Spring temperature shapes West Nile Virus (WNV) transmission in Europe
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| Anzahl der Teile | 45 | |
| Autor | 0000-0002-9921-5129 (ORCID) | |
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| Lizenz | CC-Namensnennung 3.0 Deutschland: Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen. | |
| Identifikatoren | 10.5446/51670 (DOI) | |
| Herausgeber | ||
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| Sprache | ||
| Produzent | ||
| Produktionsjahr | 2021 | |
| Produktionsort | Wageningen |
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MOOD Science Webinars3 / 45
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00:00
Computeranimation
09:13
Computeranimation
18:25
Besprechung/Interview
Transkript: Englisch(automatisch erzeugt)
00:08
So I'll talk about how spring temperature shape West Nile virus transmission in Europe. This work was led by Giovanni Marini, who unfortunately cannot attend today's presentation,
00:21
so I hope it will be as interesting as it was him presenting. So next slide please. The outline of the presentation is a little brief background on West Nile virus and then I'm going to talk about the previous work on West Nile transmission in the middle of Romania,
00:43
which is a region of northern Italy, and then how we try to extend it to the whole of Europe and try to investigate how spring temperature may affect human spillover. Next slide please.
01:01
So West Nile is a virus which is mainly circulating among mosquitoes and birds, where mosquito act as a vector, and given that the mosquito species, which is the primary vector, also bites other animals like horses and human, it can happen to have incidental infection
01:21
to, again, horses and humans, which are dead at host. So an infected human is not able to mosquito vector and so is not able to further transmission. Usually this kind of disease is asymptomatic, but in rare cases people infected can develop severe neuroinvasive implications.
01:48
So most of the time the disease goes undetected by the public health system and when the system starts to see cases, the circulation is already widespread or happening for
02:04
quite a long amount of time. So next slide please. So obviously given that there is a mosquito vector involved, temperature plays a key role because it affects mosquito dynamics.
02:22
Several works have shown how warmer conditions can speed up the development and the life cycle of the mosquito and also increase the biting rate to the host, which can be bird, in some cases also human or also rather mammals. And similarly also temperature plays a role
02:46
by affecting the pathogen transmission as warmer condition may decrease the incubation period in both the host or in the vector and increase the transmission probability to other hosts. Next slide please. So as I said there has been a previous work led by Giovanni
03:11
in which he analyzed the West Nile virus transmission in northern Italy, in particular in the region of Emilia-Romagna in northern Italy,
03:22
which is characterized to be the region where the lowland of the Po River is located. And as you can see the points are the traps deployed by the surveillance systems and in this work he set up an entomological model coupled with an epidemiological model.
03:45
So in the first entomological we analyzed the life cycle of the mosquito and the model was calibrated to mosquito captures and as that input data it was the temperature.
04:01
By this model one is able to estimate the expected mosquito abundance. And the second part coupled with the epidemiological model which models the transmission between birds and mosquitoes. In this way one can compute the prevalence on the bird on the mosquito which are the vector
04:22
and from that compute the human risk given the mosquito prevalence computed. The model was calibrated on the data in the past year and it's very interesting to note how the 2018 was a very exceptional year as it was characterized by
04:47
an earlier and higher fraction of mosquito pool resulting positive and also later in the season in about 100 narrow invasive human cases which are a lot more than the total number
05:04
recorded in the previous year. This is not specific to the Emilia-Romagna region but it's also happened in 2018 in almost all Europe. If you could please go to the next slide. These are some results as you can see spring was exceptionally warm in 2018 and this
05:27
seems to have amplified the West Nile virus transmission at the beginning of the season. So having a higher transmission at the beginning of the season resulted in more circulation during
05:41
the season and therefore in a lot of more cases than observed by the public health system. So next slide please. Having observed that pattern in the Emilia-Romagna region we now try to explore if this pattern is also observable in the rest of Europe. Again
06:06
there's a problem of data which are not available as in Emilia-Romagna for the rest of Europe. So we collected data from the ECDC which report cases from all Europe
06:24
for the period from 2011 to 2019 at the NATS3 level. As you can see in the upper right graph 2018 is a very exceptional year for all the Europe in terms of West Nile virus transmission.
