Traveler's diarrhea

Vaccines and Senior Travellers

Background: International tourist travel has been increasingly steadily in recent years, and looks set to reach unprecedented levels in the coming decades. Among these travellers, an increasing proportion is aged over 60 years, and is healthy and wealthy enough to be able to travel. However, senior travellers have specific risks linked to their age, health and travel patterns, as compared to their younger counterparts.

Methods: We review here the risk of major vaccine-preventable travel-associated infectious diseases, and forms and efficacy of vaccination for these diseases.

Results: Routine vaccinations are recommended for older persons, regardless of whether they travel or not (e.g., influenza, pneumococcal vaccines). Older individuals should be advised about the vaccines that are recommended for their age group in the framework of the national vaccination schedule. Travel-specific vaccines must be discussed in detail on a case-by-case basis, and the risk associated with the vaccine should be carefully weighed against the risk of contracting the disease during travel. Travel-specific vaccines reviewed here include yellow fever, hepatitis, meningococcal meningitis, typhoid fever, cholera, poliomyelitis, rabies, Japanese encephalitis, tick-borne encephalitis and dengue.

Conclusion: The number of older people who have the good health and financial resources to travel is rising dramatically. Older travellers should be advised appropriately about routine and travel-specific vaccines, taking into account the destination, duration and purpose of the trip, the activities planned, the type of accommodation, as well as patient-specific characteristics, such as health status and current medications.

Travelers' Diarrhea: A Clinical Review

BACKGROUND

Travelers' diarrhea is the most common travel-related malady. It affects millions of international travelers to developing countries annually and can significantly disrupt travel plans.

OBJECTIVE

To provide an update on the evaluation, diagnosis, treatment, and prevention of traveler's diarrhea.

METHODS

A PubMed search was completed in Clinical Queries using the key term "traveler's diarrhea". The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. The search was restricted to English literature. Patents were searched using the key term "traveler's diarrhea" from www.freepatentsonline.com.

RESULTS

Between 10% and 40% of travelers develop diarrhea. The attack rate is highest for travelers from a developed country who visit a developing country. Children are at particular risk. Travelers' diarrhea is usually acquired through ingestion of food and water contaminated by feces. Most cases are due to a bacterial pathogen, commonly, Escherichia coli, and occur within the first few days after arrival in a foreign country. Dehydration is the most common complication. Pretravel education on hygiene and on the safe selection of food items is important in minimizing episodes. For mild travelers' diarrhea, the use of antibiotic is not recommended. The use of bismuth subsalicylate or loperamide may be considered. For moderate travelers' diarrhea, antibiotics such as fluoroquinolones, azithromycin, and rifaximin may be used. Loperamide may be considered as monotherapy or adjunctive therapy. For severe travelers' diarrhea, antibiotics such as azithromycin, fluoroquinolones, and rifaximin should be used. Azithromycin can be used even for the treatment of dysentery whereas fluoroquinolones and rifaximin cannot be used for such purpose. Recent patents related to the management of travelers' diarrhea are discussed.

CONCLUSION

Although travelers' diarrhea is usually self-limited, many travelers prefer expedient relief of diarrhea, especially when they are traveling for extended periods by air or ground. Judicious use of an antimotility agent and antimicrobial therapy reduces the duration and severity of diarrhea.

'Holiday sickness'-reported exploratory outcome of over 500 United Kingdom holidaymakers with travellers' diarrhoea

AIMS

To ascertain any predictors of potential food poisoning pathogens and development of post-infective irritable bowel syndrome (IBS) in UK travellers. An analysis was undertaken on prospectively collected data on 527 patients reporting symptoms of suspected food poisoning between June 2012 and June 2015.

MAIN OUTCOME MEASURES

Positive stool sample indicative of food poisoning pathogens and diagnosis of post-infective IBS.

