This week on The Naked Scientists, we're getting ticked off about the uptick in ticks, as we look at what they are, the problems they cause, and what we can do to tick them off our worry list.
In this episode
What is a tick?
Jolyon Medlock, UKHSA
As someone that’s had a few run-ins with animal critters out in the field, there is little out there more shudder-inducing than finding something feasting on your body. And ticks are no exception. But we shouldn’t let the fear of running into a tick stop us from enjoying the wonderful outdoors, and so the best way to start is for us to know our enemy. So, what is a tick? Where do they come from, and how do we come into contact with them? The UK Health and Security Agency's Jolyon Medlock.
Jolyon - A tick is an invertebrate, it's an arachnid. So it's more similar to spiders than a normal insect. In the adult stage, there are four pairs of legs. So it has eight legs, whereas an insect has six. It's also what we consider to be a parasite. So it lives on a range of different animals where it will be taking a blood meal to enable it to, to lay eggs or moult through to the next stage.
Will - And I appreciate this is a question that might change as we explore this subject further on in the show, but do we know how many tick species there are in the UK?
Jolyon - People have been recording ticks in the UK for well over a hundred years. So we've got quite a lot of historical data on what, uh, ticks have been found. And that might include people who've been working on offshore islands, on seabirds, looking at certain ticks associated with puffins or cormorants or there are a couple of species associated with bats. So there's a range of different species that are specifically associated with wildlife. So we have probably about 20 species of tick that we would routinely find in the UK if we went looking for some of those species.
Will - And what is the big one for us?
Jolyon - The one species, it's called Ixodes ricinus, which has various names. It was named by sheep farmers. In the Pennines as the sheep tick. And those people who work with deer call it the deer tick and others call it the castor bean tick because when the tick is fully engorged, it looks like a castor bean, a bit like a baked bean. So that's the common tick. And what's significant about this tick and why it's also important as a disease vector is that it can pretty much feed on anything. It feeds on a range of different species and that particular tick has different life stages. So once the egg hatches, it develops into a larva, which has six legs, and then will feed and then develop into a nymph, which has eight legs, and then will feed again and develop into an adult male or female, which also has eight legs. But at each stage those tick stages feed on different animals. And what the animals they feed on largely relates to where they are within the vegetation. So this particular tick has a habit of what we call questing. It'll climb up vegetation and then will quest for an animal. So you can imagine the smaller larvae can only go so high, so they're more likely to come across small mammals. The nymphs can go a little bit higher, they'll come across bigger birds such as pheasant or squirrels, and then the adults can go even higher because they're able to withstand that desiccation for longer. So that's the stage that you're more likely to pick up on sort of dogs, deer.humans tend to come across nymphs the most.
Will - Is this sort of uniform across all grassland or do they have a particular area or habitat that they're most likely to be found? Just so I know where to never go ever again in my entire life.
Jolyon - The Ixodes ricinus is primarily a tick of woodland habitat across most of its range. So if you are in woodland or on the edge of woodland or in areas where there's long grass close to woodland, then you can often be in habitat where there are ticks, particularly if there are animals around, whether that be deer or livestock. Usually they don't tend to be found in short grass. There are other tick species that you get in some of the sort of short grassland habitats where sheep are grazing. In some places it can be found in urban parks as well. So it's not just a rural risk. So if you have been walking through vegetation that's quite high and you've brushed past it and you think it might be suitable for ticks, it's always worth just a check, knock any ticks off. And then at the end of the day, just give yourself a check again.
Will - When people talk about ticks, inevitably the first thing they think of is Lyme disease, but are the ticks themselves responsible for this disease?
Jolyon - The main aim for the tick really is to find a blood meal so that they can develop through to the next stage or in the adult stage is to get a blood meal and then produce eggs for, you know, the next progeny. So actually it's rather incidental. They then acquire pathogens that are in the blood of animals and then pass those on. But those pathogens have evolved with the tick to really use them as what we call a vector. So the tick is doing a job for the pathogen in acquiring the pathogen and then developing within the tick and then passing it onto the next animal or person.
Will - Which pathogen in particular is the one responsible for Lyme disease?
Jolyon - It's a bacterial infection, what we call a spirochete called Borrelia burgdorferi. And it's a bacteria that really exists within wildlife. So there are different types of Borrelia and they have different transmission pathways. Some can be found in mammals, some can be found in birds, but they're all being transmitted primarily by this one tick. So if you get bitten by a tick that's infected with this bacteria, you can develop different types of Lyme disease.
