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Year : 2013  |  Volume : 6  |  Issue : 1  |  Page : 112-116
The various etiological agents in the causation of gastroenteritis


1 Department of Preventive and Social Medicine, Maharajah's Institute of Medical Sciences (MIMS), Vizianagaram, Andhra Pradesh, India
2 Department of Paediatrics, Steel Plant General Hospital, Visakhapatnam, Andhra Pradesh, India

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Date of Web Publication18-Jul-2013
 

   Abstract 

Over the past many decades, the incidence of gastroenteritis has not changed much, although overall diarrhoeal mortality has declined. For children aged less than five years in developing countries, a median of 3.2 episodes of diarrhoea occurred per child-year, which is similar to that reported previously. Estimates of mortality indicate that 4.9 children per 1000 per year died in the developing regions as a result of gastroenteritis in the first 5 years of life. A wide assortment of organisms causes gastroenteritis. Thorough search regarding the subject was done in the library textbooks, journals as well as on internet. The concussed data on various etiological agents of gastroenteritis was limited in the journals. This article is an attempt to put forth the varied etiology of gastroenteritis as a disease.

Keywords: Diarrhea, etiology, gastroenteritis

How to cite this article:
Ukey UU, Chitre DS. The various etiological agents in the causation of gastroenteritis. Ann Trop Med Public Health 2013;6:112-6

How to cite this URL:
Ukey UU, Chitre DS. The various etiological agents in the causation of gastroenteritis. Ann Trop Med Public Health [serial online] 2013 [cited 2019 Dec 11];6:112-6. Available from: http://www.atmph.org/text.asp?2013/6/1/112/115173

   Introduction Top


Gastroenteritis or diarrhoea is a term used to describe a group of diseases in which the predominant symptom is loose stool. It can be best defined as: [1] An abnormal increase in stool liquidity; [2] an increase in daily stool weight (>200 grams); and [3] usually associated with increased stool frequency. [1]

Over the past many decades, the incidence of gastroenteritis has not changed much, although overall diarrhoeal mortality has declined. For children aged less than five years in developing countries, a median of 3.2 episodes of diarrhoea occurred per child-year, which is similar to that reported previously. Estimates of mortality indicate that 4.9 children per 1000 per year died in the developing regions as a result of gastroenteritis in the first 5 years of life. Gastroenteritis accounts for about 17% of under-5 mortality in the post neonatal period, and 3% of neonatal deaths. [2] Thus it is a major public health problem globally more so in the developing countries. The control of any disease requires a thorough knowledge of its etiology. A wide assortment oforganisms causes gastroenteritis. Although the etiology may not always be needed for managing the case, it does have a role in determining the epidemiological characters like occurrence of epidemics and outbreaks. Hence this review about various causes of gastroenteritis was done.

Thorough search regarding the subject was done in the library textbooks, journals as well as on internet. The concussed data on various etiological agents of gastroenteritis was limited in the journals. This article is an attempt to put forth the varied etiology of gastroenteritis as a disease.

Gastroenteritis can be considered as a group of non infectious and infectious diseases caused by various types of organisms-bacterial, helminthic, viral in nature producing clinical manifestations of loose motions with or without mucus and/or blood in stool. [3]

Mainly in developing countries, gastroenteritis is almost universally infectious in origin. [1] The etiology can be broadly considered as:

  1. Infective.
  2. Non-infective.
Infective

The infective causes are: (a) Bacteria, (b) Viruses, (c) Parasites etc. [4]

Non-infective

These are less common as compared to the infective causes. The major non-infective causes can be feeding difficulty, Anatomic defects, Mal-absorption, Endocrinopathies, Food poisoning, neoplasms etc. [4] These non-infective causes are shown in [Table 1].
Table 1: Non-infective causes of gastroenteritis

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Since the majority of gastroenteritis is infective, it has been considered here.

