A nine year old girl, Skye, comes to see you with her parents. She has a two day history of a red, circular and enlarging rash on her right calf, which they describe as looking like a ‘bull’s eye’. She has also been feeling generally unwell with headaches, muscle aches, fatigue and a fever. They tell you in passing that they came back from holiday, in Scotland, a week ago.
Since reporting began in 1986, Public Health England reports that the number of laboratory confirmed cases of Lyme disease in the UK have been steadily rising. The National Institute for Health and Care Excellence has recently published guidance designed to create a consistent approach to the diagnosis and management of patients with suspected or confirmed Lyme disease. In addition, this guidance aims to raise awareness of Lyme disease amongst healthcare professionals, so that it is considered as a possible differential diagnosis where appropriate.
What is Lyme disease?
Lyme disease is a bacterial infection caused by Borrelia burgdorferi. It is transmitted to humans through a bite from an infected Ixodes tick; these ticks are usually found in wooded and grassy areas (both urban and rural), between April and October. Lyme disease is most common in parts of the USA, Canada, Europe, and Asia. In the UK, there are approximately 1000 serologically confirmed cases annually, with the majority of cases occurring in the South of England and the Scottish Highlands.
What are the symptoms?
The most characteristic feature of Lyme disease is erythema migrans:
- A red, circular rash, with central clearing and a ‘bulls eye’
- Usually at the site of the tick bite, developing three days to three months after the bite
- Enlarging, but usually not painful or itchy
Lyme disease can also cause a variety of non-specific symptoms, including: fever, sweats, malaise, lymphadenopathy, neck pain or stiffness, fatigue, myalgia, arthralgia, headaches, paraesthesia or cognitive impairment (e.g. difficulties with memory and concentration).
Lyme disease can also present with a range of focal symptoms, including:
- Neurological symptoms (e.g. unexplained cranial nerve palsies, meningitis or unexplained radiculopathy)
- Inflammatory arthritis
- Cardiac problems (e.g. heart block or pericarditis)
- Eye symptoms (e.g. uveitis or keratitis)
- Skin rashes (e.g. acrodermatitis chronica atrophicans or lymphocytoma)
How do I diagnose Lyme disease?
Patients with erythema migrans should be diagnosed and treated for Lyme disease, in these cases lab testing is not required.
Patients without erythema migrans:
- Where Lyme disease is suspected, offer an ELISA for Lyme disease and if the suspicion is high consider starting antibiotic treatment whilst awaiting the results.
- Positive or equivocal ELISA:
- Conduct an immunoblot test for Lyme disease.
- Negative ELISA:
- Where a clinical suspicion of Lyme disease remains, in patients who had an ELISA within 4 weeks of the onset of their symptoms, repeat the ELISA 4 to 6 weeks later.
- Where a clinical suspicion of Lyme disease remains, in patients who have had symptoms for at least 12 weeks, conduct an immunoblot.
- Lyme disease should be diagnosed in those who have a positive immunoblot and Lyme disease symptoms.
- Positive or equivocal ELISA:
In patients younger than 18, the diagnosis and management of Lyme disease should be discussed with a specialist, except for cases of uncomplicated erythema migrans.
How do I treat Lyme disease?
The first line treatment for Lyme disease without focal symptoms should be:
- For those over 12, oral doxycycline 100 mg twice per day or 200 mg once per day for 21 days.
- For those aged 9 to 12, weighing 45kg and under, oral doxycycline 5 mg/kg in 2 divided doses on day 1 followed by 2.5 mg/kg daily in 1 or 2 divided doses for a total of 21 days; for severe infections, up to 5 mg/kg daily for 21 days.
- For those under 9, weighing 33kg and under, oral amoxicillin 30 mg/kg 3 times per day for 21 days.
For more detailed guidance regarding the management of Lyme disease and patients presenting with focal symptoms, please see the NICE guideline.
The BMJ has also produced this great visual summary of the antibiotic treatment used in Lyme disease.
What is the prognosis?
Most patients infected with Lyme disease, who receive prompt and appropriate antibiotic treatment, will go on to make a full recovery. However, recovery may continue for months or even years, after antibiotic treatment has ended.
- Residual neurological symptoms, if treatment was started late in the course of the disease.
- Atrophic lesions, peripheral neuropathy and joint deformities, if acrodermatitis chronica atrophicans caused severe tissue damage.
- Lyme arthritis, the majority of patients will completely recover from this over several months, but in approximately 10% of patients the recovery can be more prolonged.
How can Lyme disease be prevented?
- Keep to marked footpaths and avoid brushing past vegetation
- Wear: long sleeves, long trousers and light colours
- Use insect repellent containing DEET
- Perform tick checks: particularly skin folds and the head, neck and scalp (especially in children)
- If a tick is found prompt and correct removal can reduce the risk of Lyme Disease transmission
For more information on tick avoidance and how to remove ticks correctly, please see this patient leaflet from Public Health England.
What should I not be doing according to the new NICE guidelines?
- Ruling out Lyme disease in patients who have symptoms, but no tick bite
- Diagnosing Lyme disease in patients with a history of a tick bite, but no symptoms
- Ruling out Lyme disease in patients where the clinical suspicion is high, but test results are negative
- Not all tick bites cause Lyme disease.
- Only around 75% of Lyme disease patients remember having a tick bite.
- Only around 60-80% of Lyme disease patients develop erythema migrans.
- If a patient presents with erythema migrans, treat them for Lyme disease without further diagnostic testing.
- If a patient presents with non-specific symptoms that could be linked to Lyme disease, ask them about recent travel and any activities where they could have been exposed to ticks.
- Think Lyme disease! Include it amongst your differentials for patients with non-specific symptoms, even if it is at the bottom of your list.
Longmore M, Wilkinson IB, Baldwin A and Wallin E. Oxford Handbook of Clinical Medicine. 9th edn. OUP 2014.