Gastroenteritis

Gastroenteritis is the inflammation of intestines and stomach. The symptoms can include diarrhea, stomach pain, nausea, vomiting, fever or feeling unwell. It could be persistent, acute, or chronic, and can also be classified as infectious or non-infectious.

Diarrhea is defined as the passage of three or more loose or watery stools per day (or more frequent passage of stool than is normal for the individual). Sometimes diarrhea is so severe that a person becomes very ill and loses large amounts of body fluids.

There are three clinical classifications of diarrheal conditions:
• Acute diarrhea, lasting several hours or days
• Acute bloody diarrhea or dysentery
• Persistent diarrhea, lasting 14 days or longer

The three major types of germs that cause gastro are bacteria, viruses and parasites. While most of these are usually harmless, many can cause illness in some situations.

Gastro can also be caused by toxins that some bacteria produce in food (for example Staphylococcus aureus, Clostridium perfringens).

It is quite challenging to establish accurate incidence and prevalence of acute gastroenteritis because of under-reporting of attacks by many patients. Moreover, only 1.5% of stool samples get positive results for a bacterial cause.

Viral infection that affects the stomach and small intestine is called stomach flu. The illness is usually brief, lasting 1 to 3 days. Norovirus and Rotavirus are the most common causes of viral gastroenteritis. Reports suggest that up to twenty-five million cases of acute viral gastroenteritis occur annually in the United States.

The virus enters the stomach and intestine and inflames the lining of these organs. As a result, the stomach and intestine are temporarily unable to perform their usual functions.

The most important causes of bacterial gastroenteritis in Europe have been reported to be enteroaggregative E. coli (EAEC), Campylobacter, and enteropathogenic E. coli. A study in 2012 has concluded that Campylobacter was responsible for more cases of chronic gastroenteritis than Salmonella, with an incidence of 68 vs. 22 cases per 100,000.

Germs that cause gastroenteritis are usually spread by contamination of something that goes in human mouth. This can occur by contact with contaminated objects, including food or water, or by contact with other people who are ill.
Gastroenteritis

Foodborne gastroenteritis

Intake or handling of contaminated food and water may cause foodborne gastroenteritis. Gastroenteritis is the severe inflammation of the gastrointestinal tract, resulting in acute diarrhea and vomiting.

Acute gastroenteritis is one of the most common illnesses affecting man and may be caused by a large variety of different microbes.

The condition affects mainly children and the elderly, but increasingly also adults of all ages, often following foreign travel or the ingestion of contaminated food and water.

There are agents, many of which cause acute gastroenteritis, that are recognized as known or possible causes of foodborne illness, but for which there were insufficient data to make reliable estimates of incidence. This category includes infectious agents such as Aeromonas spp., Edwardsiella spp., and Plesiomonas spp., and non-infectious agents such as mushroom and marine biotoxins, metals and other inorganic toxins.

In Africa, Asia and Latin America, there are about 1000 million cases of gastroenteritis per year in children under the age of 5, which leads to 5 million deaths. In Mexico and Thailand, half of the children aged 0-4 years suffer from the Campylobacter-induced enteritis.
Foodborne gastroenteritis

Virus foodborne disease

Viruses are frequent causes of foodborne disease in the US and other countries. Food borne viruses infect through ingestion and are passed through the feces.

Any virus that is excreted in feces in sufficiently large numbers and manages to survive outside the body of the host long enough to contaminate food has the potential to spread through this route.

Viruses differ from bacteria in that they are smaller, require a living animal or human host to grow and reproduce, do not multiply in foods and are nor complete cells.

Viruses involved in foodborne disease outbreaks include, but are not limited to norovirus, hepatitis A virus, human rotavirus, hepatitis virus, astrovirus, sapovirus, aichi virus and adenovirus, as well as human enteroviruses such as echoviruses, polioviruses, group A and B coxsachieviruses.

The great majority of these are RNA viruses, often small and containing single-stranded RNA. They infect via the intestinal lining, but some are transported to the over (and occasionally other organs) before causing disease.

Norwalk and Norwalk-like viruses are the leading reported cause of foodborne viral illness. A member of the Calicivirus family of viruses, Norwalk virus particles are 27 to 38 nm in diameter and consist of a single positive strain of RNA.

Norwalk virus was first discovered following an outbreak of epidemic gastroenteritis in a Norwalk, Ohio, elementary school in 1968.

Outbreaks of ‘food poisoning’ or foodborne gastroenteritis over the years have been assumed to be caused by bacteria, whether or not such organisms are identified.

