Parasitic worms that can cause cancer are being found inside more travellers in Scotland than anywhere else in Europe.
Public health officials say a rise in cheap air travel and partnerships between Scotland and Malawi and Uganda have led to a rise in the number of people being infected by the trematode worms, which then lay eggs around the bowel and bladder.
A group of experts is drawing up guidance on how the condition should be treated Scotland-wide and considering whether everyone who may have been exposed should be tested after they return home.
As people can live with the parasites breeding inside them and not suffer symptoms for months or even years, the NHS surveillance agency Health Protection Scotland (HPS) is warning that the number of people infected may be much higher than figures suggest.
In a report on the condition, known as schistosomiasis or bilharzia, HPS said: “The number of imported cases in Scotland is higher than the rest of Europe with an average of 155 cases [a year] since 2011. Due to the predominantly asymptomatic nature and the lack of awareness of the disease, it is likely that the number of cases is significantly underestimated.”
Travellers can become infected with the microscopic worms while swimming in freshwater lakes and rivers and by showering in untreated water in many countries with poor sanitation.
Fresh water snails, above, release the larvae and these microscopic worms can burrow through bathers’ skin. Once in the body, the worms move through the blood to areas such as the liver and bowel and after a few weeks are mature enough to start laying eggs.
Many people are completely unaware of the invasion, but some experience a range of symptoms including fever, diarrhoea and abdominal pain. A rash can develop at the point where the worms entered through the skin.
Treatment is said to be straightforward and the most serious complications, which include bladder cancer, are more common in people who live in affected countries.
In Scotland, more than 200 people were diagnosed with the condition in 2014 and 133 last year.
Jack McConnell signed a historic agreement with Malawi when he was first minister in 2005 triggering fundraising efforts and opportunities including school trips. About 1,000 Scottish schoolchildren are said to visit the country each year and it has been reported that 13 out of 21 pupils from Kingussie High School, in Inverness-shire, tested positive for the condition after a canoeing trip on Lake Malawi in 2010.
Fiona Genasi, a nurse consultant with the HPS travel team, said: “There is a particular interest in schistosomiasis in Scotland partially due to the close Malawi contact. But not all of the cases will be Malawi.”
Groups who organise trips for schools and students are now more aware of the problem, she said, but not everyone will do as they are told when it comes to avoiding swimming in fresh water or showering.
Ms Genasi added that if one person in a group returning to Scotland is found to have schistosomiasis, infectious disease specialists will screen everyone.
The Schistosomiasis National Advice and Investigation Liaison group is examining whether the screening of travellers should be more widespread.