Approach

Classic traveller's diarrhoea (TD) is ≥3 unformed stools in 24 hours with at least one of the following symptoms in a traveller visiting a higher-risk destination: nausea, vomiting, cramps, fever, dysentery.

Key risk factors include age <30 years, adventure travel, itineraries with high exposure to food and beverages from unhygienic sources, travellers with prior residence in a higher-risk destination visiting friends and relatives, military personnel deployed to high-risk destinations, and travel during seasons of hot and wet climates.[2][4][9]​​[11][12]​​​[21]​​​​​

Traveller's diarrhoea diagnosis during travel

Self-diagnosis while still travelling is the usual approach.[1] Travellers should be informed that TD is the sudden onset of abnormally loose or liquid, frequent stools. To tailor appropriate therapy, it is important that the traveller understands how to assess the severity of their illness.[1]

  • Tolerable (mild): not distressing, does not interfere with planned activities

  • Distressing (moderate): interferes with planned activities

  • Incapacitating (severe): completely prevents planned activities.

A subset of patients may develop dysentery (bloody diarrhoea) and/or high fever >38.5°C (101°F), which indicates a more invasive, more serious infection. Persistent diarrhoea (>14 days' duration) warrants further medical investigation.

Traveller's diarrhoea diagnosis post-travel

Returning travellers with diarrhoea may warrant stool examination for detection and identification; however, clinical evidence supporting a cost-effective and pragmatic approach is lacking.[1] For acute TD in which appropriate empirical antibiotic therapy has not been tried, therapy should be initiated depending on disease severity.

Microbiological testing may be considered in the returning traveller with severe or persistent symptoms, and in the returning traveller who continues to be ill despite appropriate empirical therapy for bacterial aetiologies.[7][28][29]​ Diarrhoeal stool is the preferred specimen over formed stool or swab to detect diarrhoeal illness, except in children where swab is acceptable when there is sufficient faeces on the swab.[30]​​​​​​

If a decision to test is made, testing strategies may involve multiple methods including culture, immunoassays, microscopy and/or multiplex polymerase chain reaction, due to the myriad of potential aetiologies (i.e., bacterial, viral, parasitic).[11][28]​​ Molecular testing using one or more of the multi-pathogen platforms may be of more clinical utility when rapid results are needed, or when traditional microbiological methods have failed to establish an aetiology.

Because of the high sensitivity of molecular diagnostics, it is common to identify multiple pathogens.[4][30]​​ Results will need to be interpreted alongside epidemiological, clinical, and pre-test history in order to guide reasonable treatment decisions.

Stool cultures usually take a longer time to process and may fail to detect the causative agent.[30]​ Negative stool work-ups are very likely, and in the acute TD clinical scenario, a course of empirical therapy should be tried. In the case of persistent or chronic diarrhoea after travel, the differential diagnosis includes infectious causes (usually protozoal), and post-infectious processes (e.g., secondary lactose intolerance, small intestinal bacterial overgrowth, functional bowel disorder, tropical sprue). Structural organic disease (e.g., coeliac disease, inflammatory bowel disease, colon cancer, microscopic colitis) should also be considered, and will require a targeted diagnostic approach for the individual patient.[6][7][29]​​​​​​

The Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM) guidelines suggest considering testing for parasites in patients having persistent diarrhoea for >7 days.[30]

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