James Douglas is a GP in Fort William and is researching Lyme disease incidence in Scotland.
You don’t need to evolve as a species on earth to survive
Our UK tick Ixodes ricinus has been around for millennia. It has a 3-year life cycle, hatching under forest leaf mould, followed by an annual blood meal. The larvae search for passing rodents and birds, and, if they chance upon a wild animal carrying the pathogenic spirochete bacteria Borrelia, they will become infected and pass on the infection in subsequent blood meals.
Ticks can’t fly or see but hang around on grass and bracken before jumping onto a human. They ‘corkscrew’ down their beak to lock on, injecting alpha-gal anticoagulation to withdraw blood over 24 hours, and the pathogen in the tick’s stomach transfers to its new host.
This elegant and efficient pathogenesis has been going on for millennia. Why change? It is the microscopic equivalent of a great white shark at the top of its predatorial game for millennia!
Climate change is happening but drawing cause and effect in medicine is complex
Ticks are active above 7 degrees centigrade and the warmer, wetter weather of climate change is increasing their numbers. However, the ecosystem is complex, with many other variables. Humans are entering green spaces more often for work and to gain wellbeing. Migrant wild animals such as roe deer and foxes travel between forests, public parks, and gardens while carrying ticks. We have reduced sheep that used to ‘mop’ bracken for ticks and have not controlled deer numbers.
This elegant and efficient pathogenesis has been going on for millennia. Why change? It is the microscopic equivalent of a great white shark at the top of its predatorial game for millennia.
Ecosystems are complex and random; we can’t control them
We are trying to address climate change with more trees and rewilding for biodiversity. Great for ticks!
The Scottish louping ill virus is endemic in mountain hares and grouse on moorland. It has teamed up with the Babesia tick bacterial pathogen to cause a whole flock of sheep to die from encephalitis. Ticks are the disease vector between wild animals and humans. Louping ill encephalitis is a rare life-threatening illness in humans.
We need systemic annual tick sampling for pathogens to triangulate local risks with medical education and NHS laboratory testing. NHS funding is a complex ecosystem but tick-borne disease randomly affects people living healthy lives, with big impacts on morbidity.
We need to survey tick pathogens to guide disease risks and testing. This needs money from a complex NHS ecosystem. Changes in human behaviour and climate are increasing vector-borne disease. There is concern about mosquitoes colonising new habitats in UK secondary to air travel. Ticks are widely distributed in the UK. We need systemic annual tick sampling for pathogens to triangulate local risks with medical education and NHS laboratory testing. NHS funding is a complex ecosystem but tick-borne disease randomly affects people living healthy lives, with big impacts on morbidity.
New technology and vaccines may be the answer
It is impossible to culture spirochetes for NHS diagnosis, so we rely on post-hoc immune response testing for early disseminated Lyme disease. We use PCR to test tissues and fluids looking for genetic footprints. The ‘test of cure’ for Lyme disease after antibiotics remains elusive. This would be helpful before future immune modulation for persisting symptoms. Thus, we need to consider vaccinations for tick-borne disease in at-risk groups by location, leisure activities, and work exposure to ticks.
Keep it simple to reduce disease transmission
Tick-borne encephalitis virus has a safe, well-established vaccine if the virus becomes a UK public health risk, and a Lyme disease vaccine will be welcomed by many workers, gardeners, golfers, and campers.
However, modern health ecosystems can be disrupted by vaccine hesitancy. The fundamentals of tick-borne disease remain. Break the vector-borne disease transmission by prompt tick removal methods that do not squeeze the tick. Pyrethroid-impregnated clothing has reduced tick acquisition in forestry workers.
Leg tattoos: what will the impact of this new human behaviour be on Lyme disease?
There is now an evidence base and mechanism which shows that sunlight exposure reduces all-cause mortality in the UK, with a gradient from Cornwall to Shetland. The mechanism is blood pressure reduction from sunlight on our skins. The modern male fashion of wearing shorts all year round is a good thing! However, the effect of tattoos on legs and tick acquisition remains unknown. Does it prevent tick bites or hide erythema migrans. We still don’t know and the ticks are keeping us guessing!
Featured photo by Crispin Jones on Unsplash.
