The FDA has published guidelines to help reduce the chance of food-borne salmonellosis. Food must be cooked to 68–72 °C (145–160 °F), and liquids such as soups or gravies must be boiled. Freezing kills some "Salmonella", but it is not sufficient to reliably reduce them below infectious levels. While "Salmonella" is usually heat-sensitive, it does acquire heat resistance in high-fat environments such as peanut butter.

Antibodies against nontyphoidal "Salmonella" were first found in Malawi children in research published in 2008. The Malawian researchers have identified an antibody that protects children against bacterial infections of the blood caused by nontyphoidal "Salmonella". A study at Queen Elizabeth Hospital in Blantyre found that children up to two years old develop antibodies that aid in killing the bacteria. This could lead to a possible "Salmonella" vaccine for humans.

A recent study has tested a vaccine on chickens which offered efficient protection against salmonellosis.

Vaccination of chickens against "Salmonella" essentially wiped out the disease in the United Kingdom. A similar approach has been considered in the United States, but the Food and Drug Administration decided not to mandate vaccination of hens.

Cultures of stool samples are examined to identify the organism causing dysentery. Usually, several samples must be obtained due to the number of amoebae, which changes daily. Blood tests can be used to measure abnormalities in the levels of essential minerals and salts.

It may be difficult to associate a particular case of diarrhea with a recent wilderness trip of a few days because incubation of the disease may outlast the trip. Studies of trips that are much longer than the average incubation period, e.g. a week for "Cryptosporidium" and "Giardia", are less susceptible to these errors since there is enough time for the diarrhea to occur during the trip. Other bacterial and viral agents have shorter incubation periods, although hepatitis may require weeks.

A suspected case of wilderness-acquired diarrhea may be assessed within the general context of intestinal complaints. During any given four-week period, as many as 7.2% of Americans may experience some form of infectious or non-infectious diarrhea. There are an estimated 99 million annual cases of intestinal infectious disease in the United States, most commonly from viruses, followed by bacteria and parasites, including Giardia and Cryptosporidium. There are an estimated 1.2 million U.S. cases of symptomatic giardiasis annually. However, only about 40% of cases are symptomatic.

One study suggests that on very long trips in the wilderness, taking multivitamins may reduce the incidence of diarrhea.

With most infections, the key is to block the spread of the organism.

- Wash hands frequently

- Eat properly prepared and stored food.

- Bleach soiled laundry

- Vaccinations for "Vibrio cholerae" and rotavirus have been developed. Rotavirus vaccination is recommended for infants in the U.S. Vaccines for "V. cholerae" may be administered to individuals traveling to at-risk areas

A clinical diagnosis may be made by taking a history and doing a brief examination. Treatment is usually started without or before confirmation by laboratory analysis.

The doctor will take a medical history to make sure that nothing else is causing the symptoms. Also, the doctor might perform a rectal or abdominal examination to exclude the possibilities of inflammatory bowel disease (e.g., Crohn’s disease) and pelvic abscesses (pockets of pus). A stool culture (a laboratory test to identify bacteria and other organisms from a sample of feces) can be used to determine the specific virus or germ that is causing gastroenteritis.

Specimen: Fresh stool is collected.

Culture: Specimen is inoculated on selective media like McConkey's agar, DCA, XLD agar. Selenite F broth(0.4%) is used as enrichment medium which permits the rapid growth of enteric pathogens while inhibiting the growth of normal flora like "E. coli" for 6–8 hours. Subculture is done on the solid media from selenite F broth. All the solid media are incubated at 37 degrees for 24 hours.

Cultural characteristics: Colorless (NLF) colonies appear on McConkey's agar which are further confirmed by gram staining, hanging drop preparation and biochemical reactions.

A determination of whether or not the person has dehydration is an important part of the assessment, with dehydration typically divided into mild (3–5%), moderate (6–9%), and severe (≥10%) cases. In children, the most accurate signs of moderate or severe dehydration are a prolonged capillary refill, poor skin turgor, and abnormal breathing. Other useful findings (when used in combination) include sunken eyes, decreased activity, a lack of tears, and a dry mouth. A normal urinary output and oral fluid intake is reassuring. Laboratory testing is of little clinical benefit in determining the degree of dehydration. Thus the use of urine testing or ultrasounds is generally not needed.

"Campylobacter" organisms can be detected by performing a Gram stain of a stool sample with high specificity and a sensitivity of ~60%, but are most often diagnosed by stool culture. Fecal leukocytes should be present and indicate the diarrhea to be inflammatory in nature. Methods currently being developed to detect the presence of campylobacter organisms include antigen testing via an EIA or PCR.

