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Prevention of Travellers’ Diarrhea: Strategies To Reduce the Risk

This report is based on medical evidence presented at sanctioned medical congress, from peer reviewed literature or opinion provided by a qualified healthcare practitioner. The consumption of the information contained within this report is intended for qualified Canadian healthcare practitioners only.

MEDI-NEWS - Based on CATMAT - An Advisory Committee Statement (ACS)

November 2015

Travellers’ diarrhea affects approximately half of those who travel to low- and middle-income countries. While often self-limiting, up to half of travellers who acquire travellers’ diarrhea will be inconvenienced by the condition and will have to curtail some of their activities while away. Food and water hygiene measures are recommended to help protect travellers against common bacteria that cause travellers’ diarrhea but the vast majority will break a food and water rule within the first 24 hours of travel. A common form of enterotoxigenic Escherichia coli (ETEC) is an important cause of travellers’ diarrhea against which there is an oral vaccine that offers some protection. Other prevention strategies include hand hygiene and multiple daily doses of bismuth subsalicylates. 

Chief Medical Editor: Dr. Léna Coïc, Montréal, Quebec

The risk of getting travellers’ diarrhea (TD) varies depending on destination, duration of stay, age of the traveller, presence of certain medical conditions and style of travel. Travellers who backpack through rural areas and who stay in rudimentary accommodation are typically at greater risk to develop TD than those who stay in well-managed resorts and hotels. Symptoms of TD in adults tend to occur early during the trip, with onset reported on average during the third or the fourth day of travel. Children and youth under the age of 20 have been reported to experience a later average onset at eight days.

TD is mainly acquired through the ingestion of food and beverages contaminated with pathogens that cause diarrhea. Bacterial pathogens cause over 80% of all TD and the most common of these bacterial pathogens include Escherichia coli, particularly enterotoxigenic E. coli (ETEC) as well as Campylobacter, according to the Committee to Advise on Tropical Medicine and Travel (CATMAT).  

Although TD is usually a mild and self-limiting disease, it has been reported that between 5% to 20% of travellers consulted a physician, nurse, or pharmacist, between 30% to 60% used some form of medication, and some individuals required hospitalization. The Public Health Agency of Canada also estimated that over half of travellers who visited travel clinics due to illness on their return were ill with acute diarrhea and close to 30% of reported cases of enteric disease in Canada are associated with international travel. More recently, Steffen et al. (JAMA 2015; 313:71) reported that between 3 to 17% of individuals who get TD will develop post-infectious irritable bowel syndrome (PI-IBS). Several factors have been associated with development of PI-IBS, including severity of TD, the number of episodes, pretravel diarrhea, pretravel adverse life events, and infection with heat-labile toxin–producing ETEC (LT-ETEC).

Thus, considerable support can be mustered for the prevention of TD especially among those who either cannot afford to have any downtime while travelling or those for whom an episode of diarrhea carries a greater burden of risk. Travellers are exposed to culprit bacteria almost always by eating contaminated food or drinking water—including ice cubes—that are carrying enterotoxic strains of E. coli.  Standard CATMAT precautions thus exhort travellers not to drink the local water and to practice vigilant food hygiene in order to minimize their risk; in practice, these measures often result in less-than-optimal success.

Alternatively, there is an oral killed whole-cells plus recombinant B-subunit vaccine, WC-rBS, licensed for use in Canada (Dukoral) approved for the prevention of TD caused by ETEC as well as cholera. Most enterotoxigenic E. coli (ETEC) strains produce an enterotoxin called heat-labile enterotoxin (LT) which is structurally, pathophysiologically and immunologically similar to the B-subunit cholera toxin. The WC-rBS vaccine (Dukoral) produces antibodies against the cholera toxin B subunit which confers protection against cholera as well as LT-producing ETEC.

ETEC is the most common pathogen causing TD in Latin America, the Caribbean and Africa, whereas in Southeast Asia, including Thailand, Campylobacter more commonly occurs. There are multiple aetiologies responsible for acute diarrhea in travellers, therefore the protective efficacy of Dukoral against all-cause TD will vary depending on the prevalence of LT producing ETEC.

 Should the Routine Use of Dukoral be Recommended?

In their 2015 statement on TD, CATMAT suggests that the WC-rBS vaccine (Dukoral) not be routinely administered to Canadian travellers as a means of preventing TD. Although routine use of Dukoral for TD prevention is not recommended by CATMAT, certain selected short-term travellers at high risk for health complications or serious inconvenience from TD may find that the potential benefits of the vaccine based on their personal values and preferences, coupled with a low likelihood of adverse events outweigh the burden of their risk. As such, the following travellers may still be considered for Dukoral vaccination:

  • those for whom a brief illness cannot be tolerated (i.e., elite athletes, some business or political travellers);
  • those with increased susceptibility to TD (e.g., due to achlorhydia, gastrectomy, history of repeated severe TD, young children > 2 years);
  • those who are immunosuppressed due to HIV infection with depressed CD4 count or other immunodeficiency states;
  • those with chronic illnesses for whom there is an increased risk of serious consequences from TD (e.g., chronic renal failure, congestive heart failure, insulin dependent diabetes mellitus, inflammatory bowel disease).

