The document provides a comprehensive overview of communicable diseases, including definitions, classifications, and the chain of disease transmission. It outlines epidemiological concepts such as modes of transmission, carriers, and the natural history of diseases, as well as prevention and control measures. The document specifically addresses oral-fecal transmitted diseases and includes examples like typhoid fever, detailing their transmission, symptoms, and epidemiology.

1. Kalab W (PHO)
Communicable Disease
Control

2. Kalab W (PHO)
Unit One – Introduction
Objectives
• Define communicable disease
• Discuss classifications of disease
• Define epidemiology and epidemiological
terminologies
• Describe the factors involved in the chain
of disease transmission

3. Kalab W (PHO)
What is communicable disease?

4. Kalab W (PHO)
Communicable Disease
It is due to specific infectious agents or
its toxic products that is transmitted from
an infected person(directly), animal or
inanimate reservoir(indirectly) to a
susceptible host.

5. Kalab W (PHO)
Classifications of Disease
It may be classified in several ways, i.e
1. Clinical manifestation
2. Time course
3. Taxonomy of infectious agent
4. Mode of transmission
5. Causative agent

6. Kalab W (PHO)
Causes of disease can be classified as:
o Primary cause
o Secondary causes (risk factors)

7. Kalab W (PHO)
Primary cause
It is a factor which is necessary for a disease
to occur and without which the disease can’t
occur
If disease does not develop without the factor
being present, then the causative factor is
necessary cause .E. g: Clostridium tetanus is
necessary cause of Tetanus
o But, many of the non infectious chronic
diseases don’t have primary cause
E. g: Hypertension

8. Kalab W (PHO)
o In case of infectious diseases, the primary
cause is also known as the etiologic agent
o If the disease always results from the factor,
we call the causative factor is sufficient
E.g. Infection with rabies virus is sufficient for
developing clinical rabies disease

9. Kalab W (PHO)
o It is important to note many factors may be
necessary but not sufficient for the disease
occurrence.E.g. Mycobacterium tubercle is a
necessary cause tuberculosis but it is by no means
sufficient to develop tuberculosis
o This leads us to think about other factors whose
presence will make the tubercle bacilli sufficient
to cause tuberculosis
o These factors are called secondary causes (risk
factors)

10. Kalab W (PHO)
Secondary causes (risk factors)
o Risk Factors: any factor associated with
an increased or decreased occurrence of
disease.
o Risk factors are predisposing, aggravating or
contributing factors for a disease occurrence

11. Kalab W (PHO)
Epidemiological Terms and
Definitions
Epidemiology
• The study of the frequency, distribution
and determinants of disease and other
health related conditions in human
populations, and the application of this
study to the promotion of health and to the
prevention and control of health problems.

12. Kalab W (PHO)
Epidemiological Terms and
Definitions
Epidemics
• The occurrence of any health related
conditions in a given population in excess
of the usual frequency in that population
Endemic
• A disease that is usually present in a
population or in an area at a more or less
stable level

13. Kalab W (PHO)
Epidemiological Terms and
Definitions
Pandemic
• An epidemic disease that occurs worldwide
Disease
• A state of physiological or psychological
dysfunction
Infection
• The entry and development or
multiplication of an infectious agent in the
body of man or animal

14. Kalab W (PHO)
Epidemiological Terms and Definitions #4
Infectious agent
• An agent capable of causing infections
Infectious
• Caused by microbes and can be transmitted to
other persons
Infestation
• Presence of living infectious agent on exterior
surface of the body
Contamination
• Presence of living infectious agent upon articles

15. Kalab W (PHO)
Chain of Disease Transmission
Refers to a logical sequence of factors or links
of a chain, which are essential to the
development of the infectious agent and
propagation of disease.
Six factors:

16. Kalab W (PHO)
Chain of Disease Transmission

17. Kalab W (PHO)

18. Kalab W (PHO)
Chain of Disease Transmission
1. Infectious agent
• An organism that is capable of producing infection or
infectious disease, those are
• Parasites
• Bacteria
• Fungus
• Virus
 The outcomes of exposure to infectious agent can be depends on:
─ Infectiousness
─Pathogenecity
─Virulence
─Immunogenicity

19. Kalab W (PHO)
Exposure
Infectiousness
(Infection
Rate)
Infection
Pathogenecity
(clinical :
subclinical)
Disease
Virulence
Disease
outcome
D i s e a s e p r o g r e s s i o n

20. Kalab W (PHO)
Chain of Disease Transmission
2. Reservoir of infection
It is is the habitat in which an infectious agent
lives, grows, transforms and/or multiplies
itself. Examples:
Human beings: Measles, Mumps, Pertusis,
Poliomyelitis etc…
Animals: Mosquito for plasmodium specious
etc…
Environment (plant, soil, water): tetanus etc…
Many diseases have multiple reservoirs

21. Kalab W (PHO)
Chain of Disease Transmission #9
3. Portal of exit:
The portal of exit is the route by which the
infectious agent leaves the infectious
hosts or reservoirs
 The most common portals of exit are
respiratory tract, genitourinary tract,
gastrointestinal tract, through skin, etc…

22. Kalab W (PHO)
Chain of Disease Transmission #10
4. Mode of transmission:
Mode of transmission is the mechanism by
which the infectious agent escapes from a
reservoir and enters into a susceptible
human host
There are two major mechanisms of
transmission
Direct transmission
Indirect Transmission

23. Kalab W (PHO)
I. Direct transmission
a) Transmission by direct contact
b) Transmission by direct projection
c) Trans-placental transmission
d) Blood transfusion
e) Organ transplantation

24. Kalab W (PHO)
a) Transmission by direct contact
Transmision by contact of skin, mucosa, or conjunctiva
with infectious agents directly transferred from
another person or vertebrate animal including:
 Touching:
oTrachoma (eye-hand-eye)
oCommon cold (nose-hand-eye)
oShigellosis (feces-hand-mouth)
oViral hepatitis and HIV (through breaks in skin)
 Sexual intercourse: HIV/AIDS
 kissing : mononucleosis
 Passing through birth canal: Gonorrhea

25. Kalab W (PHO)
b) Transmission by direct projection
Transmission by direct projection of saliva droplets created
by expiratory activities such as breathing, coughing,
sneezing, spitting, talking, singing etc…
Example: common cold

26. Kalab W (PHO)
c) Trans-placental transmission
 Trans-placental transmission of infectious agent is
transmission from mother to fetus via the placental
membrane
Examples:
o HIV/AIDS
o Syphilis
o Toxoplasmosis
o Malaria etc...

