Infected deer ticks are nothing if not indiscriminate when they gorge on human blood. And when the eyeless arachnids sink their teeth into celebrity skin and transmit Lyme disease, we all hear about it. Avril Lavigne, Richard Gere and George W Bush are all said to have experienced the horrors of hosting the borrelia bacteria that can cause a range of debilitating symptoms from fatigue and joint pain to heart problems and partial paralysis.

The ticks’ latest high-profile victim? Matt Dawson, the former England rugby captain, who was bitten while relaxing in a west-London park two summers ago. After a GP failed to consider Lyme disease as a possible cause of his early symptoms – which included a bull’s eye-shaped rash and a fever – a private medical test revealed not only the presence of the disease but also damage to Dawson’s heart, which then required multiple operations.

Lyme disease “was something I’d always associated with places abroad – on the continent, in America, wherever there were deer”, the 44-year-old said this week while campaigning for tick awareness alongside the nature presenter Chris Packham. “It was a really scary time for me and my family. Such a tiny creature caused me to end up needing heart surgery.”

Dawson is now free of the disease although he still takes medication to help his heart recover. But his experience has added to the impression that Lyme disease is a grave new threat spreading far beyond the grass and shrublands of Connecticut, where it was first formally identified in the towns of Lyme and Old Lyme in 1975.

Reports abound of a deer-tick invasion, a blight moving across Europe and leaping across the Channel, leading to an explosion in human contractions. Meanwhile, victims on both side of the Atlantic have clashed with the health establishment – and, in the US, health insurers – over the disputed existence of symptoms that can last for decades.

How fearful should we be before we traipse back into our gardens, woods and moorlands? Perhaps not as fearful as the headlines suggest, says Dr Matthew Dryden, a consultant in microbiology and infection with Public Health England (PHE) and Hampshire Hospitals, and Britain’s leading expert on Lyme disease. “On one hand we need to be aware that tick bites can be dangerous but we also don’t want to discourage people from enjoying the countryside,” he says.

According to PHE, no more than 10% of the ticks in question have the bacteria that can then cause Lyme disease. The organisation estimates 3,000 people contract the disease a year (diagnoses in the US are much more common, at more than 300,000 a year).

The ticks cling to grasses or other plants in relatively moist areas (Lyme disease cases have been recorded in all parts of Britain) after hitching rides on deer or other animals. They lie in wait for animal flesh to brush past. When it does, they make the leap, swelling up to the size of a pea as they feast on blood. Doctors advise anyone to check their skin for ticks by sight and by hand and remove them carefully without squeezing their bodies. Only see a GP if a rash or flu-like symptoms then develop – and be sure to mention the bite.

Left untreated by antibiotics, the bacteria can spread around the body with various effects including Lyme carditis, the heart condition that befell Dawson. Deaths are rarer still; a 2011 review of 114 deaths supposedly caused by Lyme disease in the US between 1999 and 2003 concluded that only one could be attributed solely to the effects of the disease.

But Lyme disease is undoubtedly becoming more common. A 20-year study by Dryden in Hampshire recorded a 10-fold increase in cases by 2009. Numbers have oscillated since then. Nationally, in the second quarter of 2017, there were 283 confirmed cases, compared with 170 in the same quarter last year. “Nobody knows exactly why the figures are going up, but rising deer populations is a possible cause,” Dryden says. Warmer, humid weather typically leads to short-term spikes in cases.

These are big rises but the numbers remain very low. Yet the disease’s rarity seems out of proportion with the attention it receives – not least when victims are public figures – and the mushrooming of campaign groups that set out to raise awareness.

Stella Huyshe-Shires contracted Lyme disease almost 20 years ago after being bitten while gardening at her home in Devon. She had never heard of it. “My GP didn’t know what it was either,” she recalls from the same Devon garden. It would be three years before she was diagnosed, by which time pain had caused loss of sleep, and – ultimately – the end of a career in plant research and computing for IBM and the NHS. “I couldn’t even remember colleagues’ names,” she says.

Antibiotic treatment later worked but Huyshe-Shires, now in her late 60s, says she does not know whether ongoing symptoms including nerve pain and hearing problems can be linked to the bite.

In 2007, she joined Lyme Disease Action (LDA), a UK charity that she now chairs to promote awareness and research. She also sits on a National Institute for Health and Care Excellence (Nice) committee working on new guidelines, which are due to be published next year.

The existence of widespread so-called “chronic” Lyme disease is where faultlines have opened. “In true Lyme disease, if the bacteria is allowed to spread through the body it can still be readily treated with an appropriate course of antibiotics,” Dryden says. “Some people who are treated can get persistent non-specific symptoms but they are in a very small minority and any number of infections can be the cause; Lyme disease will be to blame in a tiny minority of cases.”

Perhaps most significantly, in 2015, the millionaire Phones4U founder John Caudwell announced that he and members of his family had been diagnosed with Lyme disease by a private clinic in Germany. He blamed the disease for a range of long-term conditions including serious mental health and thyroid problems. Caudwell said tests in Britain were not good enough, and is now helping to fund Caudwell LymeCo charity, which supports research into Lyme disease as well as a range of “LymeCo” conditions he believes are associated with it. “I am crystal clear this is one of the most dangerous illnesses to mankind today,” he told the Mail on Sunday. “Lyme disease is damaging hundreds of thousands of lives.”

Caudwell is not entirely at odds with PHE or the NHS. The disease can be transmitted from mother to baby during pregnancy. But some of his suspicions, including that the disease could be transmitted between people, are not generally accepted in the scientific community. This echoes a larger clash in the US.

A London-based specialist who preferred not to be named said the US insurance industry was partly to blame: “If you have chronic non-specific symptoms, such as ME, your health insurance often won’t cover healthcare, so this whole industry has emerged on the east coast around managing so-called chronic Lyme disease, which often is covered.” In several states, insurers are pushing for “chronic” Lyme disease not to be recognised.

Meanwhile, “Lyme literate” doctors have sprung up in the US to treat chronic symptoms, often charging sky-high prices, whether or not the treatment is covered by insurance. “In Britain, I think a lot of people are being misled by the offer of online tests from private labs, but the value of these tests has not been published or verified,” the specialist adds.

Huyshe-Shires believes some of the confusion lies between the assertions of doctors that Lyme disease can be diagnosed and treated simply, and some of the complications involved, including blood tests that can come back negative before the disease shows itself. “There is also a lack of awareness among some GPs,” she adds.

Dryden accepts that more research can be done, including into the causes of the recent rise in cases. In the meantime, he supports any campaign to raise awareness so that people avoid exposure to infected ticks in the first place. As well as checking for ticks, the NHS recommends avoiding long grass where possible and wearing long trousers and sleeves, or applying insect repellent to exposed skin. Not that he himself has avoided being bitten. “I live in a rural area and the dogs get ticks every day – and I get them two or three times a year. Touch wood I haven’t had Lyme disease yet – at least as far as I know.”

• This article was amended on 31 August 2017 to clarify references to John Caudwell.