06:45
So we take in consideration this data and we apply the statistical analysis to quantify how and if spring temperature can influence human spillover at an European scale. So please switch to the next slide. The model we use was to consider the number of
07:09
laboratory confirmed cases for an area at NATS3 level and year specific year. And we assume that given the CDC record only report positive cases, when an area has no cases
07:26
so it's not present in the database but it has already had cases in previous year we assume that there is a zero reported cases so we inflated the database with zero. And also we take into input the land surface temperature as an independent variable
07:45
in the statistical model. Can you please go ahead? Yeah, thank you. The model was a zero inflated negative binomial models. It's a two-part model. The first part is a binomial part which models the present absence of cases. We use this framework because we inflated the database
08:06
with zero. So we think it was important to model also this part. And the second part of the model is modeling the number of positive cases recorded. So as you can see by the formula
08:22
the equation here the dependent variable was the number of laboratory confirmed cases while the independent variable were the average spring temperature in the period 2003-2010. And this act as a gradient differentiating south to northern Europe.
08:46
And the second dependent variable was the temperature anomaly. So we normalize the temperature as a difference between the average temperature. So this variable indicates
09:01
characterized each year if it is a warmer or colder year with respect to the mean temperature of the area. And we also consider if the West Nile was already circulating in that area for that year in the previous year. So it's a very simple and explorative
09:23
statistical model to just see if we can find some relationship between temperature and the number of cases recorded by the CDC at European level. So next slide please. Indeed there is a correlation as expected.
09:45
And as you can see in the upper panel the upper panel shows the average number of cases expected conditional to the temperature in the average temperature in the upper left panel or with respect to the temperature anomaly in upper right panel. As you can see there is
10:06
an increasing pattern. So the warmer on the average spring temperature more cases and the warmer specific springs for the location the more probable an higher number of cases.
10:26
On the other hand the lower panel models the probability of observing a zero or a positive number of cases. As you can see again the role of temperature is showing that the more warmer
10:41
the temperature the less likely to observe a zero record. So next slide please. So to conclude the previous work on the Milia-Romagna region and the following work that is now published
11:01
in Arthrotropica at the European level shows that there is an association between previous West Nile detection and larger number of cases in the following years. It's more likely to have an higher circulation in a usually warmer region that is further enhanced
11:24
if the specific spring temperature of a year is warmer than the average temperature and that considering warmer temperature spring in particular warmer temperature as a nearly warning signal for West Nile virus you must be lower.