27. Kalab W (PHO)
d) Blood transfusion
o It is the transmission of disease through blood and
blood products
E. g. HIV and Hepatitis-B viruses
e) Organ transplantation
o It may include kidney, liver and cardiac
transplantation which transmit some communicable
diseases from the donors to the receivers

28. Kalab W (PHO)
II. Indirect transmission
a) Airborne transmission
b) Vehicle borne transmission
c) Vector borne transmission
Airborne transmission
• It is the transmission of infectious agents by
either suspended dust or droplet nuclei
Examples:
o Tuberculosis: droplet nuclei during sneezing,
speaking…
o Brucellosis: blood aerosols created during
slaughter

29. Kalab W (PHO)
b) Vehicle borne transmission
• It is the transmission of infectious agents by a vehicle.
Vehicle: is any non-living substance by which an
infectious agent can be transported and introduced
into a susceptible human host through a suitable
portal of entry.
Examples: Food, milk, water, soil, biological
products, fomites (cooking utensils, towels, bed
sheets, clothing, syringe, beddings, etc…)

30. Kalab W (PHO)
c) Vector borne transmission
It is the transmission of infectious agents by a vector
Vector: is an organism usually an arthropod, such
as insect, tick, mite, which transports an infectious
agent to a susceptible human host or to a suitable
vehicle
 A vector is responsible for introducing the agent into
the susceptible human host through a suitable portal of
entry
 Biological vector: salivarian transmission (malaria
by mosquito)
 Mechanical vector: trachoma by common fly

31. Kalab W (PHO)
Biologic transmission - when the agent undergoes
physiologic changes within the vector, the vector is
serving as both an intermediate host and a mode of
transmission
o An agent undergoes part of its life cycle inside a
vector before being transmitted to a new host
 Mechanical transmission - the agent does not
multiply or undergo physiologic changes in the vector

32. Kalab W (PHO)
Chain of Disease Transmission #15
5. Portal of entry:
• The site in which the infectious agent
enters to the susceptible host
– Mucus membrane
– Skin
– Respiratory tract
– GIT
– Blood

33. Kalab W (PHO)
Chain of Disease Transmission #16
6. Susceptible host (host factors):
• A person or animal lacking sufficient
resistance to a particular pathogenic agent
to prevent disease if or when exposed
• Immunity – describes the ability of the host
to resist infection

34. Kalab W (PHO)
The susceptibility of the human host
depends on:
 Genetic factors (including sex, blood group,
ethnicity,…)
 Immunity due past infection or immunization
 Nutritional status etc
 Personal behaviors like drinking, smoking etc

35. Kalab W (PHO)
Health care workers’ interventions used
to break the chain of infection
transmission.
Each element must be presented and lie
in sequential order for infection
occurrence.
 Intervention can be targeted at any of
those six elements of the chain of infection

36. Kalab W (PHO)
Carrier and its Type
Carrier is defined as an infected person
without manifestations of the disease but
capable of transmitting the infection to
others. E.g. History of Typhoid Marry.
Typhoid Marry was a carrier of Salmonella typhi
who worked as a cook in New York City, in different
households over many years. She was considered
to have caused at least 10 outbreaks of Typhoid
fever in New York City with several deaths. She
was the first known case of a carrier.

37. Kalab W (PHO)
Carrier and its Type….continued
Asymptomatic carriers(healthy): transmitting
infection without ever showing manifestation of
the disease
Example: Poliomyelitis
Incubatory carriers: transmitting infection by
shedding the agent before the onset of clinical
manifestations
Example: HIV/AIDS

38. Kalab W (PHO)
Carrier and its Type….continued
Convalescent carriers: transmitting infection
during convalescence, from the time of
recovery until the time the agent stops
shedding. Example: Typhoid fever
 Chronic carriers: shedding the agent for a
long period of time or even indefinite time
Example: Hepatitis-B infection

39. Kalab W (PHO)
Time Course of Infectious Disease
Incubation period
• It is the interval of time between infection
of the host and the first appearance of
symptoms and signs of the disease.
Prodormal period
• It is the interval between the onset of
symptom of an infectious disease and the
appearance of characteristic
manifestations.

40. Kalab W (PHO)
Time course of infectious disease (continued )
Period of communicability
• The period during which that particular
communicable disease is transmitted from
the infected person to the susceptible
host.

41. Kalab W (PHO)
Unit Two – Prevention and Control
of Communicable Disease
Objectives:
• Describe natural history of disease
• Identify the different levels of disease
prevention
• Apply the different control methods of
communicable diseases

42. Kalab W (PHO)
Natural History of Disease
• Refers to the course of a disease over
time unaffected by treatment.
• The four main stages:
Stage of Susceptibility
Subclinical Stage
The Clinical stage
Stage of Disability

43. Kalab W (PHO)
Natural History of Disease(continued)
Stage of Susceptibility
• The disease has not developed
• The presence of factors that favors its
occurrence
• Example
Acute or chronic alcoholism
High serum cholesterol level
An unvaccinated child

44. Kalab W (PHO)
Natural History of Disease(continued)
Subclinical Stage
• There is no manifest disease
• The patient does not know that he has any
disease
• Example:
Ova of intestinal parasite in the stool
Antibodies for polio virus in adults

45. Kalab W (PHO)
Natural History of Disease(continued)
The Clinical Stage
• The person has symptoms and signs of
disease
• There are different outcomes depending
on the agent-host interaction

