The facts about...

Lyme disease

What is Lyme disease?

Lyme disease is an illness which can affect the skin, and in some people, the nervous system, joints, heart or other tissues. It is caused by spiral shaped bacteria called Borrelia burgdorferi. The bacteria are transmitted through bites from certain types of ticks, but not every infected person develops symptoms.

Lyme disease was so named after some children developed arthritis in the town of Lyme, Connecticut, USA in 1975. Initially they were thought to have a form of rheumatoid arthritis, but further investigations showed that the illness was caused by an infection transmitted from ticks. It was not a new disease; it had been known in Europe under a variety of names since the late 19th century It is the most common vector-borne infection in temperate areas of the northern hemisphere and occurs in parts of the United States and Canada, and in countries throughout Europe and temperate parts of Asia. (Vector-borne diseases are transmitted by creatures such as ticks, flies or mosquitoes. The bacteria that cause Lyme disease are transmitted exclusively by certain types of ticks.)

It is not a common illness in the UK. About 800 cases are confirmed annually through laboratory tests, although it has been estimated that 1,000 to 2,000 infections occur in England and Wales each year . There has been some increase in reported cases in recent years. Several factors contributed to this, including greater medical and public awareness of the infection, and improvements in diagnostic tests. Other factors include increased outdoor leisure activities in tick habitat areas in the UK and elsewhere. Tick populations have increased in some parts of the UK and other countries, because of expansion of deer populations and range and changes in weather patterns. About 20% of the laboratory-confirmed cases in the UK are known to have been acquired abroad.

How is Lyme disease caught?

Borrelia burgdorferi is transmitted by the bite of an infected tick of the Ixodes ricinus family. Ticks are not insects but are tiny, spider-like creatures which are found in woodland, moorland, heathland and other grassy areas. They usually feed on blood from mammals or birds and have a complicated two to three year life-cycle with three active stages, larva, nymph and adult. The tick feeds only once during each stage by taking blood from a host. Larvae and nymphs are very tiny and usually feed on small mammals such as field mice or voles or on birds. Adult ticks tend to feed on larger animals such as deer, sheep or horses, and can reach the size of a coffee-bean after a feed. If ticks feed on an animal which is infected with B. burgdorferi they become infected and may pass on the infection to other animals (including human beings) when they feed again in a later stage of their life-cycle.

What are the symptoms of Lyme disease?

Some infected people have no symptoms at all. The most common sign of infection, seen in about 80% of people with symptoms, is a pale pink or reddish rash called erythema migrans, which spreads out from the site of a bite after three to thirty days, but usually between five and fourteen days. It is not significantly itchy or painful, and may be difficult to see on darker skin. Patients may also be feverish and have some enlargement of the lymph glands near to the site of the rash. They may also complain of aches and pains and feel very tired. The rash can spread to cover quite a large area of skin but it will gradually clear, usually from the centre outwards, which may give a target-like appearance. Erythema migrans rashes usually fade after three to four weeks, but can occasionally last much longer. They disappear rapidly with appropriate treatment.

Some people may develop nervous system complications such as facial palsy, which is a weakness or paralysis of muscles on one or both sides of the face. Other neurologic problems include mild, viral-like meningitis, abnormal sensations on the skin (described by some patients as feeling like sunburn), numbness, weakness or shingles-like pain, usually on the trunk or limbs. These complications, called neuroborreliosis, occur some weeks or months after the bite of an infected tick. Some patients with these and other complications may not remember having been bitten or may not have had an erythema migrans rash earlier.

Lyme disease can occasionally trigger arthritis, usually affecting the knee or another large joint, which settles down after antibiotic treatment in most cases. Rarely, the arthritis can be more prolonged in people who have a particular genetic predisposition to this complication, and may recur at intervals before eventually settling. It is more common in people who acquired infection in the USA than in Europe, probably related to variations in bacterial strains in different geographic areas. Lyme disease may also affect the heart, causing an abnormality of heart-beat rhythm. This may occur within a few weeks of the bite, but is very uncommon and responds well to treatment. Other complications are rare.

Non-specific symptoms of the chronic fatigue type are rarely the result of Lyme disease. The diagnosis in such cases is only worth considering if there are other factors suggesting the infection.

How is Lyme disease diagnosed and treated?

The illness can be difficult to diagnose if the patient and doctor are not aware that the person has been exposed to ticks. This particularly applies to people living in urban areas, who may only have been exposed for a brief period during a holiday or even a day trip. People can sustain tick bites and be unaware of them because of the tick's tiny size.

