Travellers' Diarrhoea

Travellers' diarrhoea is a general term applied to the common problem of diarrhoeal illness experienced by travellers usually in the first week or two of a stay in a foreign environment. It encompasses diarrhoea caused by numerous enteropathogens (bacteria, parasites and viruses) picked up from contaminated food and water in the new, foreign environment. It remains a major public health problem with significant morbidity.¹

It is estimated that there are 50,000 cases of diarrhoea in travellers around the world every day.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%.

Travellers' diarrhoea is, as described, diarrhoea occurring in travellers usually soon after a stay in a foreign environment. However it is otherwise not a distinct pathological entity. The presenting features will guide assessment of risk as well as the diagnosis. Susceptibility to diarrhoea is greatest in:

• The young.
• Those not having travelled to high risk regions in the previous 6 months.
• Where there has been indiscriminate selection of food and drink.
• Certain host genetics.¹

Presenting features

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

• The most common organsim, 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, Entamoeba, Cyclospora and Cryptosporidium is required.
• Bloody diarrhoea occurs more commonly with some pathogens (Salmonella, Shigella, Campylobacter and dysentery). 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 brief 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.
  • A drug history noting whether chemoprophylaxis of any variety has been taken.
  • Whether other travellers are affected and details if so.
• A detailed history of the presenting illness should be taken to establish severity of symptoms:
  • Frequency and type of diarrhoea. Bloody stools suggests dysentery.
  • Symptoms of dehydration. Degree of thirst, colour of urine, other symptoms suggesting dehydration.
  • Whether accompanied by nausea and vomiting which may exacerbate dehydration.
  • Whether febrile and degree of fever. High fever will worsen dehydration and influence management decisions.
• Details of the individual past medical history. This will help establish if the patient is at special risk of dehydration and complications.
  • Diabetics, particularly type 1 diabetics, are at risk of ketoacidosis and coma.
  • Other bowel disease, including inflammatory bowel diseases may exacerbate the diarrhoea (ulcerative colitis, diverticulitis etc).
  • Conditions affecting susceptibility to infection including immunosuppression (chemotherapy, HIV, AIDS etc).
• Examination will follow the history and may be adapted according to the particular age and history of the patient. It is important that the following should be included to assess whether the patient is dehydrated and if so to what extent:
  • General observations including whether drowsy or alert.
  • Skin and skin turgor.
  • Condition of oral mucous membranes and tongue.
  • Weight (to compare with weight when well).
  • Temperature.
  • Pulse and blood pressure.
  • Abdominal examination.

Diagnosis will not generally be difficult, but other causes of diarrhoea should be borne in mind. Findings which should alert to other diagnoses include:

• Abdominal pain, particularly with guarding on abdominal examination.
• Bilious vomiting.
• Pallor, jaundice.
• Haematuria.
• Systemically unwell out of proportion with level of dehydration.
• Signs of shock.

Other causes of diarrhoea can include:

• Infections. In children particularly other infections such as even otitis media may be accompanied by diarrhoea.
• Surgical causes. Consider for example appendicitis, bowel obstruction, short bowel syndrome. In children also consider intussusception.
• Systemic illness. Consider endocrine disease (such as diabetes, hyperthyroidism, congenital adrenal hyperplasia, Addison's) and immunedeficiency.
• Antibiotic related. Many antibiotics cause looseness of stool but be alert to pseudomembranous colitis in patients who have had particularly broad spectrum antibiotics.
• Dietary factors. Food allergies and food intolerance should be considered. In children lactose and cows' milk protein intolerance should be considered.
• Malabsorption. Cystic fibrosis and coeliac disease produce loose stools.
• Inflammatory bowel disease of all types.
• Other conditions which may be considered include constipation with overflow (particularly in children and the elderly), toddler diarrhoea and haemolytic-uraemic syndrome in children and irritable bowel syndrome paricularly in young adults.

Diarrhoea in returning travellers should generally be investigated with:

• FBC, U and Es, LFTs
• Stool culture including microscopy 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 on broad spectrum antibiotics in last 6 weeks.
• Diarrhoea lasting longer than 14 days requires further testing to exclude parasites (for example Giardia, Entamoeba, Cyclospora and Cryptosporidium).

It should be remembered that travellers may also be at risk of other diseases contracted in, for example, tropical countries. The febrile patient should be watched carefully and fever over 39° C requires referral and further investigation.

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.

Assessing hydration status

This will be influenced by:

• Level of risk of dehydration and /or complications (severity of symptoms, comorbid conditions etc).
• The level of hydration:
  • Less than 3% weight loss, or no dehydration.
  • Mild to moderate dehydration. This is 3%-8% weight loss. Mucous membranes will be dry, there may be sunken eyes, with no tear production and loss of skin turgor. Children particularly may become drowsy and may have deep acidotic breathing.
  • Severe dehydration is >9% weight loss with more marked symptoms progressing to circulatory collapse.

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 (>4x per day) and liquid stool (>8 per day) are at particular risk of dehydration and should be admitted for observation.

Travellers' 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.

This clearly depends on the particular cause but in the vast majority of cases travellers' diarrhoea is self-limiting and free of complications.

It is possible to reduce the rate of travellers' 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 fluoroquinolone rifaximin⁵ 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.^{5 1}
• 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 6} An efficient cholera vaccine is available and gives 50% cross-protection against E.coli enterotoxin. It is however only 23% effective against travellers' diarrhoea taken as a whole. Two new vaccines appear effective.⁶
• Probiotics. A review of prevention of travellers' diarrhoea with probiotics was not favourable.⁷