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Lyme Disease & Ticks

Lyme Disease and Ticks

There are approximately twenty species of tick that are endemic in the UK. Of these, the sheep, castor bean or deer tick (Ixodes ricinus) most commonly bite humans.

Ticks are known to transmit a range of pathogens to humans, the most common of which is the bacterial infection that causes Lyme disease. Lyme disease is the most significant tick-borne infection in England and Wales in terms of severity and incidence, the latter of which has increased in the past decade. 

We all like to enjoy being outdoors, but it's important to also be tick aware!

Deer, ticks and Lyme disease

While deer are certainly among the many species of animals and birds, which can act as hosts to, ticks, it might be a mistake to assume that they carry a notable responsibility for encouraging high numbers of them. 

Although there is some evidence that, where deer and other large herbivores such as sheep are absent, the numbers of ticks present in the environment may be reduced, scientific opinion remains uncertain as to whether, once deer and sheep are present, actual numbers have any real effect on overall tick burdens.
 
Current research on the spread of Lyme disease suggests that deer may only play a very small part and that it is likely that some species of birds are far more significant carriers of the infective organism.

Initial infection of ticks with Lyme disease (Borrelia burgdorferi) occurs not from deer, but while the subadult juvenile ticks are feeding on smaller animals (voles, mice, rabbits, and small birds). Indeed surveys of different wildlife species indicate that amongst the most significant carriers of the Borrelia bacteria are blackbirds, thrushes, and robins.

By contrast, the bacteria are unable to maintain themselves in deer of any species. Once they have reacted to their first infected bite, deer produce antibodies, which not only prevent infection of the deer but also carry on circulating in the bloodstream.

These antibodies may have an active role in cleansing any subsequent ticks, which feed on them, removing the Borrelia from the ticks system and thus preventing it from infecting anything else.

The British Deer Society is committed to encouraging public awareness of Lyme disease and supports ongoing research into the dynamics of the disease and its relationship with deer.

What are ticks?

Ticks are small, spider-like creatures that feed on the blood of animals, including people. During this feeding process, they can transmit pathogens that can result in infections such as Lyme Disease. In the UK, the most important tick species to human health is Ixodes ricinus, more commonly known as the sheep, castor bean or deer tick. This species can be found feeding on humans and is the principle vector of Lyme Disease.

Ticks are small, spider-like creatures

The life cycle of a tick

The tick life cycle is made up of three active stages; larvae, nymphs, and adults. Each stage needs an animal host on which to feed before it can moult to the next stage, or in the case of the adult females, lay eggs.

The life cycle takes on average three years to complete. When ticks search for a host on which to feed, they climb to the tips of vegetation and use special sensory organs on their front legs to detect stimulants such as carbon dioxide, changes in light and body heat given off by hosts. As a host brushes past the vegetation, ticks climb on.

Once a suitable feeding site has been found on the host, the tick will take one continuous blood meal (lasting for a varying number of days, depending on the life stage of the tick). The tick will then detach and drop off into the vegetation to digest and moult to the next stage. After mating, adult female ticks will lay several thousand eggs at ground level before dying.

Where ticks are found

Ticks are very sensitive to temperature and relative humidity, requiring areas with dense ground layer coverage of vegetation for survival, reproduction or establishment. Areas such as woodlands, grasslands, and moorlands, provide this dense vegetation layer and a suitable range of hosts on which ticks can feed.

Ticks can also be found in some urban parks and gardens. Within these habitats, ticks are often highly abundant in ecotonal habitats i.e. transition zones between different habitats that are often used by wildlife. Without larger hosts such as deer that adult ticks feed on, tick populations are unable to establish, even when suitable vegetation and temperature and humidity conditions are met.

Repeat introductions of ticks into suitable areas can occur, however, if such areas are accessible to wildlife that may inadvertently transport ticks that are feeding on them.

When ticks are active

In England, nymphal tick activity increases during spring, peaking from April to June. During this period, the risk of acquiring a tick bite is highest.

Activity reduces during the summer months, but can then pick up again in early autumn. Activity continues over the winter months but at a reduced level. Adult ticks can be active at all times of the year, but are more active in summer which is also the peak time for larval activity.

Tick bite prevention

The following guidance can be used to reduce the chance of acquiring a tick bite when enjoying outdoor activities:

  • walk on clearly defined paths to avoid brushing against vegetation where ticks may be present
  • wear light coloured clothing so that ticks crawling on clothing can be spotted and brushed off
  • use an insect repellent that can repel ticks and prevent them from climbing onto clothing or attaching to the skin (always follow the manufacturer’s guidance)
  • wear long trousers and long sleeved tops to reduce the direct exposure of ticks to your skin, making it more difficult for them to find a suitable area to attach

Video - Prevent Lyme Disease by Avoiding Tick Bites

Video by Lyme Disease UK https://lymediseaseuk.com

Recognising ticks and performing a tick check

In addition to carrying out the prevention measures outlined above, it is important to carry out a regular tick check after participating in outdoor activities (e.g. walking, running, gardening, camping, picnicking). A tick check is carried out by looking and feeling for ticks that may have attached to the skin.