RESULTS

Data on 527 patients were examined. The large majority of patients did not provide a stool sample on return from holiday (n = 430, 81.6%) as few visited a Doctor locally or in the UK. Only 18 patients (18.6%, 95% confidence interval [CI] 11.4-27.7) who provided a stool sample were positive for microbiological food poisoning pathogens. Univariate analysis indicated a significant relationship between a positive stool sample and whether the individual sought any medical assistance at the resort (odds ratio [OR] 0.24, 95% CI 0.08-0.70) and whether they took any treatment (including self-medicated), (OR 0.21, 95% CI 0.06-0.67). Of the 527 patients only 30 (5.7%, 95% CI 3.9-8.1) experienced post-infective IBS. Univariate regression indicated a significant relationship between experiencing Per Rectal (PR) bleeding and a diagnosis of post-infective IBS (OR 3.64, 95% CI 1.00-10.49). Univariate regression also indicated an increase in the risk of developing post-infective IBS with increasing duration of symptoms (OR 1.04, 95% CI 1.02-1.05). No significant relationship was found between a positive stool sample and developing post-infective IBS (P = 0.307).

CONCLUSIONS

Very few patients provide a stool sample after experiencing holiday sickness abroad. Of those that do, only a small proportion have a positive stool sample indicative of a food poisoning microorganism. Around 6% of individuals were diagnosed with post-infective IBS. Those individuals with PR bleeding and symptoms persisting for longer durations were significantly more at risk of developing post-infective IBS, whilst medical aid and treatment abroad was found to reduce the odds of a positive stool sample.

Murine immunization with CS21 pili or LngA major subunit of enterotoxigenic Escherichia coli (ETEC) elicits systemic and mucosal immune responses and inhibits ETEC gut colonization

CS21 pili of enterotoxigenic Escherichia coli (ETEC) is one of the most prevalent ETEC colonization factors. CS21 major subunit, LngA, mediates ETEC adherence to intestinal cells, and contributes to ETEC pathogenesis in a neonatal mouse infection model. The objectives of this work were to evaluate LngA major subunit purified protein and CS21 purified pili on immunogenicity and protection against ETEC colonization of mice intestine. Recombinant LngA purified protein or purified CS21 pili from E9034A ETEC strain were evaluated for immunogenicity after immunization of C57BL/6 mice. Specific anti-LngA antibodies were detected from mice serum, feces, and intestine fluid samples by ELISA assays. Protection against gut colonization was evaluated on immunized mice orally challenged with wild type E9034A ETEC strain and by subsequent quantification of bacterial colony forming units (CFU) recovered from feces. Recombinant LngA protein and CS21 pili induced specific humoral and mucosal anti-LngA antibodies in the mouse model. CS21 combined with CT delivered intranasally as well as LngA combined with incomplete Freund adjuvant delivered intraperitoneally inhibited ETEC gut colonization in a mouse model. In conclusion, both LngA purified protein and CS21 pili from ETEC are highly immunogenic and may inhibit ETEC intestinal shedding. Our data on immunogenicity and immunoprotection indicates that CS21 is a suitable vaccine candidate for a future multivalent vaccine against ETEC diarrhea.

Prevalence of gastrointestinal parasites in children from Verón, a rural city of the Dominican Republic

