Tackling schistosomiasis, the neglected tropical disease caused by parasitic worms | Wellcome

What this episode is about

Schistosomiasis, a neglected tropical disease caused by parasitic worms and spread by freshwater snails, remains a significant public health challenge affecting over one billion people worldwide, primarily in impoverished regions with inadequate sanitation. Ongoing research aims to deepen the understanding of the parasites' biology and develop effective prevention strategies to eliminate this disease linked to poverty and environmental conditions.

Key takeaways

• Schistosomiasis: a fascinating parasite with a dreadful impact, lurking in the shadows of neglected tropical diseases.
• One billion people suffer from neglected tropical diseases—proof that poverty truly shapes health on a global scale.
• Snails as disease vectors? A slick life cycle that transforms slimy mollusks into engine rooms of infection.
• With 260 million at risk, schistosomiasis is a potent reminder that prevention often lags behind treatment.
• In the battle against schistosomiasis, understanding its biology could be our greatest weapon in eliminating it.

Who speaks in this episode?

• Bonnie (Host) · 23 min speaking

What is discussed, and when

1. 0:00 – 5:00: Neglected Tropical Diseases, Schistosomiasis
2. 5:00 – 10:00: Paquantal, Resist the Resistance Evaluation, Welcome Trust
3. 10:00 – 15:00: Gates Foundation, Rasmus University

Notable quotes from "Tackling schistosomiasis, the neglected tropical disease caused by parasitic worms | Wellcome"

• The burden of neglect disease is very high. You can from this map you can see that one billion people have one or more NTDs and you can see where these diseases are globally.…

  about Neglected Tropical Diseases · at 1:18

• Associated with poverty, lack of sanitation and unsafe water sources. And we know that about 260 million people are infected or at risk. If we look at those pictures of the…

  about Schistosomiasis · at 2:06

• These water bodies and you can see that's really hard to control there is a treatment paquontal is the only drug available for the treatment of shismiasis we have no…

  about Paquantal · at 7:31

• But also potential resistance or the evolution of resistance. So the project is called resist the resistance evaluation and surveillance initiative for systemis treatment. So…

  about Resist the Resistance Evaluation · at 9:36

• Some data from what's called the Zanzibar elimination of transmission study which was funded by the Gates Foundation between 2012 and 2017. And within this study they were implementing treatment by annually so at a very high dose doing.

  about Gates Foundation · at 10:22

• University are leading the modeling of transmission and trying to understand or predict better ways of all the treatment impacts that are going to happen.

  about Rasmus University · at 12:19

Who and what is mentioned in this episode?

Companies & orgs

• Natural History Museum — Company · Business focus · 5 mentions
  Institution involved in the research and genetic analysis of schistosomiasis.
• Rasmus University — Company · Collaborator · 1 mention · first at 12:16
  Institution involved in modeling transmission of schistosomiasis.

Products & tech

• Paquantal — Product · Case study · 1 mention · first at 7:39
  The only drug available for treating schistosomiasis, with concerns about resistance.

Concepts & topics

• Schistosomiasis — Concept · Core topic · 1 mention · first at 2:38
  Primary disease discussed, focusing on its biology, transmission, and efforts towards elimination.
• Neglected Tropical Diseases — Concept · Key argument · 2 mentions · first at 0:37
  Group of diseases including schistosomiasis, associated with poverty and neglect.
• Resist the Resistance Evaluation — Concept · Strategy · 1 mention · first at 9:41
  Project aimed at understanding and addressing potential resistance to Paquantal.

Sponsors

• Welcome Trust — Company · Sponsor · 1 mention · first at 9:21
  Funding source for the research project on schistosomiasis.
  Okay. So on to the project that we've got funding from the welcome trust. So this is really to look at the drug itself present as I said we have one drug to control schismiasis.
• Gates Foundation — Company · Sponsor · 1 mention · first at 10:27
  Previously funded the Zanzibar elimination of transmission study.

