Epidemiology of Acute Diarrheal Diseases

Major killer of under 5 children, even though the toll has reduced considerably
- 10% of under-5 deaths in India
- Reduction of mortality mainly due to rehydration tech including ORS
Under 5 children are estimated to have 3 episodes per year
- Incidence hasn’t changed much but mortality is reduced considerably
- Loss of considerable number of DALYs
Leading cause of death during disasters and emergencies
- Displacement of population into temporary, overcrowded shelters and polluted water source, inadequate sanitation, contaminated food, lack of hygiene and malnutrition, all lead to spread and severity of diarrhea
Heavy economic burden on:
- Health services and Nation

Definition: Recent change in consistency or number of stools
Four clinical types have been defined:

Acute Watery Diarrhea: 3 or more liquid or watery stools in 24 h
- Main danger is dehydration
Dysentery: Presence of blood and/or mucus in stools
- Main danger is injury to intestinal mucosa and sepsis
Persistent Diarrhea: Diarrhea lasting for 14 days or more
- Main danger is malnutrition
- Persons with other diseases like AIDS are more likely to develop persistent diarrhoea
- Diarrhea associated with severe malnutrition
- Main danger is severe systemic sepsis (septicaemia)

Clinical types of diarrhea
Agent, host and environmental factors
Causes of Acute diarrhea
VIRUSES

Rotavirus
- Leading cause of severe, dehydrating diarrhea in < 5
- In developing countries, three-quarters of children acquire their first episode of rotavirus diarrhoea before the age of 12 months, whereas
- in developed countries the first episode is frequently delayed until the age of 2-5 years.
- Severe rotavirus gastroenteritis is largely limited to children aged 6-24 months.
- Re-infection known but first one only is usually severe
- Highly infectious, shed in very high concentrations, difficult to control spread
Even with clean water supplies and good hygiene practices
- Feco-oral route, person to person & via fomites
Adenoviruses
Caliciviruses
Astroviruses
Coronaviruses
Norwalk agents and Norwalk-like viruses

BACTERIAL CAUSES

Campylobacter jejuni
Enterotoxigenic Escherichia coli
- ETEC is an important cause of acute watery diarrhoea in adults and children in developing countries
Most common cause of traveller's diarrhoea.
Two types of toxins, heat labile (LT) and heat stable (ST).
Shigella
- Higher percentage of mortality
- Important cause among under 5
Salmonella
- Cause inflammation of the bowel epithelium
Campylobacter jejuni
- Slim, highly motile, S-shaped, gramnegative rods, formerly classed as vibrios.
- One of the commonest causes of enteritis, mechanism not known
Vibrio cholera - Does not invade gut mucosa
Vibrio parahemolyticus
Bacillus cereus
Staphylococcus aureus
Clostridium perfringens
Enterohemorrhagic E Coli
Aeromonas
Yersinia enterocolitica
Chlamydia
Neisseria gonorrhoeae

E. coli, Shigella and Salmonella produce potent enterotoxin similar to that of vibrio cholarae

PARASITES

Entameba histolytica
Giardia lamblia
- It flourishes in duodenum and jejunum
- Lumen teeming with very large numbers,
Tichuriasis
Cryptosporidium Spp.
- Causes diarrhea in infants, immuno-deficient patients and some domestic animals
- Diarrhea usually not severe or prolonged except in immuno-deficient sates like AIDS
In these patients it’s a common cause of persistent diarrhea and leads to wasting
Intestinal worms
Cyclospora

PARENTERAL INFECTION ESP. IN CHILDREN

Apart from these, during or after measles, there is a high risk of severe or fatal diarrhea

OTHER CAUSES

Metabolic disease
- Hyperthyroidism
- Diabetes mellitus
- Pancreatic insufficiency
Food allergy
- Lactose intolerance
Antibiotics
Irritable bowel syndrome
Parenteral Diarrhea – particularly in young children
- ENT, respiratory, urinary, infections malaria, meningitis

Until recently the pathogen could be identified only 25% of diarrhea cases
Currently, new techniques have enabled such identification in 75% cases

Causes in Developing Countries
Causes of diarrhea in developing countries

Reservoir of Infection

Host Factors

Most common in children esp. b/w 6months – 2 years age
- Highest incidence between 6 – 11 months age
This may be due to:
- Declining maternal antibodies
- Introduction of complimentary feed
- Crawling
More common in the
- bottle fed
- malnourished
Malnutrition leading to diarrhea and vice versa forms a vicious cycle

diarrhea and malnutrition-vicious cycle

ENVIRONMENTAL FACTORS
risk factors are:

Poverty
- Unhygienic conditions
- Prematurity
- Reduced gastric acid
- immunodeficiency

Seasonal patterns differ in geographical areas

Tropical areas:
- Rotavirus occurs throughout the year but increase in winter and
- Bacterial diarrheas peak during the warmer rainy season
Temperate climate:
- Bacterial diarrheas more frequent in warm season and
- Viral diarrheas in winters

Transmission

Reference:
K. Park, 2019. Epidemiology of Communicable Diseases, In: Park’s Textbook of Preventive and Social Medicine, 25th ed. Jabalpur, 2019

Lecture on acute diarrheal disaeses-1 (epidemiology): https://www.youtube.com/watch?v=8VMSn7mJgm8&t=215s
Lecture on acute diarrheal disaeses-2 (control): https://www.youtube.com/watch?v=85iOg3GNevU&t=41s
Lecture (HINDI) on acute diarrheal disaeses-1 (epidemiology): https://www.youtube.com/watch?v=c-bOaC55u-g&t=5s
Lecture (HINDI) on acute diarrheal disaeses-2 (control): https://www.youtube.com/watch?v=acc-nqkjar4&t=1s