Diseases and Immunity

Describe what a pathogen is.

A diseases-causing organism.

Describe what a transmissible disease is.

A disease in which the pathogen can be passed from one host to another.

State how a pathogen is transmitted.

By direct contact, including through blood and other body indirectly, including from contaminated surfaces, food, animals and air.

Describe the body defences.

Skin, hairs in nose, mucus, stomach acid and white blood cells.

Explain the importance of the following in controlling the spread of disease, a clean water supply.

Water can become contaminated with pathogens, which can infect people if the water is used to wash hands, for drinking or for cooking.

Explain the importance of the following in controlling the spread of disease, hygienic food preparation.

• Hygienic food preparation is crucial in controlling disease spread.

• It prevents contamination, reduces foodborne illnesses, and promotes public health.

Explain the importance of the following in controlling the spread of disease, good personal hygiene.

Washing removes pathogen from the skin. The use of tissues when sneezing or coughing, instead of hands, mean pathogens can be disposed of within the tissue.

Explain the importance of the following in controlling the spread of disease, waste disposal.

Keeping food cold to prevent pathogens from growing/reproducing, washing hands before preparing food, cleaning food preparation surfaces, utensils and equipment before preparing food, cooking or heating food to the correct temperatures to kill pathogens, covering food to prevent contamination from flies, which carry pathogens

Explain the importance of the following in controlling the spread of disease, sewage treatment.

Raw sewage should be treated to remove solid waste and kill pathogens before it is released into the environment. This prevents people from coming into contact with the pathogens in the sewage.

Describe active immunity.

A defence against a pathogen by antibody production in the body.

Describe antigen.

Antigens are molecules on the surface of cells. Each pathogen has its own antigens, which have specific shapes.

Describe antibodies.

Proteins that bind to antigens leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes.

State what antibodies have.

Specific antibodies have complementary shapes which fit specific antigens.

Explain how active immunity is gained.

Active immunity is gained by after an infection by a pathogen or by vaccination.

Outline the process of vaccination.

Weakened pathogens or their antigens are put into the body, the antigens simulate an immune response by lymphocytes which product antibodies, memory cells are produced that give long-term immunity.

Explain the role of vaccination in controlling the disease.

Vaccinated people cannot spread the disease, the disease cannot spread to the vaccinated people, levels of disease will be low enough in a vaccinated population to protect those who cannot be vaccinated.

Explain passive immunity with examples.

A short term defence against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk or by injection.

Explain the importance of breast feeding.

Breast feeding provides passive immunity to infants when antibodies pass from mother to infant via breast milk.

State what is not produced in passive immunity.

Memory cells.

Describe cholera.

A diseases caused by a bacterium which is transmitted in contaminated water.

Explain what the cholera bacterium produces.

It produces a toxin that causes secretion of chloride ions into the small intestine, an increased solute concentration in the intestine, due to the presence of chloride ions, movement of water into the gut by osmosis, diarrhoea due to increased water content of the intestine.

Explain why do the nose and lining produce mucus.

Mucus is produced to trap pathogen which can then be removed by the airways by coughing, blowing the nose or swallowing.

State the methods for controlling disease.

A clean water supply, hygienic food preparation, good personal hygiene, waste disposal and sewage treatment.

State what the memory cell does.

The memory cells quickly produce the correct antibodies.

State the symptoms of cholera infection.

Diarrhoea and dehydration.