Will - What's your advice then, if you're heading out and you want to enjoy nature this spring, what would be sort of your, your quick tip as to how hopefully avoid the worst effects or any effects of a tick bite?
Jolyon - As with all things in life, knowledge is power. The more you understand something, the more you can make decisions to minimise your risk. I spend a lot of time out in the countryside, both for recreation, also for work, as do my team. And we very rarely get bitten by ticks. And that's largely down to, I think, to the fact that we know what the ticks look like. And there's an important aspect there is that when people remove ticks from their dogs, they see what we call an engorged tick. It's a tick that's been feeding for probably about a week, and they're very large and many people believe that's what ticks look like in the countryside, actually. They're much smaller, they're more like spiders and much smaller in size. So understand what the ticks look like. I mean, I'm working, I'll be wearing long trousers usually of a light colour, and if I brush through vegetation, I will immediately look down and just see whether there are any ticks on me. They stand out quite easily, particularly the nymph and the adult stages. The larvae are a little bit harder to find and I'll immediately brush those off. Then when I get back, if I know that I've been in somewhere there's lots of ticks, I will wash my clothes and then check myself for ticks and then keep an eye on them for the next few days.
How to spot and deal with tick bites
Sally Mavin, NHS Highland
Ticks carry a passenger responsible for at least one potentially very nasty disease when they decide to borrow some of your blood. But what are the signs and symptoms of a tick bite, and what can you do in the event of finding a tick on you? I’ve been speaking to the director of the Scottish Microbiology Reference Laboratory at NHS Highland, Sally Mavin.
Sally - for the majority of people you would generally see a rash. Now some people would say it's a bullseye rash or a target rash. So it looks a bit like a dartboard with central clearing and then a quite distinctive ring. But actually it's not as clear cut as that. In some situations you can just get a general rash around a tick bite. But the trigger point for us to have further investigations and maybe some antibiotics is if the rash spreads. So it's not just a localised redness around a tick bite, just a localised reaction. It's actually the spreading rash. The bacteria can stay just within the skin and cause this rash and if treated, it'll go away quite quickly and you may never have any other problems. But you can also get a flu-like illness alongside the rash so you can feel quite grotty for a time. And sometimes even after you've had antibiotics you can still feel grotty for some time. So you can still have tiredness and headaches, maybe a little bit of brain fog. In some people though the bacteria can spread through the body so it can spread along the nerves and in the blood system and it can cause a variety of different symptoms. So it's often known as the great imitator because it can mimic lots of other conditions so it can cause neurological symptoms, joint symptoms like arthritis, occasionally cause some heart problems as well and other skin conditions. So there's a range of symptoms that you can get.
Will - All of this so far to my mind has been focused very much on Lyme disease, as it should be as this is the most common disease to contract from tick bites. But there seems to be also rumblings that there are certain other illnesses that might be coming along with tick bites as well.
Sally - Yeah, so since 2019 there have been a few cases of tick borne encephalitis that have been recorded in the UK and that's for the very first time. So tick borne encephalitis is found throughout many parts of the world, Scandinavia, throughout Europe and Russia. But we've now started to see some cases coming out from the UK So these are cases that have been caught from ticks that have bitten people within the UK themselves. So not just travelling to different countries. There's very small numbers so far, but we are aware now it is in the UK and it's something that we need to start looking out for
Will - As part of your job is to look at Lyme disease diagnostics, are you seeing an increase in the number of tick bite diseases?
Sally - Well our focus is obviously on Lyme disease because that is the most common tick-borne disease that we have in the UK and in the laboratory it's quite difficult to say if numbers are really on the rise or not. We definitely, there's an increased awareness of tick-borne diseases amongst the general public and amongst our medical professionals. But diagnostics have improved over the years as well. So I think we're picking up more cases than we did before. In parts of Europe they certainly feel that case numbers are stabilising slightly. It'll be interesting to see over the next few years. Obviously the pandemic affected the health service, affected testing and people going to their GPS and things. So it will be interesting to see how things progress over the next few years. But certainly with other tick-borne diseases, they're still thankfully very rare within the UK so you have other diseases such as anaplasmosis, you have babesiosis for example. We all need to detect very few cases throughout Europe. But again, that is something we need to be aware of and need to consider moving forward, especially with changes in climate and things and tick habitat changing, tick spreading into new areas and the diseases that they carry with them spreading into new areas.