Full transcript with timestamps

0:00 I often have this lovehate relationship with systemasis because it's such a fascinating disease in terms of it biology but it's such a a dreadful disease um and we need to have better ways to prevent it. So I'm based in the natur museum and one of our research rem is really about understanding the biology of the parasites but also using that knowledge to actually develop implementation and to advance elimination in many of the areas. Um so just to point out so we talked we've just introduced shismiasis here but it's part of a group of uh diseases known as neglected tropical diseases and we call them neglected tropical diseases because they're really diseases associated with neglected people. So the diseases of poverty um and uh in in terms of people don't have the infrastructure to actually prevent some of these diseases. So as you can see see from this slide there's various groups of these parasites um from

1:00 protozoa viruses bacteria to helmets a lot of these diseases are spread through vectors particularly insect vectors um but there's also shismasis which is spread by snails and snails are actually fundamental for the transmission of shistmiasis. The burden of neglect disease is very very high. You can from this map you can see that one billion people have one or more NTDs and you can see where these uh these diseases are globally. You can see they're very much widespread across Africa, South America and areas of Asia and some of these places people have up to six NTDs. So there is a really high burden of of these diseases.

1:44 So now focusing on shmiasis. So this is the disease I'm I is it's my expertise. I've been studying this disease for about 25 years now and there's still so many knowledge gaps around the biology of the parasites and understanding how best to prevent transmission uh infection and how to move towards elimination. As I said, it's very much a disease associated with poverty, lack of sanitation and unsafe water sources. And we know that about 260 million people are infected or at risk. If we look at those pictures uh of the morbidity, the swollen abdomen, the blood in urine and also that animal that is immalicated, the worms lay eggs which causes that morbidity. You get enlarged livers, large spleens, uh you get anemia through blood loss for urine and then in animal shmiasis, you get chronic debilitation uh wasting and uh that causes huge economic burden as well. It's a very preventable and treatable disease as

2:42 well. But it has a really complex life cycle. I I often have this lovehate relationship with systemasis because it's such a fascinating disease in terms of its biology, but it's such a a dreadful disease. Um, and we need to have better ways to prevent it. So, let's go through the life cycle. So, it's really fascinating. Um, first we're going to start right at the top of life cycle looking at the parasitic worms themselves. So around the blood vessels in the blood vessels around the kidney and the intestinal system of the parasitic worms lodge themselves and they can live in those blood vessels for many many years and we know that people who have remained infected up to 30 years. So they're very long lived parasitic worms. You can see in that parasitic worm there they have um so we actually have them here in um I've brought them they're preserved. They're not live so please don't worry about

3:33 them. They're about 5 mm in length. um they actually have separate males and females which um come together to form a pairing mate. Uh and their whole purpose is to produce eggs. The female dependent on its male and it'll pump out eggs thousands of eggs a day and those eggs then cause the problems associated with shysmiasis. They become in the lodged in the tissues. They pass through the intestine and the bladder wall and that causes that blood loss and anemia and all the other uh chronic symptoms as well. Okay, so they're small, but they're not very nice. Okay, you can see in these videos, uh, the worms out there is what we've dissected out to put in a petetrograd. They're very motile worms.

4:15 They're very active. And then these worms lay eggs, which will come out as people go to the toilet, they go if they come out in feces or urine. And if they reach a freshwater body, those eggs will then hatch. And this video um down on the shows an egg hatching and a laral stage hatching from that and swimming. The egg hatches through osmosis, water goes in and then it bursts the egg. That miridia will live for about 24 hours. It seeks out a snail. Um, and it will, if it finds the correct snail, it's not every snail, the correct snail. It'll go into that snail and then over about four weeks, it will replicate itself clonally, produce thousands of laval stages. And this is the one of the drivers in transmission. one lava steak gets into the snail and thousands to millions come out comes out every day over many many days and up to about 3 months as well. So you can see that driving in transmission that is one of

5:13 the features of the disease that is so hard to control. So then it goes into the snail and we have snails here. We have live snails. We culture snails in our laboratories and naturalist museum. This is one type of snail. It's called blinus truncatus. It's very widespread across Africa. It transmits the form of the parasite that goes into the bladder system. They are small. They're hard to find. It's hard to find them when we go and do field work. So, as I said, once in the snail, it replicates. It comes out in the in the final laval stage.