46. Kalab W (PHO)
Natural History of Disease(continued)
Stage of Disability
• There are a number of conditions which
give rise to residual defects, leaving the
person disabled.
• Disability Any limitation of a person’s activity

47. Kalab W (PHO)
Healthy Person
Subclinical Stage
Clinical Disease
Disability
Recovery
Recovery Death
The stages in the natural history of disease
and the possible outcomes at every stage

48. Kalab W (PHO)

49. Kalab W (PHO)
Levels of Prevention
• Primary Prevention
• Secondary Prevention
• Tertiary Prevention

50. Kalab W (PHO)
Levels of Prevention (Continued)
Primary Prevention
• Preventing healthy people from becoming sick
• Methods:
Immunization
Provision of safe water supply
Health education
Safe disposal of human excreta
Vector control
Protection against accidents and occupational
hazards
Good nutrition, adequate clothing, rest and recreation

51. Kalab W (PHO)
Levels of Prevention (Continued)
Secondary Prevention
• Involves early detection and treatment of
people who have the disease.
Tertiary Prevention
• Prevention of more disability and death.

52. Kalab W (PHO)
Communicable Disease Control
• Refers to the reduction of the incidence
and prevalence of communicable disease
to a level where it cannot be a major public
health problem

53. Kalab W (PHO)
Methods of communicable disease control
Elimination of the reservoir
Interruption of transmission
Protection of susceptible host

54. Kalab W (PHO)
Methods of communicable disease control (continued)
Elimination of the reservoir
• Man as reservoir
Detection and adequate treatment of cases
Isolation

55. Kalab W (PHO)
Methods of communicable disease control (continued)
Elimination of the reservoir
Animal as reservoir
Destroying the animal and excluding it from
human habitation
Vaccination
Examination
Reservoir in non-living things
Limit man’s exposure to the affected area

56. Kalab W (PHO)
Methods of communicable disease
control (continued)
Interruption of transmission
• Improvement of environmental sanitation
and personal hygiene
• Control of vectors
• Disinfections and sterilization

57. Kalab W (PHO)
Methods of communicable disease
control (continued)
Protection of susceptible host
• Immunization
• Chemoprophylaxis
• Better nutrition
• Personal protection

58. Kalab W (PHO)
Unit Three
– Oro-Fecal transmitted CD’s
Objectives
• Identify the five important “Fs” in oral-fecal disease
transmission.
• State diseases transmitted mainly in water and
soil.
• List diseases commonly transmitted by having
direct contact with feces
• Participate in the diagnosis and treatment of cases.
• Implement preventive and control methods of oral-
fecal transmitted diseases

59. Kalab W (PHO)
Introduction
• Infectious agents are excreted in the stool
of infected person.
• The portal of entry is mouth.
• Route of transmission is feces-oral
transmission.
• The 5 F’s plays an important role in the
transmission of these diseases.

60. Kalab W (PHO)
Water
Feces Soil Food
Flies
Fomites
Finger
Fig. 2.1 The five “Fs” which play an
important role in fecal oral diseases
transmission (finger, flies, food, fomites and
feces).

61. Kalab W (PHO)
Outline for discussing CD
• Definition
• Etiology
• Epidemiology
– Occurrence
– Reservoir
– Mode of transmission
– Incubation period
– Period of communicability
– Susceptibility and resistance
– Life cycle
• Clinical manifestation
• Diagnosis
• Treatment
• Prevention and control

62. Kalab W (PHO)
Typhoid Fever
Definition
• Typhoid fever is a systemic infection characterized
by fever and abdominal pain
Cause or Infectious Agent
• Salmonella Typhi
• Salmonella Paratyphi A and B
• Salmonella typhimarium (rare)
 All of which are non capsulated, gram
negative motile bacteria.

63. Kalab W (PHO)
Typhoid Fever (continued)
"Typhoid Mary“ -Mary Mallon was
a cook in New York in 1906 a
chronic carrier who is known to
have infected 50 people, 3 of
whom died
►Stubborn, uncooperative and
died after 23 years in quarantine of
a stroke
►Tony Labella caused 120
infections and 7 deaths but worked
as a labourer and met with officials
once a week

64. Kalab W (PHO)
Typhoid Fever (continued)
Reservoir
• Humans

65. Kalab W (PHO)
Typhoid Fever (continued)
Mode of transmission
Feco-oral transmission
- By water and food contaminated by feces of
patients and carriers.
- Flies may infect foods in which the organisms
then multiply to achieve an infective dose

66. Kalab W (PHO)
Typhoid Fever (continued)
Incubation period
• 1 to 3 weeks

67. Kalab W (PHO)
Typhoid Fever (continued)
Period of communicability
• From 1st
week through out convalescence

68. Kalab W (PHO)
Epidemiology
Human beings the only natural host & reservoir, so
theoretically an eradicable disease
• Chronic carriers are the source of infection harboring
the organisms in their gall bladder (especially in the
presence of gall stones) and rarely at other sites
- It affects people of all ages and both sexes
• Enteric fever is endemic in most developing countries
,including Ethiopia
• Currently the disease is observed at a great frequency
in AIDS patients than the general population.

69. Kalab W (PHO)
• Following ingestion of the organism in contaminated
food or drink, Salmonella typhi passes the gastric
barrier and reach the upper small intestine
where the bacilli invade the intestinal epithelium
and they are engulfed by phagosoms which reside in
the Peyer’s patches (lymph nodes in the walls of the
intestines near junction of the ileum and colon)
• The bacilli multiply and enter the blood stream
and cause transient bacteremia

70. Kalab W (PHO)
Typhoid Fever (continued)
Clinical manifestations
First week
• Mild illness characterized by:
– Fever
– Anorexia
– Lethargy
– Malaise and general aches
– Head ache
– Epistaxis
– Abdominal pain
– constipation

71. Kalab W (PHO)
Typhoid Fever (continued)
Clinical manifestation
Second week
• Fever continuous
• Severe illness with
– Weakness
– Mental dullness or delirium
– Abdominal discomfort and distention
– Diarrhea
– Feces may contain blood

