2. WATER BORNE DISEASES
Diseases caused by ingestion of water ,
contaminated by , human or animal
excrement , containing various pathogenic
micro-organisms.
3. WATER BORNE DISEASES
Diseases caused by ingestion of water ,
contaminated by , human or animal excrement ,
containing various pathogenic micro-organisms.
Includes :
Cholera
Typhoid
Dysenteries
4. An acute diarrheal disease, caused by Vibrio
Cholerae.
In the severe form , Painless watery diarrhea and
copious effortless vomiting occurs, leading to
hypovolemic shock and death within 24 hours.
If treated early , then the disease lasts for around
4-6 days , during which the patient loses huge
amounts of liquids and electrolytes from his body.
5. CLINICAL FEATURES :
Stool is typically , a colorless watery fluid with flecks
of mucus , called rice water stools.
Has a characteristic inoffensive sweetish odor, with
bicarbonate-rich isotonic electrolyte solution and
little protein.
It leads to diminution of ECF volume,
hemoconcentration, hypokalemia, base-deficit
acidosis and shock.
Muscular cramps, Renal failure, pulmonary edema,
cardiac arrhythmias, and paralytic ileus.
Clinical illness begins slowly with mild diarrhea and
vomiting within 1-3 days OR abruptly with sudden
massive diarrhea.
6. ORGANISM :
Vibrios are Gram –ve , rigid, curved rods.
They are actively motile by means of a polar
flagellum. The movement is vibratory motility ,
hence the name Vibrio.
They are asporogenous and noncapsulated.
Most important member of this genus is Vibrio
cholerae, causative agent of cholera.
MORPHOLOGY :
It is a short, curved, cylindrical rod with
rounded/pointed ends.
Size : 1.5µm * 0.2-0.4 µm
7. Koch described these organisms as ‘ fish in
stream’ appearance –as seen in thin films of
mucous flakes from acute cholera cases.
Strongly aerobic . In anaerobic conditions
, growth is scanty.
Temperature range that supports their
growth is 16 – 40ºC , with optimum
temperature being 37ºC.
Ph that supports their growth is 6.4 – 9.6 ;
optimum being 8.2 .
Distinguishing feature : Oxidase test : +ve
8. Nutrient Agar : Moist, translucent, round
discs, about 1-2mm in diameter, with bluish
tinge in transmitted light. Has distinctive
odor.
MacConkey Agar : Colorless colonies at first,
but later become reddish, due to prolonged
incubation- late fermentation of lactose
occurs.
Blood Agar : Initially green colored zone
appears, which later becomes clear due to
hemodigestion.
Various special media have been
employed for cultivation or orgs.
9. TRANSPORT MEDIUM :
Delicate organisms do not survive the time taken for transport
of the specimen to the diagnostic labs / they may be overgrown
by non-pathogens, Hence a special media is devised for
transporting these samples , known as Transport Media.
Examples :
Venkataraman-Ramakrishnan medium (VR)
20g crude sea salt
5g Peptone
1L Distilled water. PH is 8.6 - 8.8
Cary-Blair medium :
Sodium chloride + Sodium thioglycollate + Disodium
Phosphate + Calcium Chloride. At PH 8.4
Autoclaved Sea water also serves as Transport media.
10. Carbohydrate Fermentation
:
BIOCHEMICAL TESTS :
Glucose Mannitol Maltose Sucrose Lactose
Acid produces Acid produces Acid produces Acid produces Acid produces
No Gas No Gas No Gas No Gas Late
Fermentation
11. Carbohydrate Fermentation :
BIOCHEMICAL TESTS :
Glucose Mannitol Maltose Sucrose Lactose
Acid produces Acid produces Acid produces Acid produces Acid produces
No Gas No Gas No Gas No Gas Late
Fermentation
Indole formation and Reduction of nitrates to Nitrites,
contributes to Cholera red reaction.
