The Boma

East Coast fever: Tackling neglected livestock diseases in Africa

May 04, 2022 International Livestock Research Institute Season 2 Episode 5
The Boma
East Coast fever: Tackling neglected livestock diseases in Africa
Show Notes Transcript Chapter Markers

In the early 1900s, cattle herds across South Africa were devastated by a new livestock disease. Today, more than 100 years later, that disease is called East Coast fever, and despite scientists' best efforts to control it, the disease continues to devastate cattle and livelihoods across the dozen African countries where it is endemic. 

In this episode, presenters Elliot Carleton and Brenda Coromina speak with ILRI scientist Vish Nene as they examine what makes East Coast fever such a devastating disease, and more importantly, how modern vaccines may be able to address it. 

Elliot: Welcome Back to The Boma. A podcast from the International Livestock Research Institute where we discuss how sustainable livestock is building better lives in the Global South. 

My name is Elliot Carleton.

Brenda: And I’m Brenda Coromina. 

Elliot: Imagine that you are a pastoralist herder. Cattle are the foundation of your life and livelihood. And then, all of a sudden, your cows start to die. Fast. In a few short weeks, four out of every five of your calves are dead… and with them the source of your livelihood.

Brenda: As scary as that sounds… that’s exactly what happened 120 years ago. In 1902, cattle herds across South Africa were decimated by a new cattle disease. 

Elliot: Now, the disease had likely existed for centuries in eastern Africa. But it had been brought to South Africa by ships and trains that were transporting livestock.  

Brenda: When it reached South Africa, the disease took on a much more virulent form. In South Africa, up to 95% of the infected cattle were dying. 

Elliot: The spread of this modified, more deadly form of the disease was spurred on by the rapid spread of European settlers and their livestock across Africa. By 1904, the new form of the disease was found in Kenya. By 1906, it had reached Nairobi.

Brenda: Today, the disease is known as East Coast fever. And despite efforts to control it, it’s endemic in a dozen countries across eastern, central and southern Africa. 

Elliot: In fact, it may be more devastating now than ever before. Today, a cow dies from East Coast fever every 30 seconds. And over the course of a year, that results in a million cattle deaths and a total annual loss of $383 million.

Brenda: To make matters worse, East Coast fever doesn’t receive the attention it deserves.

Vish: You know, we're one of a handful. I think I cannot even count more than six labs that probably work on this disease in the world.

Brenda: That’s Vish Nene, a scientist here at ILRI and co-leader of the animal and human health program.

Elliot: Vish has spent much of his career improving ways to fight infectious diseases in livestock … and one disease he has spent a lot of time on is East Coast Fever.

Brenda: East Coast fever is restricted to a dozen African countries. And as a result, as Vish said, it doesn’t receive the kind of funding that more globally important diseases do. It’s one of quite a few neglected diseases, Neglected, that is, by the mainstream.

Elliot: But East Coast fever is still devastating to the countries that it does affect. It impacts cattle, of course, but also farmers and even national economies. 

Brenda: And what exactly is it about East Coast fever that makes it so dangerous?

Vish: It's a disease that is caused by a protozoan parasite. So that means this is a single-celled organism which is transmitted by ticks. And the disease has several different clinical syndromes. It can cause a mild disease, it can cause a moderate disease or it can cause severe disease. And the severe disease is the biggest problem because animals will inevitably die if they get severe East Coast fever.

The disease is described scientifically as a lymphoproliferative disease. What that basically means is it causes a cancer-like disease. So you have a protozoan parasite here that causes a cancer-like disease in cattle.

Elliot: As the disease progresses, it starts to fill the cow’s lungs with fluid. Basically, the cow ends up effectively drowning within 3 weeks of the start of symptoms. 

Brenda: And while the disease only affects cattle, other animals can still help spread it. 

Vish:  African buffalo do not suffer from the disease, but they carry the parasite. And in Africa or in areas where cattle and buffalo will graze on the same pasture, ticks can feed on buffalo and then transmit the parasite to cattle. And it causes a disease in cattle

Elliot: As we alluded to earlier, East Coast fever can end up having a really big impact on pastoral and smallholder livelihoods. 