72. Kalab W (PHO)
Typhoid Fever (continued)
Clinical manifestations
Third week
• Pt continues to be febrile & increasingly
exhausted
• If no complications occur:
– Begins to improve
– Temperature decreases gradually

73. Kalab W (PHO)
Typhoid Fever (continued)
Clinical manifestations suggestive of typhoid
• Fever
• Rose spots
• Relative bradycardia
• leucopenia

74. Kalab W (PHO)
“Rose spot”, the rash of enteric fever due to S. typhi or S. paratyphi

75. Kalab W (PHO)
Typhoid Fever (continued)
Diagnosis WBC
• Based on clinical ground
• Widal test
• Culture

76. Kalab W (PHO)
Treatment
• First line
• Chloramphenicol, 500 mg PO QID for 14
days. For children: 25mg/kg

77. Kalab W (PHO)
Treatment
Alternative
• Ciprofloxacin, 500 mg PO BID for 7 days
Or
• Amoxicillin, 1g PO QID. For children: 20 – 40 mg/kg/day PO in
3 divided doses for 14 days
Or
• Sulfamethoxazole + trimethoprim, 800 mg/160 mg PO BID
for 14 days. For children 6 weeks - 5 months, 100/20 mg; 6
months – 5 years, 200/40 mg; 6 – 12 years, 400/80 mg BID
Or
• Ceftraxone, 1g QD as a single dose or 2 divided doses IM or
IV for 5 – 7 days. For children: 20 – 50 mg /kg/day as a single
dose or 2 divided doses IM or slow IV

78. Kalab W (PHO)
Treatment
For severe cases:
• Chloramphenicol, 1g IV bolus QID until 48
hours after fever has settled, followed by 500
mg PO QID for a total of 14 days. For
children: 25 mg/kg IV bolus QID until 48
hours after fever has settled, followed by 25
mg/kg PO QID for a total of 14 days
Symptomatic treatment:
• Use of antipyretics, e.g., paracetamol to
control fever

79. Kalab W (PHO)
Typhoid Fever (continued)
Prevention and control
• Treatment of patients and carriers
• Education
• Sanitary disposal of feces and control flies
• Provision of safe and adequate water
• Safe handling of food
• Exclusion of typhoid carriers and patients.
• Immunization.
• Regular check-up of food handlers.

80. Kalab W (PHO)
Bacillary dysentery
Definition
• An acute bacterial disease involving the
large and distal small intestine, caused by
the bacteria of genus shigella.

81. Kalab W (PHO)
Bacillary dysentery (continued)
Infectious agent
• Group A= Shigella dysentriae
• Group B= Shigella flexeneri
• Group C= Shigella boydii
• Group D= Shigella sonnei

82. Kalab W (PHO)
Bacillary dysentery (continued)
Epidemiology
• Occurs worldwide
• Endemic
• Epidemic
• Common in children under 10 years of
age.

83. Kalab W (PHO)
Bacillary dysentery (continued)
Reservoir
• Humans

84. Kalab W (PHO)
Bacillary dysentery (continued)
Mode of transmission
• Direct or indirect fecal-oral transmission
• Transmission through water and milk may
occur as a result of direct fecal
contamination.
• Flies can transfer organisms from latrines
to a non-refrigerated food item in which
organisms can survive and multiply.

85. Kalab W (PHO)
Bacillary dysentery (continued)
Incubation period
• 12 hours to 4 days

86. Kalab W (PHO)
Bacillary dysentery (continued)
Period of communicability
• During acute infection and until the
infectious agent is no longer present in the
feces

87. Kalab W (PHO)
Bacillary dysentery (continued)
Susceptibility and resistance
• Susceptibility is general
• Age and nutritional status
• Breast feeding is protective

88. Kalab W (PHO)
Bacillary dysentery (continued)
Clinical manifestations
• Fever, tachycardia, vomiting and
abdominal pain
• Diarrhea
• Generalized abdominal tenderness
• Tenesmus continual inclination 2 evacuate z bowel
• Feces are bloody, mucoid & of small
quantity
• Dehydration

89. Kalab W (PHO)
Bacillary dysentery (continued)
Diagnosis
• Sign and symptoms
• Stool microscopy
• Stool culture

90. Kalab W (PHO)
Bacillary dysentery (continued)
Treatment
Supportive treatment
• Correct dehydration with ORS or IV fluids
• Relieve and pain if necessary

91. Kalab W (PHO)
Bacillary dysentery (continued)
Treatment
Drug treatment
• First line
– Ciprofloxacin, 500 mg PO BID for 3 – 5 days.
For children:7.5 – 15 mg /kg/day PO in 2
divided doses for only 3 days.

92. Kalab W (PHO)
Bacillary dysentery (continued)
Treatment
Drug treatment
• Alternatives
– Sulfamethoxazole + trimethoprim, 800 mg/160 mg
PO BID for 5 – 7 days. For children: 6 weeks – 5
months; 100/20 mg; 6 months – 5 years, 200/40
mg; 6 – 12years, 400/80 mg BID
Or
– Ceftraxone, 1-2g stat or 2 divided doses IM or slow
IV. For children: 20-50 mg/kg/day as a single dose
or 2 divided doses IM or slow IV.

93. Kalab W (PHO)
Bacillary dysentery (continued)
Prevention and control
• Detection of carriers and treatment of the
sick
• Hand washing
• Proper excreta disposal
• Adequate and safe water supply.
• Control of flies.
• Cleanliness in food handling and
preparation.

94. Kalab W (PHO)
Amoebic Dysentery
Definition
• An infection due to a protozoan parasite
that causes intestinal or extra-intestinal
disease.

95. Kalab W (PHO)
Amoebic Dysentery (continued)
Infectious agent
• Entamoeba histolytica

96. Kalab W (PHO)
Amoebic Dysentery (continued)
Epidemiology
• Worldwide
• Most common in the tropics and sub-
tropics.
• Prevalent in areas with poor sanitation, in
mental institutions .
• Invasive amoebiasis is mostly a disease of
young people (adults).
• Rare below 5 years of age especially
below 2 years.

