Ticks, tick bites and Lyme disease: how to protect yourself

What is a tick and what does it look like?

Ticks belong to the order Ixodida, part of the Acari group. All ticks are blood-feeding parasites of vertebrates - mostly mammals, but also birds and reptiles. Each stage of the tick life cycle needs a blood meal before developing to the next stage.

Ticks have a roughly round to oval-shaped body with legs attached underneath. There are two main types of tick: hard and soft. Hard ticks have a shield on their back, the scutum, which their soft tick relatives lack.

When ticks hatch from the egg, they begin as larvae with short, rounded bodies and six legs. While this might suggest ticks are insects, they are arachnids, like spiders. Ticks gain their fourth pair of legs after moulting to the nymph stage. Finally, they moult into adults.

Before feeding, ticks are at most a few millimetres long.

Hard ticks have a single nymph which feeds only once, as do the adult females. Soft ticks have several nymphs and they and the adults feed two or more times.  

The development of hard ticks may involve one, two or three hosts. All the species that live in the UK are three-host ticks. This means the larva, nymph and female each has to find a new animal to feed on before dropping to the ground to moult or, in the case of females, to lay eggs. Males rarely feed and usually only occur on a host for mating. 

Hard ticks feed slowly, taking several days to become full. Females can take up to 12 days and more than quadruple in length while feeding. Their volume may increase 100-fold.

Soft ticks tend to live with their hosts, such as in bat and bird roosts. They feed much quicker than hard ticks - meals usually take about 15 minutes to two hours - and do not increase in size as much. Soft ticks leave their host after each meal and feed on multiple animals during their life. Between meals, the ticks shelter within the hosts’ habitat.

Which ticks live in the UK?

There are 22 species of ticks in the UK, not counting those imported on exotic animals and pets. The ones most often found on people and pets are all hard ticks of the genus Ixodes.

The most widespread and abundant species in Britain and northwest Europe is Ixodes ricinus, sometimes known as the sheep tick, deer tick or castor bean tick. It is one of 11 UK species known to bite people and the main transmitter, or vector, of bacteria that cause Lyme disease here.

Ixodes ricinus is usually reddish-brown, but the inflated body of fully fed females can be grey and resemble a broad bean.

This species needs humidity to thrive. It is typically found in rough grassland, moorland and woodland areas among plants with a moisture-retaining ground layer, such as long grass and bracken.

Females lay several thousand eggs at one time, often within a mat of damp vegetation. 

Ixodes ricinus can take up to six years to complete its life cycle, although more typically two or three. It spends much of this time on the ground between feeds.

The next most common UK species is Ixodes hexagonus, the hedgehog tick, which bites many of the same animals attacked by Ixodes ricinus, including cats, dogs and humans. The shape of the female’s scutum distinguishes the two tick species. It is hexagonal- to heart-shaped in hexagonus and broadly rounded in ricinus.

Another species sometimes associated with pets is the dog tick, Ixodes canisuga. It often lives in kennels because it can withstand their dry conditions and is known to bite both cats and dogs.

Other hard tick species in the UK belong to the genera Dermacentor, Haemaphysalis, Hyalomma and Rhipicephalus. Soft tick species belong to Argas and Ornithodoros.

What do ticks eat?

Ticks feed on vertebrate blood. They vary in the range of animals they attack, or parasitize. Of the UK ticks, for example, Ixodes vespertilionis is found only on bats and Ixodes uriae on seabirds. But all stages of Ixodes ricinus use a wide variety of wild and domesticated species as hosts. 

Ixodes ricinus larvae and nymphs feed on small mammals like mice and stoats, and on birds and lizards too. They also feed on the larger hosts preferred by females, including dogs, sheep, deer and cattle.

To find new hosts, hard ticks rely on specialist sensory structures on their front legs, contained in a capsule called Haller’s organ. This detects changes in carbon dioxide levels, humidity and temperature. By waving their front legs in the air, called questing, ticks can use these cues to tell when a suitable host is near. Then, when the animal brushes past, the ticks climb on.

Humans, dogs and cats often pick up ticks while passing infested plants.

What causes tick numbers to rise?

In certain years, the right conditions allow some hard tick species to experience a boom in numbers. A wet spring followed by a warm summer can cause the rapid growth of vegetation that allows plenty of ticks to survive.

While these events are sporadic, there are signs that there might be more ticks than there used to be.

Although there are no long-term studies into tick numbers, Professor Sarah Randolph, an expert in parasite ecology at the University of Oxford, says that there are good reasons to accept anecdotal evidence and surveys that report ticks are now much more abundant in the UK than in the past. The most obvious explanation is the increased numbers of deer, on which adult ticks feed.

Higher numbers of ticks also mean a greater chance of people coming into contact with the diseases they spread, such as tick-borne encephalitis.

This viral infection occurs principally in mainland Europe and as far east as Siberia. Since 2019, a few cases of tick-borne encephalitis have also been recorded in the UK, but the risk from it here is low.

While this infection remains rare, another tick-borne illness, Lyme disease, is far more common.

What is Lyme disease?