5:42 This is called sairi. It actually has um it has a a head. It's actually lives for 24 hours. Again, it has no feeding source. So, once it's it's come up, it's used up, its energy actually dies. The head will stick to the skin of the the mamalian host that it wants to infect. It releases an enzyme. It allows it to go through the skin. You don't feel it. It's microscopic. And then it goes into the blood system. The juvenile laraval form then goes through metamorphosis and it gradually develops into the adult worms. So you can see how complex the life cycle is, but how well adapted it is and how those different life cycle stages change. And we still know um we have still fundamental knowledge gaps about those different life cycle stages as well. Once inside the blood system and it reaches those adult worm stages, it goes into the um intestinal system.

6:37 The worms pair again and then it it releases lots of eggs which goes on to cause that damage to the tissues um and that buildup of chronic morbidity. Okay. So drivers in transmission I said snails really drive transmission. Water contact drives transmission and that contamination, lack of uh sanitation and behaviors as well. These are very classic environments that we see shismiasis. This is where we've done a lot of work on the ground. We have women using water bodies for washing uh washing pots uh daily activities. is we have a lot of children playing in these water bodies and we also have water bodies that are used for agriculture and as I said it's associated with sanitation uh behavior we have um open defecation we have open urination and these people infected are churning out thousands of eggs each day which go into these water bodies and you can see that's really hard to control there is a treatment paquontal is the

7:38 only drug available for the treatment of shismiasis we have no alternative And this is one of the worrying uh aspects of control and this is what the project I'll talk about is focused on. We can put in safe water sources and sanitation. We can do snail control as well. That's often not very environmentally friendly and it's also very difficult in very big water sources. And we can implement behavioral change but again changing people's behavior is also very difficult unless you provide alternatives. So let's look at those snail habitats.

8:07 Again we saw seen the smaller snails. They are really hard to find. um and uh to actually um map them and to see where high-risisk areas are. And then the other form of the snail which we'll have a look at now is the bumper snail very widespread in Lake Victoria and also many other water bodies across Africa. Uh these again transmit the intestinal form and are very high numbers in these water bodies. They're a bit easier to find um but they are also um very very widespread and very very difficult to control. Okay, I just wanted to put this image up because this really show highlights the amount of laral stages that come out of individuals. So this is the urm of the parasite. Um this is what I've done here. This is work in Zanzibar. We filtered out the eggs from a single child in Zanzibar. Zanzibar is meant to be a place where we have control of shismiasis but we have small pockets of infection. This child was um

9:05 had thousands of eggs coming out and thousands of blavi. So you can see that um even with one child that's missed treatment or has a high infection this can really lead to problems with control as well. Okay. So on to the project that we've got funding from from the the welcome trust. So this is really to look at uh the drug itself present as I said we have one drug to control schismiasis and we're very worried about low efficacy a low performance of the drug but also potential resistance or the evolution of resistance. So the project is called resist the resistance evaluation and surveillance initiative for systemis treatment. So we're working in Zanzibar. We've been working in Zanzibbar for about 30 years now. But before my time, my mentors were working there before I took on some of this work um doing snail surveys uh doing treatment uh and implementation of prevention strategies. And Zanzibar is