97. Kalab W (PHO)
Amoebic Dysentery (continued)
Mode of transmission
• Fecal-oral transmission

98. Kalab W (PHO)
Amoebic Dysentery (continued)
Incubation period
• 2-4 weeks.

99. Kalab W (PHO)
Amoebic Dysentery (continued)
Period of communicability
• During the period of passing cysts of E.
histolytica, which may continue for years.

100. Kalab W (PHO)
TRANSMISSION
1. Cysts ingested in food,
water or from hands
contaminated with feces
ENVIRONMENT
6. Feces containing infective cysts
contaminate the environment
HUMAN HOST
2. Cysts excyst, forming trophozoites
3. Multiply in intestine
4. Trophozoites encyst.
5. Infective cysts passed in feces.*
*trophozoites passed in feces disintegrate
Fig. 2.2 Transmission and life cycle of Entamoeba histolytica

101. Kalab W (PHO)
Amoebic Dysentery (continued)
Clinical manifestation
• Diarrhea
• Abdominal cramps
• Nausea
• Vomiting
• Tenesmus.
• With dysentery, feces are generally
watery, containing mucus and blood.

102. Kalab W (PHO)
Amoebic Dysentery (continued)
Diagnosis
• Demonstration of entamoeba histolytica
cyst or trophozoite in stool.

103. Kalab W (PHO)
Amoebic Dysentery (continued)
Treatment
• First line
– Metronidazole, 500 – 750 mg PO TID for 5 – 7
days. For children: 7.5 mg/kg PO TID for 5 – 7
days

104. Kalab W (PHO)
Amoebic Dysentery (continued)
Treatment
• Alternative
– Tinidazole, 2g PO QD for 3 consecutive days.
For children: 50 – 60 mg/kg daily for 3 days

105. Kalab W (PHO)
Amoebic Dysentery (continued)
Prevention and control
• Adequate treatment of cases
• Provision of safe drinking water
• Proper disposal of human excreta (feces)
and hand washing following defecation.
• Cleaning and cooking of local foods

106. Kalab W (PHO)
Giardiasis
Definition
• A protozoan infection principally of the
upper small intestine associated with
symptoms of chronic diarrhea,
steatorrhea, abdominal cramps, bloating,
frequent loose and pale greasy stools,
fatigue and weight loss.

107. Kalab W (PHO)
Giardiasis (continued)
Infectious agent
• Giardia lamblia

108. Kalab W (PHO)
Giardiasis (continued)
Epidemiology
• Worldwide distribution.
• Children are more affected than adults.
• Highly prevalent in areas of poor
sanitation.

109. Kalab W (PHO)
Giardiasis (continued)
Reservoir
• Humans

110. Kalab W (PHO)
Giardiasis (continued)
Mode of transmission
• Person to person transmission occurs by
hand to mouth transfer of cysts from feces
of an infected individual especially in
institutions and day care centers.

111. Kalab W (PHO)
Giardiasis (continued)
Period of communicability
• Entire period of infection, often months

112. Kalab W (PHO)
Giardiasis (continued)
Susceptibility and resistance
• Asymptomatic carrier rate is high.
• Infection is frequently self limited.
• Persons with AIDS may have more serious
and prolonged infection.

113. Kalab W (PHO)
TRANSMISSION
1. Cysts ingested in food,
water or from hands
contaminated with feces
ENVIRONMENT
6. Feces containing infective cysts
contaminate the environment
HUMAN HOST
2. Cysts excyst, forming trophozoites
3. Multiply in intestine
4. Trophozoites encyst.
5. Infective cysts passed in feces.*
*trophozoites passed in feces disintegrate
Fig. 2.3Transmission and life cycle of Giardia Lamblia

114. Kalab W (PHO)
Giardiasis (continued)
Clinical manifestations
• Ranges from asymptomatic infection to
severe failure to thrive and mal-absorption.
• Young children usually have diarrhea but
abdominal distention and bloating are
frequent.
• Adults have abdominal cramps, diarrhea,
anorexia, nausea, malaise, bloating, many
patients complain of sulphur tasting
(belching).

115. Kalab W (PHO)
Giardiasis (continued)
Diagnosis
• Demonstration of Giardia lamblia cyst or
trophozoite in feces

116. Kalab W (PHO)
Giardiasis (continued)
Treatment
• First line
– Metronidazole, 250-500 mg PO TID for 5 days.
For children, 1-3 years: 500 mg daily; 3-7 years:
600-800 mg daily; 7-10 years: 1 g daily, all for 3
days.

117. Kalab W (PHO)
Giardiasis (continued)
Treatment
• Alternative
– Tinidazole, single oral dose of 2 g. for
children, 50-75 mg/kg as a single dose (may
be repeated once if necessary).

118. Kalab W (PHO)
Giardiasis (continued)
Prevention and control
• Good personal hygiene and hand washing
before food and following toilet use.
• Sanitary disposal of feces.
• Protection of public water supply from
contamination of feces.
• Case treatment
• Safe water supply

119. Kalab W (PHO)
Cholera
Definition
• An acute illness caused by an enterotoxin
elaborated by vibrio colerae.

120. Kalab W (PHO)
Cholera (continued)
Infectious agent
• Vibrio cholerae

121. Kalab W (PHO)
Cholera (continued)
Epidemiology
• Epidemic
• Pandemic
• Endemic

122. Kalab W (PHO)
Cholera (continued)
Reservoir
• Humans

123. Kalab W (PHO)
Cholera (continued)
Mode of transmission
• Ingestion of food or water directly or
indirectly contaminated with feces or
vomitus of infected person.

124. Kalab W (PHO)
Cholera (continued)
Incubation period
• From few hours to 5 days, usually 2-3
days.

125. Kalab W (PHO)
Cholera (continued)
Period of communicability
• For the duration of the stool positive stage,
usually only a few days after recovery.
• Antibiotics shorten the period of
communicability.

126. Kalab W (PHO)
Cholera (continued)
Susceptibility and resistance
• Gastric achlorhydria increases risk of
illness.
• Breast-fed infants are protected.