Ticks can transmit a range of microbes. These differ around the world, but the one that causes Lyme disease is by far the most common spread to humans in the UK. There are about 2,000-3,000 cases each year in England and Wales, with about half confirmed in a laboratory.

The disease is caused by corkscrew-shaped bacteria, called spirochaetes, belonging to the genus Borrelia - hence the other name of the disease, Lyme borreliosis.

Ticks pick up spirochaetes when feeding on an infected host. They may then pass them on to another animal via their next bite.

In the UK, small mammals such as voles are the main reservoirs of Lyme spirochaetes.

The UK Health Security Agency reports a general rise in Lyme disease cases since record collection began in 2005, although with yearly fluctuations. Suggested reasons include better monitoring of infections and increased human contact with ticks.

General tick bite symptoms

Around 2.5-5% of ticks In England and Wales carry Lyme spirochaetes, although it varies by area and year. Most tick bites won't result in disease.

Tick bites aren't usually painful, but they may cause a red lump at the bite site. Occasionally, there may be extra swelling, itchiness, blistering or bruising.

Lyme disease signs and symptoms

Early Lyme disease symptoms include a flu-like malaise that doesn’t go away.

A classic sign of Lyme infection is a circular red rash spreading out from the tick bite. The Lyme disease rash generally develops within a few weeks of being bitten by an infected tick, but it can take months. It is important to note that the rash can have a more irregular outline or may not appear at all. 

Lyme disease is treated with antibiotics and the sooner the treatment starts, the better.

A full list of Lyme disease symptoms is available on the NHS website. For more tick bite rash pictures, see the CDC website.

Where is Lyme disease found?

In the UK, Lyme disease is often associated with large numbers of deer, a common host of female Ixodes ricinus.

Larger populations of deer can support greater numbers of ticks, as they can provide blood meals to many female ticks, which go on to lay thousands of eggs.  But ticks infected with Lyme disease are also found in the vegetation of woodland, parks and gardens where hosts other than deer feed ticks.

Areas with thriving wild deer populations have been highlighted as Lyme hotspots, including Richmond Park, the New Forest, the South Downs and the Lake District. In fact, the high incidence of Lyme disease could equally be due to human recreation increasing people's exposure to ticks. These so-called 'hotspots' are usually areas that attract large numbers of human visitors.

Research shows that some activities, such as having a picnic, can increase the risk of people coming into contact with ticks. Scientists found that picnic blankets picked up more ticks than clothing, particularly around trees. Blankets allow ticks to move out of dense vegetation like bracken into the grassy areas humans often sit in.

Professor Sarah Randolph, a co-author of the study, says, ‘It’s important to assess the health risk of ticks as not only the likelihood of them being present in a certain habitat but also the likelihood of people coming into contact with them.’

‘The number of visitors to Richmond Park, for example, is around 420,000 a year per square kilometre. And these are often tourists and visitors who live in cities who are perhaps not so aware of the risks of walking in areas where ticks live.’

How to remove a tick from a person, dog or cat

To remove a tick, grasp it as close to the skin as possible with tweezers or between a thumb and forefinger. Then firmly pull it out along the direction in which the tick is lying. Specialist tick removal tools are also available.

The same removal technique works for dogs, cats and people.

Whatever method you use, make sure the mouthparts aren't left in the bite wound.

Ticks have a specialist structure with backward-facing teeth that anchors them to their host. Pulling firmly breaks this connection. It's a myth that ticks should be ‘unscrewed’ - it makes it more likely the mouthparts will detach and be left behind.

If the tick mouthparts remain in the skin, it can lead to an infection. If this does happen, clean the area well and seek medical advice if the infection persists.

While removing a tick, don't squeeze its body as this can cause more saliva and any disease organisms it contains - bacteria and viruses, for example - to enter the host. This can also happen if you try to burn off ticks, squirt them with alcohol or smother them in petroleum jelly, so avoid using these removal methods.

How to avoid tick bites and Lyme disease

The risk of tick bites is highest between April and June, when all stages are seeking hosts. Larvae and nymphs remain active in mid-summer, while adults rest until early autumn. Winter sees little tick activity.

The best way to avoid tick bites is to prevent ticks getting to your skin in the first place. Wear long sleeved tops and tuck trousers into socks or boots when walking in green spaces to make it more difficult for ticks to find somewhere to bite.

You can even use sticky tape to seal the gap between trouser bottom and footwear. Covering your head is a good idea when walking through tall vegetation.

Lighter coloured clothing can make it more obvious when a tick is crawling over you, so that you can brush it off before it bites. Tick and insect repellents, especially those containing the chemical DEET, will help deter ticks from biting.

While spending time outside in areas likely to have ticks, make sure to regularly check yourself, your clothing and your pets. Also, check for ticks when you return. Look closely: at one to two millimetres long, larvae and unfed nymphs are tiny. And while fully fed females can reach over a centimetre in length, unfed ones are only around three to four millimetres. Remove any you find as soon as possible.

Dr Anne Baker, one of our researchers who has studied ticks, says, ‘The longer a tick feeds, the more opportunity there is for disease organisms to enter the host, so regular examination and tick removal are important ways to protect ourselves. Don't forget to check more hidden areas such as armpits.’