Episode 27 - Never mind the buzzkill: How mosquitoes spread disease

Sofie (00:00)

You're still the same mosquito. Whether your, going to your human or your horse or bird. 

James 

You don't care. 

Sofie 

You don't care. I mean, you might prefer one above the other, but it's still, the same information that we need. So, it doesn't make sense that two agencies would collect the same information separately.

Intro 

Science on the menu, a podcast by the European Food Safety Authority.

James 

Hello and welcome to another episode of Science on the menu.

My name is James. I'll be your host for today's podcast. And today we're delving into the world of vector borne diseases, which is an important area of his as work on animal health. 

What are vector borne diseases, you might be wondering? Well, simply put they’re diseases, pathogens that are transmitted to humans and animals from vectors like mosquitoes, sand flies, fleas, and so on.

You'll probably be familiar with some of the more well known, diseases like malaria, chikungunya, bluetongue, maybe, and we'll be talking about those today, as well as some of the other, vector borne diseases that affect animals. 

To talk us through the work that we're doing in this area, I'm very happy to welcome our guest to the show, Sofie Dhollander.

Sofie, hello how are you? 

Sofie 

Fine, thanks. 

James 

Maybe before we jump into everything, you could just start by giving us a bit of information about your background. How you come to be working in this area at EFSA. 

We start from there. 

Sofie 

I'm a veterinarian, as you said, I'm Belgian. I’ve worked in EFSA for 17 years, but before I have been working about seven years in Africa and Asia. Because I specialized in tropical animal health. 

In EFSA for 17 years, I've been dealing with risk assessments on animal health, mainly African swine fever and vector borne diseases. 

James 

Really with field experience. You have that direct experience in the field working in Africa, where were you in Africa? 

Sofie 

I started to work in Gambia, where there is a what they call three Tryponatolerance Center at that time.

They mainly focused on Trypanosomiasis, which is a disease that is transmitted by tsetse flies and, commonly known under the name of sleeping disease or sleeping sickness.

But in West Africa, it's mainly affecting animals. Maybe sleeping disease for humans is more in East Africa.

In West Africa, in the Gambia we did research, but also, helped farmers, let's say, with horses that had sleeping diseases in return for the samples we took.

James 

Is that a big problem? 

Sofie 

Yes, especially for horses, which value a lot for farmers there, but of course for cattle, sheep and goats, they get it, but they don't die because they are tolerant. That's why it's called three panel tolerant animals. 

But horses will die and, chronically, after a long sickness, they will die if you don't treat it. 

James 

Important research there that you would think.

When we think of Africa and vector borne diseases, malaria comes to mind. 

I guess you see this around you everywhere when you’re in countries like Gambia.

Sofie 

That's right. It's very important.

People living there still get malaria, but there is a little bit of…immunity, I can't say, but if we people that have never lived in in Africa or white people, let's say, never get it, you get much sicker.

I had to live it myself.

James 

You were telling me before we came on air.

What happened in your case? 

Sofie 

I was always quite strict in thinking I should not take any treatments before it's confirmed because there's a lot of resistance. I thought, let's have a check because I didn't feel well. Then, it turned out that I was negative.

I thought “I have a flu, so let's sit it out and take some paracetamol”. But then I waited too long. After several days, my blood was so full of parasites that I was lucky that the colleague came to knock at my door to see how I was, and I was hospitalized for one week.

I almost stayed there. It can go very fast, and it causes a lot of deaths. 

James 

I can't even imagine what that must be like here in the Gambia away from friends, family. You have to rely on the local health care system there. 

What's that like? 

Sofie

It's packed with people in the hospital and they don't have beds for everyone. 

There are different conditions people have to face. 

James 

But you came out, the other side, of course, which is great.

Sofie 

Whatever doesn't kill you makes you stronger. 

James 

After Africa you came back to Europe and now you're here at EFSA.

Maybe just explain a little bit about what you do here in the EFSA team. 

Sofie 

In the EFSA team currently I'm responsible for a mandate on vector borne diseases. 

Where we are asked to assess the risk of introduction of those diseases or pathogens into Europe, but also the spreads from one country to another country and the impacts or for instance, our risk managers.