127. Kalab W (PHO)
Cholera (continued)
Clinical manifestations
• Abrupt painless watery diarrhea; the
diarrhea looks like rice water.
• In severe cases, several liters of liquid
may be lost in few hours leading to shock.
• Severely ill patients have sunken eyes and
cheeks, scaphoid abdomen, poor skin
turgor, and thready or absent pulse.
• Loss of fluid continues for 1-7 days.

128. Kalab W (PHO)
Cholera (continued)
Diagnosis
• Based on clinical grounds.
• Culture (stool) confirmation.

129. Kalab W (PHO)
Cholera (continued)
Treatment
 Symptomatic/Supportive treatment
• For mild cases
give ORS, PRN; for children <2 years: 50-100ml, 2-10
years: 100-200ml after each loose stool.
• For severe cases
Ringer lactate IV infusion (alternatively Normal Saline)
should be given 50-100 ml /min until shock is reversed;
thereafter, according t fluid loss.
KCl solution 20-40 mmol/litre may be added as required.
• In the absence of IV solution aggressive rehydration
with ORS is vital.

130. Kalab W (PHO)
Cholera (continued)
Treatment
 Drug treatment
• First line
Doxycycline, 100 mg PO BID for 3 days. For
children: 6mg/kg daily for 3 days

131. Kalab W (PHO)
Cholera (continued)
Treatment
 Drug treatment
• Alternatives
Sulfamethoxazole + trimethoprim, 800mg/160 mg
PO BID for 5 days. For children: 6 weeks – 5
months: 100/20 mg; 6 months – 5 years: 200/40
mg; 6 – 12 years: 400/80 mg BID for 5 days
Or
Ciprofloxacin, 500 mg PO BID, for 3 – 5 days

132. Kalab W (PHO)
Cholera (continued)
Prevention and control
• Case treatment
• Safe disposal of human excreta and
control of flies
• Safe public water supply
• Hand washing and sanitary handling of
food
• Control and management of contact cases

133. Kalab W (PHO)
Infectious hepatitis
Definition
• An acute viral disease characterized by
abrupt onset of fever, malaise, anorexia,
nausea, and abdominal discomfort
followed within a few days by jaundice.

134. Kalab W (PHO)
Infectious hepatitis (continued)
Infectious agent
• Hepatitis A virus

135. Kalab W (PHO)
Infectious hepatitis (continued)
Epidemiology
• Worldwide distribution in sporadic and
epidemic forms.
• In developing countries, adults are usually
immune and epidemics of HA are
uncommon.
• Infection is common where environmental
sanitation is poor and occurs at an early
age.

136. Kalab W (PHO)
Infectious hepatitis (continued)
Reservoir
• Humans

137. Kalab W (PHO)
Infectious hepatitis (continued)
Mode of transmission-
• Person to person by fecal oral route.
• Through contaminated water and food
contaminated by infected food handlers.

138. Kalab W (PHO)
Infectious hepatitis (continued)
Incubation period
• 15-55 days, average 28-30 days.

139. Kalab W (PHO)
Infectious hepatitis (continued)
Period of communicability
• High during the later half of the incubation
period and continuing for few days
following onset of jaundice.
• Most cases are non-infectious following
first week of jaundice.

140. Kalab W (PHO)
Infectious hepatitis (continued)
Susceptibility and resistance
• General.
• Immunity following infection probably lasts
for life.

141. Kalab W (PHO)
Infectious hepatitis (continued)
Clinical manifestations
• Abrupt onset of fever, malaise, anorexia,
nausea and abdominal discomfort,
followed in few days by jaundice.
• Complete recovery without sequel or
recurrence as a rule.

142. Kalab W (PHO)
Infectious hepatitis (continued)
Diagnosis
• Based on clinical and epidemiological
grounds.
• Demonstration of IgM (IgM anti-HAV) in
the serum of acutely or recently ill patients.

143. Kalab W (PHO)
Infectious hepatitis (continued)
Treatment
• Symptomatic: rest, high carbohydrate diet
with low fat and protein.

144. Kalab W (PHO)
Infectious hepatitis (continued)
Prevention and control
• Public education
• Proper water treatment and distribution
systems and sewage disposal.
• Proper management of day care centers
• HA vaccine for all travelers to intermediate
or high endemic areas.
• Protection of day care centers’ employees
by vaccine.

145. Kalab W (PHO)
Ascariasis
Definition
A helmentic infection of the small intestine
generally associated with few or no symptoms.

146. Kalab W (PHO)
Ascariasis
(continued)
Infectious agent
Ascaris lumbricoids

147. Kalab W (PHO)
Ascariasis (continued)
Epidemiology
• The most common parasite of humans
where sanitation is poor.
• School children (5-10 years of age) are
most affected.
• Highly prevalent in most tropical countries.

148. Kalab W (PHO)
Ascariasis (continued)
Reservoir
• Humans
• Soil

149. Kalab W (PHO)
Ascariasis (continued)
Mode of transmission
• Ingestion of infective eggs from soil
contaminated with human feces or
uncooked produce contaminated with soil
containing infective eggs
• Not directly from person to person or from
fresh feces.

150. Kalab W (PHO)
Ascariasis (continued)
Incubation period
• 4-8 weeks.

151. Kalab W (PHO)
Ascariasis (continued)
Period of communicability
• As long as mature fertilized female worms
live in the intestine.

152. Kalab W (PHO)
Ascariasis (continued)
Susceptibility and resistance
• Susceptibility is general

153. Kalab W (PHO)
TRANSMISSION
1. infective eggs ingested in
food or from contaminated
hands with feces
ENVIRONMENT
6.Eggs become infective (embryonated) in soil in
30-40 days
7. Infective eggs contaminate the environments
HUMAN HOST
2. Larvae hatch. Migrate through liver
and lungs
3. Pass up trachea and are swallowed.
4.Become mature worm in small
intestine.
5. Eggs produced and passed in feces.
Fig. 2.4 Transmission and life cycle of Ascaris Lumbricoids

154. Kalab W (PHO)
Ascariasis (continued)
Clinical manifestations
• Most infections go unnoticed until large worm is
passed in feces and occasionally the mouth and
nose.
• Migrant larvae may cause itching, wheezing and
dyspnea, fever, cough productive of bloody
sputum may occur.
• Abdominal pain may arise from intestinal or duct
(biliary, pancreatic) obstruction.
• Serious complications include bowel obstruction
due to knotted/intertwined worms.

