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The bug stops here: assessing the real impact of cholera for travellers

The bug stops here: assessing the real impact of cholera for travellers

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Christian Herzog
MD
DCH (London)
DTM&H (Liverpool)
Medical Affairs
Crucell

Crucell
W: www.crucell.co.uk
T: 0844 800 3907
E: info@crucell.co.uk

For many UK holidaymakers and business travellers, cholera represents a potentially unrecognised risk. Dukoral® is a drinkable oral vaccine that protects against cholera and has proven efficacy and tolerability.

Every year UK travellers return to the UK having contracted cholera abroad.1 The World Health Organization (WHO) estimates that the true extent of this infectious disease is grossly under-reported, with 90% of global cholera cases going unreported every year.2,3 Although potentially fatal, for most healthy travellers from developed countries the symptoms are non-fatal but can result in severe diarrhoeal symptoms that impair the trip and cause complications on their return.
Therefore, for many UK holidaymakers and business travellers, cholera represents a potentially unrecognised risk. Dukoral® (wholecell Vibrio cholerae O1 with purified recombinant cholera B subunit [WC/rBS]) is a drinkable oral vaccine that protects against cholera and has proven efficacy and tolerability.4

Diarrhoeal disease is the most common illness in travellers abroad, affecting 30–50% of visitors to developing countries.5 Travellers' diarrhoea (TD) may be caused by several organisms that are transmitted in contaminated food or water, with the majority of cases caused by bacteria.6,7 TD is often self-limiting, lasting three to four days, and treatment to prevent dehydration is usually sufficient. However, more severe cases require medical attention, and some patients may develop post-infection lactose intolerance or irritable bowel syndrome.6,8 In all cases, TD has a negative impact on quality of life and the enjoyment of a leisure trip or the utility of a business trip.

Travel case study
Cholera has an extremely short incubation period (2 hours to 5 days),3 which means that infection and symptoms among travellers generally occur during a trip, and mild-to-moderate courses of cholera infection may not be detected. In a report of 27 French tourists travelling in India for 9 days in 2006, 23 (85%) experienced diarrhoea during or after the trip. One of the travellers sought medical attention when back in France and was found to have cholera. The other group members were tested, and 4 of the 23 travellers with diarrhoea tested positive for cholera, highlighting that imported cases can go undetected in industrialised countries.9

Cholera, one of the bacterial causes of TD, is an acute intestinal infection caused by eating food or drinking water contaminated with the Vibrio cholerae bacteria. Mild-to-moderate cases of cholera may be indistinguishable from other causes of TD.7 Around 80% of cholera infections are mild-to-moderate in nature, with many patients experiencing no symptoms. Among the remaining cases, 10–20% of patients develop severe watery diarrhoea that can lead to severe dehydration, kidney failure and ultimately death. If untreated, cholera has a mortality rate of 50%, but this can be lowered to 1% with adequate rehydration measures.3

Cholera remains a global threat to public health and is currently present in parts of Asia, Africa and South America, with other countries reporting imported cases among travellers (see Figure 1). Global trends in the incidence of cholera show a steady increase since the beginning of the millennium, with a 24% increase for the period 2004–2008.11 The WHO estimates that fewer than 10% of global cases are reported because of surveillance difficulties and economic disincentives to report, and that the actual global disease burden is 3–5 million cases and 100,000–130,000 deaths per year.2,3

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Travel health consultations will generally include advice on standard protective measures to avoid contracting diarrhoeal disease, with avoidance of contaminated food and water being the first line of defence against water-borne illnesses.6 However, for certain travellers, there may be a requirement for vaccination to protect against cholera.

Dukoral® is the only licensed cholera vaccine in the UK.12 Dukoral® is indicated for active immunisation against disease caused by Vibrio cholerae serogroup O1 in adults and children from two years of age who will be visiting endemic/epidemic areas, and has protective efficacy of up to 85%.3 Dukoral® is well tolerated and over 94,000 doses of Dukoral® have been administered during the clinical trials. The most frequently reported adverse reactions, such as gastrointestinal symptoms including abdominal pain, diarrhoea, loose stools, and nausea, occurred at similar frequencies in vaccine and placebo groups.4

The decision to prescribe any travel vaccine will always depend on the individual patient and their planned travel itinerary. Factors informing this decision for cholera vaccination will include the epidemiology in different geographical regions, the patient's specific risk of contracting the disease, and their perception of risk and the impact diarrhoeal disease would have on their trip.4,13 For those patients suitable for vaccination, Dukoral® provides effective protection against cholera, one of the bacterial causes of TD.

Risk groups7,8

  • Travellers with a predisposition:
    - insufficient gastric acid barrier
    - immunocompromised patients
  • Travellers with a risk of a severe course:
    - chronic inflammatory bowel diseases
    - chronic diseases with higher risk of complications through imbalance of fluid and electrolytes
  • Healthcare personnel working in an endemic area
  • Travellers to endemic areas staying in
    - unsanitary and crowded conditions:
    - certain backpackers
    - travellers who are going to visit friends and relatives
    - military personnel in areas of conflict

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References
1. Health Protection Agency. Foreign travel-associated illness. London: HPA; 2007.
2. World Health Organization. Cholera vaccines: WHO position paper. Weekly Epidemiological Record 2010;85:117–128.
3. World Health Organization. Cholera Fact sheet N°107. Geneva: WHO; 2008.
4. Dukoral® Summary of Product Characteristics. March 2009.
5. Health Protection Agency. Travellers’ Diarrhoea. Available from: www. hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/TravellersDiarrhoea (accessed 21 April 2010)
6. National Travel Health Network and Centre. Travellers’ Diarrhoea. Available from: www.nathnac.org/pro/factsheets/trav_dir.htm (accessed 21 April 2010)
7. Zuckerman JN, Rombo L, Fisch A et al. The true burden and risk of cholera: implications for prevention and control. Lancet Infect Dis 2007;7:521–530.
8. Weinke T, Liebold I, Burchard GD et al. Prophylactic immunisation against travellers’ diarrhoea caused by enterotoxin-forming strains of Escherichia coli and against cholera: does it make sense and for whom? Travel Med Infect Dis 2008;6:362–367.
9. Tarantola A et al. A cluster of Vibrio cholerae O1 infections in French travelers to Rajasthan (India), May 2006. J Travel Med 2008;15:273–7.
10. Adapted from: World Health Organization. Global Health Observatory Map Gallery. Available from: http://gamapserver.who.int/mapLibrary/Files/Maps/
Global_CholeraCases0709_20091008.png (accessed 21 April 2010)
11. World Health Organization. Cholera: global surveillance summary, 2008. Weekly Epidemiological Record 2009;84:309–324.
12. Joint Formulary Committee. British National Formulary 59. London: BMA; 2010.
13. Lundkvist J et al. Cost–Benefit of WC/rBS oral cholera vaccine for vaccination against ETEC-Caused travelers’ diarrhea. J Travel Med 2009;16:28–34.

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