GASTROENTERITIS

Also known as Infectious Diarrhea or Food Poisoning, refers to the inflammation of the gastrointestinal tract which involves both stomach and small intestine. It is also called Stomach Flu. It can infect person of any age, infants, children, adults, across the world. It is one of the major causes of millions of deaths every year all over the world.

Various causes lead to gastroenteritis, which include, Viruses, Bacteria, Protozoan, some lifestyle habits including ingesting contaminated food, not washing hands before eating or cooking food, contaminated water intake. Lack of sanitation and hygiene could also contribute to it.

Major symptoms include dehydration, vomiting, nausea, stomach pain and cramps, fever, fatigue, bloody stool, sunken eyes and sunken fontanelle (in infants).

The treatments usually include Oral Rehydration Therapy against dehydration. Antibiotics and antiemetics can be prescribed in some cases. Probiotics have been emerged as a beneficial option to supply the required nutrition, thus, reducing the frequency of stool and duration of illness. Vaccines have successfully been employed as another prevention source.

Causal agents

Mostly it is due to a Virus and Bacterium belonging to different genus. Others are some protozoans.

Viral Gastroenteritis

According to the National Center for Biotechnology Information (NCBI), viral gastroenteritis is the leading cause of severe diarrhea in adults and children. (NCBI, 2012) Children under the age of five and the elderly are at particular risk of severe diarrhea.

This is caused by any of the following viruses:

Calcivirus: Calciviridae family of viruses. Numerous outbreaks of Calicivirus infection have been linked to the consumption of food prepared by infected food-handlers.

Many studies are associated with multiple strains.

Norwalk virus (Norovirus genus) is the prototype strain for the genus “Norwalklike viruses” (NLVs). These small, round-structured viruses are most commonly found in association with illness in humans. Sapporo virus (Sapovirus genus) is the prototype strain for the genus “Sapporo-like viruses” (SLVs), which can infect humans as well.

They have an incubation period of 15–50 h, associated with presence of acute symptoms (including vomiting) and/or diarrhea, average duration of symptoms of 12–60 h, a high attack rate. Shedding of NLV continues up to 22 days from the onset of infection.

Noroviruses may trigger severe outcomes in some hosts, such as older or immunocompromised patients or those with cardiovascular disease. Less than 10–100 virions can be enough to infect a healthy adult. These are highly transmissible. Norovirus transmission occurs by food, water, and airborne routes, as well as incidental hand contact with contaminated surfaces or fomites and through person-to-person contact. This type of virus is common in crowded spaces, such as nursing homes, daycares, and schools. It is a cause of gastroenteritis among adults in America, causing greater than 90% of outbreaks, especially between November and April.

NLV infection was commonly associated with gastroenteritis in all age groups in the community whereas SLV infection was mainly restricted to children aged 5 years.

Rotavirus:  This virus belongs to Reoviridae family. It is responsible for about 70% of episodes of infectious diarrhea in the pediatric age group. It is a less common cause in adults due to acquired immunity. It usually spreads through fecal-oral route. Symptoms typically appear within two days of infection. Symptoms often start with vomiting followed by four to eight days of profuse diarrhea. Dehydration is more common in rotavirus infection than in most of those caused by bacterial pathogens, and is the most common cause of death related to rotavirus infection. Viral Diarrhea is highly contagious. Outbreaks of rotavirus A diarrhoea are common among hospitalised infants, young children attending day care centres, and elderly people in nursing homes. According to the Centers for Disease Control and Prevention (CDC), this virus is most common between the months of December and June.

Adenovirus and Astrovirus are other genera which contribute to this disease.

Bacteria are other causal agents.

Different Bacteria are Campylobacter jejuni, E. coli, Salmonella, Shigella, Staphylococcus, Yersinia.

 Campylobacter jejuni is the primary cause of bacterial gastroenteritis, with half of these cases associated with exposure to poultry.  Contaminated drinking water and unpasteurized milk provide an efficient means for distribution. Contaminated food with incorrectly prepared meat and poultry is the primary source of the bacteria. The symptoms induced by these bacteria usually persist for between 24 hours and a week, but may be longer. Diarrhea can vary in severity from loose stools to bloody stools. The sites of tissue injury include the jejunum, the ileum, and can extend to involve the colon and rectum. These infect almost all age group individuals.

