Frequently Asked Questions about Lyme borreliosis

What is Lyme borreliosis?

It is an infection caused by spiral shaped bacteria called Borrelia burgdorferi that are transmitted to humans by bites from infected ticks. The infection is not transmitted directly from person to person, nor from the bites of other types of insect, or directly from animals.

Borrelia burgorferi

What symptoms can it cause?

The most common and often only symptom is a rash called erythema migrans, which gradually spreads from the site of the tick bite. It is seldom particularly itchy or painful.  It can have a distinct, well-demarcated leading edge, and the central area of the rash can start to clear, giving a target-like appearance, although many rashes are more homogeneous in appearance.  The rash can cover a large area and last for weeks if untreated. Some patients may also have 'flu-like symptoms.

More serious symptoms may appear in some untreated patients in the following weeks or months. These can affect the nervous system, joints and rarely the heart or other tissues. None of these features is unique to Lyme borreliosis.

Erythema migrans on a man's chest

What are the complications?

The main complications of Lyme borreliosis affect the nervous system, usually within a few weeks to months of infection. They include facial palsy, 'viral-like' meningitis and nerve inflammation that can lead to pain, disturbance of sensation or clumsiness of movement. Encephalitis is a rare complication.

Some patients develop arthritic symptoms which usually settle down after antibiotic treatment. A few patients, who are genetically predisposed, may have more persistent arthritis, which takes longer to resolve following appropriate antibiotic treatment, but can be helped by using anti-inflammatory agents.

Lyme borreliosis, like many other infections, may trigger a post-infection syndrome ("post-Lyme syndrome") in a small proportion of patients, despite appropriate antibiotic treatment. This condition, which is similar to fibromyalgia or chronic fatigue syndrome, does not respond to prolonged or repeated courses of antibiotics.

Can Lyme disease be treated?

Yes, with antibiotics, usually doxycycline or amoxicillin. Early treatment usually clears the rash within several days and helps to prevent the development of complications.

More serious symptoms also respond to antibiotic treatment, but the symptoms may be slower to resolve because damaged tissue takes time to heal. Nervous system symptoms such as meningitis or nerve inflammation may require treatment with intravenous antibiotics. Detailed studies have shown excellent long-term outcomes for most people who receive appropriate treatment.

Repeated or prolonged courses of antibiotics have been shown not to help the small proportion of patients with post-infection syndrome, and they may cause serious or life-threatening side-effects. Treatments used for fibromyalgia or chronic fatigue syndromes may be helpful.

(See also Diagnosis, Guidelines and Unorthodox practices pages)

Are laboratory tests available to help in the diagnosis of Lyme disease?

The most commonly available tests look for antibodies to B. burgdorferi, which an infected person produces in response to the infection. Antibodies take several weeks to develop. They may not be present in the early stages of the erythema migrans rash, but they are usually present in the later stages of the infection. More detailed tests are available to investigate complicated cases. See Lyme Borreliosis Reference Unit

How common is Lyme borreliosis in the UK?

An average of around 900 laboratory-confirmed cases are now reported annually to the Health Protection Agency (table). Most confirmed cases are acquired in the United Kingdom. Areas where infections are acquired include Exmoor, the New Forest, the South Downs, parts of Wiltshire and Berkshire, Thetford Forest, other southern woodland or heathland areas, the Lake District, the Yorkshire moors and the Scottish Highlands, but any area harbouring ixodid ticks may have the potential for Lyme borreliosis transmission. About 20% of confirmed cases annually are reported to have been acquired abroad - in the United States, France, Germany, Austria, Scandinavia, and eastern European countries.

Estimates suggest that between 1,000 and 3,000 cases of Lyme borreliosis occur in the United Kingdom each year.
 

Table: Reports of laboratory-confirmed cases of Lyme borreliosis reported to the Health Protection Agency 2000 to 2010

(See also Epidemiology of Lyme borreliosis )

What are ticks?

