epidemiology pathophysiology

1. ACUTE DIARRHEA
By: Ritu Rajan

2. Diarrhea
Definition
 Term ‘diarrhea’ (Greek) means ‘to flow through’
Diarrhea is defined as a change in consistency
and frequency of stool, i.e. liquid or watery
stools, that occur > 3 times a day.
 However it is the recent change in consistency & character of
stools rather than the number of stools that is more important.
 If there is associated blood in the stools, it is termed as dysentery.

3. Classification
Diarrhoea is classified as:-
 On the basis of duration:-
Acute ------------------------------------------ if <1weeks,
Persistent ----------------------------------- if 1–2 weeks,
Chronic -------------------------------------- if >2weeks

4.  On the basis of site of pathology
Small Bowel Diarrhea
Large Bowel Diarrhea(Dysentery/ Colitis/
Invasive diarrhea)

5. What is not a diarrhea ???????
Frequent defecation but with formed stool.
Semi-liquid stool at breast feeding.
Stool just after feeding (in 1st year infants)
Yellow-green liquid stool on 3rd – 6th days
after birth .

6. Epidemiology of childhood diarrhea
 Globally it is the 2nd most common cause of child deaths.
 Diarrhea accounts for 9% of all under five deaths.
 A loss of more than 0.71 million child live per year.
 It killed more than 1,600 children under five years of age
every day.
 Most of these deaths occurs among children less than 2 years.
 For a children aged under 5 years a median of 3 episodes of
diarrhea occurred per child year.

7. Cont.…
In India
 Acute diarrheal disease account for about 8% of death
in under 5 years age group.
 During the year 2013, about 10.7 million cases with
1,535 deaths were reported in India.

8. EDIDEMILOGICAL DETERMINANTS
ETIOLOGY
Bacterial
Viral
Parasitic
Others

9. COMMON CAUSES OF DIARRHEA- BACTERIA
 Escherichia coli:
(ETEC,EPEC,EIEC, EHEC,
EAEC),
 Shigella: S.sonnei, S.flexneri,
S.boydii & S.dysenteriae,
 Vibrio cholera,
 Salmonella,
 Campylobacter species
 Areomanas species
 Bacillus cereus
 Clostridium difficile &
pefringens,
 Staphylococcus aureus,
 Vibrio parahemolyticus,
 Yersinia enterocolitica,
 Plesiomonas shigelloides

10. COMMON CAUSES OF DIARRHEA- VIRUS
 Rotavirus
 Human caliciviruses: Norovirus spp.;Sapovirus spp.
 Enteric adenoviruses
 Astroviruses,
 Coronaviruses,
 Cytomegalovirus,
 Picornavirus

11. COMMON CAUSES OF DIARRHEA- PARASITE
Giardia lamblia,
Cryptosporidium parvum,
Entamoeba histolytica,
Cyclospora caytanensis,
Isospora belli,
Balandidium coli,
Blastocystis hominis,
Encephalitozoon intestinalis ,
Trichuris trichiura

12. COMMON CAUSES OF DIARRHEA-OTHERS
•Metabolic disease
Hyperthyroidism
Diabetes mellitus
Pancreatic insufficiency
•Food allergy
Lactose intolerance
•Antibiotics
•Irritable bowel syndrome

13. CRYTOSPORIDIUM
ST OR ST/LT ETEC
SHIGELLA SPP.
ADENOVIRUS
AREOMONAS SPP.
EPEC
NOROVIRUS
V.CHOLERAE
E.HISTOLYTICA
ROTAVIRUS
For age group
0-11 months

14. CRYTOSPORIDIUM
ST OR ST/LT ETEC
SHIGELLA SPP.
ADENOVIRUS
AREOMONAS SPP.
EPEC
NOROVIRUS
V.CHOLERAE
SAMONALLA
ROTAVIRUS
For age group
12-23 months

15. ROTAVIRUS
CRYTOSPORIDIUM
ST OR ST/LT ETEC
SHIGELLA SPP.
E. HISTOLYTICA
AREOMONAS SPP.
NOROVIRUS
SAPOVIRUS
V.CHOLERAE
SAMONELA
For age group
24-59 months

16. Risk factors
 Poor sanitation
 Personal hygiene
 Non availability of safe drinking water
 Unsafe food preparation &practices
 Lack of exclusive or predominant breast feeding
 Malnutrition (with micronutrient malnutrition vitamin A & zinc deficiency)
 Measles
 Hypo- or achlorhydria
 Selective IAg deficiency
 HIV

17. SEASONALITY
Disease Common season
Cholera Winter
Rotavirus diarrhea Winter
Shigellosis Dry summer and rainy season

18. Modes of transmission
 Most of the diarrheal agents are transmitted by the faecal-
oral route.
•Faecal-oral transmission may be:
water- borne;
food –borne: or
direct transmission which implies via fingers, or fomites
or dirt which may be ingested by young children

19. Physiological disturbance in diarrhea
TOTAL BODY WATER (TBW) 65%-75%
ECF (25%) ICF (45%)
CIRCULATING
BLOOD
INTESTINAL
FLUID
SECRETION
DIARRHEA LOOSE FROM
ECF
WHICH IS RICH IN SODIUM
&
LOW POTTASSIUM

