What is a tick?

And where can they be found?
18 March 2024

Interview with 

Jolyon Medlock, UKHSA


Deer tick


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.


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