More Tics Than We Thought?

Posted by Jeremy Windsor on Dec 08, 2019

There's nothing better than a bit of myth busting! For years it's been widely assumed that our islands are somehow protected from the tick-borne infections that affect so many people in mainland Europe. Whilst more than 230,000 cases of Lyme Disease (LD) are estimated to occur on the other side of the Channel, UK estimates range from 2000 to 3000 cases per year. Given ideal conditions for tics in many parts of the UK, is this true? A new study may provide the answer!

Ixodes ricinus is one of more than 20 species of tick that is indigenous to the UK. It is the main carrier of Borrelia burgdorferi, the commonest cause of LD in the UK. Tics typically feed on large mammals such as deer, sheep and humans.

Using a detailed algorithm, researchers were able to search through a UK primary care database of 8.4 million patients and identify all those who'd been diagnosed and treated with LD between 2001 and 2012. At present, official estimates are based upon positive laboratory findings and clinical cases reported to a central agency. But by searching through the database it was clear that this approach had significantly underestimated the total number of cases in the UK. 

LD typically present with flu-like symptoms - fatigue, fever, chills, joint pain and headache. Between 10 and 20% develop neurological and/or cardiac complications. Left untreated, symptoms may take months or even years to resolve.

Here's 3 of the study's most important findings: 

-The total number of cases was more than double what was previously thought. According to the study, an estimated 7738 LD cases were identified and treated in 2012. 

-The annual rate of LD was 12.1 per 100,000 adults. However this varied dramatically from region to region - in Scotland the incidence was 37 per 100,000 compared to just 6 per 100,000 in Wales. 

-The incidence of LD wasn't static. Between 2001 and 2012 the number of cases increased by a factor of 10.

The incidence of LD in 2012. LD was commonest in Scotland and the south west of England, whilst rarest in Wales, Northern Ireland and the north of England

It looks like LD has been underestimated in the UK for many years and is set to increase in the future. Anyone practising mountain medicine needs to be well versed in the diagnosis and management of the condition as early recognition may reduce the duration and intensity of symptoms and prevent life threatening complications.

Erythema Migrans (EM) - This distinctive "Bull's Eye" rash is often seen in LD. It is important to distinguish this from the more benign rashes caused by insect bites. The latter tend to be sore, itchy, transient and visible within a few hours. EM often goes unnoticed, can take up to 2 weeks to appear and remains visible for several weeks if left untreated. The absence of EM does not rule out LD. Only 22% of those diagnosed with LD in this study recalled seeing EM on their body.

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