The diagnosis of shigellosis is made by isolating the organism from diarrheal fecal sample cultures. "Shigella" species are negative for motility and are generally not lactose fermenters, but "S. sonnei" can ferment lactose. They typically do not produce gas from carbohydrates (with the exception of certain strains of "S. flexneri") and tend to be overall biochemically inert. "Shigella" should also be urea hydrolysis negative. When inoculated to a triple sugar iron slant, they react as follows: K/A, gas -, and HS -. Indole reactions are mixed, positive and negative, with the exception of "S. sonnei", which is always indole negative. Growth on Hektoen enteric agar produces bluish-green colonies for "Shigella" and bluish-green colonies with black centers for "Salmonella".

Gastroenteritis is typically diagnosed clinically, based on a person's signs and symptoms. Determining the exact cause is usually not needed as it does not alter management of the condition.

However, stool cultures should be performed in those with blood in the stool, those who might have been exposed to food poisoning, and those who have recently traveled to the developing world. It may also be appropriate in children young than 5, old people, and those with poor immune function. Diagnostic testing may also be done for surveillance. As hypoglycemia occurs in approximately 10% of infants and young children, measuring serum glucose in this population is recommended. Electrolytes and kidney function should also be checked when there is a concern about severe dehydration.

Recommendations include avoidance of questionable foods and drinks, on the assumption that TD is fundamentally a sanitation failure, leading to bacterial contamination of drinking water and food. While the effectiveness of this strategy has been questioned, given that travelers have little or no control over sanitation in hotels and restaurants, and little evidence supports the contention that food vigilance reduces the risk of contracting TD, guidelines continue to recommend basic, common-sense precautions when making food and beverage choices:

- Maintain good hygiene and use only safe water for drinking and brushing teeth.

- Safe beverages include bottled water, bottled carbonated beverages, and water boiled or appropriately treated by the traveler (as described below). Caution should be exercised with tea, coffee, and other hot beverages that may be only heated, not boiled.

- In restaurants, insist that bottled water be unsealed in your presence; reports of locals filling empty bottles with untreated tap water and reselling them as purified water have surfaced. When in doubt, a bottled carbonated beverage is the safest choice, since it is difficult to simulate carbonation when refilling a used bottle.

- Avoid ice, which may not have been made with safe water.

- Avoid green salads, because the lettuce and other uncooked ingredients are unlikely to have been washed with safe water.

- Avoid eating raw fruits and vegetables unless cleaned and peeled personally.

If handled properly, thoroughly cooked fresh and packaged foods are usually safe. Raw or undercooked meat and seafood should be avoided. Unpasteurized milk, dairy products, mayonnaise, and pastry icing are associated with increased risk for TD, as are foods and beverages purchased from street vendors and other establishments where unhygienic conditions may be present.

For the detection of "Staphylococcus aureus" food poisoning which can lead to staphylococcal enteritis a stool culture may be required. A stool culture is used to detect the presence of disease-causing bacteria (pathogenic) and help diagnose an infection of the digestive tract. In the case of staphylococcal enteritis, it is conducted to see if the stool is positive for a pathogenic bacterium.

Simple precautions can be taken to prevent getting shigellosis: wash hands before handling food and thoroughly cook all food before eating. The primary prevention methods are improved sanitation and personal and food hygiene, but a low-cost and efficacious vaccine would complement these methods.

Since shigellosis is spread very quickly among children, keeping infected children out of daycare for 24 hours after their symptoms have disappeared, will decrease the occurrence of shigellosis in daycares.

Although safe bottled water is now widely available in most remote destinations, travelers can treat their own water if necessary, or as an extra precaution.

Techniques include boiling, filtering, chemical treatment, and ultraviolet light; boiling is by far the most effective of these methods. Boiling rapidly kills all active bacteria, viruses, and protozoa. Prolonged boiling is usually unnecessary; most microorganisms are killed within seconds at water temperature above 55–70 °C (130–160 °F). The second-most effective method is to combine filtration and chemical disinfection. Filters eliminate most bacteria and protozoa, but not viruses. Chemical treatment with halogens—chlorine bleach, tincture of iodine, or commercial tablets--have low-to-moderate effectiveness against protozoa such as "Giardia", but work well against bacteria and viruses.