Gastrointestinal infections impose a great and often silent burden of morbidity and mortality on poor populations in developing countries. The Dominican Republic (DR) is a nation on the island of Hispaniola in the Caribbean Sea. Verón is located in La Alta Grácia province in the southeastern corner of the DR. Dominican and Haitian migrant workers come to Verón to work in Punta Cana, a tourist resort area. Few definitive or comprehensive studies of the prevalence of gastrointestinal parasitic infections have been published in the DR. Historically, most of the definitive studies of water-borne or soil-transmitted parasites in the DR were published more than 30 years ago. Presently, there is a high prevalence of gastrointestinal parasitic infections throughout the poorest areas of the DR and Haiti. In this study we report the prevalence of gastrointestinal protozoan and helminth parasites from children recruited from the Clínica Rural de Verón during 2008 through 2011. Each participant was asked to provide a fecal sample which was promptly examined microscopically for protozoan and helminth parasites using the Centers for Disease Control and Prevention (CDC) fecal flotation technique to concentrate and isolate helminth ova and protozoan cysts. Of the 128 fecal samples examined, 127 were positive for one or more parasites. The age of the infected children ranged from 2–15 years; 61 were males and 66 were females. The only uninfected child was a 9 year old female. Percent infection rates were 43.8% for Ascaris lumbricoides, 8.5% for Enterobius vermicularis, 21.1% for Entamoeba histolytica, and 22.7% for Giardia duodenalis. Of the children examined, 7.8% had double infections. Any plan of action to reduce gastrointestinal parasites in children will require a determined effort between international, national, and local health authorities combined with improved education of schools, child care providers, food handlers, and agricultural workers. A special effort must be made to reach out to both documented and undocumented immigrants working or living in the area and to pre-school aged children or those who are not part of the public education system. Lastly, it is important to address the microbial water quality and food preparation, especially during the weaning transition to solid foods and throughout childhood.

Prevalence of gastrointestinal pathogens in developed and developing countries: systematic review and meta-analysis

ABSTRACT

Diarrhoeal illness is a leading cause of child mortality and morbidity worldwide. There are no precise or current estimates of the types and prevalence of pathogens associated with diarrheal illnesses in developed and developing settings. This systematic review assessed data from 60 studies published in the English language from five developing regions and developed countries worldwide to provide regional estimates of enteric pathogens affecting children. The random-effect method was used to establish the weighted average prevalence of pathogens in adults and children for each region. Significantly more pathogens were reported by studies from developing regions compared with Organisation for Economic Co-operation and Development countries (P<0.016). The identification rates of pathogens from community based and hospital based studies were similar (58.5% and 58.1% respectively, P<0.619). The overall detection of enteric pathogens in developing countries was higher in adults (74.8%; 95% CI 63.1-83.8%) compared with children (56.7%; 95% CI 53.0-60.4%) (P<0.001). Rotavirus was the most frequently detected pathogen in all regions with the highest rate, 24.8% (95% CI 18.0-33.1%), detected in the developed countries. This systematic review is the first to provide an estimate of the prevalence of enteric pathogens associated with diarrhoeal illnesses in adults and children in developed and developing settings. While pathogen detection rate is greater in developing regions the consistently high prevalence of rotavirus in both developed and developing settings underscores the urgent need for access to rotavirus vaccines. Increased travel between developing and developed countries increases disease risk, and hence developed countries have a vested interest in supporting vaccine accessibility in developing settings.

Effectiveness of the WC/rBS oral cholera vaccine in the prevention of traveler's diarrhea: a prospective cohort study

OBJECTIVE

Traveler's diarrhea (TD) is the most frequent disease among people from industrialized countries who travel to less developed ones, especially sub-Saharan Africa, Southern Asia and South America. The most common bacteria causing TD is enterotoxigenic Escherichia coli (ETEC). The WC/rBS cholera vaccine (Dukoral) has been shown to induce cross-protection against ETEC by means of the B subunit of the cholera toxin. The aim of the study was to evaluate the effectiveness of the WC/rBS cholera vaccine in preventing TD.

METHODS

Between May 1 and September 30 (2007), people seeking pre-travel advice in ten Spanish international vaccination centers were included in a prospective cohort study of travelers to cholera risk countries. The incidence rates of TD were adjusted for variables whose frequencies were statistically different (entry point 0.10) between the vaccinated and non-vaccinated cohorts.

FINDINGS

The vaccinated cohort (n = 544 travelers) included people vaccinated with the WC/rBS cholera vaccine, and the non-vaccinated cohort (n = 530 travelers) by people not vaccinated. The cumulative incidence rate of TD was 1.69 in vaccinated and 2.14 in non-vaccinated subjects. The adjusted relative risk of TD in vaccinated travelers was 0.72 (95% CI: 0.58-0.88) and the adjusted vaccination effectiveness was 28% (95% CI: 12-42).