155. Kalab W (PHO)
Ascariasis (continued)
Diagnosis
• Microscopic identification of eggs in a stool
sample
• Adult worms passed from anus, mouth or
nose

156. Kalab W (PHO)

157. Kalab W (PHO)

158. Kalab W (PHO)
Ascariasis (continued)
Treatment
 First line
• Piperazine, 4g in a single dose; for children:
9-12 years, 3.75g; 4 – 5 years, 2.25g; 1 – 3
years, 1.5g; <1 year, 120 mg/kg as a single
dose

159. Kalab W (PHO)
Ascariasis (continued)
Treatment
 Alternatives
• Levamisole, 120 – 150 mg (3-4 tablets) PO to be
taken as a single dose
Or
• Albendazole, 400 mg PO as a single dose. For
children: 1 – 2 years, 200 mg as a single dose.
Or
• Mebendazole, 100 mg PO BID for 3 days
Or
• Pyrantel, 700 mg PO as a single dose

160. Kalab W (PHO)
Ascariasis (continued)
Prevention and control
• Treatment of cases
• Sanitary disposal of feces
• Prevent soil contamination in areas where
children play
• Promote good personal hygiene

161. Kalab W (PHO)
Trichuriasis
Definition
• A nematode infection of the large intestine,
usually asymptomatic in nature.

162. Kalab W (PHO)
Trichuriasis (continued)
Infectious agent
• Trichuris trichura (whipworm)

163. Kalab W (PHO)
Trichuriasis (continued)
Epidemiology
• Worldwide, especially in warm moist
regions.
• Common in children 3-11 years of age.

164. Kalab W (PHO)
Trichuriasis (continued)
Reservoir
• Humans

165. Kalab W (PHO)
Trichuriasis (continued)
Mode of transmission
• Indirect particularly through ingestion of
contaminated vegetables.
• Not immediately transmissible from person
to person.

166. Kalab W (PHO)
Trichuriasis (continued)
Incubation period
• Indefinite

167. Kalab W (PHO)
Trichuriasis (continued)
Period of communicability
• Several years in untreated carriers.

168. Kalab W (PHO)
Trichuriasis (continued)
Susceptibility and resistance
• Universal.

169. Kalab W (PHO)
TRANSMISSION
1. Infective eggs ingested in
food or from contaminated
hands with feces ENVIRONMENT
6.Eggs become infective (embryonated) in soil after 3 weeks.
7. Infective eggs contaminate the environments
HUMAN HOST
2. Larvae hatch. Develop in small
intestine. Migrate to caecum.
3. Pass up trachea and are swallowed.
4. Become mature worms.
5. Eggs produced and passed in feces.
Fig. 2.5 Transmission and life cycle of Trichuris trichura

170. Kalab W (PHO)
Trichuriasis (continued)
Clinical manifestation
• Severity is directly related to the number of
infecting worms.
• Most infected people are asymptomatic.
• Abdominal pain, tiredness, nausea and
vomiting, diarrhea or constipation are
complaints by patients.
• Rectal prolapse may occur in heavily
infected very young children

171. Kalab W (PHO)

172. Kalab W (PHO)
Trichuriasis (continued)
Diagnosis
• Demonstration of eggs in feces

173. Kalab W (PHO)
Trichuriasis (continued)
 Treatment
• First line
Mebendazole, 100 mg PO BID for 3 days

174. Kalab W (PHO)
Trichuriasis (continued)
 Treatment
• Alternative
Albendazole, 400 mg PO as a single dose. For
children: 1 – 2 years, 200 mg as a single dose.

175. Kalab W (PHO)
Trichuriasis (continued)
Prevention and control
• Sanitary disposal of feces
• Maintaining good personal hygiene
• Cutting nails especially in children.
• Treatment of cases.

176. Kalab W (PHO)
Entrobiasis
Definition
• A common intestinal helminthic infection
that is often asymptomatic.

177. Kalab W (PHO)
Entrobiasis (continued)
Infectious agent
• Entrobius vermicularis

178. Kalab W (PHO)
Entrobiasis (continued)
Epidemiology
• Worldwide
• Prevalence is highest in school aged
children, followed by preschools and is
lowest in adults except for mothers of
infected children.
• Prevalence is often high in domiciliary
institutions.
• Infection usually occurs in more than one
family member.

179. Kalab W (PHO)
Entrobiasis (continued)
Reservoir
• Human

180. Kalab W (PHO)
Adult worms in
caecum
Gravid females migrate through the anus to
the perineal skin and deposit eggs (usually
during the night)
Migrate down
to caecum
Eggs become infective in a few hours in
perineal area
Ingestion of eggs by
man
Larvae
hatch in
duodenum
Fig. 2.6 Transmission and life cycle of Enterobius vermicularis

181. Kalab W (PHO)
Entrobiasis (continued)
Mode of transmission
• Direct transfer of infective eggs by hand
from anus to mouth of the same or another
person
• Indirectly through clothing, bedding, food
or other articles contaminated with eggs of
the parasite.

182. Kalab W (PHO)
Entrobiasis (continued)
Incubation period
• 2-6 weeks

183. Kalab W (PHO)
Entrobiasis (continued)
Period of communicability
• As long as gravid females are discharging
eggs on perineal skin.
• Eggs remain infective in an indoor
environment for about 2 weeks.