They are tiny spider-like creatures commonly found in woodland and heathland areas. Unfed ticks may only be the size of a poppy seed. They usually feed on blood from mammals and birds but will occasionally bite humans. Peak times of the year for tick bites are late spring and early summer and in the autumn, but there may be a low level of tick feeding activity during mild weather conditions at other times of the year. Ticks usually take between three and seven days to complete their blood meals. Studies of tick populations in the UK have shown that only a small proportion of ticks carry Borrelia burgdorferi, the organism which causes Lyme borreliosis. The risk of transmitting infection from an infected tick is low in the first 24 hours that it is attached, so early removal of the tick greatly reduces the risk of infection.

Tick feeding on a person

How can ticks become infected with the Lyme bacteria?

Ticks have three active stages in their lifecycle - larva, nymph and adult - usually over two to three years, and they feed only once during each stage.  Larvae are rarely infected with Lyme bacteria when they are newly hatched, but may become infected during their first feed, usually taken on a small mammal such as a field mouse or bank vole, or a ground feeding bird, e.g. a blackbird or pheasant.  If the feeding host carries the Lyme bacteria (i.e. it is a “reservoir host”) the larva can take in the infection during its blood meal.  It then drops off the host, returning into the undergrowth for many months until it matures into a nymph, when it will again seek a blood meal.  If an infected nymph feeds on an uninfected animal or bird, it can transmit the infection, and this second host then becomes a “reservoir host”.  In this way, the infection is maintained in nature.  If the nymph is uninfected this second feed provides another opportunity for it to acquire the infection.  Following the feed the nymphs again drop back into the undergrowth and mature into adults, when they will take a final feed from a deer or other large animal, mate and lay their eggs in sheltered undergrowth.

People can be bitten by ticks from any stage of the lifecycle, but larvae are not a significant risk for transmitting Lyme disease as they are rarely infected.  Nymphs are the most likely to transmit the bacteria, as they remain small in size even after feeding, so they can easily be missed unless people check themselves over carefully for attached ticks.  Adult ticks are easier to spot because of their larger size, and are more likely to be removed before they have had a chance to pass on the infection.

Are all ticks infected?

Tick populations are found in many areas of the United Kingdom, but only a minority of ticks in any area are infected with B. burgdorferi. As a precautionary measure, any Ixodid tick should be regarded as potentially carrying infection, but the actual risk will vary from area to area.

What parts of the world are high risk areas for Lyme disease?

In the USA it occurs mostly in the northeastern seaboard states from Maine to Maryland, the midwestern states of Minnesota and Wisconsin, and in parts of northern California.  Some cases have also occurred in Canada, mainly in southern Ontario.  It is widespread in Europe, from southern Scandinavia to northern Spain and Portugal, and case numbers increase from the west of the continent to the east, with large numbers of infections occurring in forested areas of Germany, Austria and central European countries.  In recent years these have become increasingly popular destinations for activity holidays, including hunting, stalking and wildlife watching.  Estimates suggest that there are over 100,000 cases in Europe annually. Lyme disease is also common in many parts of Russia and probably occurs in temperate areas throughout northern and central Asia, although there are no detailed studies of these regions.  It does not occur in tropical regions or in Australia or New Zealand.

How can Lyme borreliosis be prevented?

There is no vaccine available so be tick aware!

• Remember that they are often very small and difficult to see
• Avoid tick bites by keeping skin covered as much as possible when visiting a tick-infested area
• Consider using insect repellents
• Keep to footpaths and avoid long grass where possible
• Check the skin for any ticks that have become attached and remove them promptly
• Check thoroughly for attached ticks at the end of the day, including skin folds such as armpits, groins, the waistband area and behind the knees

• A shower or bath after returning from a tick-infested area helps to reduce risk

• Make sure that young children have been properly checked for attached ticks, including the scalp
• Brush off clothes and pet's coats before returning indoors to remove any unattached ticks that might later seek a feed
• Consult your doctor if a rash or other symptoms develop within a few weeks of a tick bite

See also Prevention and Tick Awareness pages

Last reviewed: 23 March 2012