Catalase Oxidase Methyl Red Urease
+ve +ve -ve -ve
Other Tests :
14. PATHOGENESIS : origin and development
Vibrios enter orally via contaminated food and water
In small intestine, vibrios cross mucus and reach
epithelial cells by chemotaxis, motility, mucinase and
with help of other proteolytic enzymes.
Hemagglutinin-protease cleaves mucus & fibronectin
thereby releasing the vibrios to bowel mucosa
facilitating their spread to remaining parts of
intestine.
Adhesion to the epithelial surface is due to presence
of ‘toxin co-regulated pilus’ , special type of fimbria.
15. Mechanism:
Throughout the course of infection , vibrios remain bound
to the surface.
Vibrios multiply on the intestinal epithelium and produce
a toxin, ‘cholera enterotoxin’ of 84K Daltons MW.
The toxin inhibits intestinal absorption of Na and clˉ .
Thereby causing clinical manifestations of cholera i.e.,
depletion of massive water and electrolytes.
Vibrios also possess lipopolysaccharide O antigen -
endotoxin; It has no role in pathogenesis , but helps in
providing immunity induced by killed vaccines.
16. Laboratory Diagnosis :
Stool collected at the acute stage, before
administration of antibiotics, is most useful
specimen in diagnosis.
Isolation is easy, as vibrios are present @106
– 109 /ml.
Samples are collected by lubricated
catheters, rectal swabs – absorbing around
0.1 – 0.2 ml.
Vomits are not useful, as they have
negligible amount or no amount of morgs.
Collected samples ought to be preserved at
4ºC, as vibrios die at tropical temperatures.
They are sent to labs in T.M. and then asap
are transferred to Monsur’s medium.
17. Lab tests:
No direct microscopic examination is
done.
Motility of vibrio is seen under dark-
field/phase contrast microscope.
Non-specific fluorescence is common
yet complicated technique.
Slide-agglutination tests may also be
done, followed by chick red cell
agglutination.
The strains are sent to NICED :
National Institute of Cholera & Enteric
Diseases, Kolkata ; for further tests.
18. TREATMENT:
Up to 80% of cases can be treated through oral
rehydration salts
Severe cases require intravenous fluids
Parenteral Vaccine :
2 doses administered 2 weeks apart
50% efficiency
provides 6 months protection
Killed Vaccine :
Killed whole-cell + recom. B-subunit of CT
Safe even during pregnancy & breastfeeding
Efficiency is 75-80%,decreases to 50% - 3yrs
19. Prevention & Control
Hygiene education
Good nutrition
Good sanitation
Water related issues should be addressed immediately
Public health infrastructure is of utmost importance to
control outbreaks
Avoid contacting soils that may be contaminated with feces
Do not defecate outdoors ~ rural areas
Wash /Sanitize our hands before eating
While travelling to places with poor sanitation , avoiding
contaminated water
22. Also Known As :
Enteric Fever
Bilious Fever
Yellow Jack
23. Typhoid fever is caused by Salmonella
typhi.
The term ‘Enteric fever’ consists of both
typhoid and paratyphoid fever.
Typhoid was once not demarcated from
normal fevers, but a detailed study of the
diseases was given by Bretonneau, 1826 –
identified the intestinal lesions.
Louis gave the name ‘Typhoid’ in 1829
24. Salmonella:
Belongs to Enterobactericieae family
Gram –ve rods causing intestinal infections
Facultative anaerobes & Aerobes
Size :1-3µm * 0.5µm
Motile with peritrichate flagella
CULTURAL CHARACTERISTICS :
• Grows readily on simple media
• PH range : 6-8
• Temperature : 15-41ºC
• Large colonies,2-3mm in diameter- circular, low convex
translucent and smooth
25. Growth on media :
MacConkey & Deoxycholate Citrate media :
Colorless colonies – due to absence of
lactose fermentation .
Wilson and Blair bismuth sulphite medium :
Jetblack colonies with metallic sheen- H2S
forms
Selenite F and Tetrathionate broth are
employed as Enrichment media.
26. Salmonella possess the following 3 antigens , based on
which they are classified and identified.