20. LOSS OF WATER FROM BOBY
REDUCTION OR SHRINKAGE OF ECF VOLUME
EXCESSIVE SODIUM LOSS IN STOOLS
RELATIVE DECLINE IN SERUM SODIUM
FALL IN ECF OSMOLALITY
MOVEMET OF WATER FROM ECF TO ICF
CAUSES FURTHER SHRINKAGE OF ALREADY REDUCE
ECF COMPARTEMENT
HYPONATREMIC DEHYDRATION

21. Mechanisms of Diarrhea
PRIMARY MECHANISM DEFECT
Secretory Decreased absorption, increased
secretion, electrolyte transport
Osmotic Maldigestion, transport defects ingestion
of unabsorbable
Increased motility Decreased transit time
Decreased motility Defect in neuromuscular unit(s) Stasis
(bacterial overgrowth)
Decreased surface area (osmotic,
motility)
Mucosal invasion
Decreased functional capacity
Decreased Inflammation, decreased
colonic reabsorption, increased motility

22. VIRAL AGENTS CAUSING diarrhea
GASTROENTERITISMAJOR VIRUSES OTHER VIRUSES (MINOR):
1. Rotavirus
2. Enteric adenoviruses
3. Noroviruses :
a. Norwalk-like
viruses
b. Calicivirus
c. Astrovirus
1. Coronaviruses
2. Parvoviruses

23. ROTAVIRUS
 Family Reoviridae
 Genus Rotavirus

24. ROTAVIRUS
• 60-80nm in size
• Non-enveloped virus
• Double capsid
• EM appearance of a wheel with radiating spokes
• Icosahedral symmetry
• double stranded (ds) RNA in 11 segments

25. •Genome is composed of 11 segments of double-stranded RNA,
six structural VP1-7
coding for proteins
six nonstructural NSP1-6

26. PATHOGENESIS
TRANSMISSION:- Person to person via the faeco-oral route
After oral inoculation ---------- infect cells in the villi and enterocytes
of small intestine -------- leads to cell death and sloughing of villus ----
------ ---resulting in villus blunting ----------causes loss of absorptive
function due to the destruction of mature enterocytes --------- causes
osmotic diarrhea
Also produces secretory diarrhea
Rotavirus --------- opening of calcium channel ---------- influx of
calcium and efflux of sodium and water (NSP4)
INTRAENTROCYE CALCIUM ALSO LEAD TO CELL DEATH

27. WATER FOLLOWS THE MOVEMENT OF ELECTROLYTES AND GLUCOSE
Glucose, Na+, K+, Cl-, Water
Gut lumen
Enterocyte

28. Villus Tip: Absorption
Crypt: Secretion
NORMAL STATE

29. NORMAL VILLI BLUNTED VILLI

30. Destruction of enterocytes:
rotavirus,
Defective absorption
Hypersecretion:
rotavirus,
IMBALANCE BETWEEN ABSORPTION AND SECRETION
ACUTE WATERY DIARRHEA (VIRAL)

32. Clinical features
 Vomiting
 Diarrhea watery & without blood or visible mucus
 Fever
 Dehydration(lethargy and even shock)
 Transient lactose intolerance --- perianal excoriation

33. Bacterial AGENTS CAUSING diarrhea
 Vibrio cholera (serogroups O1 & O139)
 Escherichia coli (EHEC,ETEC)
 Shigella
 Salmonella
 Campylobacter

34. cholera
Vibrio cholerea
motile, gram negative, non spore forming
v.cholerae
o139
o1
Classic
Eltor

35. pathogenesis
 Bacteria -------- reaches to small intestine --------
multiplying in intestinal epithelium -------- produces
enterotoxin (CT) -------- attached to GM1(ganglioside
receptor) -------- cAMP -------- fluid secretion (rich in k+ &
bicarbonates)
 CT also inhibit absorption of sodium and chloride
 Cause massive water and electrolyte loss.

37. CLINICAL FEATURE: CHOLERA
 Rice-watery stool
 Marked dehydration
 Projectile vomiting
 No fever or abdominal pain
 Muscle cramps
 Hypovolemic shock
 Scanty urine

38. E.coli
 Gram negative, rod shaped, motile by peritrichate flagella.
 Types of diarrheagenic E.coli:-
Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enteropathogenic E. coli (EPEC)
Enterohemorrhagic E. coli (EHEC) (E. coli O157:H7)
Enteroaggregative E. coli (EAggEC)

39. Pathogenesis

40. CLINICAL FEATURE:
E. COLI DIARRHEA
Watery stools
Vomiting is common
Dehydration moderate to severe
Fever– often of moderate grade
Mild abdominal pain

41. shigella
Gram negative, rod shaped, non motile, non capsulated.
Cause bacillary dysentery.
The major serotypes of Shigella that cause diarrhea are:
Dysenteriae type 1 or Shigella shiga
Shigella flexneri
Shigella sonnei
Shigella boydii

42. pathogenesis

43. Shigella spp.
Superficial invasion of colonic mucosa
Which invade through M cell located over peyer patches
After phagocytosis
Multiplication
A series of events occurs
Spread of bacteria to
adjacent cell
Apoptosis of
macrophage

44. Transmigration of neutrophils in the lumen of colon
Neutrophilic necrosis & degranulation
Further breach of the epithelial barrier
Mucosal destruction

45. CLINICAL FEATURE:
SHIGELLOSIS
 Frequent passage of scanty amount of stools, mostly
mixed with blood and mucus
 Moderate to high grade fever
 Severe abdominal cramps
 Tenesmus– pain around anus during defecation
 Usually no dehydration

46. thanks