UK Lyme Disease Cases 'Three Times Higher Than Estimated'

Tim Locke

August 01, 2019

Current annual estimates of confirmed Lyme disease cases are between 2000 and 3000 in England and Wales, according to Public Health England.

However, research published in BMJ Open suggests the real figure for the tick-borne disease could be three times higher and may reach more than 8000 this year although an expert has urged caution, saying the findings could be an overestimation.

A second study published in the same journal supported targeted public health intervention at identified Lyme disease hotspots.

General Practice Data

The research team analysed anonymised data from Clinical Practice Research Datalink (CPRD) between 2001 and 2012. This covered around 8.4 million individuals from 658 general practices - around 8% of the UK population.

Lyme disease diagnoses were categorised as

  • Diagnosed clinically (1702, 42%)

  • Suspected and treated (1913, 47%)

  • Possible and treated (468, 11%)

Summers saw the highest number of Lyme disease cases and the largest amount were in Scotland. This was thought to be due to the popularity of hiking, and a rainier climate. The regions coming second and third for Lyme disease incidence were South Central England and South West England, but cases were seen in all areas.

CPRD recorded cases rose from 60 in 2001 to 595 in 2012, and a UK-wide estimate of 7738 for 2012.

Unsurprising Findings

"I wasn't very surprised, because plenty of people have been suggesting that the incidence is higher than has been estimated," one of the study authors, retired doctor Victoria Cairns from Oxford told Medscape News UK.

With some diseases, incidence can rise along with public and medical awareness of symptoms. However, "There's more I think," Dr Cairns said: "Every year there is more."

The new research paper doesn’t speculate about the reasons for the growth in cases. "Other people have speculated that it's climate change, Dr Cairns said. "There are all sorts of explanations. Partly, climate change is warmer. In some places, there are more deer so ticks are feeding off different animals, so that could be part of it."

She has a personal interest in the subject: "I have had Lyme disease, quite a long time ago."

She documented it – and post-Lyme disease symptoms - in the International Journal of Epidemiology in 2005.

"My problem was I was not diagnosed early, because I didn't know that the rash I had is a sign of Lyme disease," she said. "I was very busy working and I ignored it. That's the main thing I would say to people - don't ignore it. And if you think you have symptoms, go to the doctor.

"The problem that some people have is a delay in treatment. And so they have rather long-term symptoms that take ages to disappear."

Dr Cairns says the public should be more aware of tick risks and Lyme disease symptoms. "I think it's very important that people become aware of it and take preventive measures.

"Because it's so hard to diagnose, only about a quarter of all patients get this particular rash, it's called erythema migrans, otherwise Lyme disease would not be such a big issue because everyone would instantly get treatment. It's easily treated if it is caught early enough."

Latest Guidelines

Last year, the National Institute for Health and Care Excellence (NICE) guidelines changed so that  doctors can begin treatment without blood tests.

"One of the problems is the symptoms are very varied. It has been called 'the great imitator'," Dr Cairns said. "The range of symptoms is quite broad. It turns into neurological problems, joint problems, brain problems, memory problems, heart trouble, all sorts of things."

Dr Cairns believes GPs are ready to help spot symptoms: "I think GPs know nowadays so that's not really the issue. It's not really the GPs, it's the public.

"The main point of this study is to say there are more than you think, so be on the alert."

Caution Urged

Reacting to the findings in a statement through the Science Media Centre, Prof Sally Cutler, professor of medical microbiology, University of East London (UEL), said: "This study reports a different way to calculate the number of cases of Lyme disease in the UK. Their results differ to previously reported rates that have been based on officially reported cases of Lyme disease that fulfil a rigid set of criteria and require positive blood tests for the disease to be counted, this established method reports some 3000 cases per year."

She continued: "In this study, three categories of patients are included: clinically diagnosed; treated suspect cases with a positive diagnostic test; and treated possible cases. Including patients who were only ‘suspect’ and ‘possible of Lyme disease cases’ in this study will result in over-estimation of cases."

Prof Cutler concluded: "I would advise caution when interpreting the number of Lyme disease cases provided in this study as they are likely to be an overestimation."

Responding to Prof Cutler's comments, Dr Cairn's told Medscape News UK: "We have discussed in detail in the discussion section of our paper the possibility of overestimation and also of underestimation in the study.  

"Overall, we took a conservative approach to identifying cases. We write that counting only the number of LD cases recorded by specialist laboratories will lead to an underestimate, and that the annual number of positive laboratory diagnoses of LD in England and Wales is low, but this excludes clinically diagnosed cases with erythema migrans rash, other clinically diagnosed and treated cases, suspected and treated cases, and cases with a negative test result within 4 weeks of infection who are not sent for further laboratory investigation.

"We also say in the beginning that cases that were diagnosed in hospital or in specialist clinics are not counted in our study. The true total could be higher than our study shows."

Targeted Messages

The second study in BMJ Open looked at geographic hotspots of laboratory confirmed cases, and the socioeconomic profiles of affected patients.

It analysed 3986 cases from 2013 to 2016.

It found:

  • Patients were more likely to be male

  • Cases were higher in rural areas

  • More cases were found in patients who lived in better off areas (rather than where they were infected)

The authors concluded: "Identification of the Lyme disease hotspots in southern England, alongside the socio-demographics described, will enable a targeted approach to public health interventions and messages."

Incidence of Lyme disease in the UK: a population-based cohort study. BMJ Open. doi 10.1136/bmjopen-2018-025916 .

The demographics and geographic distribution of laboratory-confirmed Lyme disease cases in England and Wales (2013–2016): an ecological study. BMJ Open. https://bmjopen.bmj.com/content/9/8/e028064

Editor's Note, 1st August 2019: This article was updated to include Dr Cairns' response to Prof Cutler's comments.

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