Epidemiology

It is estimated that 20-60% travellers will be affected by traveller's diarrhoea around the world.^[2] It particularly affects travellers from industrialised countries to developing countries, especially tropical and semi-tropical destinations.^[1] The risk and aetiology are determined by the place of destination. It is common in travellers to Latin America, Africa and Southern Asia. Diarrhoea in high-risk areas is experienced by 40% of travellers.^[1] The most common causes are bacterial (60-85% of cases) and the most important bacterial pathogen is E. coli. Parasites account for about 10% and viruses for 5%.

Presentation

These will be, to some extent, consistent with the pathogen responsible.

• The most common organism, E. coli, will usually cause mild self-limiting diarrhoea for less than 72 hours.
• Diarrhoea lasting longer than 14 days suggests more unusual organisms and testing for Giardia spp; Entamoeba spp; Cyclospora spp. and Cryptosporidium spp. is required.
• Bloody diarrhoea (dysentery) occurs more commonly with some pathogens (Salmonella spp; Shigella spp. and Campylobacter spp.) Some pain may accompany Campylobacter infection.
• In children under 5 years rotavirus is a common pathogen.

However, it is not possible to make a reliable diagnosis from the history alone.

Further assessment

A more detailed assessment of the illness is required and this should include travel details.

• Travel details help the diagnostic process:
  • Place of travel and the level of risk for the particular destination. Knowledge of the local disease prevalence and conditions is required.^[3]
  • Purpose of travel, including information on conditions of stay (including dietary habits).
  • A drug history noting whether chemoprophylaxis of any variety has been taken.
  • Whether other travellers are affected and details if so.
• Examination:
  • General observations including whether drowsy or alert.
  • Level of hydration (and is the patient shocked), eg skin turgor, mucous membranes, pulse and blood pressure.
  • Temperature.
  • Abdominal examination especially looking for the presence of a surgical abdomen.

Differential Diagnosis

Diagnosis will not generally be difficult, but other causes of diarrhoea should be borne in mind (see Gastroenteritis in adults and children article).

Investigations

• FBC, U and Es, LFTs.
• Stool culture including microscopy, culture and sensitivity and tests for ova, cysts and parasites (3 samples on 3 separate days). This should be done in all patients with severe symptoms or bloody diarrhoea and in patients not improving after 48 hours.
• Additional stool tests may be done according to history and travel destination, whether stool is bloody, whether recent antibiotics have been taken, in young children under 5 (rotavirus).
• Clostridium difficile toxin may be tested for if recently in hospital or if patient has taken broad spectrum antibiotics in the preceding 6 weeks.
• Diarrhoea lasting longer than 14 days requires further testing to exclude parasites (for example Giardia, Entamoeba, Cyclospora and Cryptosporidium).

Management

The vast majority of cases will be managed at home with oral rehydration. However it is important to identify patients who should be managed differently. The state of hydration will need monitoring in all patients but particularly those with more severe symptoms and those at risk of dehydration.

Oral rehydration and home monitoring

This is appropriate for low risk patients with mild or no dehydration and mild symptoms with favourable home circumstances. The young, the elderly and other higher risk patients should be monitored particularly closely.

Oral rehydration and consider admission

Mild to moderate dehydration can often be managed at home if all other factors are favourable and the patient can be reviewed. In patients at risk of worsening dehydration with severe symptoms or with other risk factors (the young the elderly or other comorbid conditions), admission should be considered.

Admission and referral

• Patients with 5% or more dehydration should usually be admitted.
• Specialist advice needs to be sought for acute, severe or persistent diarrhoea in HIV positive patients or patients with AIDS.
• Children less than 6 months old with vomiting (>4 x per day) and liquid stool (>8 x per day) are at particular risk of dehydration and should be admitted for observation.

Complications

traveller's diarrhoea is typically self-limiting and postinfectious complications are unusual. The most significant effect is that of the illness itself and the associated morbidity and disability. By definition it can be disruptive to people travelling for whatever reason, whether for holiday or business.

Prevention

It is possible to reduce the rate of traveller's diarrhoea with:

• Good advice on precautions to be taken with food and drink. This remains the most important preventive measure.^[4]
• Chemoprophylaxis: empirical therapy with drugs like the fluoroquinolones rifaximin^[5] or azithromycin has demonstrated reduced duration of illness and lower morbidity in travellers. Rifaximin is a new drug which is minimally absorbed. This non-systemic approach has advantages over current antibiotics and appears to be both effective and well tolerated.^[1][5] Further, bismuth subsalicylate and probiotics have been trialled, but the former is associated with adverse effects.^[2] Probiotics: a review of prevention of traveller's diarrhoea with probiotics was not favourable.^[6]
• Collaboration between local governments and public health researchers. This could improve hygiene in high-risk areas and reduce risk to travellers.
• Vaccines and immunoprophylaxis may be helpful in certain circumstances.^[1][2] An efficient cholera vaccine is available and gives cross-protection against E. coli enterotoxin. It is however only marginally effective against traveller's diarrhoea when taken as a whole.^[2]