Food hygiene and safe drinking water

• These recommendations are based on guidance issued by the World Health Organization (WHO) on reducing the risk of traveller's diarrhoea [WHO, 2007; WHO, 2009].
• They are supported by UK and other international guidelines, and by experts [Health Canada, 2004; Al-Abri et al, 2005; Castelli et al, 2006; Hill et al, 2006; Health Protection Scotland, 2007; NaTHNaC, 2007; DuPont, 2008; Hill and Ryan, 2008; CDC, 2009; DuPont et al, 2009b; Foreign & Commonwealth Office, 2009; WHO, 2009].

Prophylactic treatments

• Apart from the use of prophylactic antibiotics for certain at-risk groups (see Prophylactic or empirical antibiotics), WHO does not recommended any particular measures for the prophylaxis of traveller's diarrhoea [WHO, 2009]. WHO warns that antidiarrhoeal medicines such as loperamide are contraindicated for prophylactic use.

Probiotics

• Probiotics are not recommended for the prevention of traveller's diarrhoea because CKS found insufficient evidence to support their use.

Bismuth subsalicylate (Pepto-Bismol^®)

• The use of bismuth subsalicylate (off-label indication) for prophylaxis for traveller's diarrhoea is not recommended because:
• Although it was up to 60% more effective than placebo in reducing the incidence of traveller's diarrhoea, this was based on limited evidence from three small trials.
• Antibiotics are a more effective option and are estimated to be around 80% effective (provided they have activity against the enteropathogens in that geographical region) [Ericsson, 2003].
• The usefulness of bismuth treatment may be limited by the following:
• Compliance may be difficult as the treatment (30 mL or two tablets) needs to be taken four times a day.
• Prophylaxis is recommended for up to 3 weeks (based on duration of trials) and the quantity required might be inconvenient to carry.
• Adverse effects are common (particularly black tongue and stool) and the risk of tinnitus is of concern.
• The salicylate content is high: one day's treatment is equivalent to taking four 325 mg aspirin tablets daily [Thomas, 2000; Ericsson, 2005]. Consequently, it is not suitable for people with aspirin allergy, renal insufficiency, gout, or those taking anticoagulants [Hill and Ryan, 2008; CDC, 2009], as well as those with a history of peptic ulcer disease or at increased risk of gastrointestinal bleeding.
• Pepto-bismol^® is not licensed for children younger than 16 years of age due to a possible association between salicylates and Reye's syndrome [ABPI Medicines Compendium, 2009a; ABPI Medicines Compendium, 2009b].

Vaccination

• A universal vaccine to protect against the general syndrome of traveller's diarrhoea is not possible due to the wide range of possible causes.
• An oral cholera vaccine (Dukoral^®) may produce cross-protective immunity against enterotoxigenic Escherichia coli (which expresses a heat labile enterotoxin similar to cholera toxin). However, the effectiveness of this vaccine is limited, because [Hill et al, 2006; Hill and Ryan, 2008]:
• Up to 50% of enterotoxigenic E. coli strains do not express this particular heat labile enterotoxin.
• Protection is variable. It is estimated that the vaccine will only prevent 1–7% of cases of traveller's diarrhoea, depending on the destination and prevalence of enterotoxigenic E. coli strains which produce this heat labile enterotoxin.