UV light is effective against both viruses and cellular organisms, but only works in clear water, and it is ineffective unless manufacturer's instructions are carefully followed for maximum water depth/distance from UV source, and for dose/exposure time. Other claimed advantages include short treatment time, elimination of the need for boiling, no taste alteration, and decreased long-term cost compared with bottled water. The effectiveness of UV devices is reduced when water is muddy or turbid; as UV is a type of light, any suspended particles create shadows that hide microorganisms from UV exposure.

With colonoscopy it is possible to detect small ulcers of between 3–5mm, but diagnosis may be difficult as the mucous membrane between these areas can look either healthy or inflamed.

Asymptomatic human infections are usually diagnosed by finding cysts shed in the stool. Various flotation or sedimentation procedures have been developed to recover the cysts from fecal matter and stains help to visualize the isolated cysts for microscopic examination. Since cysts are not shed constantly, a minimum of three stools are examined. In symptomatic infections, the motile form (the trophozoite) is often seen in fresh feces. Serological tests exist, and most infected individuals (with symptoms or not) test positive for the presence of antibodies. The levels of antibody are much higher in individuals with liver abscesses. Serology only becomes positive about two weeks after infection. More recent developments include a kit that detects the presence of amoeba proteins in the feces, and another that detects ameba DNA in feces. These tests are not in widespread use due to their expense.

Microscopy is still by far the most widespread method of diagnosis around the world. However it is not as sensitive or accurate in diagnosis as the other tests available. It is important to distinguish the "E. histolytica" cyst from the cysts of nonpathogenic intestinal protozoa such as "Entamoeba coli" by its appearance. "E. histolytica" cysts have a maximum of four nuclei, while the commensal "Entamoeba coli" cyst has up to 8 nuclei. Additionally, in "E. histolytica," the endosome is centrally located in the nucleus, while it is usually off-center in "Entamoeba coli." Finally, chromatoidal bodies in "E. histolytica" cysts are rounded, while they are jagged in "Entamoeba coli". However, other species, "Entamoeba dispar" and "E. moshkovskii", are also commensals and cannot be distinguished from "E. histolytica" under the microscope. As "E. dispar" is much more common than "E. histolytica" in most parts of the world this means that there is a lot of incorrect diagnosis of "E. histolytica" infection taking place. The WHO recommends that infections diagnosed by microscopy alone should not be treated if they are asymptomatic and there is no other reason to suspect that the infection is actually "E. histolytica". Detection of cysts or trophozoites stools under microscope may require examination of several samples over several days to determine if they are present, because cysts are shed intermittently and may not show up in every sample.

Typically, the organism can no longer be found in the feces once the disease goes extra-intestinal. Serological tests are useful in detecting infection by "E. histolytica" if the organism goes extra-intestinal and in excluding the organism from the diagnosis of other disorders. An Ova & Parasite (O&P) test or an "E. histolytica" fecal antigen assay is the proper assay for intestinal infections. Since antibodies may persist for years after clinical cure, a positive serological result may not necessarily indicate an active infection. A negative serological result however can be equally important in excluding suspected tissue invasion by "E. histolytica".

To date, no licensed vaccines specifically target ETEC, though several are in various stages of development. Studies indicate that protective immunity to ETEC develops after natural or experimental infection, suggesting that vaccine-induced ETEC immunity should be feasible and could be an effective preventive strategy. Prevention through vaccination is a critical part of the strategy to reduce the incidence and severity of diarrheal disease due to ETEC, particularly among children in low-resource settings. The development of a vaccine against this infection has been hampered by technical constraints, insufficient support for coordination, and a lack of market forces for research and development. Most vaccine development efforts are taking place in the public sector or as research programs within biotechnology companies. ETEC is a longstanding priority and target for vaccine development for the World Health Organization.

Treatment for ETEC infection includes rehydration therapy and antibiotics, although ETEC is frequently resistant to common antibiotics. Improved sanitation is also key. Since the transmission of this bacterium is fecal contamination of food and water supplies, one way to prevent infection is by improving public and private health facilities. Another simple prevention of infection is by drinking factory bottled water—this is especially important for travelers and traveling military—though it may not be feasible in developing countries, which carry the greatest disease burden.

The following types of diarrhea may indicate further investigation is needed:

- In infants

- Moderate or severe diarrhea in young children

- Associated with blood

- Continues for more than two days

- Associated non-cramping abdominal pain, fever, weight loss, etc.

- In travelers

- In food handlers, because of the potential to infect others;

- In institutions such as hospitals, child care centers, or geriatric and convalescent homes.

A severity score is used to aid diagnosis in children.

