Lyme disease Dr Rob Hicks Lyme disease is an infection caused by bacteria called Borrelia burgdorferi, which is transmitted to humans by ticks that live on animals such as deer or sheep, mice, hedgehogs, pheasants, hamsters and squirrels.

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What is Lyme disease? Symptoms

Causes and risk factors Treatment and recovery

The infection was first described in 1975 after several cases occurred a town called Old Lyme, in Connecticut, USA. However, the link between tick bites and a condition affecting the nervous system has been recognised for much longer and was known as tick-borne meningoencephalitis

When a tick carrying the bacteria bites someone, it first causes a typical lump accompanied by a scab on the skin's surface. If the tick soon drops off, then Lyme disease is very unlikely. But if the tick remains on the body, for at least two to three days, the bacteria may get into the bloodstream leading to the condition.

This contact time is needed because at first the ticks only have a small number of bacteria in their gut. But once attached to the human they take a blood feed which allows the bacteria to multiply.

After a couple of days some of these bacteria then pass into the tick’s salivary gland and are injected into the human as the tick feeds. For this and other reasons, only about one per cent of bites from ticks where Lyme disease is found will lead to the condition.

Once the B burgdorferi bacteria has been injected into the person, there are several possible outcomes. The infection may be cleared without problems (some people have no symptoms but develop antibodies showing they have been exposed to the bacteria).

Alternatively the bacteria may spread through the body causing symptoms of infection, or in some cases it triggers an immune response that leads to symptoms such as arthritis.

The initial tick bite may be so small that more than half of those bitten don’t even notice or remember a bite. But then, between two days and four weeks later, an expanding, circular red rash appears, usually at or near the site of the bite.

Sometimes several of these rashes appear, which may itch or burn. Tiredness, headache, joint pains and flu-like symptoms may also occur. If no treatment is given, the rash will persist for two to three weeks. After that about one in three people have no further problems.

If no treatment is recieved, more than 60 per cent of those with Lyme disease will go on to stage 2 of the condition within six months. The main problem here is recurrent episodes of intermittent painful inflammation of the joints or arthritis, usually affecting either the knee, ankle or wrist. These episodes may go on for several years. There may also be problems with nerve palsies (for example, weakness of the nerves to the muscles of the face), inflammation or damage of the nerves, abnormal heart rhythms, and severe malaise.

For some people Lyme disease then persists in a chronic form or Stage 3, where arthritis, encephalitis and fibromyalgia (severe aching and weak muscles) continue to affect them long term.

The symptoms of Lyme disease are partly determined by the particular strain of B burgdorferi bacteria. The strain most often seen in Europe tends to lead to neurological or nerve disease.

It's no longer just visitors to rural North America who might be exposed to these tick-borne infections. Anyone who enjoys exploring the woodlands of the UK may also be at risk. People like gamekeepers, farmers and hunters are also at risk.

More recently, cases have occurred when people have visited areas in towns too. The common factor is the presence of animals such as deer that provide a home for ticks to live on.

Avoid being bitten. Ticks are tiny and spider-like, so difficult to see (the type of ticks that cause Lyme disease are much smaller than the common dog or cattle ticks, which you may be more familiar with). They can attach to any part of the body, especially to moist or hairy areas in the groin, armpits, and scalp.

When camping or walking in places where the ticks may be, the following measures are helpful:

• Wear long sleeves and trousers
• Tuck trousers into socks
• Wear light-coloured clothing so ticks are easier to see
• Try not to sit on the ground in areas of vegetation
• Keep to pathways and, where possible, avoid areas of overgrown vegetation
• Check for ticks regularly during the day and especially before going to bed
• Remove any ticks found attached to the skin straight away

If you think you may have been bitten, tell your doctor, and mention where you've been walking, especially if you know that deer are in that area. When infection with Lyme disease is suspected, blood tests can be used to help support the diagnosis.

Once Lyme disease has been confirmed, treatment is with antibiotics which may need to be given as a prolonged course and sometimes even intravenously for maximum effect. Some complications of Lyme disease need specific treatments – for example if a person develops a slow heart rhythm, they may need a pacemaker.

In most cases symptoms settle (even if treatment isn’t given, symptoms do usually eventually get better) but very occasionally Lyme disease causes more serious long term problems.

This article was last medically reviewed by Dr Trisha Macnair in March 2009.