10:04 two islands off the coast of Tanzania. And if we think we can eliminate shmiasis, this is probably the best chance we've got because it's an island population. We have one species of snail which is modern transmission. And we have one species of the parasite as well. But treatment um so this uh gives you some data from what's called the Zanzibar elimination um of transmission study which was funded by the Gates Foundation between 2012 and 2017. And within this study uh they were implementing treatment by annually so at a very high dose doing behavioral change snail control. Um but what we actually found is we had persistent transmission in some places and no long-term prevention by even doing that implementation. This graph just shows you the ups and downs of prevalence in different communities. And you can see in red there even at the end of uh in 2021 where we've had long-term drug treatment, we still have areas of

11:03 high transmission. But it's it can be very very dynamic as well. It's very much affected by environment, climate um and lack of or um when interventions stop as well. So this just shows you uh how those hotspots of um transmission change over time as well. It's just a very nice visual aspect. And we were looking back at the data of 2017 to identify we have some areas which are really hard to um to actually gain control of shmiasis and we have huge bounceback of infection once we stop intervention. So the overall aim of resist is to understand whether presontal resistance has potentially is has potentially contributed or is contributing to the existence of persistent shimmiasis on pea the northern island zanzibar and if we find it how do we address this going forward it's very much a collaborative project um it is very much led from the ground by s muhammad who runs the labs in pea in phl

12:08 Swiss TPH support them in the fieldwork epidemiology. My team at the Naturalist Museum, we collect the parasites and we're doing a lot of the genetics and then we have a modeling component Rasmus University uh are leading the modeling of transmission um and trying to understand or predict better ways of um all the treatment impacts that are going to happen. So very briefly I'll show you the work plan um and then I'll show you some of the data that we've got of um we've only done the first year. We've done a lot of the field work. It's been very very busy but we've also learned a huge amount as well. So the work plan starts with surveillance and the way we're doing surveillance is we're filtering urine.

12:49 We're looking for eggs and we want to gain an understanding of the true prevalence levels. We're working in 17 places in Xander, 17 schools in fact and within those schools we have participation from 800 to,000 children within each school. So it's a large number of participants. This is a very big study for two of those schools. These are two hotspot schools that have always been hotspots for as um for as long as been recorded. We have high levels of infection. it's very difficult to get down to low levels and when treatment is um stopped or interventions are stopped we get bounce back very very fast. In those two schools we're doing intensive surveillance. We collect urines over five days to look at to try and get a true prevalence level. And in the other 15 schools we survey children at one time point to get a baseline prevalence for those um lowlevel areas. We treat everybody. Then we do mass drug

13:43 administration, not those just those infected, but the whole um school community even if we know they're not infected. We wait two weeks and then in those two intensive schools, we're collecting urines again after treatment. We're doing over five days to see if anybody is still infected and if they've not been cured for their infections. The data we're gathering is about spatial infection levels and intensity to build those models but also to give us a better understanding what's actually happening on the ground. Large numbers of treatments will be given to actually uh support elimination and to prevent that chronic morbidity buildup in these communities. And we're very interested in those treatment outcomes looking at cure and egg reduction rates. And then from my side we're very interested in the genetics of the parasites as well. And this has really come about because of some groundbreaking work in 2019 by two

14:36 groups in the USA which have found discovered how the drug present actually works on the parasites. Even though we've been using this drugs for decades, we did not have know how it works. And this work has actually shown that it's targeting a certain area of the parasite called the TRPM channel. And now we can look at mutations in that channel to actually track how well the drug is working. And that's very much what might museum is doing um from these collections. This work is very difficult. Uh it's logistically uh very it needs a lot of resources. It needs a lot of teams. But it's driven very much from the ground.

15:16 There's a lot of community engagement working with the communities, the schools, the teachers and the local ministries of health. We work with them to develop the ethics. We register all the participants um and we get the consent from those children um and very much work with those uh those individuals to actually allow this study um to go forward. The infection levels are screened through diagnostics the looking for eggs in urine. Again this is a logistically challenging operation looking at 17,000 plus urines. Um the team on the ground in the labs in Pembber are excellent.

