The Pharmaceutical Journal
Vol 268 No 7204 p917-918
29 June 2002

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Travellers' diarrhoea

by Larry Goodyer, PhD, MRPharmS

There is little doubt that for travellers the most commonly encountered health problem is that of an episode of diarrhoea, usually lasting no more than two or three days but in some case resulting in weeks or even months of illness. This condition is termed as "travellers' diarrhoea" (TD).

Symptoms

The defining characteristics of TD consist of three to four unformed stools in 24 hours and at least one of the following (enteric) symptoms: abdominal pain, nausea, vomiting, fever, cramps, blood or mucus in the stools and faecal urgency.

Symptoms that do not meet these criteria might be termed simply as "loose motions". If symptoms last more than 14 days the term persistent diarrhoea is used, and if lasting more than 30 days it is referred to as chronic diarrhoea. Extreme morbidity requiring admission to hospital is rare, although an episode of diarrhoea could well ruin an itinerary. It has been estimated that anywhere between 30 and 50 per cent of travellers from industrialised to developing countries will suffer from TD.

Causes

The cause of the problem is related to the ingestion of the causative organisms in food and drink. In about 30 per cent of cases the organism will be enterotoxigenic Escherichia coli (ETEC), which results in watery diarrhoea of usually no more than five days' duration. Other bacteria may induce more severe and prolonged diarrhoea, examples being Shigella spp and campylobacter. Parasites such as Entamoeba histolytica and Giardia lamblia are less common agents, responsible overall for about 5 per cent of cases and often causing a chronic diarrhoea. The type of organism does determine to an extent the presentation of the diarrhoea. Shigella spp for instance tends to result in dysentery, ie, blood and pus in the stools, and fever. Giardia lamblia is notorious for causing a great deal of flatulence and bloating, with a foul smelling loose motion.

A question sometimes asked by travellers is that if the cause of TD is ingestion of contaminated food and water, why does the local population not suffer from the same incidence of diarrhoea as the traveller? The answer lies in the observation that the incidence of TD in some destinations is similar to the incidence of diarrhoeal illness in children that are living in that country. Furthermore, it has been found that travellers who normally live in a developing country will have less diarrhoea than those from industrialised countries. The poor sanitation and hygiene that exists in some developing countries allows the widespread contamination of food and water, severely affecting babies and children, resulting in a high incidence of mortality. Those who survive develop a degree of resistance in adulthood. However, travellers should not assume that if they suffer one or two episodes of diarrhoea during their trip that they will develop immunity. It was found in a large study among expatriates living in Nepal that the incidence of diarrhoea due to ETEC did not fall until after three months of residence. One curious finding, that no one has been able to explain, is that those travelling from the UK have a significantly higher incidence of diarrhoea than those people travelling from other industrialised nations.

Prevention

To reduce the risk of contracting TD it is recommended to avoid contaminated food and water. Unfortunately there is little strong evidence that those who do follow such advice actually suffer fewer bouts of diarrhoea, probably because it is hard to stick completely to the recommendations throughout a trip. None the less it is appropriate to try to avoid the riskiest situations, if only to reduce the likelihood of contracting one of the more severe or chronic forms of TD. The advice "Boil it, peal it or forget it" should be followed, where in general it is safest to only eat freshly cooked and hot food, or raw fruit and vegetables that have been peeled. In addition travellers should be aware of the risks from poorly cleaned cutlery and cups. Water is also best boiled or sterilised with a halogen such as chlorine or iodine. Alternatively bottled water is often easily obtained. However there is a danger that such bottles might have been simply filled with "counterfeit" water from a tap.

Management

TD is not thought of as a clinically dehydrating condition in healthy adults. So, providing an adequate fluid intake is maintained, with most moderate bouts of diarrhoea dehydration should not occur. For this reason the use of oral electrolyte solutions is not strictly necessary, other than in the very young or elderly. Hydration is adequately maintained by ordinary drinks while continuing to eat reasonably bland foods; the combination of sugary drinks with salt crackers has been claimed to be ideal. It is best to avoid fruit and cola drinks, which may contain more fructose exerting an osmotic effect holding fluid in the bowel. Despite this I still often recommend that some travellers carry a supply of rehydration salts, because in some situations access to suitable drinks and food may be limited. One drawback to the aggressive use of electrolyte salts is that a fluid diarrhoea is still produced adding further to the inconvenience of the problem. In this respect Dioralyte Relief seems to offer a potential solution because, being starch rather than glucose-based, this formulation is claimed to form a bulkier stool.

There has been reluctance among health professionals to recommend the use of antidiarrhoeals for TD. This is based on the fear that the offending organism and any associated toxins are held in the bowel, prolonging the course of the diarrhoea. There is no evidence that this is a danger, except possibly in the presence of dysenteric symptoms. Therefore, a short course of loperamide can usually be recommended for adults to relieve the symptoms of diarrhoea, particularly when they might otherwise disrupt travel plans. It would be prudent to ensure a good level of hydration even if taking loperamide.

The other somewhat contentious issue is whether or not to use antibiotics. Just a single dose of 500mg ciprofloxacin has been shown to reduce the duration of TD to under 24 hours, although TD is not a licensed indication for this antibiotic. Some would argue that since TD is a self limiting condition the use of antibiotics is not warranted. On the other hand for those on short important trips, eg, business or political, the duration of the illness may be critical. Those with protozoal infections would require metronidazole. There are few indications for prophylactic antimicrobial therapy.

In summary the following course of action might be recommended for the self management of TD in healthy adults:

• Mild TD with only one or two loose stools in 24 hours would require no particular treatment, provided the person remains hydrated
• For mild-to-moderate diarrhoea, loperamide could be used, perhaps adding an antimicrobial if the symptoms worsen or are distressing. A single dose is sufficient, but if symptoms persists longer than 24 hours or there are dysenteric symptoms a full three-day course may be required, eg, ciprofloxacin 500mg twice daily
• For severe dysenteric symptoms a full course of an appropriate antimicrobial should be taken