Washing hands and cooking foods are probably the two measures that contribute the most to preventing foodborne viral disease.
Virus foodborne disease

Acute gastroenteritis

Acute gastroenteritis is characterized by stomach and intestinal mucosal inflammation secondary to viral or bacterial infection, food poisoning, chemical irritants or food allergies.

The most common etiology of gastroenteritis is foodborne infections. The most common culture-confirmed infections were Salmonella, followed by Campylobacter and Shigella.

Regardless of the source, patients often present complaining of some combination of anorexia, nausea, abdominal pain, vomiting, diarrhea and dysentery (bloody diarrhea), and fever

Vomiting may prevent oral intake, leading rapidly to dehydration, especially when diarrhea contributes to fluid losses. Diarrhea may be debilitating or fatal even in the absence of vomiting.

In term of virus, Norwalk virus are the most common cause of infectious acute gastroenteritis and are transmitted feco-orally through food and water directly from person to person and by environmental contamination.

These viruses are often responsible for protracted outbreaks in closed stetting, such as cruise ships, nursing homes and hospitals. Norwalk virus alone is estimated to account for more than half of cases of gastroenteritis.
Acute gastroenteritis

Salmonella: significance as a pathogen

Salmonella: significance as a pathogen
Two clinical entities cause by Salmonella are recognized: enteric fever (a severe, life threatening illness) and the more common food poisoning syndrome. In both cases, the organisms enter the body via oral route.

Enteric fever, commonly referred to as typhoid fever, is primarily caused by the one species Salmonella typhi, but other salmonella are potentially capable of producing this syndrome. The symptoms of enteric fever are generally not elicited through the intestinal tract, although the route of entry into the body is primarily oral. However, a short period of vomiting and diarrhea sometimes occurs in the first day or two in typhoid fever. The onset times vary considerably between typhoid and paratyphoid enteric fevers. Onset times for typhoid are usually 8 – 15 days, seldom as short as 30 – 35 days: while onset time for paratyphoid fever tends to be shorter, and may be so short as to suggest food poisoning. The usual symptoms of salmonellosis are headache, malaise, anorexia, and congestion of the mucous membranes, especially of the upper respiratory tract. Bacteremia generally occurs on the first week of illness.

The food poisoning syndrome is characterized by a self-limiting acute gastroenteritis. Contaminated food or water is the usual, but not the only, vehicle. The incubation period varies from 6 to 48 hours and generally falls within a range of 12 – 36 hrs. Variation in the incubation time may be attributed to the size of the infecting dose, the virulence (degree of pathogenicity) of the organisms, the susceptibility of the host, and the physicochemical composition of the transmitting food. Symptoms include diarrhea, abdominal cramps, vomiting and fever which generally last from 1 - 7 days. However, the organisms may be excreted in the feces for many weeks after symptoms subside.

Salmonellosis may be confused clinically with staphylococcal intoxications, but there are important distinctions. Salmonella has a longer incubation period than staphylococci and is usually accompanied by fever, which is absent in staphylococcal intoxication. And, unlike Salmonella food poisoning, the acute symptoms of staphylococcal food poisoning normally disappear within 24 hrs.

In some case, the gastroenteritis may be followed by extraintestinal invasion resulting in enteric fever, which is more, likely to occur in the very young, the aged and debilitated patients.
Salmonella: significance as a pathogen

Foodborne disease

Foodborne disease
The pattern of Foodborne disease has changed substantially in industrialized countries in recent decades. Outbreaks are more likely to be far reaching, and some are even global in scale because of widespread food distribution and changes in methods of food preparation. Further changes in the incidence of foodborne disease and the pattern of food-related illness can be anticipated from global warming. As a result of changed conditions in food production and better laboratory detection techniques, new foodborne pathogens continue to be identified. In particular, we are now faced with the emergence of antimicrobial drug–resistant bacteria and a number of viruses not previously recognized.

Foodborne disease is a public health concern in all parts of the world. In the United States, foodborne disease causes an estimated 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths each year. In the United Kingdom, an estimated 2.37 million cases of foodborne gastroenteritis occurred in 1995. Previous estimates of foodborne gastroenteritis in Australia have ranged from 1–2 million to 4 million episodes per year. The effect of such large numbers of persons with gastrointestinal illness is considerable.

A recent national survey of gastroenteritis in Australia found that one third of working adults miss ≥1 days of work when they have gastroenteritis, and another third of cases result in a caregiver missing work. In Australia in 2003, 99 reported outbreaks of foodborne disease affected 1,686 people and caused 6 deaths. Any evidence of food contamination can also have a major effect on food industry and trade. The food industry in Australia generates >$29 billion in food production, with >20% of products exported, and $57 billion in food processing.
Foodborne disease