Numerous studies have shown that improvements in drinking water and sanitation (WASH) lead to decreased risks of diarrhoea. Such improvements might include for example use of water filters, provision of high-quality piped water and sewer connections.

In institutions, communities, and households, interventions that promote hand washing with soap lead to significant reductions in the incidence of diarrhea. The same applies to preventing open defecation at a community-wide level and providing access to improved sanitation. This includes use of toilets and implementation of the entire sanitation chain connected to the toilets (collection, transport, disposal or reuse of human excreta).

The World Health Organization recommends the following:

- Food should be properly cooked and hot when served.

- Consume only pasteurized or boiled milk and milk products, never raw milk products.

- Make sure that ice is from safe water.

- If you are not sure of the safety of drinking water, boil it, or disinfect it with chemical disinfectant.

- Wash hands thoroughly and frequently with soap, especially after using the toilet and after contact with pets and farm animals.

- Wash fruits and vegetables thoroughly, especially if they are to be eaten raw. Peel fruits and vegetables whenever possible.

- Food handlers, professionals and at home, should observe hygienic rules during food preparation.

- Professional food handlers should immediately report to their employer any fever, diarrhea, vomiting or visible infected skin lesions.

A rapid dipstick test is available to determine the presence of "V. cholerae". In those samples that test positive, further testing should be done to determine antibiotic resistance. In epidemic situations, a clinical diagnosis may be made by taking a patient history and doing a brief examination. Treatment is usually started without or before confirmation by laboratory analysis.

Stool and swab samples collected in the acute stage of the disease, before antibiotics have been administered, are the most useful specimens for laboratory diagnosis. If an epidemic of cholera is suspected, the most common causative agent is "V. cholerae" O1. If "V. cholerae" serogroup O1 is not isolated, the laboratory should test for "V. cholerae" O139. However, if neither of these organisms is isolated, it is necessary to send stool specimens to a reference laboratory.

Infection with "V. cholerae" O139 should be reported and handled in the same manner as that caused by "V. cholerae" O1. The associated diarrheal illness should be referred to as cholera and must be reported in the United States.

Treatment for colitis-X usually does not save the horse. The prognosis is average to poor, and mortality is 90% to 100%. However, treatments are available, and one famous horse that survived colitis-X was U.S. Triple Crown winner Seattle Slew, that survived colitis-X in 1978 and went on to race as a four-year-old.

Large amounts of intravenous fluids are needed to counter the severe dehydration, and electrolyte replacement is often necessary. Flunixin meglumine (Banamine) may help block the effects of toxemia. Mortality rate has been theorized to fall to 75% if treatment is prompt and aggressive, including administration of not only fluids and electrolytes, but also blood plasma, anti-inflammatory and analgesic drugs, and antibiotics. Preventing dehydration is extremely important. Nutrition is also important. Either parenteral or normal feeding can be used to support the stressed metabolism of the sick horse. Finally, the use of probiotics is considered beneficial in the restoration of the normal intestinal flora. The probiotics most often used for this purpose contain "Lactobacillus" and "Bifidobacterium".

Dysentery is initially managed by maintaining fluid intake using oral rehydration therapy. If this treatment cannot be adequately maintained due to vomiting or the profuseness of diarrhea, hospital admission may be required for intravenous fluid replacement. Ideally, no antimicrobial therapy should be administered until microbiological microscopy and culture studies have established the specific infection involved. When laboratory services are not available, it may be necessary to administer a combination of drugs, including an amoebicidal drug to kill the parasite and an antibiotic to treat any associated bacterial infection.

Anyone with bloody diarrhea needs immediate medical help. Treatment often starts with an oral rehydrating solution—water mixed with salt and carbohydrates—to prevent dehydration. (Emergency relief services often distribute inexpensive packets of sugars and mineral salts that can be mixed with clean water and used to restore lifesaving fluids in dehydrated children gravely ill from dysentery.)

If "Shigella" is suspected and it is not too severe, the doctor may recommend letting it run its course—usually less than a week. The patient will be advised to replace fluids lost through diarrhea. If the infection is severe, the doctor may prescribe antibiotics, such as ciprofloxacin or TMP-SMX (Bactrim). Unfortunately, many strains of "Shigella" are becoming resistant to common antibiotics, and effective medications are often in short supply in developing countries. If necessary, a doctor may have to reserve antibiotics for those at highest risk for death, including young children, people over 50, and anyone suffering from dehydration or malnutrition.

No vaccine is available. There are several "Shigella" vaccine candidates in various stages of development that could reduce the incidence of dysentery in endemic countries, as well as in travelers suffering from traveler's diarrhea.