Generality
The traveler's diarrhea is an enteritis (infectious disease of the digestive tract) that affects subjects coming from countries with a high hygienic content when they go to developing areas. The areas at greatest risk are South-East Asia, India, Bangladesh and some countries in Africa and Central America, especially Mexico; the syndrome is particularly frequent also in North Africa and in the Middle East area.
The traveler's diarrhea is manifested by diarrheal syndromes of a secretory type, of varying severity, supported by E. Coli strains that do not invade the mucous membrane of the intestine, but are capable of determining alterations of intestinal transit through the production of enterotoxins.
In reality, however, the cause of traveller's diarrhea is variable and can be in 80% of cases of bacterial origin (in particular enterotoxigenic strains of E.Coli and less frequently Salmonella, Campylobacter, Staphylococci ), but also viral ( Rotavirus ) or from protozoa (parasites); in some cases it may be multiple.
The most severe form is generally the one supported by Campylobacter and the most mild by enterotoxic E.Coli (ETEC).
Epidemiology
The enterotoxigenic strains of E. coli have an ubiquitous spread (they are found everywhere), although their frequency is variable in the different geographical areas: they are particularly common in the countries of the South of the world, probably also due to the lower hygienic level observed in the there resident populations, and they are the most frequent cause of bacterial diarrhea worldwide.
To learn more: Which countries are at greater risk for traveler's diarrhea?
The "traveler's diarrhea" is the most frequent clinical problem during travel, with a much higher risk for those occurring in tropical areas, where food and beverage hygiene is not always perfect.
Risk factors
Furthermore, other problems such as the lack of sanitation infrastructure make it easier to contaminate water and food.
There may be factors favoring the extreme ages of life (children and the elderly), hypochloridria (the poor production of hydrochloric acid from the stomach), a deficit of the immune system and the adoption of lifestyles of local populations.
To learn more: Diarrhea of the traveler: what are the risk factors?
Contagion
The transmission is mostly fecal-oral: the infectious agent is eliminated with the faeces from the sick subject and who is infected comes to contact by oral way with the contaminated material of the same infected feces.
The transmission of the disease is therefore mainly linked to the quality of the water and the drinks taken . Among the non-infectious causes, the modification of eating habits and travel-related stress play an important role, which can exacerbate a pre-existing infectious diarrhea or bring out a quiescent intestinal pathology. The enterotoxigenic strains of E.Coli are however also widespread in the industrialized countries, where they can sustain as much epidemics more or less extended as sporadic cases in adults and children.
Mode of action of E.Coli
E. coli is a Gram Negative bacillus, ie it has an elongated shape and is colored red with the Gram stain, and belongs to the family of enterobacteria ( Enterobacteriaceae ). It is widespread in nature and is a normal inhabitant of the bacterial flora of the human intestine, as well as of the urinary tract, skin and vagina. The enterotoxigenic E. coli strains (ETEC) are capable of producing one or two distinct protein-based toxins: the thermostable toxin (ST) and the thermolabile one (LT), similar to that of cholera and capable of causing chlorine secretion and water in the lumen of the intestine. In addition to enterotoxin production, other factors appear to be necessary to cause the disease, including the ability of ETEC to adhere to epithelial cells of the small intestine. Due to the absence of invasive properties, ETEC strains are very rarely involved in extraintestinal E. coli infections.
Symptoms
To deepen: Symptoms Diarrhea of the Traveler
The onset is generally acute, brutal, after a short incubation period (24-48 hours), and is characterized by the presence of a watery diarrhea, accompanied by abdominal cramps and sometimes even vomiting and low-grade fever. The stools are liquid and light in color, they contain neither mucus nor blood nor white blood cells; the number of daily discharges is widely variable, but is usually between 4 and 8 in the 24 hours. The symptomatology appears more frequently during the first days of the journey (2nd-10th day).
Curiosity: Find out why the traveller's diarrhea is also called "Montezuma's revenge"
Diagnosis
The diagnostic ascertainment of cases suspected on the basis of epidemiological and clinical conditions is carried out by coproculture (faeces culture), which often allows to highlight the growth of E.Coli strains belonging to the enterotoxigenic ones. However, only special methods performed in specialized laboratories can demonstrate the precise mechanism responsible for individual cases; in this regard, tests (radioimmunological and immunoenzymatic) capable of identifying the thermolabile and thermostable toxin producing strains have been on the market only a few years ago.
Course and prognosis
In the adult the course is usually benign: the symptoms regress in 24-48 hours and disappear within a few days. In children, and particularly in infants, the clinical picture may become complicated due to the appearance of dehydration and alterations of the water balance and salts, which may evolve towards a clinical picture that may very closely remind that of cholera. The "traveler's diarrhea" usually has a rapid spontaneous healing (3-4 days); in 10% of cases it can last for more than 1 week.
Care and Therapy
To learn more: Drugs for the treatment of Traveler's Diarrhea
The treatment is mainly symptomatic and based on rehydration (administration of fluids orally and via a drip) and on the reintegration of salts lost with faeces and vomiting (especially potassium); antispasmodics and anti-diarrheal drugs are also useful, as are lactic acid supplements to restore intestinal flora integrity. In severe forms of the infant both rehydration therapy and supplementation with salts must be conducted according to the patterns usually used in cholera. Antibiotic therapy is indicated in cases where the symptomatology is very pronounced and / or protracted over time: in adults the first-choice drugs are fluoroquinolones, in children cotrimoxazole. If diarrhea is profuse (more than 4 shocks a day) and symptomatic therapy is not resolutive after 2-3 days, antibiotic treatment with a fluoroquinolone ( ciprofloxacin or norfloxacin ) is recommended; the "early" empirical therapy with a single dose of quinolonico is not shared by all.
Prevention
Prevention is based on hygienic rules suitable for reducing the occurrence and spread of infection in pediatric communities (control of both staff and laundry, immediate isolation of infected cases); it is also based on compliance with simple food hygiene rules and on the prophylactic use of drugs in selected cases. In countries at risk, the consumption of water and other beverages of dubious origin that are not sterilized or contained in sealed bottles should always be avoided, if possible for some hygienic practices such as cleaning the oral cavity, as well as for ingesting raw vegetables, fruit that cannot be peeled, raw meat and fish, seafood, cheese and homemade ice cream; cautiously the ban can be extended to any kind of food prepared or sold outdoors. Prophylaxis with fluoroquinolones in single doses ( doxycycline and cotrimoxazole, once used, are today less effective due to the widespread diffusion of E. Coli antibiotic resistance) is not advisable in all subjects who go to risk areas, given the potential toxicity of drugs and the risk of facilitating the appearance of resistance; instead, it should be reserved for those at risk of serious forms, such as people suffering from chronic intestinal inflammatory diseases due to HIV / AIDS or gastric hypoacidity, even pharmacologically induced, as well as for those who for work reasons cannot suspend their activity even for short periods periods. Vaccines against enterotoxigenic E.Coli strains are not yet available: partial coverage from traveller's diarrhea is provided by the oral anticolera vaccine.