Vish: So because it kills, obviously a farmer can lose his or her investment in the animal. If an animal survives a moderate disease or even a severe disease, those animals are not as productive as an animal that's been fully vaccinated and immune to disease. And so there is a loss of productivity, which is due to the morbidity that's created by the disease. And so there's a loss of income that's associated with that. And so there've been a fair number of studies that have shown that this has an impact on household income, which then has an impact on the livelihoods of parents, children's ability to be able to go to school for example, and things of that nature.

Brenda: OK, so, all of this makes me wonder if we have any vaccines for East Coast fever…

Elliot: Well, there is one. But much like the disease itself, it’s pretty complicated. 

Vish: So historically, it was field observations that gave rise to this live vaccination process, which is called the infection and treatment method of immunization. Right—ITM. And if you remember  ITM involves giving the animal a potentially lethal dose of the parasite and then treating it with oxitite at the same time.

But very early on, because they recognized that an animal that was infected and naturally recovered was immune, they tried to replicate that process through science and research. And so very early on, for example, there was inoculation of crude material from an animal into other animals to try to see if they could get infection.

So there were multiple crude events. I mean, we call it crude now, but it was good science at that time in terms of how to infect those animals.

Elliot: Eventually, scientists learned how to preserve the disease-causing parasites in liquid nitrogen. And basically, this made it a lot easier to store the biological materials needed to make a vaccine. 

Brenda: This gave rise to a new era of ITM vaccines that remains at the foundation of the East Coast fever vaccine used today.

Vish: So basically, the way that this vaccine is made is that ticks are allowed to feed on infected cattle. And ticks then become infected with the parasite. And then once those ticks have matured and the parasites have matured in the ticks, the ticks are essentially just ground up. They’re ground up in a buffer.

That is basically used as the infectious material. And so you can then do titration experiments to identify how much of that material can be injected into a cow and how much antibiotic cover do you need to give to the animal for animals to respond to the disease but not kill the animal. And so this process essentially started in the late 1900s, early 1900s, and the modern-day, as we call it now, ITM vaccine was actually developed not far from here at the East African Veterinary Organization, the Muguga site here. 

Elliot: Despite the great strides made in vaccination, there was still one major problem.

Vish: The parasite exists, as I was saying , in different strains. And unfortunately, what we know through a lot of work that was done in the early seventies to the eighties is that you can get breakthrough of the immunity. So a little bit like what everybody was worried about with COVID 19.

Brenda: So have scientists come up with any ways to address those breakthrough infections?

Vish:  Now, to overcome that breakthrough, a lot of effort was spent in trying to make a cocktail vaccine. So currently there is a commercial vaccine that's available called the Muguga Cocktail, which consists of three different isolates of the parasite. And when you vaccinate with the Muguga cocktail, you get a broad-spectrum immunity, which most likely provides immunity against all cattle type parasites and a lot of buffalo type parasites.

 So the Muguga cocktail is very good. It's available commercially. As I said, it's produced in Malawi, and it's registered for sale in a few countries and some in eastern Africa. And it's a really robust vaccine, and it's used a lot, particularly by the pastoral community.

 Where it's been used, it's been highly effective. And there's a lot of data coming out to show in communities where the vaccine has been used that there's a lot of improvement in the livelihoods. I believe nutritional status as well, and newer opportunities for youth, and gender opportunities as well.

Elliot: So far, the Muguga cocktail has been used to vaccinate around 2 million cattle across Africa. Between 1997 and 2014, the vaccine helped prevent the deaths of some 400,000 animals. And by saving those animals, it ended up saving households around $74 million.

Brenda: And these benefits can be especially important for pastoralists. In Maasai communities, up to 60% of calves can die of East Coast fever. But when those calves are vaccinated, many of them that would have died can be raised for a couple more years and then sold. And the profits can then pay for things like children’s education and food supplies and even investments into new businesses. 

Elliot: It’s pretty amazing the benefits vaccination can deliver. I’ve actually been reading some research by Katherine Homewood, a Professor of Anthropology at University College London about the impact of East Coast fever vaccines among Maasai communities. 

