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
– 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.