Bacterial entero-pathogens

These may cause either inflammatory or non-inflammatory gastroenteritis and specific enteropathogens may be associated with either of the typical form. [4] Generally, inflammatory gastroenteritis is associated with enteroinvasiveE.coli (EIEC), enterohemorrhagic E.coli (EHEC), enteroaggregative E.coli (EAEC), Shigella,  Salmonella More Details, Aeromonas, Campylobacter jejunii,  Clostridium difficile Scientific Name Search   Yersinia More Details enterocolitica. Non-inflammatory gastroenteritis is caused by enteropathogenic E.coli (EPEC) enterotoxigenic E.coli (ETEC), V. cholerae and several other pathogens which are also associated with inflammatory diarrhoea. [5]

  1. Vibriocholerae: It causes Cholera-a devastating disease due to the rapidity with which severe dehydration occurs. The organisms are short, curved, comma shaped, rapidly motile, uniflagellate, gram-negative bacteria that grow aerobically. [6] There are many O serogroups of V. cholerae, but only serogroups O1 and O 139 cause epidemic human disease. Serotypes are Ogawa, InabaandHikojima. Serogroup O1 has two main biotypes: classic and El Tor. [7] Cholera is one of the major infectious diseases with epidemic potentials especially amongst communities living in congested urban slums without proper sanitary facilities, which are typical of endemic area. [8] The clinical course of cholera caused by the classical cholera vibrio was conventionally divided into 5 stages, viz. [1] stage of predominant diarrhoea, [2] stage of copious evacuations, [3] stage of collapse, [4] stage of reaction and [5] stage of uraemia. [9] However, the presentation of El-tor cholera (which is milder as compared to classical type owing to its non-haemolytic properties etc.) is described in 3 stages i.e.(i) Stage of Evacuation, (ii) Stage of Collapse and (iii) Stage of Recovery. [2] The typical stool in cholera is alkaline in reaction and has a rice-water appearance, being completely devoid of any biliary color or of any fecal matter. However, the presence of fecal matter or of a yellowish or even of a pinkish color does not necessarily exclude a diagnosis of cholera. [9] Cholera toxin (CT) stimulates adenylcyclase to inhibit sodium chloride absorption and stimulates chloride secretion in the small intestinal epithelium. A reflex neural action also appears to be important in CT induced secretion. [6]
  2.  Escherichia More Detailscoli: It is the predominant aerobic, colliformspeciesin the normal colon. [7] Five different strains have been described in its pathogenecity namely, Enteropathogenic E. coli (EPEC), Enterotoxigenic E. coli (ETEC), EnteroinvasiveE.coli (EIEC), Enterohemorrhagic E. coli (EHEC) and Enteroaggregative E. coli (EAEC). [10]
    1. ETEC have a worldwide distribution and a major health hazard in adults and children in developing countries. [10] ETEC produces enterotoxins and has long been known to be capable of causing diarrhoea. These organisms are transmitted through contaminated food and water. Two types of toxin (heat-labile or LT, and heat-stable or ST) are produced that induce fluid secretion in the intestine acting through cyclic AMP (LT) or through cyclic GMP (ST). LT-producing ETEC induce an illness similar to cholera. ST-producing ETEC are important causes of traveler's diarrhoea. [6]
    2. EIEC: This is a small group of E.coli that produce inflammatory diarrhoea by invading and killing colonic enterocytes. The organisms resemble Shigellae in O antigens and in being non motile. The clinical features of EIEC infection are similar to those of Shigellae but the latter often produced more severe diarrhoea. [11]
    3. EHEC: The very young and the aged are most at risk from developing diseasedue to this organism. The infection involves the caecum and right colon and, in its most severe form, produces hemorrhagic colitis. Infection with EHEC can cause a wide range of manifestations, including asymptomatic infection, non-bloody diarrhoea, hemorrhagic colitis and hemolytic uremic syndrome (HUS). Severe illness is characterized by cramp-like abdominal pain, marked abdominal distention, and grossly bloody diarrhoea, and carries a high fatality rate. [6]