Will - Absolutely. I think the last thing we need to do right now is get complacent if numbers are stabilising, but I would be doing everyone a disservice if I didn't have you here and ask you to talk us through what you should do should you be bitten by a tick.
Sally - Okay, well I know it can be scary for those especially that have been bitten by a tick for the very first time, but you shouldn't panic. It's really important to remember that not everybody that gets bitten by a tick is going to get poorly. Not everyone's going to get Lyme disease or one of those other diseases, but it is important to remove a tick as quickly as possible after you notice it because that will reduce any chance of the disease passing on to you from the tick. I think it'd actually be really important if everybody had tick removal devices within the first aid kits at home or at work or in your cars. So you can buy purpose made tick removing devices. You have tick removal cards that they're the size of a credit card that you can keep in your wallet. You also have tick twisters that I know you can buy from your vets. They're all very helpful and very useful for removing ticks. And you can also use fine tip tweezers as long as you hold them parallel to the skin and then pull up. They're very useful tools as well, especially for the very small ticks that you might come across. It is really important though, I just want to emphasise, that you shouldn't try and burn ticks off or smother them in Vaseline or anything like that because that could potentially distress the tick and cause it to regurgitate its contents into you, which you really wouldn't want. But yeah, there's a large number of devices out there that you can safely remove ticks.
13:35 - Climate change may drive an increase in UK tick numbers
Climate change may drive an increase in UK tick numbers
Nick Ogden & Catherine Bouchard, Public Health Agency of Canada
The number of ticks bite cases may be stable or steadily rising, although that might just be because we’re becoming better at spotting and diagnosing cases. But, to quote myself about 5 minutes ago, the last thing we want to do is become complacent, particularly when another, omnipresent threat is rearing its ugly head: climate change. The shift to warmer drier summers is threatening to cause an up-tick in tick numbers here in the UK. Fortunately, or unfortunately, this is a phenomenon occurring all around the world, so other countries can provide valuable information about what we might expect climate change to do to tick numbers and distribution. One such country is Canada, as the Public Health Agency of Canada’s Nick Ogden and Catherine Bouchard explain.
Catherine - When I was a PhD student 15 years ago, I used to harvest ticks in the environment or collect ticks from rodents and deer. And back then I would collect about 2000 ticks over a 12 month sampling. Nowadays, if I return to the same study region, I will harvest 2000 ticks within a two month period. And since, well, I've been studying these ticks for 15 years now. They are still quite fascinating. Last summer I did a lab experiment with a University of Montreal colleague, involving live ticks. And ticks were calm, sort of on pause and kept at the high humidity level. But whenever I would blow on top of the vial, they would reactivate like little zombies, I call them. Driven by the CO2, the vibration and the humidity of my breath. And for me, that image explains it all. They are so resilient.
Will - Yes. You're painting a quite striking and concerning picture with that, the fact that it's increased so much and these things are so resilient to bring you in. Nick, could you talk us then through what is going on in terms of their relationship with the climate? What is the climate modelling saying?
Nick - Around about 2003, we started to work on developing a model of the lifecycle of the tick, really to understand what is the impact potentially of climate on the survival of tick populations and we're talking here about the Ixodes scapularis, or the blacklegged tick, which is our version of the Ixodes ricinus tick that you have in the UK, which transmits lyme disease. What we hypothesised was that it was another significant effect of temperature, which is on the development rates of the ticks from each life stage. So an engorged lava through to nymph, engorged nymph to adult, engorged adult female to producing eggs and then eggs developing to larvae. All of those stages are dependent on temperature or how long they last depends on temperature. The warmer it is, the shorter the life cycle becomes. And we hypothesised that Canada, for the most part, was too cold because it meant that the life cycle was too long. But with climate change, that would change, more and more parts of Canada would have a climate that would allow the ticks to complete their life cycle.
Will - If this is the case, then, if an increase in temperature is kind of speeding up all aspects of the life cycle of the tick, does this increase the distribution in which ticks might be found?
Nick - It does, and we are seeing a number of things happening at the same time. Firstly, the ticks are spreading northwards, so there are greater areas of Canada where the tick populations have set up and where people are now getting bitten by ticks. We're also seeing the abundance of the ticks increasing behind that kind of advancing frontline as it were. And the proportion of ticks infected with the agents of lyme disease, the bacteria and Borrelia burgdorferi, the proportion of ticks infected is increasing as well.
