Download Epidemiology Lecture2010-10

COMMUNICABLE DISEASE
EPIDEMIOLOGY,
CONTROL &
PREVENTION
Community medicine is the art and science
of studying and assessment of community
health needs, organization and provision of
comprehensive
health
services
and
evaluation and development of health care
programs with the objectives of promotion
of health and prevention of disease.
SOURCES OF INFECTION
* CASE OF DISEASE
* CARRIER
Incubatory carrier
Convalescent carrier
Chronic carrier
In-apparent carrier
* ANIMAL RESERVOIR (ZOONOSIS)
* INANIMATE RESERVOIR (THE SOIL)
CHANNELS OF
TRANSMISSION OF
INFECTION:
1- AIR-BORNE
2- FOOD AND DRINK-BORNE
3- ARTHROPOD-BORNE
4- CONTACT TRANSMISSION
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Water-washed dis.
(Skin, eye)
Faecal-oral dise.
(Viral, bact., parasitic)
Soil -mediated infections). (Tetanus, intestinal parasites)
Diseases of water contact. (Bilharzia, Guinea work)
Food-borne dis.
(F.P., intestinal flukes)
Infectious skin rashes.
(Chickenpox, smallpox)
Respiratory infections.
(Viral, bacterial)
Dis. Transmitted via body fluids. (STD)
Insect-borne.
(Viral parasitic)
Zoonoses.
(Ectoparasite, domestic)
1-AIR-BORNE
- Droplet infection (direct spread):
CSM,Whooping cough
- Droplet nuclei (direct air-borne):
Measles, Chickenpox
- Infected dust (indirect air-borne):
TB, Diphtheria
1-AIR-BORNE
Inhalation Infections:
* Respiratory Tract:
Pulmonary Tuberculosis.
Common cold
Influenza
Sore-throat
Pneumonia
AIR-BORNE
Other Specific Fevers:
Measles
Whooping cough
Diphtheria
Scarlet fever
Chicken pox
Mumps
Rubella
Cerebrospinal fever
(Small Pox)
(Cont’d.)
2-FOOD AND DRINK-BORNE:
* The enteric group
(salmonellae)
* The dysentery group
(shigellae)
•The rotaviruses (G.E.)
•Hep A
* Cholera
* Food poisoning
(staph).
* Amoebic dysentery.
* Helminths.
METHOD OF TRANSMISSION:
* The human hand
* Flies.
•Milk: Excellent medium
T.B
F.P
Diphtheria
- Dirty udder
- Dirty hands of milking man
- Dirty bottle
* Water
: Very serious
METHOD OF TRANSMISSION:
•Meat:
Diseased animal
Contaminated meat
* Fresh Vegetables and Fruits:
- Poor medium
- Can be contaminated by:
- Flies
- Washing Water
- Dirty hands
- Manure
3-ARTHROPOD-BORNE
* Can be:
Biological
Transovarian
Mechanical
* Means of transmission.
- Inoculation by a vector.
- Contamination
(skin or mucous membranes).
- By infectious foeces.
- Body fluids (when crushed).
ARTHROPOD-BORNE (Cont’d.)
FLIES:
-Enteric fevers.
-Mucopurulent conjunctivitis.
-Ascariasis.
-Amoebic dysentery.
-Food poisoning.
-Poliomyelitis.
THE LOUSE (Pediculum humanus).
- Epidemic typhus.
- L.B. relapsing fever.
ARTHROPOD-BORNE
THE FLEA (Xenopsylla Cheopis: rat flea).
- Bubonic plague.
- Endemic typhus
THE MOSQUITO (female of):
- Culex sp (filariasis)
- Anopheles sp (malaria)
- Aedes sp (yellow fever)
THE SAND FLY:
- Cutaneous Lishmaniasis.
4- CONTACT
Can be:
- Direct
- Indirect
- Fungal Infection of the skin
- Tinea capitis (ring worm).
- Tinea pedis (athlete’s foot).
- Tinea cruris.
4- CONTACT
- STD
-
Syphilis
Herpes simplex
Lymphogranuloma
(AIDS)
- Mycosis
- Actinomycosis
- Moniliasis
- Mycetoma
- Scabies
- Trachoma and other eye infections.
HOST-PARASITE RELATIONSHIP
Agent
(Seed)
(Climate)
Environment
(Soil)
Host
Intrinsic Properties of “Agent”
- Antigenic make-up.
- Growth requirements.
- Ability to survive outside the host
(milk, water, soil).
- Viability under varying conditions
(temp, humidity).
