A communicable disease can be transmitted from one person to another in several ways, such as contact with blood or body fluids, inhalation of an airborne virus, or insect bites.

1. DiseasesAffectingtheGastro-IntestinalSystem
LECTURE3

2. • These are diseases that affect the digestive system. Diseases affecting the
gastro-intestinal can be further divided into as follows:
Common bacterial diseases that affect the gastrointestinal system
Common helminthic diseases that affect the gastrointestinal system
Common protozoan diseases that affect the gastrointestinal system.
Introduction

3. In this section you will look at three common communicable diseases of the gastro-
intestinal system. These are the following:
Cholera
Typhoid fever
Shigellosis
CommonBacterialDiseasesthatAffecttheGastrointestinal System

4. • Cholera is an infectious gastroenteritis caused by enterotoxin-producing, gram
negative bacteria strains of the bacterium vibrio cholerae.
There are two classes (serotypes) of vibrio cholera bacterium that are associated
with cholera outbreaks in humans, these are the following:
Vibrio cholerae O1 serotypes
Vibrio cholerae O139 serotypes
Cholera

5. The vibrio cholerae O1 serotype is further divided into two serotypes these are; classical and
El Tor and each biotype has two distinct serotypes as follows:
Vibrio cholerae Inaba
Vibrio cholerae Ogawa
Vibrio cholerae Hikojima.
Conti…..

6. • Transmission of cholera is through oral faecal route and because this organism is
sensitive to acid that is present in the stomach, one has to ingest large amounts for
the infection to occur.
• Vibro cholerae can live in fresh or salty water for two weeks. They can survive and
multiply in shell fish, thus making cholera a zoonotic disease. It can also multiply
readily in milk and boiled rice. The reservoirs of infection are the carriers.
Transmissionofcholera

7. The following are symptoms of cholera:
Upset and massive watery diarrhoea
Terrible muscle and stomach cramps
Vomiting
Fever in the early stages
SymptomsofCholera

8. • In a later stage the diarrhoea becomes ‘rice water stool’ (almost clear with flecks of
white). The ruptured capillaries may turn the skin black and blue with sunken eyes and
cheeks with blue lips.
• Symptoms are caused by massive body fluid loss induced by the enterotoxins that the V.
cholerae produce (Todd et al., 2002).
Conti….

9. • In epidemic situations a clinical diagnosis is made by taking a history of symptoms
from the patient and by a brief examination only. Treatment is usually started
without or before confirmation by laboratory analysis of specimens.
DiagnosisofCholera

10. The presence of vibrio cholerae is confirmed in the laboratory using the following
specimens:
Faeces (preferred specimen).
Rectal swabs are normally collected when a patient is having watery diarrhoea (fluid
stool).
LaboratoryDiagnosisofCholera

11. Stool specimens should be collected early, preferably within the first
24 hours of the onset of illness, and before the administration of any
antibiotics.
In case of watery diarrhoea, specimens for laboratory investigation
should be collected using sterile swabs which are inserted through
the rectum of suspected patients.
Specimen Collection, StorageandReferral forDiagnosisofVibrioCholera

12. The rectal swabs and/or stools specimens should be kept in transport medium
(cary-blar) and transported to the laboratory in cold temperatures (cool box), for
safety purposes (both to people handling the stool specimens and the
community), the specimens should be transported using the triple pack system
shown in the diagram that follows.
Always wear protective gears such as gloves and lab coats when handling
cholera patients.
Conti……

13. Thefollowing diagramillustrates thetriplepacksystem oftransportingcholeraspecimen

14. In lower level laboratories, rapid tests are recommended for the diagnosis of
cholera.
This a rapid immunochromatographic assay for the qualitative detection of vibrio
cholerae serogroups in human faecal specimens, environment water or solid food
specimens.
LaboratoryTestsforCholerain LowerLevelLaboratories