Like the commission can see where they have to focus their resources on, what is at a higher risk, but also the people in the member states, they can see what type of surveillance, etc. is more appropriate to be more preventive or more prepared for these diseases. 

James 

We just spoke about malaria, which is obviously vector borne disease that people primarily associate with humans, affecting human health.

Here at EFSA we're focused, primarily, I would say on animal health. 

Maybe you could give us a couple of examples of the kind of vector borne diseases that we are keeping an eye on or have to be careful about here in the EU. 

Sofie

Of course we are collaborating with our, let's say sister agency in Stockholm, the European Centre for Disease Control that is focusing on the public health aspects.

We are more focusing on the animal health, like you said. 

Many of those vector-borne diseases are zoonotic, so they actually affect both human and animals. But some of them will have no clinical signs in animals and others will. 

We are of course, prioritizing as animal health team those vector-borne diseases that have more impact on animal health.

But of course, we also deal with zoonotic diseases and we collaborate with the ECDC for those. 

James

What's the most concerning or impactful vector-borne disease that affects animal animals in the EU at the moment? 

Sofie 

That's a good question. I think we have several diseases at the moment.

We have bluetongue that had a very big impact in 2023-24. 

It was a new serotype of bluetongue, bluetongue three, that was introduced in the Netherlands and it was mainly affecting sheep and caused a lot of mortality. I'm speaking about, thousands of animals that have died because bluetongue.

It spread in the meanwhile to other countries throughout the year. 

We have, of course, EHD that is a new introduced disease. 

James 

EHD?

Sofie 

EHD it's episodic haemorrhagic disease. 

It's affecting, deer, whitetail deer mainly, and cattle. It will cause, mortality mainly in deer, but also in cattle.

It was introduced in Italy and then has further spread to Spain and

James 

Bluetongue is not zoonotic, is that right? 

Sofie 

That's right. 

James 

Okay. But it can have a massive effect, impact on trade, local economy, national economies. 

Sofie 

Yeah. That's right.

We had another epidemic of bluetongue, that was more known to everyone maybe, in 2006. 

That was due to a change in vector competence, it moved northwards and it was killing about 1.5 million animals. It can have a huge impact. 

James 

Really? What do you mean by vector competence? 

Sofie 

In this case they are biting midges for bluetongue, not all midges are the same. You have many different species and some species are capable of transmitting a specific virus and others not.

When they are capable of transmitting it then we call them competent vector. 

Maybe I should also mention there are different types of vector-borne diseases because we have those that are biological, transmitted by biological vectors.

That means that the virus also gets a cycle in the insect. But you have also vector-borne diseases where vectors that sit on the animal and then transported to some other animal just by transporting it like a vehicle outside or on the mouthparts. 

But it's not really getting a cycle of development in the insect so that we call it mechanical transmission, but both are vector transmission.

James 

With those two examples that you gave EHD and bluetongue, I guess there We're talking about, the effect, the impact it might have on farm animals, for example. 

But I know from being a dog owner recently that there are also vector-borne diseases that can affect pets as well.

Leishmania I think is one people might be familiar with. 

Can you talk to us about that

Sofie 

Yes. Leishmania is not transmitted by midges but by sand flies. 

The competent sandfly vectors are more in the Mediterranean area you will get a leishmania as a dog when you live in Italy, but not, for instance, in the Netherlands.

Of course, you can go on holiday in Italy and get it there, but they are not locally established these vectors that can transmit. 

It causes, rashes on the skin and it can also affect people.

In Europe we have mainly the cutaneous form of Leishmania, but worldwide you also have many people dying from Leishmania also from the visceral form of Leishmania that is rarer here. 

James 

The advice I got from my vet was vaccinations. 

Sofie 

Exactly and collars I would say definitely, also vaccines are protecting but not 100%like you remember with the Covid you don't have 100% protection.

I would definitely also put collars or spray to protect from insects, from the sandfly bites. 

James 

We talked a bit about different types of vector-borne diseases, some affecting humans, other animals, sometimes both. 

You mentioned also the work that we're doing with our sister agency, the European Centre for Disease Prevention and Control.

Can you just explain a little bit more how that works and what exactly it is we are doing together with ECDC and maybe the member states, when it comes to sort of combating vector-borne diseases?

Sofie 

We have worked with ECDC for more than ten years now, a collaboration that we call Vector nets.

