OVERVIEW
Traveler’s diarrhea (DT) is defined as intestinal disturbances with three or more unformed stools per day, or a variable number of unformed stools accompanied by fever, abdominal pain, or vomiting, or even including more minor but sufficiently severe disturbances to interfere with travel plans, during or after travel.
Etiology
Currently, it is believed that DT is not caused by climate, food, soil or water, etc. The majority of DT is contagious, and its pathogens include bacteria, viruses, parasites, fungi, etc. In recent years, many new clinical findings have been discovered. In recent years, a number of new intestinal pathogens have been clinically identified, but some patients with diarrhea still fail to identify the cause and are referred to as non-specific acute gastroenteritis.
Symptoms
Pathogens that cause traveler’s diarrhea can be divided into two categories: non-invasive and invasive.
Most of the bacteria that cause food poisoning are non-invasive pathogens, systemic symptoms of poisoning is not obvious, no fever or obvious abdominal pain, diarrhea for watery stools, volume, not accompanied by acute and severe, easy to lead to water loss and acidosis, no inflammatory cells in the stools, the course of the disease is generally shorter.
Diarrhea caused by invasive pathogens, intestinal lesions are obvious, and inflammatory exudate can be excreted. Clinical features are systemic toxaemia symptoms are more obvious, there is fever, abdominal pain and urgency, diarrhea is mostly mucous blood stools, or bloody water stools, stools more often but less. Shigella, Salmonella, Pseudomonas aeruginosa, Campylobacter jejuni and some special viral diarrhea belong to this type.
Examination
1. Fecal microscopy
Fecal leukocytes are classified under a slide with 2 drops of methylene blue, in which the fecal specimen is coated well and a coverslip is added for 2-3 minutes for microscopic examination, and the exudative lesions are mainly multinucleated leukocytes.
2. Fecal culture
Routine fecal culture of pathogenic bacteria for 3 consecutive times and repeat if necessary.
3. Measurement of circulating antibodies
Most antibody detection systems (including hemagglutination inhibition, ELISA, etc.) are specific for viruses and bacteria, and changes in serum antibody titers have been used to determine the prevalence of norovirus, rotavirus, and the identification of ETEC, but immunofluorescence for antibodies against Giardia lamblia is prone to cross-reactivity.
4. Detection of enterotoxins
(1) Biological identification of ST toxin (because of its small molecular weight, other immunodiagnostic difficulties), hydrophilic Aeromonas enterotoxin, etc., can also be used in rabbit intestinal loop secretion test to detect ST and LT enterotoxin.
(2) Tissue culture method The classification of cytotoxins and LT enterotoxins can be performed with Y1 adrenal cells, Chinese vole oocytes (CHO) and other tissue culture cells.
(3) Biken test Consisting of the principles of the Elek and Ouchtertory test, it produces LT clones on agar plates that are able to differentiate enterotoxins by forming precipitation lines with anti-cholera antisera.
5. Viral RNA gel electrophoresis
Viral RNA can be extracted directly from fecal specimens, and the classification and rapid diagnosis of rotavirus can be carried out by polyacrylamide gel electrophoresis and silver staining according to characteristic RNA electrophoretic profiles.
6. DNA molecular hybridization test
Radiation autoradiography radionuclide labeling method is used for the detection of rotavirus and the detection of homologous DNA coding gene of EIEC enterotoxin.
7.DNA homology test
Genetic engineering technology to identify pathogenic Vibrio vulnificus, Escherichia coli enterotoxin-producing plasmids.
Diagnosis
According to the epidemiological history of the place where the patient traveled, the onset of the season, the clinical manifestations and stool characteristics are easy to make a clinical diagnosis, at the same time must determine whether there is dehydration (degree and nature), electrolyte disorders and acid-base imbalance, etc., and pay attention to the search for the cause of the disease.Diagnostic procedures of DT
1. Accurate collection of epidemiologic data
(1) Ask the patient about his/her diet, water intake, daily life and medication before diarrhea.