The rash may appear quite shortly after a tick bite, but blood tests will be negative initially. The blood test detects antibodies to B. burgdorferi produced by the body in response to the infection, but they are not produced in detectable amounts for several weeks after infection has occurred. Most patients with untreated Lyme disease have positive blood tests within three to six weeks of being infected. A positive screening blood test must always be confirmed; the Western Blot technique is currently used to do this. The rash usually has a characteristic appearance, so the diagnosis can be made without a blood test, especially if a tick exposure risk has been recognised. Treatment with doxycycline or amoxicillin for 14 days is usually very effective in shortening the duration of the rash, and curing the infection. If untreated, nervous system, arthritic or other complications may develop weeks or months after the infection has occurred, by which time blood tests for antibodies to B. burgdorferi are almost always positive. Again, it is important for the patient and doctor to be aware that there has been possible exposure to ticks, so that Lyme disease can be considered as a cause of the symptoms and appropriate blood tests performed. Treatment of some later complications of Lyme disease may require antibiotics to be given by injection for several weeks. Full recovery may take some time, as damaged tissue takes time to heal, especially if symptoms have been present for a long time.

What are the outcomes of Lyme disease?

Most patients who have had Lyme disease make a good recovery, even without treatment. Early treatment is strongly recommended, to prevent the possible development of complications, especially affecting the nervous system, which can be painful and cause significant tissue damage that may be slow to heal. Rarely, a patient who has had Lyme disease actively affecting the nervous system for a long time before being treated may have tissue damage that will not fully recover after appropriate treatment, even though the infection has been eradicated by the antibiotics.

A small minority of patients may have continuing symptoms for some time following treatment, particularly fatigue and muscle pain, similar to those that can occur after other infections. Several research studies have shown that there is no evidence for active infection in patients with these symptoms who have previously received appropriate treatment, and that repeated or prolonged courses of antibiotics do not help, and may even be dangerous. Unfortunately some patients with chronic illnesses of varying causes have been misdiagnosed with “chronic Lyme disease”, and prescribed prolonged courses of antibiotics and other agents. Many patients have had severe ill-effects from these treatments, and some have died. The Association of Medical Microbiologists strongly recommends that patients do not take prolonged courses of antibiotic and other treatments for “chronic Lyme disease” without consulting a physician with specialist accreditation in infectious diseases or medical microbiology, who can review the diagnosis can be reviewed and recommend appropriate treatment.

How can Lyme disease be avoided?

Points to remember:

Ticks live in areas where there is long grass and access to their feeding-host animals. Woodland and heathland areas are particularly suitable tick habitats.
Ticks usually seek feeds most actively in the spring, summer and early autumn
Most ticks are not infected with B. burgdorferi
Not every bite from an infected tick will transmit the infection. An infected tick will not usually pass on B. burgdorferi unless it has been attached to the host for more than 24 hours

Simple common sense measures can reduce the small risk of becoming infected:

Wear long trousers, preferably tucked into your socks or boots, and long-sleeved shirts with cuffs fastened if walking in grassy, bushy or woodland areas where the habitat is suitable for ticks. Wear shoes or boots rather than open-toed sandals. DEET-based insect repellent is a useful additional protection, especially if it is not practicable to cover up. Permethrin-based treatments can be used on clothing, as they kill ticks on contact, but they are not suitable for use directly on skin. They are particularly useful for people who are likely to have heavy and prolonged exposure to ticks
Try to keep to paths in woodland and heathland, and avoid areas of long grass where ticks might be present.
It is sensible to inspect skin and clothing for ticks every three to four hours, especially if you are likely to be in a tick habitat for a prolonged period. Make sure that childrens’ skins and clothes are properly checked.
Check again for ticks on clothing, picnic rugs etc when returning from a tick infested area, so as not to bring unfed ticks indoors.
Make a thorough check for any attached ticks at the end of each day in a tick infested area, paying particular attention to skin fold areas, such as the groins, armpits, under the breasts, behind the knees and around the waist. Make sure that children are thoroughly checked over, including the scalp area, as very young children in particular are at risk of bites around the head and neck.
Remove a tick as soon as possible, grasping it as close to your skin as you can, preferably using tweezers, forceps or proprietary tick removal hooks. Take care to remove it entirely, if possible, using gentle but firm upward pressure, Following removal, use a skin disinfectant on the affected area to reduce the risk of ordinary skin infections. If mouth parts break off and remain in the skin the risk of transmitting Lyme disease is not increased and the retained fragments of mouth parts usually come out within a few days. It is not necessary to attempt to remove them, as this can damage the skin and increase the risk of ordinary skin infections. .Proprietary tick removal implements are useful for people who are frequently exposed to ticks. These are available from some veterinary surgeries and pet stores, and are inexpensive and easy to use.
Do not try to burn a tick off with a match or lighted cigarette, or apply volatile oils, as these methods may cause skin damage and may also potentially increase the risk of transmitting Borrelia burgdorferi.
The use of antibiotics to prevent the transmission of Lyme disease following a tick bite is not routinely advised. Most ticks do not carry infection, and those that are infected must be attached for some time before infection can occur. See your doctor for advice if a rash or other symptoms develop in the weeks after a tick bite.
Check your pets for ticks. Tick repellent collars or “spot-on” treatments such as “Frontline” ® (available from vets) are useful, and are also effective against fleas.
See your doctor if you develop a rash or become unwell with other symptoms in the weeks following a visit to a tick infested area. Let your doctor know that you have been exposed to ticks.

Simple commonsense precautions minimise the risk of Lyme disease. Don’t let the small risk of infection spoil your enjoyment of areas where ticks may be present.