Both ECDC and EFSA, we are putting money together to fund a consortium that organises a lot of work to help us with our risk assessment, but mainly to collect data on vectors. 

Where are the mosquitoes that are competent for instance Rift Valley fever? Another disease is the West Nile fever. 

There are many vector-borne diseases that have different vector species that are relevant.

We collect this information in the harmonised way and we support their vector nets to organise that, but also to organise an annual meeting with our One Health Vectornet Entomological Network, which is like about 40 people from both veterinary and the public health side that come together and they are really experts on this type of data collection.

When there is new evidence or new events in the EU then we discuss how we better can control and prevent. 

James 

We hear a lot about this One Health approach. It's something EFSA is really fully supportive of and behind and this is One Health in practice.

Sofie 

Yes, absolutely. 

James 

The public health bit with the animal health bit. 

Sofie 

I think here for instance if you're a mosquito transmitting West Nile fever, you're still the same mosquito, whether you are, going to your human or your horse or bird. 

James 

You don't care. 

(soft laugh)

Sofie 

You don't care. I mean, you might prefer one above the other, but it's still the same information that we need.

It doesn't make sense that two agencies would collect the same information separately. 

James

These experts that you're talking, are they coming from the member states?

Sofie 

Yes. We have a system: we have an official network that they are appointed by our focal points and they see which expert is the best representative to come to such a network.

James 

It's really a European wide approach.

Sofie 

Yes, and also the neighbouring countries, the accessing country. 

James 

Very good. You touched there just a moment ago on looking at competent vectors, the spread and so on. 

What factors influence or have an impact on how vectors spread? And do we notice changes in the way that vectors have been spreading over recent years?

Sofie 

That's a good question because there are many ways how a vector can spread. 

What we do see is, for instance, some reports of the World Organization of Animal Health report that more and more new events or extreme events are more north. Vectors are influenced by temperature or by humidity, by vegetation.

Like all of us, we are actually impacted by climate change. So definitely mosquitoes will be impacted by climate change. 

But of course, it's always difficult to find the direct cause of an outbreak because, like I mentioned, the bluetongue outbreak in 2006 moved very suddenly: the whole Europe was infected by this new BTV8 serotype.

This is not because of climate or weather it cannot go so fast. It was because of a change in the competence of the vector that were more limited to the south of the EU and then suddenly all the vectors in the north, not all, but some were also competent.

It can completely change the picture, so sometimes we have to also be careful if we say it's climate, because it's not always climate. But clearly climate does have an impact because seasons are getting longer, so temperatures are higher in in February, it's humid so mosquitoes start coming up earlier in fact. 

James 

Well, I noticed that even in my own garden here in Parma, north Italy we have the tiger mosquito.

I think when I came here ten, 15 years ago, there was a clear kind of period during the year when you would see the presence of the tiger mosquito and then it would stop during the winter months. But now it seems that they’re more present for longer during the year and in some cases, you see them in December, January.

Sofie 

Yes. This tiger mosquito is a real nuisance in Parma. 

It has been introduced in Italy in the 90s and now it's in more than 20 countries in the EU, definitely spreading all over the place. 

It's especially a nuisance because it's attacking during day like compared to our usual mosquitoes that we were used to have that attack you more in the evening and at dawn.

James 

What tips would you share with us? How do we protect ourselves from some of the more common diseases that we might get from these nasty vectors? 

Sofie

Well, for the human diseases, like you said it's very important to wear long clothes and socks in the evening and use repellents and mosquito nets.

Of course, if you're going to the tropical areas, it's very important to protect you to get vaccinations for those that are having a vaccine. 

And that's the same for the dogs, like you mentioned before, you can vaccinate some animals. You can protect them with repellents, it's very important. 

James 

Great. Thanks a lot Sophie.

Sofie 

Thanks to you. 

James 

That's all we've got time for on today's podcast. 

Thank you very much for being with us. If you'd like to listen to more about EFSA’s work, you can find our podcast series Science on the menu anywhere you get your podcast. 

We mentioned the European Centre for Disease Prevention and Control during this episode. They too have a very interesting podcast, so if you'd like to hear more about what they do, I encourage you to check that out and we'll see you next time.

Thank you very much and goodbye.