Diarrhea is a clinical syndrome of diverse etiology. it may be defined as an increased frequency of motions whose consistency varies from loose/liquid (taking up the shape of the container) to watery stool. Passage of frequent loose or liquid stool with or without blood and/or mucus is the main feature of acute diarrhea. Acute watery diarrhea begins abruptly and lasts for less than two weeks whereas chronic or persistent diarrhea episodes can be divided into two broad groups based on the stool character— non-dysenteric group and the invasive dysenteric group. The presence of blood and mucus in stool, which often is accompanied by fever, differentiates dysenteric episodes from non-dysenteric ones in which blood is absent in the stool but may contain little or no mucus. Diarrheal diseases are responsible for a substantial proportion of childhood morbidity and mortality, particularly in the developing world. Over three million deaths occur due to diarrhea throughout the world each year; most of these deaths take place in the developing countries of Asia. Africa and Latin America. Moreover, diarrhea is the main cause or perpetrator of malnutrition in children, and diarrhea patients occupy about 30% of pediatric beds in hospitals of developing countries.
Bangladesh and other countries of South-east Asia are well known in history for giving rise to numerous epidemics of cholera which often became pandemics by spreading to many other countries. However, during the non-epidemic period, it is not cholera but other causes of infectious diarrhea and dysentery that cause the highest morbidity and mortality. In Bangladesh alone diarrhea and dysentery kill some 270.000 children: and estimates from various studies suggest that about 2-4 episodes of diarrhea per child per year occur in the under-five age group. Thus diarrhea) illnesses put a heavy burden on the meager health facilities and resources of a poor country like Bangladesh.
Epidemiology of Diarrhoea
There are many causative agents of diarrhea of which the common ones are : (a) Viral infections: Rotavirus, Enteroviruses, Norwalk virus; (b) Bacterial infection: Enterotoxigenic E. colt (ETEC)„ Vibrio cholera, V. parahaernolytica, Shigella,•Salmonella (non-typhoid), Enteropathogenic E. colt (EPEC), Campyloba_cior jejune, Escherichia coil; (c) Protozoal infections: Entamoeba histolytic, Giardia lamblia; (d) Helminthiasis: Trichuriasis, Ascariasis; (e)Other intestinal factor; Lactose intolerance, (f)Malabsorption. states; (g) Miscellaneous: Magnesium.. containing drugs, antibiotics, psychogenic.
Host. Age specificity of Diarrhea
A hospital surveillance report from the International Centre for Diarrhoeal Diseases Research, Bangladesh (ICDDR,B) showed that the Enterotoxigenic E. coll. (ETEC) was the commonest enteropathogen detected in all age groups (detection rate 20%), followed by Rotavirus (19%), C. jejune (14%), and Shigella (12%) In infants and children under two years are most often infected with rotavirus, enteropathogenic E. colt (EPEC) and E. histolytic.
Host characteristics which facilitate transmission of diarrhoeal diseases are (1) Presence of high number of susceptible persons in the community, especially the children: (2) Lowered body defense due to malnutrition, immunodeficiency or immunosuppression due to other ..conditions like measles, reduced gastric acidity; (3), Decreased intestinal motility ; (4) Presence of healthy carriers in the community; (5) Unhygienic personal and food habits.
Environment Seasonality for diarrhea Disease
Seasonal variation in the occurrence of different diarrhoeal diseases is observed but is • not explainable always. In a temperate climate, bacterial diarrheas tend to occur most often in the warm season, while rotavirus infections peak during winter. In tropical areas. rotavirus diarrheas occur throughout the year, with an increase in the colder and drier months: 2003
bacterial diarrheas tend to peak in the warmer and rainy season. In Bangladesh. V. choler–0e shows the most pronounced seasonality with a large number of isolates after the monsoon (September to December). Detection of enterotoxigenic E. colt is most common in the hot dry summer (March to June), rat uterus in the autumn and winter (September to March), and Shigella in the winter (October to January).
Environmental characteristics which facilitate the transmission of diarrhoeal diseases are (1) Moist and warm climate: (2) Overcrowded living condition; (3) Natural or man-made disasters: (4) Scarcity of safe water: (5) Unhygienic home surroundings; (6) Improper excreta disposal system. –
Geographical distribution. Certain causative agents are more common in some areas of the world because of multiple factors favoring the survival and transmission of the agents concerned. Rotavirus is found in both the developed and developing countries. Of the Shito species. Sh. Flexner is the usual organism for bacillary dysentery in the less developed countries. Again. Salmonella food poisoning is rare in poor countries like Bangladesh. whereas cholera. amebiasis and giardiasis arc almost unknown in the rich industrialized countries.
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Mode of transmission
Most enteropathogens are transmitted by fecal contamination of food or drinks (fecal-oral transmission), either directly or indirectly. But in some cases, as in Shigella infection, spread by person-to-person transmission also occurs. This kind of direct transmission may also take place in the case of E. histolytic. G. arribada, and possibly also in a case of Rotavirus and V. cholera. Domestic animals and their products like meat, milk, and eggs are some natural sources for Salmonella and Campylobacter, and if taken inadequately cooked, can cause infection. Sometimes Salmonella and Staph. aureus produces enterotoxin which causes, food-poisoning without the presence of the offending organisms in the food.