Tick bites and Lyme disease

Tick bites and Lyme disease in British forests, by Edward Wilson

This is the full version of an abridged article, which appears in the April 2008 issue of FTN.


Introduction

Ticks are carriers of several bacterial diseases, of which Lyme disease is the most important in Britain. Reported cases of Lyme disease have risen dramatically from 292 in 2003 to 768 in 2006 and unreported cases are estimated to be 1000-2000 per year. Much of the recent increase has been credited to mild winters that enable infected ticks to survive and expand their range. Among those most at risk are forestry workers and woodland visitors.

About ticks

Ticks are small, blood-sucking (parasitic) arthropods, closely related to spiders and mites. Many species are native to Britain.  Each feeds on the blood of several animals, including birds, deer, sheep and dogs. The hard-bodied tick, Ixodes ricinus, commonly known as the sheep or woodland tick, carries the risk to human health. Tick bites often go unnoticed, even though a tick's body swells with blood to several times its original size after being attached for several hours or days. But not all ticks carry the bacteria and not all bites will result in infection.  Ticks usually have to be attached for hours before the bacteria transfers to the host. If a tick does bite you, there are some simple steps for its safe removal (box 1).

There are three stages in the life-cycle: larva, nymph and adult. Ticks are most likely to bite when nymphs. Even adults measure only a few millimetres in length prior to feeding, making them difficult to detect (Download Image >>) and they are hard to avoid.  Ticks are found anywhere that there is vegetation, including gardens and parks. They are most common in forested, heathland and moorland areas, though less prevalent in conifer plantations. Their favoured location is tall grass and foliage, from where they latch on to animals or people brushing past. Areas with a high deer population are likely to have large numbers of ticks. The best protection is increased awareness (Download Image >>).

Lyme disease

Lyme disease, or Lyme borreliosis, was described at Old Lyme, Connecticut, in 1975, but is now known to have a global distribution. The cause is a spirochete bacterium, Borrelia burgdorferi. The Health Protection Agency keeps close records of known infections. Research is underway on various aspects of the disease, including the ecology of ticks. The proportion of ticks carrying the disease and the location of "disease hotspots" are still being studied. The HPA notes that over 50 percent of reported cases have been in the south of England and FC reports that known areas of infection include the New Forest, East Anglia, the West Country, the Welsh uplands and the Scottish Highlands.

Signs and symptoms

Lyme disease is sometimes difficult to diagnose, as symptoms are similar to those in many other illnesses. A debate (October 2007-January 2008) in the letters page of the British Medical Journal (www.bmj.com/) has highlighted some of the challenges for clinicians. Currently, tick-borne infections cannot be classed as a simple infection and must be viewed in conjunction with other possible diseases. Mis-diagnosis of any one of these conditions can have serious implications for patient health, making it important to consult your GP as soon as you suspect something is not right. There is no vaccine against Lyme disease and research is still required to improve early diagnosis.

Generally, early symptoms appear within a few days or weeks of infection. They may include flu-like symptoms (fever, fatigue, headache, aching muscles or joints), or enlarged glands in the neck, armpit or groin. There may also be a skin rash, Erythema migrans. This starts as a "spot" at the point of the tick bite and then enlarges to form a faint pink ring 2-3 cm wide around a central clear area. The rash is a commonly mentioned feature of the disease and often appears in alarmist newspaper reports. However, it does not occur in all cases and is not definitive proof of infection. More information can be obtained from the links below.

Although blood testing has the potential to detect antibodies for the bacteria, there is currently no completely reliable test for Lyme disease. It is therefore important that you provide your GP with as much information as possible about your outdoor activities and general health if you suspect you are suffering from a tick-borne infection. Many doctors in Britain, especially in urban general practices, have little experience with tick-borne infections and will need these details to make a differential diagnosis. One way of helping is to save and label any dead ticks removed, in case symptoms of infection develop, and can be sent for testing later.

The key point when you suspect infection is to take prompt action.  Do not ignore the symptoms. The best and simplest treatments partly depend on early detection, when it can be cleared with antibiotics. Delayed diagnosis can lead to more serious and chronic disorders of the joints, heart and nervous system that present slowly over months and years, requiring specialist medical attention.

Concluding comments

This article provides general information only. It is not a substitute for professional medical advice. You should consult your GP promptly, if you become ill after being bitten by a tick. Lyme disease is potentially serious, but most people should not be put off a woodland visit. By taking sensible precautions, being aware and then checking afterwards, it should be possible to avoid or minimise risk.

Further information

Edward Wilson has spent over 20 years as a forester, educator and research scientist. He is currently studying medicine at the University of Sheffield. ted.wilson@yahoo.co.uk


Safe removal of ticks

If you find a tick on you, don't panic.  Act quickly with the aim of removing the complete tick, including its mouthparts.  This minimises the risk of infection or regurgitation of harmful bacteria into the bite wound.

What you should do:

  • If possible use a tick-removing tool (available from pet shop or vet).  Follow instructions carefully.  These tools ensure safe removal by gripping the head of the tick.
  • The best alternative is fine-pointed tweezers.
  • Image download: Use as shown in diagram.
  • If you don't have a handy tool, tie a thread of cotton around the tick's head and mouthparts.  Gently pull the tick upwards and outwards from your skin.
  • After removing the tick, use an antiseptic solution to wash the bite location, the tool and your hands.

What you should not do:

  • Avoid squashing, burning or using solvents to remove a tick, which may cause the tick to regurgitate its stomach contents and increase the infection risk.
  • Avoid twisting the tick during removal, which often causes the head to separate and remain embedded in the skin.
  • Don't try to extract the tick with your fingernails, as this increases the risk of infection through cracks in your skin.

Woodland visits checklist

There are some simple precautions you can take yourself and for children in your care.  It is also important to check dogs for ticks as they be a subsequent source.

During your visit:

  • Keep skin covered when in "brushy" areas.
  • Wear trousers rather than shorts or skirt.
  • Light coloured clothing makes ticks easier to spot.
  • Button up collars and cuffs, wear a hat, tuck trousers into socks.
  • Wear boots, not sandals.
  • Apply insect repellent on clothes or exposed skin.
  • Be extra aware May-July and September-October.

After your visit:

  • Brush off clothing and check pets before returning home.
  • Inspect yourself and children for ticks, as soon as possible, paying most attention to armpits, navel, groin and hairline (especially in children).

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