CONCLUSIONS

The WC/rBS cholera vaccine prevents TD in 2 out of 7 travelers (preventive fraction: 28%). The number needed to vaccinate (NNV) to prevent 1 case of TD is 10.

Designing probiotics with respect to the native microbiome

It is now well known that genetic and environmental factors affect the intestinal microbiome in an individual’s lifetime and thus, different individuals possess different intestinal microbiomes and microbial metabolomes. The intestinal microbiome has been shown to differ among individuals from the same sex, between sexes and between individuals of different ages. Different families and, from a larger perspective, different communities, possess different microbiomes, and thus corresponding metagenomes. Therefore, it can be deduced that each individual human being can be characterized by his/her own intestinal microbial fingerprint. This understanding may prove helpful in future individualized medicine. These microorganisms are natural beneficial symbionts of the GI tract, have adapted to their human host over million years of coevolution and are now regarded as the second human genome. The difference in intestinal microbiome of different populations may explain why the results from different clinical trials on probiotic efficacy do not match with each other. People pay much, but they benefit little. In this article, it is recommended to isolate probiotics from natives’ microbiomes and in the interest of efficacy, to use them in the same population. This line of thought can be considered in future guidelines from the Food and Agriculture Organization and the WHO on evaluation of probiotics in foods.

Loop-mediated isothermal amplification assay for rapid detection of common strains of Escherichia coli

We developed a highly sensitive and specific LAMP assay for Escherichia coli. It does not require DNA extraction and can detect as few as 10 copies. It detected all 36 of 36 E. coli isolates and all 22 urine samples (out of 89 samples tested) that had E. coli. This assay is rapid, low in cost, and simple to perform.

Acute gastroenteritis in children: role of anti-emetic medication for gastroenteritis-related vomiting

Acute gastroenteritis is associated with significant morbidity in developed countries and each year is the cause of death of several million children in developing countries. Acute gastroenteritis is usually self-limiting. Oral rehydration therapy (ORT) is effective and successful in the majority of patients. Vomiting is common at the outset of viral gastroenteritis and can limit the effectiveness of ORT. Treatment with newer anti-emetic medications has been reported to facilitate ORT and to minimize the risk of dehydration and the need for intravenous hydration and hospitalization. The role of anti-emetic medications in the treatment of gastroenteritis-related vomiting is not clear. Some physicians agree with the use of anti-emetic medications because vomiting is unpleasant and distressing for the child and parents alike, and because vomiting can increase the likelihood of dehydration, electrolyte imbalance, and the need for intravenous hydration or hospitalization. Several surveys have shown that anti-emetic medications are commonly prescribed in the treatment of pediatric gastroenteritis and that adverse events are uncommon. Efficacy studies of the newer anti-emetic medications are now available and reveal that some are effective and help facilitate ORT. Other physicians disagree with the use of anti-emetic medications because acute gastroenteritis is a self-limiting condition, vomiting might help rid the body of toxic substances, there was previously a relative lack of published evidence of clinical benefit, and there are potential adverse events associated with the use of an anti-emetic medication. Anti-emetic medications that are currently available include ondansetron, granisetron, tropisetron, dolasetron, ramosetron, promethazine, dimenhydrinate, metoclopramide, domperidone, droperidol, prochlorperazine, and trimethobenzamide. Randomized, placebo-controlled trials suggest that ondansetron is efficacious and superior to other anti-emetic medications in the treatment of gastroenteritis-related vomiting. A recent double-blind clinical trial showed that a single oral dose of ondansetron reduces gastroenteritis-related vomiting and facilitates ORT without significant adverse events. Ondansetron shows promise as a first-line anti-emetic, and judicious use of this agent might increase the success of ORT, minimize the need for intravenous therapy and hospitalization, and reduce healthcare costs. Ondansetron should be considered in situations where vomiting hinders ORT, but a larger randomized, placebo-controlled trial is necessary before the medication can be routinely recommended for the treatment of gastroenteritis-related vomiting in children.