(2) Find out the patient’s previous illnesses, bowel habits, work and environment.
(3) Identify the epidemiologic history of diarrhea in the patient’s local area among people with the same diet.
(4) Understand the local circulating spectrum of pathogenic bacteria, the prevalence of bacteria (virulent) strains and group immunization status.
2. Objective understanding of clinical signs
Focus on the following clinical information: ① diarrhea mode of onset and course of the disease. ② diarrhea frequency, character and time pattern. The accompanying symptoms and signs of diarrhea. Abdominal signs include pressure, rebound pain, and bowel sounds. ⑤ The patient’s general condition includes consciousness, blood pressure, pulse and skin elasticity.
3. Rational selection of auxiliary laboratory tests
Clinicians must personally and carefully observe with the naked eye to understand the fecal characteristics and changes of diarrhea patients, rather than only relying on the laboratory report, in order to make a correct judgment, such as fecal characteristics can determine the location of the lesion: watery stools, no urgency, most of the lesions in the small intestine; mucus stools, most of the lesions in the colon; mucus with jam-colored blood stools, most of the lesions in the upper colon; peach blossom red pus and blood stools, most of the lesions in the lower colon; stool with blood on the surface or with obvious urgency, or with a clear blood in the colon; feces, blood in the surface or with a clear urgency. If there is blood on the surface or accompanied by obvious acute and post-acute symptoms, most of the lesions are in the rectum or the terminal colon, and the nature of the lesions can also be determined by the nature of the feces: watery stools, no inflammatory cells, and most of the lesions are non-invasive; mucus pus and blood stools, with a large number of inflammatory cells, and most of the lesions are invasive.
Treatment
DT is self-limiting and resolves spontaneously without specific treatment, however, oral rehydration and intravenous fluids help to replace lost water and electrolytes, and most patients do not become rapidly dehydrated, so mineral water (low-tension fluids with glucose) can usually be taken, providing a simple electrolyte fluid recipe: 1000 ml water with 1 tablespoon salt, 1 tablespoon soda and 4 tablespoons sugar; 1000 ml water with 1 tablespoon salt and 8 tablespoons sugar, both of which can be flavored with a small amount of apple juice, orange juice or honey.
When travelers develop diarrhea, they should fast for 8 to 12 hours and replenish electrolyte fluids, and should be hospitalized for severe cases.
For bacterial diarrhea, now mostly use fluoroquinolone antibiotics, microecological therapy helps to restore the ecological balance of the normal intestinal flora, inhibit pathogenic bacteria colonization and invasion, conducive to the control of diarrhea, commonly used bifidobacteria, lactobacillus and Streptococcus faecalis preparations. Intestinal mucosal protective agents can adsorb pathogens and toxins, maintain the absorption and secretion function of intestinal cells, and intestinal mucus glycoproteins interact with the barrier function can be enhanced, to prevent the attack of pathogenic microorganisms, such as hexadecagonal montmorillonite (Simida). Antidiarrheal drugs are intestinal peristalsis inhibitors, opioids (such as loperamide) act on the opioid receptors in the intestinal wall, preventing the release of acetylcholine and prostaglandins, thereby inhibiting intestinal peristalsis, indirectly by enhancing the synergistic transport of Na+, Cl-, or inhibiting secretion of calcium-dependent secretagogues-induced secretion of a direct role, reducing the loss of water and electrolytes, the drug has its strict indications and contraindications, and it is advisable to use the drug under the guidance of a doctor. The drug has its strict indications and contraindications, and should be used under the guidance of a doctor, in addition to astringent drugs (such as bismuth, activated charcoal) and anti-intestinal fluid secretion drugs.
For DT caused by Cryptosporidium and Cyclospora, if the patient’s immune function is sound and the symptoms are mild, generally no chemical treatment is needed, and supportive and symptomatic treatment can be given. For DT caused by fungi, supportive and symptomatic treatment should be accompanied by active antimicrobial therapy. Viral diarrhea is mostly self-limiting, and attention should be paid to correcting dehydration in pediatric and debilitated individuals.