15. Thefollowing isadiagramillustratingthecrystaldipstickrapidtestkit.

17. After overnight incubation of stool specimens or rectal swabs from
suspected cholera patients, colonies of V. cholera on TCBS agar are large (2-
4mm) and yellow in colour. because of the fermentation of sucrose.
LaboratoryCultureMethod forVibrioCholera
Yellow colonies of v.cholera after incubation

18. Most cases of cholera can be successfully treated with oral rehydration therapy.
Oral rehydration therapy or ORT is highly effective, safe, and simple to administer.
In severe cholera cases with significant dehydration, the administration of intravenous
rehydration solutions may be necessary.
TreatmentofCholera

19. • Tetracycline is typically used as the primary antibiotic, although some strains
of V. cholerae have shown resistance. Other antibiotics that have been
proven effective against V. cholerae include cotrimoxazole, erythromycin,
doxycycline, chloramphenicol, and furazolidone. fluoroquinolones such as
norfloxacin also may be used, but resistance ha been reported (Todd et al.,
2002).
Conti…..

20. Although cholera may be life threatening, prevention of the disease is
normally straightforward if proper sanitation practices are followed.
Travelers should be aware of how the disease is transmitted and what can be
done to prevent it. Effective sanitation practices, if instituted and adhered to
in time, are usually sufficient to stop an epidemic.
PreventionofCholera

21. Other preventive measures include the following:
Sterilisation: Proper disposal and treatment of infected faecal wastewater
produced by cholera victims and all contaminated materials (such as
clothing, bedding, among others are essential.
Conti…….

22. All materials that come in contact with cholera patients should be
sterilised by washing in hot water using chlorine bleach, if possible.
Hands that touch cholera patients or their clothing, bedding, among
other things, should be thoroughly cleaned and sterilised with
chlorinated water or other effective anti-microbial agents.
Conti……..

23. Sewage treatment: Anti-bacterial treatment of general sewage by chlorine,
ozone, ultra-violet light or other effective treatment before it enters the
waterways or underground water supplies helps prevent undiagnosed
patients from inadvertently spreading the disease.
Otherpreventivemeasuresincludethefollowing:

24. A vaccine for cholera is available in some countries, but prophylactic usage is not
currently recommended for routine use by the Centres for Disease Control and
prevention (CDC).Sensitive surveillance and prompt reporting facilitate rapid
containment of cholera epidemics.
Conti…….

25. TyphoidFever
• Typhoid fever is transmitted by the ingestion of food or water contaminated
with faeces from an infected person.
• The disease is caused by gram negative rods bacteria called Salmonella
typhi.

26. SymptomsofTyphoidFever
• First Week
• In the first week the patient will have fever, headache, myalgia,(muscle aches and pain, ) relative
bradycardia ( pulse rate is lower than expected for a given body temperature), constipation, diarrhoea
and vomiting in children.
• Second Week
• In the second week the patient will have rose spots on the trunk, splenomegaly, cough, abdominal
distension and diarrhoea. At the end of the second week the patient will present with delirium (a
serious disturbance in mental abilities), then coma and death (Todd et al., 2002).

27. DiagnosisforTyphoidFever
• Diagnosis is made by doing a blood, bone marrow or stool culture.
• In epidemics and less wealthy countries, after excluding malaria, dysentery
or pneumonia, a therapeutic trial with chloramphenicol is generally
undertaken while awaiting the results of blood cultures (Todd et al., 2002).

28. LaboratoryDiagnosisofTyphoid
• You have already learnt that typhoid also called enteric fever is an illness that is
characterized by abdominal pain and high fever. The disease is caused by a
bacterium called salmonella which is a gram-negative rod-shaped bacterium.
• The Salmonella Laboratory Diagnosis of Typhoid
• species that are responsible for the enteric fever are the following:
• Salmonella enterica serotype typhi (formerly S. typhi).
• Salmonella enterica serotype paratyphi A, B or C.

29. Conti……..
• The specimen for laboratory investigation is collected before the patient
takes any antibiotics. These include the following:
• Fresh Stool: Collected when the patient is having abdominal pain.
• Whole blood: Collected when the patient is having high fever.

