Travellers' diarrhoea (TD) is one of the most common travel-related health problems. The evidence shows that some people are simply more prone to it and some destinations are also a particular risk (e.g. Nepal and Madagascar).

Definitions

A slight change of bowel habit or loosening of the stools is to be expected with travel, which may be partly due to the stress of catching planes, different water, shaking hands, spicy food etc. This is not true travellers' diarrhoea...

Two working definitions for TD in adults are:

• You know it when you've got it, or
• Are you inconvenienced by it, i.e. incapacitated or have to change your planned activities as a result?

In children, a suitable, more cautious definition would be a doubling of the usual number of stools per day. Children are much more susceptible to fluid and electrolyte imbalance and tend to deteriorate more quickly.

Causes

In Europe, most cases of diarrhoea are viral in origin, so treatment is mainly supportive.

In tropical and developing countries, most TD (up to 80%) is likely to be caused by common bacteria, such as enterotoxigenic E. coli (ETEC), Campylobacter, Shigella, and non-invasive Salmonella species. Viruses typically account for about 15% of cases, and exotic protozoa (giardia, amoeba etc.) only 5%.

Prevention

• Good hand hygiene, including washing and rinsing your hands with soap and water is one of the best preventive measures. Alcohol hand gels/sprays, although always present on cruise ships, offer no significant protection against norovirus infection.

• Choice of food and establishment: Well-cooked, local food is generally the safest option when travelling. Salads or food (e.g. rice) that may have been sitting around for flies to land on, or reheated quickly for a tourist menu is much more likely to cause problems. The strongest predictive factor for travellers' diarrhoea in Nepal was found in one large, local study to be eating in a restaurant in Kathmandu (!), not drinking tea in a trailside teahouse, as one might expect.

• Vaccinations: The cholera vaccine, Dukoral, also provides 50% cross-protection against ETEC and is licensed for the prevention of travellers' diarrhoea in Canada. We tend to prescribe this vaccine (off label) much more for prevention of TD than for cholera, which is actually a very low risk in most travellers from the Global North, who have access too clean water and simple antibiotics.  'Hands-on' healthcare workers or this working on the ground in refugee camps would be an obvious exception to this.  

Oral typhoid vaccine (Vivotif) is also reported at international conferences to provide some protection against non-invasive species of Salmonella, which may cause TD.  However, this claim is not made by the manufacturer.

Self-treatment

• Rehydration with proper oral rehydration solution (ORS) is unquestionably the best treatment for travellers' diarrhoea. However, more readily available, improvised solutions such as flat Coca Cola with a lick of salt, or simply sipping clear fluids such as herbal teas can also make you feel a lot better.

• Over-the-counter medicines, such as loperamide (Imodium), can be of benefit for long plane, train or bus journeys. However, these only act to temporarily stop the gut moving, they do not address the disease process within or make you feel much better. In tropical countries, particularly high-risk destinations, or if on a short business trip, cycling or or mountain climbing, it may be worth considering taking some with you.

• Standby antibiotic treatment, such as azithromycin or ciprofloxacin (depending on the geographical location).  There are valid arguments for and against prescribing standby antibiotics for travellers' diarrhoea. Travel Medicine professionals internationally hold strong and widely divergent opinions on the matter. We at TrExMed certainly would not wish to encourage the unnecessary or reckless use of antibiotics, as they can do more harm than good both for the individual and at a population level. However, they can in some individual circumstances help to prevent long-term problems, such as post-infectious irritable bowel syndrome (PI-IBS), as well as providing a marginally quicker recovery.

• For young children, especially the under age two, if ORS fails to work, having some standby antibiotic suspension for parents to give sooner rather than later is certainly a very sensible precaution.

A couple of possible red herrings:

Diarrhoea that does not settle with rest, rehydration +/- antibiotics may be a symptom of dengue: One third of people with dengue fever present with diarrhoea, which is often mistaken (even by doctors in Asia) for gastroenteritis.

Diarrhoea may also be the presenting symptom for malaria.

In the summer months in Nepal, there are regular outbreaks of Cyclospora cayetanensis infection. There has also been an outbreak of this in 2016-17 in the Riviera Maya tourist area of Mexico. Cyclospora is a protozoal infection, which in addition to watery diarrhoea, can lead to prolonged symptoms of loss of appetite, weight loss, abdominal cramps, low-grade fever and profound fatigue lasting a few months. It needs a special stain or antibody test to confirm the diagnosis. There is a simple and effective treatment, although it is not an obvious choice for most Western doctors.

© Jim Bond, Apr 2019