Pathogens
Definition
• An organism or virus that causes disease in its host.
Example # 1
• Influenza is
caused by
viruses
Example # 2
• Tuberculosis is
caused by
bacteria
Example # 3
• Thrush is caused by
fungi
– aka yeast infection
(candida albicans)
Example # 4
• Malaria is
caused by
protozoa
• P. falciparum,
P. vivax,
P. ovale, and
P. malariae
Anopheles mosquito
Example # 5
• Schistosomia
sis (bilharzia)
is caused by
flatworms
Example # 6
• Hookworm is
caused by
roundworms
• Ancylostoma
duodenale and
Necator
americanus.
Transmission of Pathogens
• Contact
– Touch, pathogen enters through skin
• Cuts
– Skin cut or punctured by infected object
• Droplets
– Droplets containing pathogens are sneezed out by infected person and
breathed in by another
• Food or Water
– Enter body through soft gut wall
• Sexual Intercourse
– Enter body through soft mucus membranes of penis or vagina
• Insects
– Suck blood out of infected person and transmit pathogens to another
Tuberculosis—A Bacterial Disease
• Cause
– Mycobacterium
tuberculosis
– Rod-shaped bacterium
– Malnutrition,
overcrowding, stress
increase chances of
infection
Tuberculosis
• Transmission
– Droplets
– A rare form of TB can pass from cow’s milk to
humans
Tuberculosis
• Effects
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Lungs infected with TB bacteria
Phagocytes move to lungs and engulf bacteria
Bacteria survive and breed inside phagocyte
Tubercles form in lungs—small, rounded swellings containing
infected phagocytes
First infection is usually not severe
Re-infection results in chronic TB which gradually destroys the
lung tissue
Fever, loss of appetite, weight loss, persistent cough, coughing
up blood
Infection can spread to lymph nodes, bones, and gut
Over 3 million deaths/year world-wide caused by TB
The next slide is kind of gross
Antibiotics
• Used to treat bacterial diseases
• Bacterial cells are very different
than human cells so bacteria
can be targeted and killed
without harming human cells
• Viruses use human cells as
hosts. If a virus was targeted
with an “antibiotic,” human
cells would be harmed.