15:51 They are very well um they're very they've done this through many treatment programs. The way we do this the urine is uh put through a a filter. The eggs are captured in the filter and then the microscope is looked is used to actually look for those eggs and we then we can get an intensity level and a prevalence level from those communities and then treatment happens. Um this is one of the most rewarding parts of uh the work that I've been doing on Zanzibar being involved in these treatment um the administration of the treatment. So the way this is done as well we go into the schools the children are very um used to being given treatment there and the teachers uh really support that children's children come into the schools we go in with the team to actually uh administer that treatment. the children actually get fed at the same time. This helps the metabolism of the drug, but it also allows them to have a meal um during

16:46 their school time. So often it's often an incentive to come in to get that treatment as well. You can see the children actually participating in this develop um brewing up the porridge in the morning to actually give the children before they're actually treated with the drug. And then they're given the treatment. It's based on their height def and the height determines how many tablets they have. And then they're given the treatment. They observed taking the treatment and they're observed to see if there's any side effects and they're observed to see if they're um vomiting or hiding those drugs as well. We do get children that hide the drugs because they're actually not very nice to take. So we're trying to get really good coverage and observe treatment to actually make sure um this treatment is taken are being taken at the um the appropriate level and the to have the maximum effect. So we hope to

17:35 reduce treatment, reduce prevalence, pre prevent that chronic morbidity, improve the overall health and well-being and eventually hope towards to move towards elimination. And so on the genetic side, how do we do this? Uh so it's actually not that difficult to collect the parasites. As I said, this is an image of lavi coming out of a single child. We capture the eggs, you put them in water, they hatch very, very quickly. Within minutes, they're hatching. And we take we capture single lavi using a um a laboratory pipette and we store them on these DNA storage cards and we can capture up to 60 lavi per child and we store them on these cards and then we do the genetics on that. So what we're doing is we're going to look at about 576 Miracidia from these different communities particularly those post treatment to see if we've got any um mutations that are appearing that show we've got lack of uh efficacy of this

18:33 drug as well. Okay, just to finish off um very preliminary data, one of the key things we've found so far is that we have much higher prevalence than we thought particularly in these hotspot sports. Um we know that if we sample a child on just one day our prevalence is about 20%. But if we look at that child across five days our prevalence jumps to about 35%. So we know that our di our routine diagnostics are not good enough to giving us true prevalence levels and we have much higher levels of infection than we thought. Cure rates are about 76%. Um in our mind that is not good enough. We need it much higher. And again, we're very much looking at these post-t treatment uh parasite colle um populations to see what's actually going on there. And our next steps is to analyze the data from all 17 sites, look at the genetics and then also advance the strategies to enable um shismas to move towards

19:30 elimination in Zanzibar and that's our ultimate goal. And then in the broader scale, what's this project um contributing? Well, it'll really help us know if we need an alternative to treatment or better interventions. Um, we hope this kind of surveillance approach is going to be adopted uh across Africa because we need to look at these parasite populations across all endemic sites and we also want to advance who guidelines for shm control and sh elimination and also in terms of diagnosis to give us true prevalence intensity levels as well. So there's much broader aspects that we're considering. And with that, I'll stop there. Just lots of thanks particularly the Zanzibar team. This in the down this image down here is uh the team uh that of all the collaborators um when we're working in Zanzibar and all the participants as well that take part in this study. Thank you.

20:38 Yes, snail control is needed, but we need a novel way of doing it. Um, and also we use Zanzibar as an example for snail control sometimes, but we can't do that in Lake Victoria. Lake Victoria, it would have no impact at all. So, we need to think about how we're broadening that approach as well. So, behavioral change did have an impact. Um what we were doing with behavioral change, we were giving particularly women washing platforms. So they were not going into the water bodies and that those behavioral changes were very much about culture as well. Women like to go and wash their clothes together as a community. It's a way of coming together and um communicating. Um so we provided those facilities for them and that actually reduced um transmission and also they were not taking their children to the water bodies as well. So it did have an impact. It's the sustainability.