 Evidence-based Recommendations

The 2015 CATMAT statement on TD contains additional recommendations on preventative measures. For example, CATMAT highly recommends adult travellers at significant risk to consider taking bismuth subsalicylates (Pepto-Bismol) although they have to be willing to take multiple doses a day—ranging from 2.1 to 4.2 grams a day, divided into four daily doses. Based on CATMAT estimates, bismuth subsalicylates should result in 250 fewer cases of travellers’ diarrhea for every 1000 travellers treated. As a general rule, antibiotic use for prevention of TD should be avoided due to adverse events and increasing resistance patterns. However, CATMAT suggests that antibiotic use (e.g. fluoroquinolones, rifaximin) may be considered as an option in the prevention of TD in select high-risk short-term populations where chemoprophylaxis is considered essential.

Other Preventative Best Practices

Appropriate selection of food and beverages can reduce the risk of TD. Travellers should avoid consumption of undercooked or raw meats, including shellfish, as well as fruits and vegetables that are difficult to clean or peel. Foods that are prepared, stored, or served in unsanitary conditions should also be avoided. Interventions that promote hand washing can also reduce diarrheal episodes. Therefore, hand washing with soap and water is recommended before preparing meals, before eating meals, and after urination or defecation. In the absence of ready access to soap and water, alcohol-based hand sanitizers may aid in reducing the risk of diarrheal illness among travellers.

Questions and Answers

Questions and answers with Darin Cherniwchan, Medical Director, Fraser Valley Travel Clinic, Abbotsford, B.C. 

Q: Do you have any practical tips that you could share with us about what kind of advice you give your patients to avoid TDs?

A: The adage “Boil it. Cook it. Peel it. Or, Forget it.” is easy to say but hard to do. Studies have shown that well over 95% of travellers will break a traveller’s diarrhea food and water prevention rule within 24 hours of arrival overseas. Having said this, it is important to follow the TD “do’s and don’ts” to reduce pathogen load ingestion and the risk of ingesting spoiled or contaminated foods. If any of my patients experience “eater’s remorse,” I recommend they immediately chew two tablets of Pepto Bismol. (Eater’s remorse is when a traveller recognizes that a food tastes “off” or after a few swallows doesn’t appear well cooked). Prophylactic antibiotics are rarely used but may be considered in those at highest risk of the consequences of traveller’s diarrhea.

Q: CATMAT does not recommend routine use of Dukoral for all travellers but in your practice, what type of patients do you feel really can benefit from this vaccine? 

A: The CATMAT report unfortunately does not take into consideration the travel destination when considering Dukoral as a potential benefit. Dukoral has the greatest potential when travellers visit countries with the highest ETEC rates such as Mexico, Central America and Northwest South America. Certain countries in Africa such Tanzania and Indonesia have low ETEC rates and Dukoral may not be as beneficial in these areas. “High expectation” travellers such as honeymooners, business travellers, athletes and those who travel infrequently to higher risk destinations would all benefit from Dukoral. In addition, travellers to cholera risk areas such as Haiti should consider Dukoral as part of their pre-travel preparation. 

Q: Have you had any positive (or negative) feedback from your patients who have taken the vaccine before a trip?

A: I have received expressions of gratitude and thanks from travellers on a countless number of occasions who have taken Dukoral especially ones who have travelled in groups with significant numbers of Americans (Dukoral is not available in the USA)—reports from Canadian travellers who did not experience TD while the rest of the American contingent got sick despite everyone eating the same food and drinking the same beverages. If a traveller can afford approximately $45 per dose for Dukoral, then the decision to take the vaccine is an easy one especially if one has extended health benefits coverage. Prevention with a vaccine is a better approach than treatment with an antibiotic.

Q: What can parents do to protect their children?

A: Travelling with children is wonderful but can present unique challenges. I recommend that parents test a child’s food first as a child doesn’t have the luxury of having Pepto Bismol available if one experiences eater’s remorse.

Q: If patients do get TD, what advice do you give them to mitigate the symptoms? 

A: Hydration is the key for everyone—oral rehydration salts with reliable drinking water. The use of anti-motility agents such as loperamide helps reduce the frequency of the diarrhea and dehydration risk. A short course of a fluoroquinolone or azithromycin has been also shown to reduce the duration of the illness in most travellers. Diarrhea of unclear onset in travellers with longer itineraries are more likely to have parasitic infection requiring a much different treatment course of antimicrobials.

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