Gastroenteritis is a disease where the wall of the stomach or intestine gets inflamed. In the past it was thought that most gastroenteritis that causes diarrhea would be caused by various viruses. Since then lab techniques have been refined and we now know that there are many other causes for gastroenteritis, which will be discussed in more detail below.
Common causes of vomiting and diarrhea (gastroenteritis)
Bacteria : Vibrio cholera (cholera), Salmonella typhi (salmonella or typhoid fever), Shigella sonnei (shigellosis), Staphylococcus aureus, E. coli 0157:H7 and other types, Clostridium perfringes (necrotizing enteritis), Clostridium botulinum (botulism), Campylobacter, H.pylori
Viruses (see below): rotavirus (children 3-15 months), enteric adenovirus (children less than 2 years), astrovirus, calicivirus (Norovirus, affects older children and adults), echovirus (newborns, preterm infants), rarely polio virus (in unimmunized children)
Parasites (“Traveler’s Diarrhea”) : Giardia lamblia, Cryptosporidium parvum, Entamoeba histolytica, Isospora, Cyclospora, Microsporidia, hookworm
The common denominator is that due to a chemical or bacterial toxin there is a tremendous irritation of the lining of the digestive tract, which leads to a loss of fluids and electrolytes. For the period of the gastroenteritis or the food poisoning there is some degree of slowing of absorption of food products through the gut wall (malabsorption). Children, older people and immunocompromised patients are most vulnerable to this.
Reasons for developing gastroenteritis
What do we know about why gastroenteritis occurs and how does it affect the body? Perhaps the best studied example is the disease called cholera, which is still a problem in development countries, but has been eradicated in industrialized countries because of thorough scientific studies. These studies lead to the recognition that the bacterium, called Vibrio cholerae, produces a toxin, which by itself can cause the same symptoms as if the cholera bacterium were there. Further research led to the sanitation of drinking water (chlorination).
Also, we have now effective improved vaccines for travellers going to cholera infested areas. This model has taught us that a specific enterotoxin,different for every pathogen, can play a major role in many gastroenteritis cases. Examples for this can be found in many cases of traveler’s diarrhea or nursery diarrhea, where we know that enterotoxins from Escherichia coli (E.coli) are responsible for this. In other cases such as in Salmonella, Shigella and some other E.coli strains there are local toxic factors, which the bacteria release upon contact with the mucous membrane of the gastrointestinal tract, which then causes tiny ulcerations and leakage of blood, fluids and electrolytes as well as protein.
It is this loss of fluids, electrolytes and proteins, which potentially can kill the affected person, if it is not attended to in the hospital setting by intravenous replacement of whatever is missing according to blood tests.
The same cause in two different persons can make the one deadly sick, while the other one will only be slightly inconvenienced. It depends on prior exposure and antibody pool that determines every person’s resistance. It also depends on genetic factors, on age (infants and senior Citizens are most vulnerable), and the type of toxin, bacterium, virus, parasite or chemical that caused the condition. Some persons may be weakened by a chronic H.pylori infection (see link for H. pylori under “gastritis” below in the “Related Topics” section) in the stomach or in a duodenal ulcer making them more vulnerable to other infections in the gastrointestinal system.
Most transmissions occur from person to person such as in infection with Campylobacter, Shigella, Giardia and Escherichia coli 0157:H7. Salmonella can be transferred through animals (turtles, iguanas, diseased chickens), but also from meat handlers, if they are chronic carriers from a prior infection that never cleared. Eggs can also be infected with Salmonella. A soft boiled egg allows Salmonella, if present, to survive, but a hard boiled egg cooked for 10 minutes will be free of Salmonella. Meat can be contaminated from meat handlers who have open sores or boils on their hands and staphylococcal toxin from these pus bacteria can cause food poisoning.
Many viruses such as caliciviruses (Norwalk virus), rota viruses, adenoviruses, and astroviruses are transmitted through water/food or through the fecal-oral route. The most well known of these perhaps is the poliovirus, which is almost unknown in the Western world now, but is still a killer in development countries without child vaccination programs or in pockets of the population that refuse vaccination.
Children or young adolescents with no antibody level against poliovirus will get a slight fever, throat infection and vomiting after about 4 to 5 days. In about 90% it is a relatively minor clinical disease. However, the more severe major poliomyelitis that occurs in the other 10% presents after an incubation of about 1 or 2 weeks as an acute disease with a high fever, a severe headache and neck stiffness. It is extremely contagious. There can be swallowing and breathing problems depending on what centers in the spinal cord are affected. A progressive asymmetrical limb weakness and muscle paralysis will subsequently occur with preserved sensitivity in the skin. Even when the person survives polio, decades later a postpoliomyelitis syndrome can produce muscle weakness and extreme fatigues, which are disabling.
Many outbreaks of gastoenteritis on cruise ships or in nursing homes are due to Norovirus, which used to be called Norwalk agent.
The list above gives you an idea about the common causes of gastroenteritis (vomiting and diarrhea). Apart from these causes there are many other agents that can produce diarrhea and vomiting, the major symptoms of gastroenteritis. Such toxins as found in mushrooms, garden plants, diseased seafood(clams, fish and mussels), or heavy metals such as mercury, lead, arsenic or cadmium. Use of antibiotics for various medical conditions can change the gut flora and give rise to a chronic inflammation of the colon with the bacterium Clostridium difficile, which is difficult to treat.
Signs and symptoms
Generally speaking the patient is feeling sick, often vomiting, but then developing diarrhea and abdominal cramps. Dehydration sets in fast as the vomiting and diarrhea continues and any fluids by mouth are not kept down. Depending on what the underlying cause for the digestive tract disease is, there are different typical symptoms, which might become apparent. Typhoid fever, which is caused by the bacterium Salmonella typhi, is causing constipation more often than diarrhea. However, due to ulcerations in the lining of the small bowel, there can be serious blood loss into the gut and also 1% of cases present with bowel perforation (Ref. 28) and resulting peritonitis.
With a viral gastroenteritis the onset is usually slower over one or two days, and the diarrhea that ensues is watery without any blood.
For further details and for a description of the treatments for the various causes of gastroenteritis see the links below under “Related Topics”.
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