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Methods of Disease Transmission and Causes of Malaria, HIV/AIDS, and TB
1. 2.2.6. Transmission of Diseases
Learning Outcome:
Describe the causes and means of
transmission of malaria, HIV/AIDS and
TB
2. Methods of Disease Transmission
Droplets – coughing & sneezing
Faecal/Oral – usually from food &
drink
Direct physical contact – touching,
kissing, sexual intercourse
Indirect contact – touching a
contaminated object
Vector transmission – by an insect or
other creature
3. Malaria - parasite
Caused by a protozoan parasite of the
genus Plasmodium
Mainly P. falciparum but other species
include P. vivax, P. ovale and P.
malariae
P. knowlesi can cross the species
barrier from monkeys to humans
The parasite lives in subtropical areas
of Africa, Asia and the Americas
6. Spread of Malaria
Mainly transmitted via the vector
method
The female Anopheles mosquito feeds
nocturnally on blood
It transfers the sporozoite phase of the
parasite from its salivary glands to the
host (mosquito saliva acts as an anti-
coagulant)
If the host already has malaria the
mosquito sucks up the gamete stage of
the parasite
Zygotes develop in the mosquito
8. Other means of malarial transmission
It is also possible to spread the
parasite via unhygienic conditions
mainly in a hospital environment
Unsterilised needles and
unscreened blood transfusions also
play a part
The parasite can also pass across
the placenta from mother to foetus
9. HIV/AIDS cause
Human Immunodeficiency Virus
The virus can sit dormant for many
years (HIV Positive stage)
Once active it destroys T helper cells
rendering the immune system
ineffective
Then the person has Acquired Immune
Deficiency Syndrome
Death usually soon follows due to
secondary infections
10. HIV Transmission
Rectal, vaginal or oral sex
Intravenous drug use – reusing
syringes
Blood transfusions from unscreened
donors
In Utero / Perinatal from mother to
foetus
Breast feeding can also spread the
virus
11. Tuberculosis - Cause
Causative agent is a rod-shaped
bacterium
Mycobacterium tuberculosis or M.
bovis are the main species
There are many other species that
can cause symptoms
Over 2 billion people are infected
with TB worldwide
Mostly the body’s immune system is
able to keep the disease at bay
12.
13. Tuberculosis - Transmission
Transmitted by the droplet method
Needs prolonged contact with a carrier
or sufferer to become infected
Infected meat or milk of cattle
Conditions of deprivation makes
infection more likely
Overcrowding
Poor health or diet
Inadequate ventilation