THEY have long blighted hillwalkers in the Highlands. But now hikers have a new reason to beware of ticks as scientists believe a bite from the insect can lead to anaphylactic shock.
The blood-suckers carry a sugar in their saliva known as galactose-alpha – or alpha-gal – which is also found in most red meats, but can trigger an allergic reaction when it enters the body through a tick bite.
Research has found the tick bite helps the alph-gal enter the bloodstream, where the immune system detects it as a foreign agent and sends antibodies to fight it.
The next time the person eats meat, or certain dairy products, they can go into anaphylactic shock.
Dr Malcolm Shepherd, a consultant at the West of Scotland Anaphylaxis Service, in Glasgow, has seen a number of recent cases, mostly believed to have been contracted in the Highlands.
He said: “Allergy to meat is rare, and the emerging understanding of alpha-gal allergy shows it can present in unusual and unexpected ways.
The danger is that people won’t know the risk of meatDr Malcolm Shepherd
“The mechanism isn’t really well understood but there’s a series of studies now that have shown a link between a history of tick bites to this sudden allergy to meat.
“Most allergies manifest very quickly, so if you are allergic to peanuts then you will have a very quick reaction.
“This has only recently been identified as there is a delayed response to the allergen, so it was hard to trace back to the cause.”
Two patients who presented in Glasgow both went into anaphylactic shock while they were sleeping, nearly four hours after they had consumed meat, said Dr Shepherd.
Reported symptoms include itching, swelling of the mouth and wheezing, which had to be treated with a shot of adrenaline.
Dr Shepherd, an honorary clinical associate professor at Glasgow University, warned that many Scots could be suffering from the allergy without realising.
He said: “We just don’t know how many people have it. Patients who present with it have suffered anaphylaxis without it being immediately clear what was wrong with them.
“The first thing is it needs to be recognised, as the danger is people won’t know the risk of eating meat. I think it could be something that is a big problem in Scotland as we have such a large tick population, particularly in the north east.”
A simple blood test has been developed to confirm alpha-gal allergies but it is currently not licensed for use in Scotland.
Dr Shepherd plans to work with colleagues from Glasgow University to make a case for its use in Scotland.
He said: “The new test for alpha-gal will allow doctors with an interest in allergy to identify patients in whom allergy to meat may previously have been missed or discounted.
“As ticks appear to be on the increase, this may become an increasing allergy in the future.”
The castor bean ticks that can carry alpha-gal are found in woodland, heaths, forests and dense underbrush in places such as the Highlands and Dartmoor National Park.
NHS Highland was handed £180,000 earlier this year to work on an interactive map identifying tick hotspots.
Roger Evans, a clinical scientist with NHS Highland, said at the launch of the scheme: “Using the latest technology we can create an interactive and accurate Lyme disease identification and risk management system.”
Untreated tick bites can cause neurological problems and joint pain.
Walkers are advised to tuck trousers into socks and check for ticks after walking in long grass.