Potential endemisation of West Nile and Usutu viruses in the South of France
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| License | CC Attribution 3.0 Germany: You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
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MOOD Science Webinars21 / 45
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Transcript: English(auto-generated)
00:10
So what I'm going to present you today is a collaborative work. It has been done by many groups that have participated. You can see the logos on the bottom of my slide.
00:24
And we're going to talk about the West Nile Anusuitu viruses. Most of you know them quite well. But just in case some of you don't, very, very short introduction. These viruses are flaviviruses. There's like dengue virus, mosquito-borne. But they are avian virus. But they infect many different species,
00:43
most of the times without symptoms. But sometimes you can see a severe disease. For example, in European settings, it's the case of raptors, like the ghost hawk on the slide, due to West Nile infection. In the case of an Anusuitu virus,
01:00
it's mainly blackbirds that go endure severe disease. But of course, it's not this impact that has triggered the research on these viruses. They can infect certain mammals, mainly humans. And in the case of West Nile, also horses, leading to severe disease, sometimes even death.
01:22
Most of the times, the transmission is due to a mosquito bite. But in the case of humans, organs and blood from donors can also serve as an infant transmission. So the question is then how to control them. And luckily, so far, we have very, very few,
01:44
we have very few tools. We only have, well, we don't have any drug, antiviral drug against them, specific against them. We have no vaccine for humans, only a vaccine for horses, for West Nile virus. So most of what we can do is based on surveillance.
02:04
That is surveillance is used to get information required to establish management strategies for blood and organs from donors, and also for the control of mosquito populations. However, surveillance of these viruses,
02:21
as for many other viruses, is not an easy task. So the first problem we have in European settings is the prevalence. It is extremely low, most of the times, that demands loads of sampling. And then it is not the same to sample wild birds, mosquitoes, humans, horses. It's very different.
02:41
So you require multidisciplinary teams to do this. So how to optimize these surveillance, just like, or any other pathway. And what do you need to know is the epidemiological situation in detail. And the problem we have now is that it is probably changing in Europe. In the past, these viruses were thought to be exotic,
03:03
brought into Europe from their endemic headquarters in Africa, thanks to bird migrations. Outbreaks did not happen every year. The pattern was rather erratic with several years without any outbreak.
03:21
But now the pattern has changed, at least in some regions, and probably they are endemic. Why we think the pattern is changing? Well, we say the pattern is changing because first, because we see much more cases, at least some years. This is an example from West Nile, but the pattern is exactly the same for us.
03:41
So these are human cases in Europe, in European countries. You can see these huge epidemics in 2018 with more cases than in some of the previous years. The distribution is changing as well. We see them, for example, again, the same pattern for us too, but I use a West Nile example.
04:02
We see them, we see West Nile virus, for example, far north than previously, with now outbreaks in the Netherlands, in Germany. We haven't seen before in 2019. And I think that the more worrying point that we are observing is that in some regions, we see almost yearly outbreaks
04:24
and above all by the same genotypes. This is strongly suggested that the virus is becoming endemic in this arena, or it's already endemic. For example, I have surrounded here in Northern Italy, where we have exactly this situation.
04:40
So I think when we think that it's interesting to study, which is exactly the situation, you know, those European regions at risk. And we work in one of these regions. This is what I've said that the South of France, but to be precise, it's not all the South of France, it's just these rectangles you see here,
05:01
which is the surroundings of the city of Montpellier, the Delta of the River Rhone, which is called Camarga. And we go up to almost to the Spanish border. So why here? Well, ecologically, this is the perfect place for them, for above all the Camarga, because it's a natural park with marshlands.
05:25
It's a stop for bird migration and it's packed with mosquitoes. But of course, this is a long history of outbreaks of these viruses. The first case in horses in France was committed here. The first clinical case in humans of the virus
05:43
was also documented here by us. So this is why we think we are at risk. So we wanted to study the ethnicity, but then we faced this problem, how to establish that we have an endemic situation. It's not that trivial.
06:02
In fact, how can you distinguish between a scenario where you have introductions every year, followed by extinction versus a scenario where you have an ethnicity that is a virus overwintering, or even a mixture of both of them. It is difficult to obtain the data,
06:20
robust data that allows you, just as with which scenario it takes place. So what we have done is go, we have gone to tackle two more simple questions. The first one is, which is the prevalence in recent years of these viruses? The second one is, which are the genotypes that are present in the region? And to do so, we have sampled the main host
06:44
from an epidemiological point of view, that is wild birds, mosquitoes, horses, and humans. And we have also sampled dogs. Dogs don't develop symptoms, but they can become infected, they can still convert.
07:00
And they had been proposed as group sentinels in surveillance schemes because of their obesity with humans. And also because it is rather easy to partner with veterinary clinics and obtain samples. So this is why we have included them. So for results, I'm going to present you is per host.
07:21
So always the same structure. So you have the host, the number of individual sample, the period of the sampling. In blue, you have the results for Western high virus and red for eucytovirus. Okay. So the Nixomonos team has analyzed the human and the dog samples. This is through ELISA on certain transition stage.
