest. Could you talk about the role they played and how scientists leveraged their knowledge?

Their knowledge was key in two senses. One, they were very good at identifying rinderpest. It's such an important disease for them that they had names for it. They could describe it. It was part of their oral history. The history would actually be handed down from fathers to sons about the different names of the disease. And you could talk to them about how it was behaving in the community, where it had been last year, where it was last week, and they could tell you where it was today. When we figured that out it was much easier for us to target the programs because we were able to use their information to know where we needed to focus.

The other aspect of their knowledge was the fact that they treat their animals, and they have good knowledge of disease. When we came up with the idea of training them to vaccinate, they were very receptive. They couldn't dream of anything more exciting than going to a training course to vaccinate their own cattle. It was amazing. Although most of them weren't literate, we were teaching them by demonstrating and step-by-step training and with some infographic materials. They were very interested and very good learners, and they handled the vaccine very well and were able to do those complicated steps, such as rehydrating the vaccine and using the proper time interval.

And because they were vaccinating their own cattle, they did it properly. You're not going to not do it well on your own animals. Whereas with government services and programs where it's a huge thing, they do it every day for years and things can get a bit sloppy. But if you're doing your own herd and your father's herd and your uncle's herd, then you're going to do a good job because the incentives to do it right are there.

In order to eradicate a disease you need widespread buy-in; people in diverse parts of the world must allow their livestock to be vaccinated. Did you meet with any pockets of resistance or groups that were reluctant to vaccinate their cattle? If so, how did you deal with them?

For the vaccination that would have been uncommon, if it ever occurred. Sometimes it would be a lower priority. For instance, in an area where the disease was endemic, they might have a higher priority problem that also needed attention. And the way we would resolve that is we would go and actually talk about what their needs were for animal health, and oftentimes we would deliver solutions for their three or four most important problems, not just rinderpest. So the community animal health program is actually a broad-based program and just one of the things we do usually is rinderpest. So that was to make sure that we were being relevant to their needs and kind of matching up everybody's goals in this situation.

The area where we actually met resistance was in more conventional circles like veterinary services. Convincing them that they needed to hand over vaccination activities to illiterate herders was often a major policy challenge that we had to struggle with over the years. The veterinary profession is rather conservative, and there's lots of talk about ethics - what you can hand over to who, and who can inject and those sorts of things. We had to contend with 'I have a medical degree, and they don't' and all those kinds of questions.

We were also trying to help people understand that what' s appropriate in the developing world maybe isn't appropriate in the first world, and what's appropriate in the first world may not be appropriate in the developing world. If you insist on certain practices, you're actually denying millions of people service. And there's an ethical question there in how you balance that while at the same time being realistic and appropriate in a developing country.

And for us it was very clear that farmers all over the world could handle their own livestock and were doing a super job when they had training, so they should be given power to do that.

Financially how do you support such a widespread eradication effort? That's a lot of vaccine that must reach some very remote places. Where did the funding come from?

In the last 20 years of the eradication program the major donor was the European Union, and I don't know the exact figures but hundreds of millions of Euros were spent in this process. A lot of the money went to things like purchasing vehicles and helping to build veterinary infrastructure and only a small percentage of it actually went to eradicate rinderpest. The funding that actually went to eradicate the disease in really key areas, such as South Sudan and far regions of Ethiopia, was in the tens of millions of dollars over 10, 15 years - relatively small amounts of money for the size of the population.

I think that's one of the lessons, too. If you're really targeted about what you're doing and understand the key things, you don't have to spend that much money. Some programs go into a country and buy 150 Land Rovers and 140 of those Land Rovers would be used in places that had no rinderpest because they'd be apportioned out over the country as part of the general services. So there's something to be said for doing just what you need to do to get the job done, as opposed to politics and perks.

Many of us have heard of avian flu and mad cow disease yet the eradication of rinderpest in 2011 went largely unnoticed. It could be argued that rinderpest has a larger impact on the human condition than some of these other diseases - any thoughts on why it received so little attention?

There's two sides to that. One, of course, is that mad cow disease is in the developed world, and it threatened people with money and influence. It was also partially emotive because people feel very paranoid about eating food and dying. So it became a big issue, but compared to the size of the problem, you wonder.

When you look at rinderpest, by the modern era, it wasn't in developed countries so they weren't hearing about it - they didn't feel threatened by it. It wasn't a disease you weren't going to catch. Whereas with avian influenza, people were worried about that because it could have come to the United States. They were afraid they could catch it. With rinderpest it was very unlikely that it would move back to the United States or Europe in the modern era because it was relatively easy to control.

But the other side, and I'll say this frankly, is the international community, the animal health community, dropped the ball. When rinderpest was eradicated, this was a tremendous achievement, and it also showed that the animal health profession could really do something complicated and useful. But the major international players didn't make proper use of the event. So a part of that is our fault as a profession - that we didn't carry that message forward in a correct way and with enough enthusiasm about it.

What actually happened was that for the teams of people who were responsible for the eradication, many of them retired and new people came and replaced them. These newcomers really weren't the people who eradicated rinderpest and now they had the job of closing it up and announcing it to the world. Sadly, many of these guys broke down into competing for who got credit but forgot to take the message forward. It was very sad because the lessons from it could have been used as a tool about how we can address more issues, and how we can mobilize more support so that people in the developed world hear about things like rinderpest and mobilize support for eradicating them.

One of the many problems that we had with rinderpest was that many times donors or governments would say that these countries don't have the capacity to eliminate it. They would ask, 'So why should we give them money when it's going to be wasted?' With rinderpest they proved they could do it, they proved they could use the investment, but the message didn't get carried on that they have that capacity.

What next? Now that you've eliminated rinderpest have you set your sights on eliminating another pestilence?

We have. It's peste des petits ruminants (PPR), also known as "goat plague." There's international interest in developing a progressive, controlled program. It's a disease that's high impact, and it's also spreading. It's across Africa, it's across the Middle East and South Asia, it's even reached to places like China in the last couple years, so it's a disease that's spreading.

It affects small ruminants (sheep and goats), which are actually a very important species for the poor. Small ruminants are marketed much more easily so they have a lot more to do with household food security than cattle.

So we're working on taking the lessons from rinderpest and developing those to help control and eventually eradicate PPR. I've been working in the lab to make the PPR vaccine thermally stable, and we have succeeded with that.

Now we'll bring it into the field to look at different approaches to vaccination, similar to what we did with rinderpest, looking at how to involve the community and rural health workers in the remote areas and private practitioners. How do we combine all of those parties into public-private partnerships? And we're starting to go back to Uganda and to Sudan again - I'm leaving for Sudan next week.

Where there any key lessons that you took from your work with rinderpest that you're going to apply moving forward?

The two situations are remarkably similar. PPR has a good vaccine that just needs to become more stable. The key issues are again how to do the vaccination, and what's the right way to combine the community and the veterinarians and so that everyone works together to accomplish the task. The other is: which are the key populations that we need to vaccinate? How do we target the vaccination to get maximal impact? So those are the epidemiological and sociological research questions, if you like, and that's really where we need to focus our efforts now.

Small ruminants, sheep and goats, there are more of them than cattle, and they replace themselves more quickly - they don't live as long. So you actually have to do a lot more vaccinations. Efficiency, efficacy and how to best target vaccinations are the key questions that we need to address in tackling PPR. I think it will happen, I think there's a good international momentum building to address PPR, so that's what I'm working on at the moment.

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