Acute diarrhoea is defined as frequent passage of loose or watery stools mixed with mucus and causes morbidity and mortality particularly in children. The scope of the book is to present information on acute diarrhoeal diseases in relation to clinical features, dehydration, management and prevention. When the stool contains blood, it is called dysentery. Acute diarrhoea is an ancient problem with tremendous public health significance. Acute diarrhoeal diseases comprise of acute watery diarrhoea and acute bloody diarrhoea (dysentery). The prototype of acute watery diarrhoea is cholera, while the same for dysentery is shigellosis. It caused extensive epidemics during flood, famine, war and earthquake when large number of people is shifted to refugee camps.
2. Disease burden
According to an estimate  by the World Health Organization, 3–5 million cholera and cholera-like cases occur worldwide, and 100,000–120,000 million cases die with a case-fatality rate of 2.25% (range 1–10%). This figure is actually grossly underestimated, because of under-reporting. These diseases, under the overarching syndrome of acute diarrhoea, cause tremendous pressure on the healthcare delivery system, and during epidemics and pandemics, this is compounded as a real public health problem. There have been seven pandemics (epidemic all over the world) of cholera which spread to more than 102 countries worldwide and killed millions of people.
3. New strain Vibrio cholerae O139
An unprecedented happening occurred in the epidemiology of acute diarrhoea  when a novel strain of Vibrio cholerae non O1 was found to produce an exotoxin akin to cholera toxin and caused large-scale epidemics. The stain was named as Vibrio cholerae non O139 Bengal because the strains were isolated from the coastal region of the Bay of Bengal. The disease caused by this stain was indistinguishable from O1 cholera. The same strain of Vibrio was isolated from the UK, Germany, the Netherlands, Nepal, Bhutan, Indonesia and Japan. This was thought to be the beginning of eight cholera pandemic, but this actually did not happen so.
Acute watery diarrhoea comprises of about 20–25 pathogens which fall under the categories of bacterial, viral and parasitic agents. The bacterial pathogens causing diarrhoea include Vibrio cholerae O1 and O139, enterotoxigenic Escherichia coli, Vibrio parahaemolyticus and Salmonella; the viral pathogens include Rotavirus and Norwalk virus; the parasitic agents include Entamoeba histolytica, Giardia lamblia and Cryptosporidium. Shigella and Campylobacter jejuni cause dysentery. Rotavirus is a diarrhoeal disease, which affects children aged between 6 months and 2 years. Early vomiting is an important symptom of Rotavirus diarrhoea. Children suffering from Rotavirus diarrhoea occupy about 40% of beds in a children hospital.
5. Cholera toxin and dehydration
Vibrio cholerae O1 and O139 produce an exotoxin known as cholera toxin (CT) . CT attaches to gut mucosa and helps in outpouring of fluid and electrolytes, and when the fluid loss exceeds the absorbing capacity of the colon, watery diarrhoea ensues. This leads to a condition called dehydration. Classically, dehydration is categorized as mild, moderate and severe dehydration. Other scoring methods of dehydration have been proposed and will be useful.
The treatment of acute diarrhoea is based on the correction of fluid deficit and replacement of ongoing loses. Mild and moderate dehydration can be corrected by oral rehydration therapy [3, 4, 5, 6] using oral rehydration salt solution. On the other hand, intravenous fluid is required for the management of severe dehydration. The WHO recommended ORS containing sodium chloride of 2.5 g, potassium chloride of 1.5 g, sodium bicarbonate of 2.9 g and glucose of 20 g dissolved in 1 L of drinking water. ORS is given slowly particularly in children. If vomiting occurs, one has to wait 5–10 minutes and again start giving ORS very slowly. Recently, hypo-osmolar ORS has been recommended. On the clinical aspect of acute diarrhoea, new scoring method has been suggested. It has been reported that epileptic seizures are a manifestation of acute diarrhoea. This is a new area where lots of research may be done.
7. Role of antibiotics
Antibiotics are used in the treatment of acute diarrhoea only for severe cholera and shigellosis. Antibiotic therapy reduces the duration of diarrhoea/dysentery and hastens recovery. The antibiotics of choice for cholera are tetracycline or single dose (300 mg) of doxycycline. Norfloxacin and ciprofloxacin are effective. Herbal medicines may be effective in the treatment of acute diarrhoea. This mode of therapy will be cheap and safe.
8. Drug resistance
Drug-resistant strains of Vibrio cholerae have been reported. Shigellosis is treated by various antibiotics including ampicillin, co-trimoxazole, and the fluoroquinolone. However, multiple drug resistance is a huge problem and poses as a therapeutic challenge. The drug resistance is particularly seen in Shigella dysenteriae type 1 strains. These strains produced large-scale sporadic, epidemics and pandemic. The drug-resistant shigellosis epidemic that occurred in Bangladesh and Central America caused large morbidity and mortality. A number of complications have been reported in association with S. dysenteriae type 1 including hemolytic uremic syndrome (HUS) characterized by hemolysis, renal failure and thrombocytopenia.
Prevention of acute diarrhoea is a formidable challenge. These include sanitation, safe water and handwashing. Vaccination is an attractive disease prevention strategy. Health education plays a crucial role in the adoption of the strategy, particularly handwashing. This should start at the preschool level to form a habit in later life. Vaccination is an attractive disease prevention strategy. Recently, an oral cholera vaccine has been developed which has been found to protect up to 66% people among those vaccinated . Vaccines against Rotavirus are available.
10. Final words
Finally, this book comprises of chapters of topics, which have significance in relation to clinical feature, dehydration, and management and prevention of acute diarrhoea. The reader will find the topics new, informative, and interesting.