    4. EAEC: These are amongst the most recently its discovered pathogenic group. They are named for there characteristic pattern of adherence to tissue culture cells-in large aggregates. They can cause both acute and chronic gastroenteritis. [6]
    5. EPEC: It has been described as a cause of infantile gastroenteritis. EPEC has also been associated with travelers' diarrhoea. [11]
  3. Shigellae: These are non motile gram negative bacilli belonging to the family Enterobacteriaceae. [12] Four species, S. dysentery, S. flexneri, S. boydii and S. sonnei are known. S. dysentery and S. flexneri are responsible for most infections in the tropics. [11] Shigellae causes shigellosis also called as bacillary dysentery which is an acute bacterial infection in the form of colitis affecting predominantly the rectosigmoid colon. The disease is characterized by diarrhoea, dysentery, fever, abdominal pain and tenesmus. [12] Shiga toxin is an additional pathogenic factor produced by some species. It is a cytotoxin, causing cell death due to suppression of protein synthesis and may result in hemolytic uremic syndrome (HUS) in children. [6] In infant and children the infection may not manifest as classical dysentery but may present as an acute gastroenteritis. [13]
  4. Salmonellae: These are motile, gram negative, non-spore-forming bacilli. [14] They are common cause of gastroenteritis in developed countries. [6] In humans the most common clinical manifestation of salmonella infection is entero-colitis with diarrhoea as the major symptom. Salmonella food poisoning is more commonly responsible for gastroenteritis. S. typhi, a pathogen of humans only causes enteric fever also called as typhoid fever. [14] It is characterized by prolonged fever abdominal pain, diarrhoea, delirium, spleenomegaly and complicated some times, by intestinal bleeding and perforation. [15] The classical picture of typhoid fever has changed over the years. Early diarrhoea i.e., diarrhoea as a presenting feature or diarrhoea during first week of illness and acute gastroenteritis at onset may also be seen, though not a regular feature. [16]
  5. Yersiniaenterocolitica: It is a small gram negative rod with peritrtrichousflagellae. [11] It is an enteric pathogen that can cause gastroenteritis primarily in children. The organism is transmitted through contaminated food (particularly milk) and water and many animals are reservoirs for infection. It causes disease through invasion of the intestinal mucosa and also produces a heat-stable enterotoxin. In adults, it usually causes acute gastroenteritis followed two or three weeks later by joint symptoms and skin rash. [6]
  6. Campylobacter: Campylobacter (meaning "curved rod") is a curved or spiral, motile, non spore forming, and gram-negative rod. Enteric infection with a member of the genus Campylobacter usually results in an inflammatory, occasionally bloody diarrhoea or dysentery syndrome in industrialized temperate areas. Campylobacter jejuni Scientific Name Search  is often a recognized cause of community-acquired inflammatory enteritis. The diarrhoea also may be watery, especially in developing tropical areas. [17]
  7. Others: Infection by few other organisms like Aeromonas and Plasiomonas, Clostridium difficile, Clostridium perfringens, and  Vibrio parahaemolyticus Scientific Name Search olyticus may also result in gastroenteritis. Aeromonashydrophilia and the closely related bacterium Plasiomonasshigelloides may both induce diarrhoea. A variety of toxins, including heat-labile enterotoxin, and cytotoxin are produced. Aeromonasdiarrhoea is usually noted in children, although it may cause sporadic adult diarrhoea. Many cases resolve spontaneously. Specific treatment is reserved for patients who are immunocompromised or acutely ill. Plasiomonas is often associated with consumption of raw oysters or other seafood. [6] Vibrio para-hemolyticus is a food borne cause of gastroenteritis. It is a halophilic vibrio that contaminates seafood and fish. [18]  Clostridium perfringens Scientific Name Search roduces an enterotoxin that is a common cause of food borne illness. It produces Heat-resistant spores that survive normal cooking. [6] If these foods are consumed uncooked, gastroenteritis can be a result. [18]
Viruses