07:43
And what you can see is that between 2019 and 2020, we got more or less between 0.5, 1% per prevalence, same procedure, right? In the samples, which strongly shows that there has been transmission among humans,
08:02
also in vicinity to humans. And so yes, we believe that they could be used, they could be included in surveillance schemes. And even there's a positive rate we have found. Then horses, this analysis has been done by Stephanie interesting in the center for.
08:22
Luckily we had samples only from 2016, but even though what we have is very high, relatively very high, zero positive rates by ELISA. So between four and 13%, this is in line with the results by other studies,
08:42
which I think strongly shows that the horses are among the best sentinel hosts for the two viruses. Wild birds have been analyzed by Nixomonos team. These wild birds and derived from passage surveillance, we have collected wild birds either injured,
09:01
ill or dead in the wild. Around 200 deaths were tested by RT-PCR and only five. So it was different and only two suited for us. And among these five birds, which is interesting is that one of them, this atonia like in the picture you see on the screen,
09:22
this is a sedentary bird that was found infected, which means that it's not only about migratory birds infected, it's also about sedentary birds. So transmission, ongoing transmission within the real. And finally, the mosquito data. This is by the work by my group in collaboration with the EID Meditane,
09:43
which is the main organism in charge of mosquito control. Thanks to this collaboration, we have access to a rather large network of sampling sites for mosquitoes. Around 20 that we can follow every week
10:02
between May and October. We have done this for three years, 2018, 2019, and 2020. We've got thousands and thousands of mosquitoes and we have analyzed in total around 17,000 females of Culex lignans, which is the main vector in OE.
10:21
Between these three years, this is by RT-PCR, the prevalence rate, as you see, the infection rate is low, extremely low. In fact, below one per thousand mosquitoes. You might find this really frustrating to screen so many mosquitoes
10:40
to find these prevalence rates. But in fact, we got two very interesting results thanks to this work. The first one is that the geographical distribution. So first the response for West Nile. So you can see here, we only found West Nile in 2018 in these two sites, but we saw two virus, we found it in the same sites in the same year
11:01
and others in 2020 in other sites. And we have previously published a study from 2015. I added it for the sake of completeness. So you can see that most of the viruses have been found more or less all around the Khmer Valley, yeah. Sometimes in overlapping West Nile,
11:22
and there are sites where the virus has been found in the three years, we could consider these sites as hotspots, and that should be integrated into variant systems. The second result that I really like is the genetics,
11:40
because we were able to sequence the virus. So these are the results first for West Nile. The dysbiotic tree cells sequences, so you have the two main lineages circulating in Europe, one and two, in blue sequences from France, in red from this study,
12:01
and black dots stand for sequences from the Khmer Valley. So because probably you don't see really the GIS, let me show them. So what you see here is that this cluster here, this cluster A of lineage one has been regularly observed in the Khmer area,
12:23
and the other lineages circulating in France. Interestingly, we have seen it three years in a row is by our work and others. For example, this study from Lambert et al has shown very close to our sites a sequence from the same cluster in 2020.
12:43
The problem is that they haven't sequenced the same region as us. And we haven't been able to add it in the foliage tree. So the virus has been found these three years. I like this vulnerability tree because there's another interesting observation here. It shows the complexity of what we find
13:01
when we study these viruses. For example, you see, you have found the viruses in 2000 and 2004, have been observed by the groups. And then for 11 years, we have an observer in the virus. Whether it is because it has gone undetected or it was because it was endemic, but not detected,
13:23
or it has been gone extinct and then introduced again in 2015, that we cannot understand. So as I've said, this cluster one A in lineage one, and the results for each group is the same. You have all the lineages here.
13:40
There are many more for each two virus and they are, their names stand for Europe, origin, Europe two, Africa three, and so on. So you can say in blue, as I've said, is the French sequences. You can see that there are three lineages in France. Okay, let me show you the years. And what you see is that two lineages in the Camargo area,
14:02
sometimes the same years, but only one lineage has been repeatedly observed in the area. This is lineage Africa three. Again, we have a problem with another study, in fact, by us, where the sequence was another part of the genome.
14:20
We can kind of mean included, but even though we have the same genotype, similar genotype observed three years, you have like four ways my virus. So it's not only about low prevalence, it's that we have observed repeatedly, observed the same over years and the same genotypes.
14:42
And most of these work, most of the data are now have just been published and you should have a look at the paper. To end my talk, I just would like, okay, three take home messages. If they are becoming endemic,
15:00
maybe it's time to rethink the surveillance as it is so far. We have happened in France, we haven't a surveillance program as good as the one that, for example, in Italy, Northern Italy, which is also clear is that we need to sequence the full genome each time now. Not all, not only us, but everybody else to help you in pharyotic studies.
15:23
And finally, there's a result that I think it's interesting because it has been discussed in the paper, but it is, which is the influence of the genetics of West Nile virus in the potential for in this body. So, as I've said, in each one here in the South of France, as I've said before in the introduction,
15:43
is leading to in Northern Italy. In fact, some people have said that there should be an influence of the lineage, but now you see there are different ones already established or in the process of being established. And it's also the case in other places with a similar ecological situations.
