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

http://upload.wikimedia.org/wikipedia/commons/9/92/TB_CXR.jpg

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.