E.coli is a type of bacteria that lives in the intestines of humans and animals. Most of the time, it does not cause any problems. However, certain types (or strains) of E. coli can cause food poisoning. One strain, E. coli O157:H7, can cause a severe case of food poisoning. Symptoms develop 24-72 hours after being infected. Symptoms of rare but severe E. coli infection include the bruises on the body, pale skin, red or bloody urine, reduced amount of urine.

Salmonella are rod shaped bacteria belonging to family Enterobacteriaceae. These spread through uncooked or poorly cooked eggs and chicken. The infection begins after 12-72 hours of consuming the contaminated food.

Shigella is a genus of Gram-negative, facultative anaerobic, nonspore-forming, nonmotile, rod-shaped bacteria, belonging to family Enterobacteriaceae.

Toxigenic Clostridium difficile is an important cause of diarrhea that occurs more often in the elderly.^[12] Infants can carry these bacteria without developing symptoms.  Acid-suppressing medication appears to increase the risk of significant infection after exposure to a number of organisms, including Clostridium difficile, Salmonella, and Campylobacter species. The risk is greater in those taking proton pump inhibitors than with H2 antagonists.

Apart from viruses and bacteria certain protozoans can also cause gastroenteritis – most common is Giardia lamblia, but Entamoeba histolytica and Cryptosporidium species have also been implicated.

Transmission:

Symptoms:

Most prominent are diarhhea (Diarrhea is defined as daily stools with a mass greater than 15 g/kg for children younger than 2 years and greater than 200 g for children 2 years or older. Adult stool patterns vary from 1 stool every 3 days to 3 stools per day; therefore, consider individual stool patterns) and vomiting, accompanied by abdominal cramps, fever, nausea, headache, muscle pain and fatigue. Children with a significant degree of dehydration may have a prolonged capillary refill, poor skin turgor, and abnormal breathing, increased thirst.

Some viral infections may produce benign infantile seizures. 

Certain other physical findings associated with gastroenteritis may include the following:

·        Dehydration (primary cause of morbidity and mortality)

·        Malnutrition (typically a sign of a chronic process)

·        Abdominal pain

·        Borborygmi

·        Perianal erythema

Diagnosis:

Gastroenteritis is typically diagnosed clinically, based on a person's signs and symptoms.

Neither of the two major causal viruses, namely, Rotavirus and Norovirus can be grown in routine cell cultures. Rapid antigen testing of the stool, either by EIA (>98% sensitivity and specificity) or latex agglutination tests (less sensitive and specific as compared to EIA), is used to aid in the diagnosis of rotavirus infection. Expect antirotavirus antibodies (i.e., immunoglobulin M, immunoglobulin A) to be excreted in the stool after the first day of illness. Antibody tests can remain positive for 10 days after primary infection and longer after reinfection; therefore, they can be used as an adjunct to diagnosis.

Fecal viral concentration of norovirus correlates with duration of illness. As in most viral infections, active viral replication determines clinical disease. High fecal viral concentrations suggest the need for both aggressive fluid replacement and stringent infection control measures

ELISA test can be readily performed in the routine laboratory without specialized equipment, thus offering useful diagnostic and prognostic information.

Systemic features that can guide empiric therapy and help narrow the differential diagnosis of the causative organism include the following:

·        Onset and duration of symptoms

·        Presence or absence of vomiting

·        Presence or absence of fever

·        Presence or absence of abdominal pain

Treatment

Usually oral rehydration therapy is given against dehydration. Intravenous delivery is preferred in case of decreased levels of consciousness due to dehydration. Probiotics are given to reduce fever duration and frequency of stool.

Antiemetic medications may be helpful for treating vomiting in children. Antibiotics can also be helpful against bacterial infection. While the most common drug administered in patients with viral gastroenteritis has zinc gluconate.