30. Conti…..
• The following are the tests that can be done in the laboratory to
diagnose typhoid:
• Rapid diagnostic test
• Microscopy of stool specimen
• Microscopy of blood films
• Culture of stool and blood specimens

31. RapidDiagnosticTestsforTyphoid
• These are screening tests which are used to detect specific antibodies against
specific Salmonella typhi antigen in human serum or plasma. The specimen is taken
from serum or plasma.
• Serum is the fluid portion of clotted blood sample while plasma is the fluid portion
of whole blood sample which has anticoagulants. There are different types of rapid
tests kits for diagnosis of typhoid and the procedure for each test is based on
manufacturer’s instructions for each test kit.

32. RapidDiagnosticTestsforTyphoid
• These are screening tests which are used to detect specific antibodies against
specific Salmonella typhi antigen in human serum or plasma. The specimen is
taken from serum or plasma.
• Serum is the fluid portion of clotted blood sample while plasma is the fluid
portion of whole blood sample which has anticoagulants. There are different
types of rapid tests kits for diagnosis of typhoid and the procedure for each
test is based on manufacturer’s instructions for each test kit.

33. Conti………
• The RDT kits for typhoid diagnosis have many advantages which fulfil the
requirement of typhoid diagnosis. These advantages include the following:
• Early and specific diagnosis of typhoid fever
• Fast, simple and reliable
• Simple to perform and no additional sample preparation required
• No special equipment is needed

34. Conti…..
• Results are easy to interpret
• Minimal sample volume used

35. diagramshowsexamplesofRDTkitsusedfortyphoiddiagnosis.

36. MicroscopyandCultureofStoolorBloodSpecimens
• Stool specimens involve the following:
• Microscopy through wet preparation
• Use of specific culture media as outlined in isolation of shigella
Blood specimens involve the following:
• Complete blood count (CBC) which shows a high number of white blood cells
• Blood culture during the first week of the fever which shows S. typhi bacteria

37. CONTI…
• Microscopy and Culture of Stool or Blood Specimens
• After microscopy, suspected stool specimens (those with pus cells and red
blood cells) will be packaged in appropriate transport media (caryblair) and
transported in the triple-package system to the reference laboratory for
culture to isolate and characterise the Salmonella bacteria. Packaging is done
in the same way that you learnt for cholera specimen.

38. Conti……..
• The culture of stool and blood sample for isolation of Salmonella species follows the
same procedure used for diagnosis of shigellosis as follows:
• Primary isolation media when using stool specimen: XLD agar incubated in air at 35
to 37°C for 18 to 24hr.
• Colonies on blood agar are moist and –two to 3mm in diameter.
• Salmonella species on XLD agar produce red colonies usually with a black centre
(some serotypes, for example, salmonella paratyphi A and salmonella typhi, may
not produce a black centre).

39. TreatmentofTyphoidFever
• Where resistance is uncommon, the treatment of choice is a fluoroquinolone
such as ciprofloxacin. Otherwise a third-generation cephalosporin such as
ceftriaxone gramocef-or cefotaxime is the first choice.
• Cefixime is a suitable oral alternative. (Todd et al., 2002)

40. PreventionofTyphoidFever
• You are now going to learn about the prevention of typhoid fever. Sanitation and
hygiene are the critical measures that can be taken to prevent typhoid.
• Typhoid does not affect animals and, therefore, transmission is only from human to
human.
• Typhoid can only spread in environments where human faeces or urine are able to
come into contact with food or drinking water.
• Careful food preparation and washing of hands are, therefore, crucial to preventing
typhoid.

41. Conti……..
• There are two vaccines currently recommended by the World Health
Organisation for the prevention of typhoid. These are the live, oral Ty21a
vaccine (sold as vivotif berna) and the injectable typhoid polysaccharide
vaccine (Nordberg and Kingondu, 2007).