21:33 When we go back now and we see those w those platforms that we've built, they've degraded. The women are not using them anymore. Um we put in um latrines as well, pit latrines and again they were not maintained so they're not being used again. So it's sustainability um which is hard. I think in terms of vaccines absolutely if if we can come up with a vaccine um that is going to be good enough. I think that is a way forward at the moment. I think some of the data shows it's going to be in combination with treatment as well. Uh it's it's vaccine development for helmets is hard. You probably know more than I do about that. Um but it is it is um the ultimate intervention in the long run but also is infrastructure and putting those alternative interventions in as well.

22:28 Yes, absolutely. So, um children are a um a lot of the mass struggle demonstrations done in in schools because they are a contained unit. So, you can do cohort studies with children, they're also the ones that are most infective and the ones that are contributing to transmission um at the highest level. Uh if we had all the resources available then we'd do communitywide um participation as well. Um yes um so in terms of climate change there is two factors to this. So we know we have shistiasis or we've they've just announced actually they don't think it in Corsica which is the Mediterranean Mediterranean Ireland. Uh it is the urine genital form. So it was the transmission through urine that actually occurred in Corsica. Um there is data suggests that it has it has allowed to itself well it's enabled itself to establish there because of increases in temperature. The snails have always been

23:38 there. So it was just a factor of people migrating into Corsica um and introducing the parasite but that slight increase in temperature is probably allowing that um transmission to continue. Um so with climate change and in introduction of shmisitis into new areas you have to have the three factors you have to have water contact you have to have excretion of eggs in urinal feces so bad sanitation you have to have the snails. So in some areas where you got the snails but you haven't got people in the water or bad sanitation you're not going to have shysmiasis. So again you have to have those three factors in play um which is important in terms of climate change. So again we know that we get um we're getting floods that obviously in places like Africa is going to introduce new areas. We also have droughts so it's coming out of certain areas as well. We also know that too high temperatures the

24:34 snails are not happy and also the parasites not happy. So as temperatures get to a really high level that's also going to be detrimental to smises. So there's a lot of things to think about in terms of climate change and not to just always go with the yes it's going to have a massive impact as well. So

24:56 uh so snails are very attracted by uh food. Um so that is their main uh attractant and there has been groups that have developed it's called a it's like a snail gel um and actually uh we feed our snails on it and as soon as you put it in they are on it and there is a group actually wanting to trial this in sites to actually attract snails to a certain area so that they can be removed to actually bring down the snail population. So yeah, so that would be a nice way to have and you know snail traps, they would love to develop snail traps for that. So thank you so much. I think if everyone can join me again in saying thank you to Bonnie and for a really interesting talk.

Questions about this episode

Who speaks in "Tackling schistosomiasis, the neglected tropical disease caused by parasitic worms | Wellcome"?

Bonnie (Host).

What is "Tackling schistosomiasis, the neglected tropical disease caused by parasitic worms | Wellcome" about?

Schistosomiasis, a neglected tropical disease caused by parasitic worms and spread by freshwater snails, remains a significant public health challenge affecting over one billion people worldwide, primarily in impoverished regions with inadequate sanitation. Ongoing research aims to deepen the understanding of the parasites' biology and develop effective prevention strategies to eliminate this…

What is mentioned in this Wellcome episode?

8 people, works and ideas are mentioned, including Schistosomiasis, Paquantal, Natural History Museum, Neglected Tropical Diseases, Resist the Resistance Evaluation, Rasmus University. Each one on this page links to its own page with every episode that mentions it.

How long is "Tackling schistosomiasis, the neglected tropical disease caused by parasitic worms | Wellcome"?

The episode runs 26 min; the transcript is about 4,412 words in 30 timestamped sections.

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