11:46
Having said that thank you for your attention and if there is any question I will be glad to answer it. Okay thank you Mathias and my apologies for some technical
12:02
problems but we're still on time so please questions maybe I will start if somebody has a yeah question. Oh no it was me. You can start please go ahead and start. Mathias nice talk
12:31
thank you. Your first point there previous West Nile detection is associated with larger outbreaks I mean that implies that I mean if you've had a large outbreak let's say in 2018 that conclusion
12:46
would suggest you're likely to have another one in 2019 is that right? No surely not. No large outbreaks is probably a catch phrase for the presentation you just say that
13:01
if you have had in a specific area which is the last three level cases in the previous year you are expecting to have further cases to next year obviously quite. So the the when you look at the 2018 data as you say there were far more cases
13:24
were there also far more places as opposed to cases? Yeah West Nile is spreading across Europe it seems that in most of most area it's when it's a prior 10 it's bound
13:42
to stay a lot of problem going on with the detection they think because given that it's not really symptomatic for most cases it's difficult to detect but if you look for it in the mosquito vector when you are an area that result positive for West Nile
14:06
virus circulation that the following year is likely to observe again circulation and in time you pile up cases and when again 2018 it was an exceptional year but by probably condition
14:24
aligned warmer temperature previous circulation a lot of vertical transmission from the previous season you have this outbreak happening which by the moment was 2018 was the highest level the peak level observed. Okay thank you we have one more question from Wim I think
14:52
yes yeah thank you I thank you for your nice talk on West Nile I see for your ECDC
15:02
data you use data from 2011 to 2019 was there any specific reason not to have 2010 into the database this was also the start of the West Nile to the large West Nile to
15:20
circulation in Europe a large outbreak in Greece if I remember well with also very specific climatic conditions 2010 was also a very strong winter I think I don't know what the spring temperature did was there any specific reasons not having 2010 in your analysis we use the
15:43
temperature data from 2003-2010 as a reference and then we started the database from the for the dependent variable from the 2011 as you say I think the 2010 is the first year of the
16:01
appearance of West Nile in Europe for the ECDC so we discarded the first year I think yeah because it was also a very large outbreak of course very I think at that time mainly focusing on Greece so it was included in your reference point okay no at the moment no
16:25
okay yeah right okay thanks any other questions I have a question I was wondering do you plan
16:49
to include other variables except a temperature like the rainfall yeah we would like water areas in the model yeah it would be nice I think it's a future direction for research to include more
17:08
variable again this was to explore an association we find we found on Emilia-Romagna region in the previous work but yeah West Nile virus circulation is a very complex system and mechanism
17:22
cannot be explained only by temperature and yes indeed we should include more variables also relating to the species involved Matthew one question for me also what about if you
17:41
would extrapolate this model to future if you will assuming like a climate change in future temperatures have you have you tried doing that like just extrapolating the model you fitted with a future like projected climate scenarios I would would have been nice to do that but we we were not so much confident about the
18:05
reliability of the result because again it's an indication that with temperature things in terms of West Nile are going worse and worse so if we expect it to be an increasing temperature again we have to expect an increase in West Nile virus transmission and circulation across
18:24
all Europe temperature most likely affect the transmission of West Nile because it acts as a boost the mosquito population which act as a vector because warmer condition
18:45
can speed up development of the mosquito and also can speed up the incubation period within the vector of the viruses so if you have a warmer condition most likely you can have a more aggressive and more abundant vector population and if the viruses
19:08
is introduced in the system or in the in the area then it can be circulating more with much more velocity and so yeah that's the main reason I think for temperature being
19:25
very important in the modeling and in understanding of the West Nile virus circulation again there are a lot of different factors because we know that birds are the primary host but there is not so much information on which kind type species of birds is really maintaining
19:46
and sustaining the viruses in the in the environment West Nile is able to overwinter through the mosquito population which enter in diapose and then by vertical transmission and will start the virus cycle in the next season there are some observation of
20:06
diaposing mosquito vector which are infected with West Nile founded in during winter time and at least in the USA there are also horizontal transmission between birds but there are no
20:22
evidence of that because there is a lack of study also in Europe about the role of birds in the maintaining overwintering of West Nile so yeah I think overwintering at the moment is probably due to the mosquito vector which carry on the virus to the next season
20:44
I don't think there is much of relation between the two viruses but for sure the spread and the spread and the present situation with covid is worsening a possible West Nile virus outbreak because the restriction measurement enact at the moment for covid again limit the movement of
21:09
people render more difficult maybe do some entomological control or intervention and also I've stressed the public health care system so maybe symptomatic West Nile virus cases
21:26
could have less access to cure or be confused with the other I mean if you develop a fever now the likely a fear that you have covid rather than the West Nile so you may have
21:41
a wrong diagnosis at the moment so yeah surely covid have impacted the health care system and is reflect with to West Nile but it's too early in the season to predict or have an idea how much the West Nile will circulate or where but yeah if you are going to see another
22:04
outbreak like 2018 it will be worsened by the covid situation