Will - Catherine, does this also increase the variety of species that we'll encounter?
Catherine - Yes, we do have more ticks now, but we do have more species in more regions. So on our side, in North America, three main tick species bite humans - the black legged tick, the American dog tick and the lone star tick. So Canada does watch for the establishment of the lone star tick population while the other two species that I mentioned are already present and occurring. We're also on the lookout for the Asian longhorn tick, which was first found in the US in 2017 and it was likely introduced through various pathways including importation. So yeah, more species are expected.
Will - And I suppose it goes without saying then does an increased number of species kind of lead to an increased number of diseases that we should be concerned about too?
Catherine - Exactly. Emerging tick borne diseases pose an increasing public health challenge. So in Canada we've witnessed this first hand with Lyme disease emerging more significantly 20 years ago, but followed recently by anaplasmosis with a large outbreak in 2021. They're both transmitted by black legged ticks. Both of them are bacteria, but the different tick species spread different diseases. And so when I mentioned the black legged tick, it does transmit Lyme disease and anaplasmosis, human babesiosis, miyamotoi relapsing fever and also powassan encephalitis. The American dog tick now can spread Rocky Mountain spotted fever. And then lastly, the one we're on the lookout for, the lone star ticks, can transmit the human alkalosis and the southern tick associated with rash illness. So we're monitoring those different tick species, but also testing the specimen and trying to detect the incoming pathogens.
Will - And Nick, to bring you back in, obviously a lot of this, in fact almost entirely the show so far, has been quite rightly centred on the disease and health aspects of ticks and tick bites. But are there other impacts that we should be considering too in terms of, say, economics?
Nick - Yes, we did a study recently to assess the potential economic impact of emerging Lyme disease in Canada. So by the 2050s, somewhere between half a billion a year or 2 billion a year, depending on what's the kind of final incidents that we see when the ticks have moved in, it's quite a substantial potential economic impact.
Will - So to put this all together then, given what you've known and what you've learned in the case of Canada, what might we be able to expect in the UK when it comes to the future of ticks?
Catherine - Well, from our experience for sure, the ecological and climate changes that we've seen mostly driven by human activities did lead to an increase in species diversity distribution, like we mentioned. But in your case, you do have the Ixodes ricinus, which is long established in the UK. And that tick is really like a cousin for our Canadian black legged tick. It is a vector for diseases like tick-borne encephalitis and Lyme disease. And from the literature we can see and it is documented that it is still expanding its range, a bit going even northward. And similarly, the are ticks called Hyalomma, sometimes they can be vectors for haemorrhagic fever virus and they are becoming more occurrence in Europe, across Europe. So this is something that has been monitored and is being monitored actually by different European tick experts, but the common underlying trend being more ticks, northward, I think this is something that we share. More tick species in more regions.
21:47 - What can be done to prevent tick bites?
What can be done to prevent tick bites?
Kayleigh Hansford, UKHSA
What is the plan to keep track of ticks and, more importantly, bring this information to the relevant people and bodies, so that we can all go out and enjoy what’s left of nature. This is part of the rationale behind the Tick Surveillance Scheme, and, to explain it, the UK’s Health and Security Agency's Kayleigh Hansford.
Kayleigh - The Tick Surveillance Scheme was set up in 2005. And essentially what we wanted to do was to digitise our kind of existing knowledge of the distribution of ticks across the UK. And this is important because where we know ticks are present and where people can come into contact with ticks, that's where you get a potential disease transmission risk. It allows us to map and monitor the different tick species that we have in the UK. It can also give us an indication of when they're active and when they're sort of peaking in activity or when their activity periods sort of overlap with when people are out in the environment. Normally when the weather's nice and if we sort of look at the data over time it allows us to start assessing potential changes in distribution of our key tick species. And we're starting to see some of those initial changes in our data sets. Now the other thing that the scheme allows us to do is to detect rare species that we don't always find in the UK. So sometimes these can be imported into our country from animals or people. And with these they bring some novel and different disease risks with them, but ultimately it allows us to have a channel where we can communicate with members of the public about what they're finding as well because people can send things in and we send information back. So it's a good sort of communication channel for us.