Nonbacterial gastroenteritis anddiarrhoeas are usually caused by viruses. Infection is seen in all parts of the World, especially in infants and young children. Viral gastroenteritis is not distinguishable clinically from other types of gastroenteritis. The viruses are specific to human, and infection follows general rules of fecal-oral transmission. Although outbreaks of gastroenteritis often have viral etiology, it may be difficult to be sure about the exact role of a given virus when it is identified in feces, as there are number of viruses that replicate in gastrointestinal tract which are not associated with acute gastroenteritis. [18]

  1. Rotaviruses: Human rotaviruses are the most important etiologic agents of acquired diarrhoea in infants and young children worldwide. These are morphologically characteristic viruses, with a genome consisting of 11 separate segments of double-stranded RNA. [19] The classification of Rotavirus into seven different groups (A-G) is based on the antigenic specificity of the VP6 (structural viral protein) capsid proteins and patterns of the electrophoretic mobility. Only groups A, B and C are known to infect humans. [20] Rotaviruses, after replicating, cause diarrhoea by damaging transport mechanism in the gut. For unknown reasons, respiratory symptoms such as cough and coryza are quite common in these infections. The disease is more severe in infants in developing countries. [18] The rotaviruses can also cause gastroenteritis in elderly patients. [6]
  2. Otherviruses: Other viruses causing gastroenteritis in human include Norwalk agent calciviruses, enteric astroviruses, adenoviruses and coronaviruses. Many of these agents are usually responsible for mild sporadic diarrhoea in the community, with negligible mortality. [18] However, Norwalk virus causes epidemics of gastroenteritis in the temperate countries in the winter. It spreads through the fecal-oral route. Raw shellfish are major sources of infection.It affects all ages. Symptoms include diarrhoea, nausea and vomiting and abdominal cramps. [6]
In general, the illnesses caused by bacterial pathogens are more serious, than those due to viruses (Sethi 1989). [21]

Parasites

These commonly result in gastroenteritis secondary to an infection; most cases are asymptomatic and go unnoticed. This group has an increased concern nowadays due to the increased infection rate in the immunocompromised. [6]

  1. Entamoebahistolytica: Amoebiasis is an acute as well as chronic infection caused by protozoan parasite-E. histolytica. The common anatomical site of amoebiasis is the colon and the rectum, but extraintestinal foci occur secondarily either by hematogenous metastasis or direct extension. E. histolytica may multiply and colonize in the lumen of colon and rectum as a harmless non-invasive parasite or may invade the bowel wall, causing amoebic colitis or amoebic dysentery. Intestinal amoebiasis may or may not be associated with amoebic extra-intestinal disease. However, extra-intestinal amoebiasis is always preceded by intestinal lesion and does not exist without intestinal amoebic disease. [22]
  2. Giardialamblia: Giardia intestinalis or Giardia lamblia is a flagellated protozoal parasite with a trophozoite and cystic stage. It localizes and multiplies in the intestinal tract from the duodenum to caecum. It does not appear to have invasive properties as of E. histolytica. Giardiasis is a common intestinal parasitic infection of man, particularly affecting children causing diarrhoeal stool, abdominal pain or discomfort usually in the upper segment with or without flatulence and vomiting, loss of appetite, often gripping pain in the lower abdomen relieved by defecation and irregular fever. [3]
  3. Other: parasites like Cryptosporidium parvum, Cyclospora, Strongyloidesstercoralis, and Balantidium coli can also result in gastroenteritis. The clinical manifestations of Cryptosporidium parvum range from asymptomatic infection to chronic diarrhoea. In developing countries the primary affected group is children. In immunocompetent adults, infection is usually self-limited. In immunocompromised individuals (e.g. those with HIV). Infection results in debilitating life threatening chronic illness. Cell mediated immunity is required to prevent heavy infection. Strongyloidosis leads to chronic diarrhoea and mal-absorption. Cryptosporidiosis outbreaks are reported as a result of contaminated drinking water. [6]
The illnesses due to all these agents can range from mild inconveniences to life-threatening epidemics. Although diarrhea can be caused by a vast array of pathogens, the cornerstone of prevention is provision of a safe food and water supply, application of basic hygiene principles, and the development and administration of vaccines. The cornerstone of treatment is rehydration. Selection of specific antimicrobial therapy should be based on disease presentation and epidemiologic factors. [23]

Hence wherever possible the etiology of gastroenteritis should be identified based on such factors and laboratory investigations wherever possible. This in turn will help to reduce the global burden of gastroenteritis.

 
   References Top

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Correspondence Address:
Ujwala U Ukey
Department of Preventive and Social Medicine, Maharajah's Institute of Medical Sciences, Nellimarla, Vizianagaram - 535 217, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1755-6783.115173

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