3.1 Communicable Diseases PART 1

Question 1

What is a communicable disease?

Answer 1

A disease caused by a pathogen which can be passed between animals or plants eg. flu

Question 2

What is a pathogen?

Answer 2

A disease-causing microorganism e.g. bacteria.

Question 3

How do bacteria cause disease?

Answer 3

Once inside the body, they divide rapidly by binary fission. They kill cells and produce harmful toxins.

Question 4

How do viruses cause disease?

Answer 4

They invade and reproduce inside living body cells, leading to cell damage.

Question 5

Give three ways in which pathogens can be spread

Answer 5

● By air - flu, tuberculosis and the common cold are spread by droplet infection.
● By water - fungal spores in water spread plant diseases.
● By direct contact - common in plant diseases and sexually transmitted infections.

Question 6

Give four ways in which the spread of pathogens can be reduced

Answer 6

● Hygiene - handwashing, disinfectants, tissues.
● Reducing contact with infected individuals - quarantine.
● Removing vectors - use of pesticides and insecticides, removal of habitats.
● Vaccination.

Question 7

Why is it especially important to prevent the spread of viral diseases?

Answer 7

Scientists have not yet developed cures for many viral diseases.

Question 8

What is measles?

Answer 8

Measles is a serious viral disease that can cause blindness and brain damage.
The main symptoms are a fever and a red skin rash.

Question 9

How is measles spread?

Answer 9

By air - through the inhalation of droplets from coughs and sneezes.

Question 10

What is HIV/AIDS?

Answer 10

HIV is a virus which attacks and damages the immune system until it can no longer function properly.

AIDS is the condition resulting from a long-term HIV infection. There is no cure or vaccine for HIV/AIDS.

Question 11

How is HIV spread?

Answer 11

Direct sexual contact and the exchange of bodily fluids eg. blood, breastmilk.

Question 12

How can the spread of HIV/AIDS be prevented?

Answer 12

● Use of condoms
● Screening of blood for transfusions
● Not sharing needles
● Bottle-feeding by HIV positive mothers
● Use of antiretroviral drugs to prevent the development of AIDS

Question 13

What is tobacco mosaic virus?

Answer 13

A plant pathogen which causes leaf discolouration when cells are damaged. Affected areas cannot photosynthesise, reducing the crop yield. As there is no treatment, farmers grow TMV-resistant crop strains to avoid infection.

Question 14

How is tobacco mosaic virus spread?

Answer 14

Contact between infected and healthy plants. Insects may act as vectors which transfer the virus between different plants.

Question 15

What is salmonella?

Answer 15

A type of bacteria found in raw meat, poultry and eggs. If they enter the body via food poisoning, they can affect natural gut bacteria.

Question 16

What are the symptoms of salmonella food poisoning?

Answer 16

● Fever
● Abdominal cramping
● Vomiting
● Diarrhoea

May be fatal in very young or elderly populations due the risk of dehydration.

Question 17

How can the spread of salmonella be limited?

Answer 17

● Vaccinating animals intended for consumption
● Keep raw meat away from cooked meat
● Disinfect hands and surfaces after contact with raw meat
● Thoroughly cook meat

Question 18

What is gonorrhoea?

Answer 18

A sexually transmitted bacterial infection caused by unprotected sex with an infected individual. Early symptoms include yellow/green discharge from genitals and painful urination, although it may be symptomless.

Its spread can be controlled through the use of antibiotics (no longer penicillin as many strains are resistant) and using condoms.

Question 19

What is rose black spot?

Answer 19

A fungal disease which causes purple or black spots to develop on rose leaves. It reduces the area of the leaf which is available for photosynthesis and causes leaves to turn yellow and drop prematurely.

Question 20

How is the rose black spot fungus spread?

Answer 20

Fungal spores are spread by the wind and in water.

Question 21

How can the rose black spot fungus be treated?

Answer 21

● Using fungicides

● Destroying infected leaves

Question 22

What is malaria?

Answer 22

Malaria is a disease caused by protist pathogens. The disease is carried from host to host by mosquitoes, and the protists enter the human bloodstream when they feed.

Symptoms include fever and shaking, and it may also be fatal in some cases.

Question 23

How can the spread of malaria be reduced?

Answer 23

● Using insecticides
● Using insect nets to avoid bites
● Prevent mosquito breeding by removing stagnant water
● Antimalarial drugs

Question 24

How does the skin prevent pathogens from entering the body?

Answer 24

● Acts as a physical barrier. ● Scab formation after skin is cut/wounded.
● Antimicrobial secretions which can kill pathogens.
● Healthy skin flora compete with pathogens and act as an additional barrier.

Question 25

How does the respiratory system prevent pathogens from entering the body?

Answer 25

● Nose - has hairs and mucus which trap pathogens.

● Trachea and bronchi - have mucus that traps pathogens. Ciliated cells move mucus to the mouth so it can be swallowed.

Question 26

How does the stomach prevent pathogens infecting the body?

Answer 26

● Secretes hydrochloric acid - kills any pathogens present.

Question 27

How does phagocytosis protect us against disease?

Answer 27

White blood cells (phagocytes) ingest and destroy pathogens so they cannot infect more cells.

Question 28

How does antibody production protect us against disease?

Answer 28

White blood cells produce antibodies which are complementary to a specific antigen on a pathogen. The binding of antibodies to antigens causes pathogens to clump together, making them easier to destroy. In the case of a second infection, the correct antibodies can be produced rapidly, preventing the person getting the same disease again.

Question 29

How does antitoxin production protect us against disease?

Answer 29

Antitoxins bind to toxins released by pathogens and neutralise them.