Blood-sucking mites at root of Lyme disease
If you’re exposed to ticks, do a daily tick check, writes MUIRIS HOUSTON
DEER AND especially fawns are beautiful creatures. During a recent holiday in rural Canada, we stayed for some days in a densely wooded area where deer wandered freely between houses and along roads. But we also had encounters with less welcome creatures; we were bitten with ticks which we were careful to remove with tweezers.
Why the fuss? Lyme disease is spread by tick bites, ticks are especially common among deer and the best way to prevent infection is the prompt removal of ticks before they get the chance to burrow under the skin. An infection caused by a spiral-shaped bacterium called Borrelia burgdorferi, it is transmitted to humans by bites from ticks infected with the bacteria. The infection is generally mild, affecting only the skin, but can occasionally spread to cause a debilitating illness.
First described in 1977, Lyme disease is named after the town of Lyme in Connecticut where it was identified as the cause of an outbreak of arthritis in children. Since somewhat disparagingly referred to as the “Lyme capital of the world”, the northeastern US town is typical of the lightly forested areas where the bug is most frequently found. But it has spread and is now the most common vector-borne disease in Europe and is found all over North America, Australia, China and Japan.
You don’t have to travel to contract the disease; experts reckon there are at least 50-100 cases in Ireland each year. Unlike many infectious illnesses, Lyme disease does not have to be reported by doctors here or in England or Wales, hence the uncertainty about exact numbers.
The ticks responsible are generally hard-bodied ticks called Ixodidae. Ticks are tiny, spider-like creatures, which are commonly found in woodland, moorland and other grassy areas. 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. The proportion of ticks infected with B. burgdorferi varies depending on the region; in Europe it is only a small minority (10-15 per cent) of ticks.
In general, the longer the tick has been attached to the skin, the greater the risk of passing on infection. It needs to be attached and feeding for up to 24 hours before transmission of the bacterium takes place. Exposed parts of the skin are most likely to receive bites. Women tend to receive most bites to the legs, while children (especially those under 10) tend to be bitten on the head and neck.
“Only a minority of ticks carry infection. If a tick is removed within a few hours, the risk of infection is low,” says Dr Paul McKeown, of the Health Protection Surveillance Centre. “The entire tick, including any mouthparts which might break off, should be removed with a tweezers by gripping it close to the skin. The skin where the tick was found should then be washed with soap and water and the area checked over the next few weeks for swelling or redness. Anyone who develops a rash or other symptoms should visit their GP and explain that they have been bitten by a tick.”
What symptoms should you look out for? The commonest evidence of infection is a rash called erythema migrans seen in about 80-90 per cent of patients. A red, raised skin rash in the shape of a bull’s eye develops between three 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 fatigue. Occasionally, there may be more serious symptoms involving the nervous system, joints, the heart or other tissues.
Treatment with oral antibiotics for up to three weeks prevents complications in most cases. But for campers and walkers, a daily “tick check” represents the best protection against the disease.