3 main antigenic factors are :
Flagellar antigen or H antigen
Somatic antigen or O antigen
Surface antigen or Vi antigen
H antigen : Antigen on flagella. Heat labile protein, i.e.
destroyed on heating. When mixed with antisera,
agglutinate rapidly producing large, fluffy, loose clumps.
Strongly Immunogenic.
O antigen : Phospholipid-protein-polysaccharide complex.
It is an integral part of cell wall. Identical to endotoxin.
Heat resistant. On mixing with antisera, a compact,
chalky, granular clumps are formed.
Vi antigen : known as surface antigen or encapsulation
antigen, as it encapsules or serve as a outer cover for O
antigen. Heat labile, HELPS cause clinical diseases more
consistently .
27. MODES OF TRANSMISSION :
Ingestion of contaminated food or water
Rarely , from person to person – fecal-oral route.
Food handlers/ Carriers. . .
‘Typhoid Mary’, is a classic example of
carrier transmission of the diseases. Mary Mallon, a
cook in New York City in early 1900s was affected
by Typhoid fever; She was responsible for infecting
at least 78 people and killing 5 people . She was
later put in prison, to avoid passing of the infection
further.
28. CLINICAL FEATURES :
ENTERIC FEVER
SEPTICEMIA- with(out) local suppurative lesions
GASTROENTERITIS / FOOD POISONING
Typhoid fever is a septicemia
characterized by fever, bradycardia, splenomagaly,
abdominal symptoms, and ‘rose spots’- which are
clusters of pink mauls on the skin.
Complications viz., intestinal haemorrhage or
perforations develop in untreated patients or when
there is a delayed treatment.
29. PATHOGENECITY:
The organisms penetrate ileal mucosa reach
mesenteric lymph nodes via lymphatics, multiply,
invade blood stream via thoracic duct.
In 7-10 days , they infect Liver, Gall-Bladder,
Spleen, Kidney, Bone-Marrow.
After multiplication, bacilli pass into blood causing
secondary and heavy Bacteremia.
Mechanism:
From gall bladder, invasion occurs in intestines.
Involvement of peyer’s patches, gut lymphoid
tissues leads to inflammatory reaction.
Finally leading to necrosis and formation of
characteristic typhoid ulcers.
30. SYMPTOMS:
Diarrhea
Severe headache
Abdominal pain
Anorexia
Fever
Ulcers on intestinal wall
Shock
Rose spots
intestinal hemorrhage + perforations
31. Blood cultures:
In adults, 5-10ml blood is collected by
venepuncture inoculated into 50-100ml bile
broth (0.5%)
Bacteremia occurs early in blood :
Week 1 90%
Week 2 75%
Week 3 60%
Week 4 =< 25%
32. Biochemical tests
IMViC Test
:
Name of the
test
Result
Indole test -ve
Methyl Red +ve
Voges-Proskauer -ve
Citrate utilization +ve
Urease -ve
Sugar
Fermentation :Sugars Glucos
e
Maltose Mannito
l
Sorbitol Sucros
e
Lactose
Acid +ve +ve +ve +ve -ve -ve
Gas +ve +ve +ve +ve +ve -ve
Further confirmatory tests done by Slide agglutination
tests
33. Widal Test :
The Widal test is used to make a presumptive
diagnosis of enteric fever. Although the test is no
longer performed in the U.S. or other developed
countries, it is still in use in many developing
countries where enteric fever is endemic and
limited resources require the use of rapid,
affordable testing alternatives.
the method relies on a reaction in a test tube or on
a slide between antibodies of the infected
person's blood sample and specific antigens of S.
typhi, which produces clumping that is visible to
the naked eye.
34. Control & Prevention :
Simple hand hygiene and washing can
reduce several cases of typhoid.
Choose processed foods for safety
All milk and dairy products should be
pasteurized.
Control fly populations
Any bleeding from rectum, bloody
stools, sudden acute abdominal pains
should be reported at once to the
physician.