Brenda: What did you discover?

Elliot: Well, a couple of things. For one, the Maasai are very keen on the vaccine. And there’s good reason for that… as you just mentioned, when more cows survive, pastoralists – and their children – reap the benefits.

But there are also downsides. Professor Homewood found that the vaccine is still hard to access and afford for many poorer pastoral families. In one study, wealthy households could afford to vaccinate 90% of their calves, but the poorest households could manage only about 30%. 

Brenda: Wow! That’s a really big disparity and I think it gets at some of the lingering problems with the current vaccine, which as Vish explains, all begins with the production process. 

Vish: So that whole process takes a long time. Traditionally, it used to take about 18 months. That timeframe can be reduced now, and it is being reduced. But you have to do a lot of quality control in that whole production line, and you then also have to ensure that the parasites are stored appropriately in liquid nitrogen, as I said. The vaccine then has to be transported in liquid nitrogen. It is then distributed to the end user in liquid nitrogen as well. And it requires a skilled person to administer the vaccine because if by mishandling the parasites end up dying, then you've basically got no vaccine and the animals will not be immune. Or if you give less than the optimal dose of the tetracycline, the animals could potentially die of infection. So it's a difficult vaccine to produce. It's a difficult vaccine to store. It's expensive. It's a difficult vaccine to deliver as well. 

So there are lots of manufacturing and processing issues associated with this vaccine.

Brenda: In light of these challenges, back in the 1980s ILRI scientists started thinking… OK, so the ITM vaccine is very effective. But wouldn’t it be great if we had an even better vaccine—one that was equally effective… but easier to produce and distribute?

Elliot: So they started working on what is called a subunit vaccine for East Coast fever. Basically what that means, is that rather than taking the whole live parasite and using that to make a vaccine—like the infection and treatment method does—a sub-unit vaccine only includes specific parts of the disease-causing parasite.

And by the way, many people have already encountered subunit vaccines, even if they don’t realize it. The hepatitis B vaccine has been made this way for decades. So have the modern vaccines against COVID-19.

Brenda: But what makes the subunit vaccine better than the current ITM vaccine? 

Elliot: Well, that’s the problem. Right now, it isn’t better. The subunit vaccine is only delivering around 50% immunity against East Coast fever on average. And that just isn’t enough for it to be viable.

Vish: The level of immunity needs to be up to 70, 80%.

Elliot: But this is something that ILRI scientists like Vish are continuing to work on, with the hopes of ending up with a vaccine that is much simpler to produce and distribute—not to mention cheaper, so that even the poorest pastoral and smallholder households will have access to it. 

Brenda: And I guess an improved vaccine would likely amplify the benefits vaccines can have for pastoral communities, in terms of greater opportunities for education, food purchase, household income…

Elliot: Exactly. And I think this all underscores the importance of addressing globally neglected diseases more broadly. While it can be easy to overlook diseases like East Coast fever that aren’t of global significance, it’s pretty clear that efforts to address them are incredibly important for the people and animals they affect. 

Brenda: Right. The ultimate goal should be to make sure that, unlike the last 120 years, diseases like East Coast fever don’t continue to wreak havoc on African cattle and farmers in the future.

(And as we said, ECF is just one of these diseases that’s neglected. There’s also Bovine TB, Brucellosis…) 

Elliot: And I think that’s a great place to leave off for today. Thank you so much to Vish Nene for helping us better understand the devastating history of East Coast fever and the vaccines that may finally address it.

Brenda: And thank you to our listeners for joining us. We would love to hear your feedback on today’s episode or the whole podcast series. So please reach out to us on Twitter at BomaPodcast to let us know your thoughts, and also, what topics you’d like us to cover moving forward. And if you enjoyed today’s episode, please don’t forget to share and subscribe. I’m Brenda Coromina.

Elliot: And I’m Elliot Carleton.

History of East Coast fever
A neglected disease
Why is East Coast fever so dangerous?
East Coast fever's impact on livelihoods
And what about vaccines?
But there's one big problem...
The Muguga cocktail
The benefits of vaccination
Remaining challenges with current vaccines
A subunit vaccine for the future