Lyme disease is an infection caused by being bitten by an infected tick. The first and typical symptom is usually a rash that spreads out from the site of the tick bite. Left untreated, the germs (bacteria) can spread to other areas of the body. In some cases this can cause serious symptoms - often months after the initial tick bite. A course of antibiotic medication will usually clear the infection.
What is Lyme disease?
Lyme disease is an illness caused by being bitten by a tick that is infected with a germ (bacterium) called borrelia. There are various types of this bacterium but Borrelia burgdorferi causes Lyme disease. It is called Lyme disease after the name of the town in the USA where it was first described.
Where is Lyme disease a problem?
Since 1975 when it was first noted, thousands of cases have been reported in the USA. Lyme disease is less common in the UK. 998 possible cases were reported in 2012 in England and Wales. Not all are reported so the total number of cases each year is unknown. However, it is estimated to be 2,000 to 3,000. This is because many cases are not formally diagnosed and clear away without any treatment. Most people affected are forestry workers and other outdoor workers but visitors and holidaymakers to countryside areas where ticks are found are at risk.
Over half of infections acquired in the UK are known to have been caught in the southern counties of England. Areas where it is most common tend to be centres of outdoor activity - in particular, the New Forest, Thetford Forest, the South Downs, Exmoor, the Lake District, the North York moors and the Scottish Highlands. Up to a fifth of Lyme disease is caught while abroad - in particular, the USA, France, Germany, Austria, Scandinavia, and eastern and central Europe.
How do humans get Lyme disease?
The germ (bacterium) that causes Lyme disease lives in certain animals. These are mainly rodents such as mice, some birds and some other small animals. The bacterium is usually harmless to the animals.
Ticks are small insect-like creatures, about the size of a pinhead. Ticks feed by biting the skin and sucking blood from animals such as mice, and sometimes humans. In this way, some ticks get infected with the bacterium that causes Lyme disease.
Ticks cannot jump or fly, but climb on to passing humans from long grass or foliage. If an infected tick bites a human, then the bacteria may be passed into the human. The bacterium that causes Lyme disease is not passed from person to person. Note: most ticks in the UK are not infected by the bacterium that causes Lyme disease. Therefore, most tick bites will not cause Lyme disease.
After a human has been bitten by a tick, it usually takes 24-48 hours for the bacteria in the tick to pass into the human. (Ticks are tiny and 'cling on' to you once they bite you. They then suck blood and become swollen ('engorge') with blood which they feed off. The bacteria are normally carried in their gut, and only travel up to their mouth and into your skin once they have been fed and are engorged. This normally takes about 24 hours, but can be less if the tick was already partially fed.) Therefore, if you remove a tick soon after being bitten - within 24 hours - you are much less likely to develop Lyme disease, even if it was an infected tick.
So, it is only certain ticks, that are infected, that bite, and are not noticed clinging on to the skin, that cause Lyme disease. However, ticks are very small, and often do not hurt when they bite so it is quite easy to have a tick bite without noticing. Many people who develop Lyme disease cannot remember being bitten by a tick.
Once bacteria are passed from the infected tick into your skin, they then multiply and travel in the bloodstream to other parts of the body to cause symptoms. The parts of the body that are mainly affected by this bacteria are the skin, joints, nerves and heart.
What are the symptoms of Lyme disease?
The symptoms and effects of Lyme disease can be divided into three stages:
Stage one - early reaction to the local skin infection
This can develop at any time between 3 and 36 days after being bitten by an infected tick.
Erythema migrans rash
Rash - the classical symptom of Lyme disease is a typical rash called erythema migrans. However, this does not always occur. It may depend on which species of borrelia is involved. In the UK, most people with Lyme disease have or have had this rash.
The rash is usually a single circular red mark that spreads outwards slowly over several days. The circle gets bigger and bigger with the centre of the circle being where the tick bite occurred. As it spreads outwards, a paler area of skin emerges on the inner part of the circle. Therefore, the rash is often called a 'bullseye' rash.
The rash usually spreads over at least 5 cm, but may be much bigger.
The rash is not usually painful or particularly itchy. You may not even notice it if it is on your back. Without treatment, erythema migrans typically fades within 3-4 weeks. However, just because the rash fades does not necessarily mean the infection has cleared from the body.
Note: many insect bites cause a small red blotchy 'allergic' rash to appear soon after the skin is bitten. These soon go away. The rash of erythema migrans is different in that it usually develops several days after the bite, lasts for longer, and has a typical spreading circular appearance.
Flu-like symptoms - these occur in about a third of cases. Symptoms include tiredness, general aches and pains, headache, fever, chills and neck stiffness. These symptoms are often mild and go within a few days, even without treatment (but the infection may not have gone).
In some cases, the infection does not progress any further, even without treatment, as the immune system may clear the infection. However, in some cases that are not treated, the disease progresses to stage two.
