Download transmission of disease

Mechanism of disease transmission:
There are 3 actions (step) for disease transmission:
1. Escape of the agent from the source or reservoir
2. Conveyance of the agent to a susceptible host.
3. Entry through appropriate entry point
There are 2 ways of conveyance of agent to susceptible host•
A.)Direct, immediate, where no vectors is involved from
person to person through actual physical contact i.e.
transmission through direct contact between susceptible host
and reservoir (infected person, e.g. gonorrhea, syphilis.
B.) indirect: involve the use of vector as:
1.) Animate (living e.g. blood sucking arthropod), transmission
occur after incubation period during which agent multiplies in the
arthropod vector.
2.) Inanimate (non- living) which facilitate indirect transmission
e.g. personal articles as keys, pens.
Portal of entry:
The path by which infectious agent enter the susceptible host
e.g. respiratory, gastrointestinal.
Portal of exit:
This is the pathway through which infectious agent leaves the
reservoir.
e.g. respiratory : (coughing, sneezing, talking)
- genitourinary: (Foley catheter, sexual transmitted disease)
- skin, mucus membrane :( wounds, skin breaks, needle sticks,
blood transfusion).
- vertical e.g. :( transplacental transmission).
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Type of
disease
infectios
exit
respiratoty
secration
Site of entry
Mode of transmission
respiratory
tract
inhalation of by
Droplets of
infectious agent
serum
hepatits
malaria
skin
Intravenous (I.V) or subcutaneous
inoculation
mosquito sucking infected
Blood
gonorrhea
syphilis
genital
mucous
membrane
G.I.T
Person sexual intercourse ot
person
infected
exudates
By ingestion of infected water, food
(stool)faece
s
respiratory
secration
Cold
measles
common
Typhoid
fever
Diphtheria
tuberculosis
(T.B)
skin broken
insect bite by
Upper Person To person by inhalation of
respiratory infected droplets
tract
Blood
* Person to person or serial transfer transmission:
Def: the spread of a disease agent through contact between infection and
susceptible persons.
Examples of disease: measles, syphilis, gonorrhea.
*mode of transmission
The mechanism of transfer of an infective agent from the reservoir to a
susceptible host.
1. Air –born. (Droplet infection) respiratory system.
Organism contained within droplet nuclei or dust particles. (Droplet nuclei of
tuberculosis).
For example if the agents viral in origin affecting the respiratory tract, e.g.
measles, rubella, whooping cough, mumps
If the agent is bacteria in origin e.g. tuberculosis, diphtheria, sore throat
(streptococcus)
2. faeco-oral (gastrointestinal) transmission:
The source is usually contaminated food (milk, water).flies and fingers are potent
routes for transmission.
Agent is mostly bacterial in origin e.g. typhoid fever, cholera, bacillary dysentery.
It may also be protozoa or amoebic e.g. amoebic dysentery.
3. Sexually transmitted (venereal) disease (STDS):
It occurs by closely body contact because agent is usually killed outside the body
e.g. gonorrhea, syphilis, AIDS.
4. Contact transmission (other than STDs):
this occur through direct contact through skin or mucus membrane.
Examples: 1) some dermatological disorders (tenea vercicolor, herpes simplex by
kissing)
2) Eye infection e.g. trachoma by flies or contaminated finger or towels
5. animal transmitted diseases (zoonoses):
Where an animal is the mode of transmission. Example: intestinal T.B. by ingestion
of row milk contaminated by bovine T.B.
6. Insect –borne disease (vector- born):
Examples:
1.) Malaria is protozoa diseases where the parasite multiplies inside the
body of the mosquito to be mosquito bite.
2.) Yellow fever viruses .external vector- born transmission by
mechanical transfer on external appendages (feet of flies), so the insect play an
essential role in disease transmission.
7. Vertical transmission:
It occur by transmission of infectious disease from mother (one generation )to
an infant (next generation).
During:
A) Pregnancy (through transplacental way e.g. rubella in the first three months
of pregnancy)
B.)Delivery (through infection e.g. toxoplasmosis, cytomegalovirus)
C.) Breast feeding
*transmission of HIV from mother passes to the baby:
1. during pregnancy through placenta.
2. during delivery through process contact.
3. after delivery through breast feeding
*person to person
_disease agent is transmitted through contact between infected and susceptible
person.
_can spread by means of respiratory, anal, oral, genital routes.
Transmitted infectionviral
Transmitted diseasebacteria
HIV
chlamidia
Hepatits B
gonrrhea
Genital herps
vaginitusbacterial
Genital warts
trichomoniasis
Rubella
syphilis
Cytomegalovirus