MicrobiologyBytes

Travelers’ diarrhea is one of the most common illnesses affecting those who cross international borders for holiday, visiting family and friends, business, service work, or education. The World Tourism Organization estimates that nearly 1 billion people travel each year; travelers’ diarrhea will affect 20–60% of those who visit low-income countries. Because millions of travelers will be affected by travelers’ diarrhea, with many experiencing disruption to their planned activities and the potential loss of their investment in the trip, there has been much interest in the prevention and treatment of this common condition over the last five decades. Much of the evidence for the clinical description and management of travelers’ diarrhea was generated years ago, however, there is new information on geographic and host risk, etiology, and prevention strategies.

Travel to South Asia, followed by sub-Saharan Africa and South America, carries the highest risk for diarrheal syndromes in returned travelers. Women are more susceptible to travel-related diarrhea than men. Host genetic studies have demonstrated that single nucleotide polymorphisms in the lactoferrin, osteoprotegerin, and IL-10 genes are associated with small but increased risks for diarrhea and enteric pathogens. Enterotoxigenic Bacteroides fragilis is likely to be a new agent identified as causing travelers’ diarrhea, and heat-stable toxin-producing Escherichia coli appears to be more common than heat-labile toxin E. coli. Overall levels of sanitation at the travel destination, including individual eating establishments, are strong predictors for acquisition of travelers’ diarrhea. A new transdermal LT vaccine shows promise in modifying the severity of travelers’ diarrhea. It remains uncertain whether prophylaxis or prompt self-treatment of travelers’ diarrhea will prevent late-onset irritable bowel syndrome. For self-treatment, azithromycin is the drug of choice in travelers to areas where there is a high risk of fluoroquinolone-resistant Campylobacter spp., such as South and Southeast Asia and possibly North Africa, Central and South America.

There is increased understanding of the determinants of travelers’ diarrhea. Despite this travelers’ diarrhea remains one of the most common illnesses in travelers. Continued focus on intervention strategies may ultimately lead to decreased incidence.

Travelers’ diarrhea. Curr Opin Infect Dis. Jul 29 2010

Related:

• Viruses causing childhood diarrhoea in the developing world
• Metagenomic Analysis of Human Diarrhoea

Rotaviruses were discovered in 1972 when the virus was seen by direct electron microscopy visualization in the intestinal biopsies of children with acute diarrhoea. The authors of a new review discuss the most relevant information in the field of rotavirus vaccines published from October 2007 to June 2009; new information on the virus, host response and disease burden that relate to our understanding of vaccine mechanisms and impact are discussed. The review focusses on the role of the vaccines for the developing world but this does not preclude the relevance of these vaccines for children living in the industrialized world.

Immune mechanisms involved in rotavirus-associated immunity potentially relevant for vaccine-associated immunity continue to be identified including anti-NSP4 antibodies, cellular and mucosal mechanisms. Rotavirus-associated disease burden is high, causing approximately 40% of diarrhea-associated hospitalizations in children less than 5 years of age worldwide; G12, G8 and P[6] antigenic types emerging in developing countries are increasing in prevalence and may share worldwide circulation with the other five more common serotypes. The two currently available vaccines, based on different immune concepts, (VP7/VP4 homotypic specificity for RotaTeq vs. homotypic and heterotypic specificity for Rotarix) have demonstrated high and sustained efficacy in middle and high-income countries. Recent efficacy and effectiveness studies demonstrate acceptable protection levels in the poorest countries of the world against most antigenic types, leading to universal vaccine recommendation. Postlicensure surveillance has not detected any signal of increased risk for intussusception in children vaccinated with any of the two vaccines.

Rotavirus vaccines are well tolerated and provide adequate protection against moderate to severe disease in high, middle and low-income regions. Partnerships between governments, industry, and funding agencies will now be urgently needed to promote vaccine use, especially in the less privileged countries of the world.

Rotavirus vaccines for the developing world. 2009 Current Opinion in Infectious Diseases 22 (5): 483-489

Related:

• Rotavirus Infection: A Systemic Illness?

Globally, it is estimated that diarrhoeal disease results in about 1.87 million deaths in children less than 5 years, accounting for 19% of total child deaths. The majority of these diarrhoeal deaths (1.46 million, 76%) occur in the developing countries of Africa and south-east Asia. In industrialized countries, viral agents of gastroenteritis are the leading cause of acute watery diarrhoea in children. Recently, with improvements in hygiene, sanitation and water supply in developing countries, there has been a marked reduction in the number of bacterial pathogens, and an increasing proportion of diarrhoea hospitalizations that are attributed to viruses. This review focuses on recent studies that contribute to our understanding of the role of enteric viruses as important causes of diarrhoea in children in the developing world, examining epidemiology, pathogenesis and susceptibility.

With the use of sensitive molecular techniques, it is evident that a significant proportion of childhood diarrhoea is attributable to enteric viruses, with at least one viral agent in nearly 43% of samples from childhood diarrhoea in developing countries. Rotaviruses remain the most common pathogens in children, followed by noroviruses in almost all countries. There is increasing evidence that both rotaviruses and caliciviruses spread beyond the gut in a large proportion of infections. The review highlights the importance of viral agents of gastroenteritis in developing countries. Wider use of molecular techniques is resulting in rapid identification of new or emerging strains and in the detection of extra-intestinal spread. There is a need to better understand susceptibility and immune response to these agents to be able to design suitable interventions.

Viruses causing childhood diarrhoea in the developing world. 2009 Current Opinion in Infectious Diseases 22 (5): 477-82

Related:

• Metagenomic Analysis of Human Diarrhoea
• UK Norovirus Outbreak January 2008