Will - Given what we know about the slightly grim way in which humans and animals come into contact with ticks. How is this data collected?
Kayleigh - People can send ticks to us through the post. So anytime anyone comes across the tick, be it they've been on a walk locally, or they might have found a tick on their dog, they can take the ticks off and actually pop them in in an envelope in the post to us and when we ask people to send things in, we ask for information around the data they collected the tick, what host the tick was found on. So was it on themselves, was it on a pet. And the sort of location where they think they picked up the tick. We bring all this information in, we then look at the ticks under a microscope in our labs and identify the different tick species that we found. Enter all of this into a database so we can create these maps and then we send an information email back to the person that sent the tick to us explaining what the species is. And we also share some links to some public health information on those associated risks.
Will - Presumably then that data can also then be fed into larger data studies as well.
Kayleigh - Yeah, exactly. Yeah. So we can start doing things with the data set such as looking at trends in sort of temperature. So we're thinking about climate change. We can also look at the data alongside disease data sets. So we can start to try and potentially link tick exposure to our Lyme disease incidents data. And with that kind of information we can feed and push all of that into our sort of communication with local authorities or other organisations at the local level who might be responsible for raising tick awareness locally based on that evidence that we are kind of generating through the scheme.
Will - So what is it telling you then if this scheme has been in place for almost two decades now, are you starting to see some trends?
Kayleigh - If we look at the data over time, we can see that we have had some expansion in the distribution of our main tick species that we find in the UK. The kind of driving forces or reasons behind this are many. There are multiple sorts of different reasons why we might be seeing this one. It could just be increased awareness and better engagement with the scheme. So more people are sending ticks to us. Other things that could be causing these potential changes are changes in hosts, host distribution, animal distribution in the UK. Potentially deer are really important for feeding ticks. So if deer are moving around and changing their distributions, that's likely going to have an impact as well.
Will - It feels like we've almost got a really unfortunate and perhaps unavoidable scenario as we see sort of an increase in population and we do end up moving more into their territory. If, if Woodland gets teared down to make stuff like housing, are we inevitably going to see an increase in interactions with these as well?
Kayleigh - It's a really important point actually. Anything that we're doing to kind of modify or change the habitat that we're in can have an impact on any different kind of part of the tick-borne disease transmission cycle. So if we're changing the habitat and that has an influence on the hosts that are in the local area that are feeding the ticks, that can ultimately have an impact on the tick population density and also the specific interactions that we have with ticks. Although urbanisation, urban sprawl can put us into potentially closer contact with these sort of more natural habitats where we might find ticks. We've also got the opposite of where we're sort of greening everything. So greening our cities and introducing and increasing and expanding our woodland habitat. So all of these kinds of things could potentially have an impact on future tick borne disease transmission risks.
Will - If that is the case then, what is, so to speak, the plan?
Kayleigh - Some of the key things that we can do are have discussions about ticks and the associated risks. You know, increasing awareness and having those open discussions to make people more aware so that they know if they're in certain spaces where ticks might be present that they need to engage in those sorts of personal protective behaviours, removing ticks quickly, that kind of thing. There's also engagement with different stakeholders. From our perspective, we need to be speaking to people who are sort of working with wildlife, people who are doing these kind of developments, urban development or biodiversity projects so that we can kind of get everybody in the same space to actually talk about what we can do about the potential risks for a tick-borne disease
Will - At a sort of more personal or even local council level. Is there anything that you can provide these people that can sort of help out those who want to go out into the countryside, want to enjoy it, but might have a slight fear of encountering a tick?
Kayleigh - We've worked over the last couple of years to develop our tick awareness toolkit. So this is exactly for local organisations that might want to increase awareness about ticks and Lyme disease or other tick-borne pathogens. And essentially what this toolkit provides is background information on ticks, like sort of tick ecology, biology, lyme disease risks and transmission risks. And it explains to people how you can run local campaigns to engage with your local communities and to identify your local stakeholders to bring everybody together to start raising awareness of ticks.
Will - And it does seem in this instance, with this particular set of diseases and illnesses and perpetrators, that prevention is way easier to manage than cure.
Kayleigh - Exactly. Exactly. And what we're trying to do with these kinds of messages is empower people to actually take on board these personal protective measures that they can do. You can go out and you can still enjoy nature and you can still be out in the countryside. You just need to check for ticks and remove them quickly if you find them.
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