Traveller's diarrhoea is an extremely common occurrence, affecting up to half
of travellers to high risk areas such as Africa, Asia and South America. Even
travellers to low risk areas such as Northern Europe, North America, Australia
and New Zealand have a 5 to 10% risk of developing symptoms. In general traveller's
diarrhoea is mild and short lived but can seriously disrupt holidays or business
trips. A number of organisms can cause diarrhoea in travellers, although in
up to 60% of cases no organism is identified, and it may be that diarrhoea is
caused by a change in diet or medications. The commonest infective cause world-wide
is Escherichia coli, a bacterium that produces a toxin which irritates the gut.
Other bacterial causes include Shigella, Salmonella and Campylobacter, all of
which can cause dysentery, that is diarrhoea with blood. A smaller proportion
of cases overall are caused by parasites such as Giardia, Cryptosporidium and
Amoebae, or viruses.
Mode of Transmission
Traveller's diarrhoea is transmitted by so-called faeco-oral spread, most commonly
through swallowing contaminated water or food. It is most common in areas of
poor sanitation where human or animal faeces enter the water supply. Traveller's
diarrhoea can also be picked up from swimming pools or from sea water contaminated
The world can be divided intoareas of high, intermediate or low risk of traveller's
diarrhoea. High risk areas include Africa, South America, Asia and the Middle
East. Intermediate areas are southern Europe, Israel, Japan, South Africa and
the Caribbean, while low risk areas are North America, Northern Europe, Australia
and New Zealand. However there is a large degree of local variation, for example
in some national parks in New Zealand there is a high risk of Giardia, and this
organism is also found in the Moscow water supply. Local knowledge is invaluable.
The most important preventative measure is education regarding simple measures
to avoid traveller's diarrhoea. These include hand washing, drinking only boiled,
bottled or treated water, avoiding ice in drinks, peeling all fruit and vegetables
and avoiding undercooked foods and particular risky foods such as shellfish
or unpasteurised dairy products.
Antibiotics such as Ciprofloxacin, Doxycycline or Co-trimoxazole can be taken
to prevent traveller's diarrhoea and are extremely effective. However they are
not recommended routinely as their use may lead to side effects and the development
of bacterial resistance to these agents. They may be used exceptionally for
cases where it would be devastating to develop diarrhoea, for example a national
leader visiting a high risk area. Bismuth salts may also reduce the risk, but
taste unpleasant, cause sickness and blackening of the tongue. Live yoghurt
has been reported to be of benefit in some studies, but others dispute this.
Cholera is an uncommon cause of traveller's diarrhoea and the vaccine for this
is minimally protective. There is a vaccine against typhoid, caused by Salmonella
typhi but this does not give protection against the usual Salmonella strains
causing traveller's diarrhoea.
Symptoms and Signs
Patients usually develop abrupt onset diarrhoea, sometimes with vomiting and
often associated with crampy abdominal pains and fever. The diarrhoea may contain
blood. Patients may become dehydrated, particularly if they are vomiting, causing
sunken eyes, dry mouth and faintness. If they develop very severe dehydration
(for example cholera) kidney failure may ensue.
The most important test is to examine samples of the diarrhoea for bacteria
or parasites which may cause tra