16:02
For example, on the Othea and Catalonia in Spain. So you have this patching network of lineages that strongly suggest that lineage is not a key factor in explaining in the research. With that, I would like to thank all the people that have participated. And you, thank you very much for your attention.
16:23
Thank you. Thank you, Serfain. And I would like to leave space for questions now from the audience. You can either write it in the chat or even unmute yourself and please pick up. Well, maybe I could just ask a very general questions about if you seen any other endemization
16:47
of these diseases in other regions in Europe. Yeah, well, as I've shown in one of my last slides, you can see that we are still to have data. This is a partial, I haven't shown all the regions.
17:06
For example, Germany, now they haven't seen, I think it's 2018, they have seen regularly every year the same genotype circulating in Greece and the Balkans probably is the same case. It's probably in the lineage too.
17:21
And even in some places like in, but the points that we lack is still the genetics of the viruses in some places. Or because most of the times we see cases, but the sequences are not obtained. I think there should be much more effort on that.
17:40
There is a question from Pauline. Do you see an increase in horse vaccination for West Nile virus? If so, what do you think the consequences would be for using horses as sentinel animals? That's a really good question. And in fact, I'm afraid I don't have the data for that,
18:00
but I'm sure I'm going to get that one. I will come back to you. I will ask the experts in horse and West Nile, because that's a good point. I will read a slide, another question from Giovanni Marini. How do you explain lineage one while lineage two is the most spread in other European countries?
18:21
Yeah, that's a surprising, isn't it? We didn't expect that, in fact. But then we're going to have a look at the databases and we have seen that lineage one is... In fact, even lineage one is also present in Southern Spain, and clearly now for a few years.
18:42
It seems it's not about the lineage. Even there are... It has been proposed that lineage one was less virulent than lineage two. But the problem, the point is that, for example, in the outbreak in 2020 in Southern Spain, in Andalusia, you have around 80 cases, severe disease among them, eight deaths.
19:03
So I think that's a quite consistent number of cases and deaths. I think maybe other factors have helped now to this need to establish. Which ones? I'm afraid I cannot tell you, but I guess maybe it's just a matter
19:20
of a high increase of virus circulation thanks to higher temperatures. So do you have questions to our audience? Since maybe you might have an overview of what the MOOD project is, and definitely this West Nile virus is one of our topics of interest, and we have experts in the audience.
19:44
So one of my questions is whether you consider that surveillance should be modified in the Southern France or in the other region whenever West Nile virus is found to have become anemic.
20:02
Maybe you could discuss a little bit what are your next steps in this research? So probably you already mentioned it, but maybe this could be of interest for the foreigners. See where you're going now after four years of study. So what's next? I think we haven't finished yet with this situation
20:23
in the Southern France. In fact, you have seen it in some of the fire related trees. You can find the virus for several years and then it disappears again. So I think it's a long-term work and we are continuing the work
20:42
above all the mosquitoes that are showing humans and horses and dogs. So that's for France. And what we are, we think it's missing is, which is the real diversity of these viruses. The point is that most of the sequences we have come from Europe,
21:03
but we start to work a lot in Africa above all the Burkina Faso. We try to find, well, all these birds, what they carry with them. I think it's a very interesting question and we are also working on that.
21:21
And I can imagine you work in close collaboration with bird ecologists and GPS tracking is something you were planning to track? We are planning to do that. Okay. We had started net trapping and bird net trapping here of migratory and non-accidentary birds to establish whether there were differences
21:42
in virus diversity among the two of them. But I must say that I thought mosquito trapping was tricky, but yeah, getting enough numbers of birds in this even more tricky.
22:01
I think that given the size and the intensity of the dengue epidemics this year, it is surely something that we should consider. Maybe because, well, as you know, dengue virus can be transmitted by mosquitoes vertically. So we could have,
22:21
given that there has been a lot of virus transmission, we could have a prominent infected mosquito population that has laid eggs that leads to infected mosquitoes. Yes, surely. Evidently, dengue virus is on the primate virus with mosquitoes.
22:41
So that reduces the number of hosts to test. But yeah, clearly I think we should do that. In fact, we are working on a proposal to get funding to this type of work. Well, it is clear that each host
23:01
has provided a different result. Interesting in their own and different, their complimentary server. And that clearly shows how interesting it is to have, for example, mosquitoes and getting the genetics, the genetics of the virus. Of course, you need an estimate of the virus transmission to humans,
23:21
or wild birds, you know, stress, stress allows us to see the same type of birds infected. I think that's the complementarities is clear in this case. And this is why we believe that this is the way to go forward in the future. We are, we, then this team, this network is of teams working on West Nile
23:42
is going to continue to work together. The problem is that I don't know how much, how far did these results go beyond the scientific community? This is why I have asked the question whether you believe it. I hope they are taking into account.
24:03
My impression is that if there is no epidemics or episodics in the near future, well, they are not going to be taken into account, but maybe I'm too pessimist. I hope so. So I don't think they are going to be taken into account in the near future, but I hope to be wrong.