Stage two - early disseminated disease
This may develop in untreated people weeks or months after the bite. Disseminated means spread around the body away from the site of the original infection. Symptoms are variable but can include one or more of the following:
Joint problems in one or more joints. They most commonly affect the knee joint. The severity of joint problems can range from episodes of mild joint pains, to severe joint inflammation (arthritis) causing a lot of pain. Episodes of joint inflammation last, on average, three months.
Nerve and brain problems. Some affected people develop inflammation to nerves, particularly the nerves around the face. This may cause the nerve to stop working and result in facial weakness. Inflammation of the tissues around the brain (meningitis) and inflammation of the brain (encephalitis) may occur.
Heart problems. Some affected people develop inflammation of the heart (myocarditis) and other heart problems. This may cause symptoms such as dizziness, breathlessness, chest pain and a feeling that your heart is beating in a fast, irregular way (palpitations).
Rash. Several areas of the skin (not where the tick bite occurred) may develop a rash similar to erythema migrans (described above). These 'secondary' rashes tend to be smaller than the original stage one rash. These tend to fade within 3-4 weeks. Occasionally, blue-red nodules called lymphocytomas may develop on the skin, particularly on ear lobes and nipples.
Rarely, other organs such as the eyes, kidneys and liver are affected.
Stage three - persistent (chronic) Lyme disease
This may develop months to years after infection. It may develop after a period of not having any symptoms. A whole range of symptoms have been described in joints, skin, nerves, brain and heart. The brain problems may include mild confusion, and problems with memory, concentration, mood, personality and balance. It occasionally may cause a schizophrenic-like illness. There may be tiredness and joint pains which have been called "post-Lyme syndrome" with symptoms similar to fibromyalgia or chronic fatigue syndrome.
How is Lyme disease diagnosed?
In most cases, Lyme disease is diagnosed in stage one of the disease by the typical symptoms. That is, the typical rash, sometimes also with a flu-like illness, in someone who has been bitten by a tick. Other tests are not needed in this situation and treatment is usually given.
The diagnosis of stage two or three is more difficult. Blood tests are helpful (but not always conclusive) in diagnosing the disease if it is suspected from the symptoms. Occasionally the fluid from an inflamed joint or skin samples are sent for tests. There is one specialised laboratory in the UK where samples are sent to be tested.
What is the treatment for Lyme disease?
A course of antibiotic medication will usually clear the infection. The type of antibiotic, and the length of the course can vary depending on individual circumstances. Your doctor will advise. Most people are diagnosed in stage one when treatment will clear the symptoms and prevent the development into stages two or three.
Can Lyme disease be prevented?
The following will reduce your risk of developing Lyme disease:
- If possible, avoid areas where infected ticks live - particularly in the summer months. When out in the countryside, keep to paths and away from long grass or overgrown vegetation, as ticks crawl up long grass in their search for a feed.
- If living or visiting a tick-prone area, when outdoors wear appropriate clothing. That is: long-sleeved shirts and long trousers tucked into socks. Light-coloured fabrics are useful, as it is easier to see ticks against a light background.
- Inspect your entire body each day to check for ticks and remove any that are on the skin. Make sure that children's head and neck areas, including scalps, are properly checked.
- Consider using a tick repellent spray, cream, etc, on your skin, such as one that contains N,N-diethyl-m-toluamide (DEET).
- Shower or bath after returning from a tick-infested area.
- Check that ticks are not brought home on clothes.
- Check that pets do not bring ticks into the home on their fur.
To remove a tick that is attached to your skin
- Gently grip the tick as close to the point of attachment to the skin as possible. Do this preferably using fine-toothed tweezers or forceps, or a tick removal device.
- Pull steadily upwards, away from the skin. Take care not to crush the tick.
Inexpensive tick removal devices may be available at veterinary surgeries and pet supply shops, and are useful for people who are frequently exposed to ticks. These should be used in accordance with manufacturers' instructions.
Do NOT do any of the following:
- Burn the tick off (for example, using lighted cigarette ends or match heads).
- Apply petroleum jelly, alcohol, nail varnish remover, or other substances (as this may stimulate the tick to regurgitate potentially infected material into the skin, which may increase the risk of transmission of infection).
- Use your fingers to pull the tick off.
- Squeeze the tick.
After removal, DO clean the skin with soap and water, or skin disinfectant, and wash hands.
What is the outcome (prognosis)?
If you are treated with antibiotic medication in stage one of the disease, you have a very good chance of a complete cure with no further problems.
If you are not treated in stage one, you may go on to develop some symptoms of stage two or three. However, these are often mild and transient symptoms such as a skin rash or mild joint pains. Some people develop more severe symptoms if they progress to stage two or three. Treatment with antibiotics during stage two or three is also usually curative. However, a prolonged course of antibiotics may be needed. It may be difficult to treat post-Lyme syndrome as it is not yet known what causes these ongoing symptoms. However, most eventually clear up with time.
Further help & information
Dr Tim Kenny
Dr Mary Harding
Prof Cathy Jackson