184. Kalab W (PHO)
Entrobiasis (continued)
Susceptibility and resistance
• Universal.

185. Kalab W (PHO)
Entrobiasis (continued)
Clinical manifestations
• Perineal itching
• Disturbed sleep
• Irritability
• Secondary infection of the scratched skin

186. Kalab W (PHO)

187. Kalab W (PHO)
Entrobiasis (continued)
Diagnosis
• Stool microscopy for eggs or female worms

188. Kalab W (PHO)
Entrobiasis (continued)
Treatment
 First line
• Mebendazole, 100 mg PO BID for 3 days
 Alternative
• Albendazole, 400 mg PO as a single dose.
For children: 1 – 2 years, 200 mg as a single
dose.

189. Kalab W (PHO)
Entrobiasis (continued)
Prevention and control
• Educate the public
• Treatment of cases
• Reduce overcrowding in living
accommodation.
• Provide adequate toilets

190. Kalab W (PHO)
Strongyloidosis
Definition
• An often asymptomatic helminthic infection
of the duodenum and upper jejunum.

191. Kalab W (PHO)
Strongyloidosis (continued)
Infectious agent
– Strongyloids stercolaris

192. Kalab W (PHO)
Strongyloidosis (continued)
Epidemiology
• In tropical and temperate areas.
• More common in warm and wet regions.
Worms can be free-living in the soil or
live in a host.
 The definitive host is humans, but
may also affect other primates and dogs

193. Kalab W (PHO)
Strongyloidosis (continued)
Habitat
Has both free living and parasitic generations
Parasitic Adult females: hidden in the mucosal
epithelium of the small intestine of man
Rhabditiform larvae: Passed in the faeces and
external environments
 Filariform larvae: soil and water the infective
stage

194. Kalab W (PHO)
TRANSMISSION
1. Infective filariform
larvae penetrate skin,
e.g. feet. Autoinfection
also occurs.
ENVIRONMENT
6. In soil larvae become free living produce more
rhabditiform larvae.
7. Become infective filariform larvae in the soil.
HUMAN HOST
2. Larvae migrate, pass up trachea and are swallowed.
3. Become mature worms in small intestine.
4. Eggs laid. Hatch rhabditiform larvae in intestine.
5. Rhabditiform larvae:
- passed in feces, or become filariform larvae in
intestine causing autoinfection
Fig. 2.7 Transmission and life cycle of Strongyloids stercolaris

195. Kalab W (PHO)
Strongyloidosis (continued)
Mode of transmission
• Commonly by penetration of skin by filariform
larva
• Ingestion of food or water contaminated with
filariform larva( oral rout)
• Rarely: Transmamary & Organ transplantation
• Autoinfection with rhabidit form larva

196. Kalab W (PHO)
Strongyloidosis (continued)
Incubation period
• 2-4 weeks

197. Kalab W (PHO)
Strongyloidosis (continued)
Period of communicability
• As long as living worms remain in the
intestine
• up to 35 years in cases of autoinfection.

198. Kalab W (PHO)
Strongyloidosis (continued)
Susceptibility and resistance
• Universal.
• Patients with AIDS or on immune-
suppressive medication

199. Kalab W (PHO)
Clinical manifestation
• It is usually asymptomatic,
In symptomatic cases
1.Cutaneous phase
 large number of larva produce itching and erythema at
the site of infection within 24 hours of invasion
2.Pulmonary phase:
The migratory larva in the lung producing
bronchopneumonia and full blown pneumonitis

200. Kalab W (PHO)
3. Intestinal phase : Invasion by adult worms may
produce abdominal pain and mucus diarrhea ,
nausea vomiting and anemia

201. Kalab W (PHO)
Strongyloidosis (continued)
Diagnosis
• Identification of larvae in stool specimen

202. Kalab W (PHO)
Strongyloidosis (continued)
Treatment
• First line
–Thiabendazole, 1500 mg, PO BID, for
children: 25 mg/kg PO for two
consecutive days.

203. Kalab W (PHO)
Strongyloidosis (continued)
Treatment
• Alternatives
–Albendazole, 400 mg PO as a single
dose. For children: 1 – 2 years, 200 mg
as a single dose.

204. Kalab W (PHO)
Strongyloidosis (continued)
Prevention and control
• Proper disposal of human excreta (feces)
• Personal hygiene including use of
footwear
• Case treatment

205. Kalab W (PHO)
Hookworm disease
Definition
• A common parasitic infection with a variety
of symptoms usually in proportion if the
degree of anaemia.

206. Kalab W (PHO)
Hookworm disease
Infectious agent
• Ancylostoma duodenale and
• Necator americanus

207. Kalab W (PHO)
Hookworm disease
Epidemiology
• Widely endemic in tropical and subtropical
countries

208. Kalab W (PHO)
Hookworm disease
Reservoir
• Humans

209. Kalab W (PHO)
Hookworm disease
Mode of transmission
• Through skin penetration by the infective
larvae

210. Kalab W (PHO)
Hookworm disease
Incubation period
• Few weeks to many months depending on
intensity of infections and iron intake of the
host.

211. Kalab W (PHO)
Hookworm disease
Period of communicability
• Several years in the absence of treatment.

212. Kalab W (PHO)
Hookworm disease
Susceptibility and resistance
• Universal.
• No evidence that immunity develops with
infection.

213. Kalab W (PHO)
Hookworm disease
Clinical manifestation
• Transient, localized, Maculopapular rash
associated with itching called ground itch.
• Cough, wheezing and transient
pnumonitis
• Light infection - no symptoms
• Heavy infection - result in symptoms of
peptic ulcer disease like epigastric pain
and tenderness.
• Further loss of blood leads to anaemia

214. Kalab W (PHO)
Hookworm disease
Diagnosis
• Demonstration of eggs in stool specimen

215. Kalab W (PHO)
Hookworm disease
Treatment
• First line
–Mebendazole, 100 mg PO BID for 3
days
• Alternative
–Albendazole, 400 mg PO as a single
dose. For children: 1 – 2 years, 200 mg
as a single dose.

216. Kalab W (PHO)
Hookworm disease
Prevention and control
• Sanitary disposal of feces
• Wearing of shoes
• Case treatment

217. Kalab W (PHO)
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