By performing a tick check, the chance of infection is reduced because feeding ticks are spotted and removed promptly.

Prompt and correct tick removal

Evidence suggests that Lyme disease transmission risk increases the longer a tick is feeding. Prompt and correct tick removal can reduce this risk and the need to prescribe antibiotics. The safest way to remove a tick is to use a tick removal tool or fine-tipped tweezers. 

Grasp the tick as close to the skin as possible, and taking care not to squeeze the body, pull upwards slowly and firmly.

What is Lyme disease

Lyme disease is a bacterial infection that can be spread to humans by infected ticks. It's usually easier to treat if it is diagnosed early.

Early symptoms of Lyme disease in humans may include mild flu-like symptoms including:

  • a high temperature, or feeling hot and shivery
  • headaches
  • muscle and joint pain
  • tiredness and loss of energy

Symptoms can sometimes be accompanied by a characteristic bulls-eye rash (called erythema migrans). The rash appears usually around 1 to 4 weeks after being bitten and is often described as looking like a bulls-eye on a dartboard. The affected area of skin will be red and the edges may feel slightly raised.

It is important to know, however, that not all cases of Lyme disease have this rash, in fact, 1 in 3 people do not report seeing a rash.

Lyme disease: signs and symptoms 

NHS - Overview of Lyme disease 

More serious symptoms may develop several weeks, months or even years later if Lyme disease is left untreated or is not treated early on.

You should see your GP promptly if you feel unwell with any of the symptoms described above after being bitten by a tick, or if you think you may have been bitten.

How Lyme disease is treated

Lyme disease is treatable with a course of antibiotics. However, if left untreated, the infection can develop to late manifestations, affecting the joints, nervous system, or the heart. Prophylactic antibiotic treatment following a tick bite is not recommended.

How Lyme disease is transmitted

In nature, the bacteria that cause Lyme disease are carried in the blood of wild animals (hosts), primarily small mammals and birds. Ticks feeding on an infected animal will take in the bacteria, which remain in the tick for the rest of its life. When an infected tick bites and feeds on a human, the bacteria can be passed on via the ticks’ saliva.

It should be remembered that not all ticks will carry the bacterium which causes Lyme disease and not all bites from an infected tick will result in human Lyme disease.

Tick bites are not always painful. You may not notice a tick unless you see it on your skin.

Regularly check your skin and your children's or pets' skin after being outdoors.

Who is at risk of acquiring Lyme disease

Approximately 1000 laboratory-confirmed cases are reported annually in England and Wales, with around 15% of these cases acquired overseas. People of all ages can be affected and both sexes are equally susceptible. Highest rates occur in people aged between 24 and 64 years.

Cases have been reported from most counties in England and Wales, but more frequently from the southern counties. When there is a risk of acquiring Lyme disease LD is more commonly diagnosed during the summer season, coinciding with tick activity and high levels of outdoor human activity that may result in tick exposure.

Cases are reported throughout the year but nearly half of the diagnosed cases occur in July, August, and September. Most of these cases were probably acquired in late spring (when tick activity is high) and early summer, allowing for the time period between being bitten, developing symptoms, and developing levels of antibodies high enough to give positive results in laboratory tests.

Increasing risk identified in England and Wales

Cases diagnosed and treated on the basis of clinical features and a history of tick bite/exposure but without laboratory-confirmed tests are not recorded. Only laboratory-confirmed cases are recorded, and the number of such cases in England and Wales has been increasing annually.

Several factors have likely contributed to this rise in cases including; increased awareness, improved diagnostics and enhanced surveillance of LD, geographical expansion of ticks and possible extensions of tick activity periods, changes in wildlife population abundance and distribution and human-induced habitat or behavioural changes that have resulted in more chance encounters between humans and infected ticks.

How Lyme disease can be prevented

There is no vaccine for Lyme disease, so improving tick awareness and adopting tick bite prevention behaviours are the best measures to reduce the risk of developing Lyme disease.

Useful Resources

Tick Leaflet

Tick Poster

NIHR School aged leaflet 
http://www.hpruezi.nihr.ac.uk/about-us/news-and-events/tick-awareness-leaflet/

Lyme disease: signs and symptoms 
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/
file/718980/LymeDisease_SignsAndSymptoms_requested_changes_June_2018_final_Clean.pdf

PHEs Tick Surveillance Scheme 
https://www.gov.uk/guidance/tick-surveillance-scheme

Public health matters blog
https://publichealthmatters.blog.gov.uk/2014/03/24/tips-and-tricks-to-stay-safe-from-ticks/ 

Overview of Lyme disease
https://www.nhs.uk/conditions/lyme-disease/

Insects – bugs that bite
https://www.nhs.uk/conditions/insect-bites-and-stings/symptoms/