Lyme Disease

What is Lyme disease?
Lyme disease (also known as Lyme borelliosis) is an infection caused by a spiral-shaped bacterium called Borrelia burgdorferi that is transmitted to humans by bites from ticks infected with the bacteria. The infection is generally mild affecting only the skin, but can occasionally be more severe and highly debilitating.   

The ticks responsible are generally hard-bodied ticks (Ixodidae). Ixodes ticks are hosted by a wide range of mammals including deer, sheep and cows; their tiny size (less than 2mm unfed) means they can remain undetected for long periods. Ticks are not insects but tiny, spider-like creatures, which are commonly found in woodland, moorland and other grassy areas, particularly in damp undergrowth. They feed by biting and attaching to the skin and sucking blood, normally from animals such as sheep and deer. If ticks feed on an animal infected with B. burgdorferi they will also become infected, and can pass on the bacteria to people and domestic animals. Unlike humans and domestic animals, infected wild animals do not seem to show symptoms of Lyme disease. Ticks grow through a number of stages, all of which bite humans. The proportion of ticks infected with B. burgdorferi varies depending on the region, but overall in Europe it is only a small minority (10-15%) of ticks.

In general, the longer the tick has been attached to the skin, the greater the risk of passing on infection. All the evidence suggests that ticks need to be attached and feeding for quite some time (as long as 24 hours according to some authorities) before there is a risk of becoming infected. What is clear is that the tick needs to be attached and feeding for a number of hours before transmission of the bacterium takes place. All the evidence suggests that if a tick is removed as soon as it bites, the risk of infection is very low. Exposed parts of the skin are most likely to receive bites. Women (and to a lesser extent men) tend to receive most bites to the legs, children (especially those under 10) tend to be bitten on the head (above the hairline) and on the neck.

How do you come in contact with Lyme disease?
Lyme disease has been reported from North America, Europe, Australia, China and Japan. Infected ticks are most likely to be encountered in heathland and lightly forested areas of North America and Northern Europe. Ramblers, campers and those who work in such areas especially if they come into contact with large animals are at greatest risk of being bitten by ticks and of going on to develop disease.

What symptoms can it cause?
Many infected people have no symptoms at all. The commonest noticeable evidence of infection is a rash called erythema migrans that is seen in about 80-90% of patients. This red, raised skin rash (often called a bulls-eye rash) develops between 3 days and a month after a tick bite and spreads outwards from the initial bite site. This rash can last up to a month and be several inches in diameter. People can also complain of 'flu-like symptoms such as headache, sore throat, neck stiffness, fever, muscle aches and general fatigue. Occasionally, there may be more serious symptoms involving the nervous system, joints, the heart or other tissues.

What complications can result from Lyme disease?
Complications following Lyme disease while not terribly common, do occur. They tend to occur less frequently in Europe than in North America. Complications tend to occur quite some time after initial infection and are common in people who did not realise they had been infected or who were not initially treated. Complications can affect different parts of the body including:

• Joints: swelling and pain in large joints (arthritis) which can recur over many years
• Heart: inflammation of heart muscle (myocarditis) with irregularities of heart rhythm
• Eye: conjunctivitis and eye pain.
• Nervous System: numbness and weakness, meningitis/encephalitis and Bell's palsy (facial paralysis).

How is Lyme disease diagnosed?
Lyme disease is diagnosed by medical history and physical examination. Diagnosis can be difficult if there has been no erythema migrans rash. The infection is confirmed by special blood tests. The tests used, look for antibodies to B. burgdorferi, which are produced by an infected person's body in response to the infection. Antibodies will take several weeks to develop and may not be present in the early stages of the rash. They will usually be present in the later stages of the infection. More sophisticated tests can be used if the diagnosis is not clear. 

How common is Lyme disease?
A number of cases are diagnosed each year, but the true figure is not known for certain. However, recent estimates suggest that there are at a minimum 50-100 confirmed Irish cases per year. It is likely that the true figure would be higher than this. In Europe, the incidence is highest in people aged 30-50 years, but is also quite common amongst children.

Who is at risk for Lyme disease?
Lyme disease can affect anyone but is commonest among ramblers, hill-walkers, hikers, campers and others whose leisure activities or work takes place in heathland, light woodland and other grassy areas or brings them in contact with certain animals e.g. deer. Summer and autumn is the period when most cases occur.

Is there a treatment for Lyme disease?
Yes, common antibiotics such as doxycycline or amoxicillin are effective at clearing the rash and helping to prevent the development of complications. They are generally given for up to three weeks. If complications develop, intravenous antibiotics may need to be used.  Fuller information is available in the Treatment section of the Epi-Insight article Lyme disease often under diagnosed says HPSC.

Is there a vaccine against Lyme disease?
There are Lyme disease vaccines available for dogs. Currently, however there is no vaccine available against human Lyme disease in Ireland. A US human vaccine was withdrawn in 2002. Research into vaccine development is taking place in Europe and the US.

How can I protect my family and myself from Lyme disease?
The best protection against Lyme disease it to protect yourself against tick bites, when walking in grassy, bushy or woodland areas, particularly between May and October:

• Cover arms and legs; wear long trousers tucked into your socks or boots, and long-sleeved shirts with cuffs fastened
• Wear shoes or boots rather than open-toed sandals.
• Use insect repellent on clothes if desired, or on limbs if it is not practicable to cover up. DEET or permethrin can be used - your local pharmacist can advise you.
• Inspect skin and clothing for ticks every three to four hours; check children's skin and clothes frequently.
• At the end of the day, check your and your children's bodies thoroughly for attached ticks, including skin folds such as armpits and groins.
• Remove a tick as soon as you see one attached to the skin (grasp it as close to your skin as possible with tweezers if necessary and take care to remove it entirely using gentle but firm pressure; as the tick's head can break off and be left behind). See here for suggested tick removal technique.   
• It is not recommended that antibiotics are given to prevent the transmission of Lyme disease following a tick bite. Only if the area becomes inflamed may treatment be required; your doctor can advise you.
• Following a tick bite, there is likely to be an area of redness; the vast majority of these look like nettle or bee stings and are just allergic reactions to the tick's saliva and do not indicate infection.
• Check your pets for ticks as they are also at risk of infection. Tick repellent sprays or collars may also help. 
• See your doctor if you develop a rash or become unwell with other symptoms. Let your doctor know if you have been exposed to ticks.

HPSC has produced a Lyme and tick leaflet on Protecting Yourself Against Tick Bites and Lyme Disease. An A3 poster has been prepared. (If you own or manage land on which people walk, you can download the poster and place it in a prominent position at the entrance and exit areas of the land).

Where can I get further information about Lyme Disease?
Further general information on Lyme disease and photographs of erythema migrans can be found on the websites of the UK's Health Protection Agency and the US's Centers for Disease Control and Prevention.

The  European Center for Disease Prevention and Control has an excellent section on Lyme disease and has a very useful Factsheet for health professionals.

For health professionals, the European Union's Concerted Action on Lyme Borreliosis provides extensive information on Lyme disease. In addition, a detailed article on Lyme disease is available in Epi-Insight.  

Updated: 18th November 2011