- Spectrum of hosts.
- Resistance to treatment.
- New genetic information.
Properties Subject
to Interaction
-
Infectivity
Pathogenicity
Virulence
Immunogenicity
Properties Subject to Interaction
- Infectivity
- Pathogenicity
- Virulence
-Immunogenicity
-
Dose
Source
Route
Duration before
reaching the host
- Host factors
- Age
- Race
- Nutritional Status
THE RESERVOIR:
Human
Human
• Most viral and bact. RTIs
• Most staph and strept.
• Childhood exanthemata
• STD
THE RESERVOIR:
Animal
Animal
Zoonoses
- Bovine T.B
- Brucellosis
- Anthrax
- Rabies
Human
THE RESERVOIR:
Complex Cycles:
- Malaria
- Bilharzia
- Tape worm
Disease Mechanism:
– Tissue invasion
– Toxin production
– Hypersensitivity
CONTROL OF COMMUNICABLE
DISEASE
Can be classified into:
I-Controlling the source of infection
II-Blocking the channels of transmission
III-Protecting the susceptible population
I. CONTROLLING THE SOURCE OF INFECTION:
(CASES, CARRIERS AND ANIMAL RESERVOIR)
-
Early diagnosis
Notification
Isolation
Treatment
Quarantine
Surveillance
Disinfection
I. CONTROLLING THE SOURCE OF INFECTION:
(CASES, CARRIERS AND ANIMAL RESERVOIR)
-
Early diagnosis
Notification
Isolation
Treatment
Quarantine
Surveillance
Disinfection
II. BLOCKING CHANNELS OF
TRANSMISSION.
* Air-borne:
- Bed-spacing
- Dust-control
- Suitable ventilation
- Good health habits
- Air disinfection
- Use of masks
- Minimize over-corwding
Food and Drink-borne:
– Provision of safe and clean water.
– Pasteurization or boiling of milk.
– Proper personal hygiene.
– Sanitary sewage disposal.
– Control of flies.
– Washing fresh vegetables.
– Meat and slaughter house control.
– Refrigeration of unused food.
– Control of food handlers and vendors.
– Labs for food examination.
* Arthropod-borne:
- Lice:
• Personal cleanliness.
• Avoiding overcrowding.
• Dusting by insecticides.
* Fleas:
- Cleanliness of dwellings.
- Avoid dust collection.
- Spraying & dusting by insecticides.
- Rodent control.
* Mosquitos:
Vector control.
Personal protection.
Contact Diseases:
-
Case finding and treatment.
Tracing of contacts.
Serological examination.
Control of sexual behaviour.
Personal cleanliness.
Contact Diseases:
- Avoid use of common articles:
- Comb.
- Hair brush.
- Towels.
- Handkerchief.
- Underwear.
- Footwear ……. etc.
III.PROTECTING THE SUSCEPTIBLE
POPULATION
- Primary Prevention:
- Health promotion.
- Specific protection.
- Secondary Prevention:
- Early diagnosis and
- Prompt treatment.
- Tertiary Prevention:
- Limitation of disability.
- Rehabilitation.
Primary Prevention:
Health Promotion:
- Adequate nutrition.
- Health education.
- Socio-economic development.
- Environmental sanitation.
- Personal hygiene.
- Genetic counseling.
Primary Prevention:
Specific Protection:
- Specific immunization.
-
Protection against occupational hazards.
Protection against accidents.
Protection from carcinogens.
Avoidance of allergens.
Primary Prevention:
Specific Protection:
- Specific immunization.
-
Protection against occupational hazards.
Protection against accidents.
Protection from carcinogens.
Avoidance of allergens.
Secondary Prevention:
- Screening for sub-clinical disease.
- Case finding
- Health education.
Tertiary Prevention:
Limitation of disability.
- Adequate treatment.
Tertiary Prevention:
Rehabilitation.
Vocational:
- (Occupational) restoration of
capacity to earn.
Social:
- Restoration of family and
community relationship.
Tertiary Prevention:
Rehabilitation.
Psychological:
- Restoration of personal
confidence and independence.
Medical:
- Physical restoration of function.
ENDEMIC
EPIDEMIC
Host Factors:
Immunity
- Change in behaviour
- Population movement
ENDEMIC
EPIDEMIC
Environmental Factors:
-
Vector:
Mosquitos
Flies
- Adverse conditions:
- War
- Famine
ENDEMIC
EPIDEMIC
Environmental Factors:
- New or
-
Exposure
- Change in climate
- Irrigation scheme
- Energy plants
Control measures