Component 3A - Disease

Question 1

How does the human body act as a host?

Answer 1

Many organisms live in or on the human body in symbiotic and parasitic relationships. Help us defend against disease or cause disease

Question 2

What is cholera caused by and what is its current status?

Answer 2

Gram-negative bacteria and it is endemic in parts of the world

Question 3

How does cholera affect a person?

Answer 3

Its toxins affect the gut lining causing watery diarrhoea leading to severe dehydration and frequently death.

Question 4

How is cholera transmitted?

Answer 4

Humans act as reservoirs or carriers and contaminate water supplies in which the organism is transmitted, although it only multiplies in the human host.

Question 5

Control method for cholera

Answer 5

Cholera prevention is by the treatment of water, good hygiene and the provision of clean drinking water.

Vaccine (killed organism or possibly genetically engineered) may provide temporary protection.

Question 6

What is the treatment for cholera?

Answer 6

1) Antibiotic treatment of water

2) Rehydration - giving patients electrolytes orally

Question 7

What is tuberculosis caused by and what is its status?

Answer 7

A bacterial disease that is again on the increase, partly due to the link with the HIV epidemic (immune system in those with HIV-AIDS is less efficient)

Question 8

How is tuberculosis transmitted?

Answer 8

It can be spread rapidly in overcrowded conditions and is transmitted in airborne droplets when infected people cough and sneeze.

Question 9

What parts of the body are effected by TB and what are the symptoms of the disease?

Answer 9

The most common form of TB attacks the lungs and neck lymph nodes. Symptoms include coughing, chest pain and coughing up blood.

Question 10

How is TB prevented?

Answer 10

By a BCG vaccination programme for children

Question 11

What does the treatment of TB involve?

Answer 11

Treatment involves a long course of antibiotics.

Question 12

What is smallpox caused by and what is its fatality rate?

Answer 12

It is caused by the virus Variola major and can have a 30 to 60% fatality rate

Question 13

How is smallpox transmitted?

Answer 13

Inhaled or transmitted in saliva or from other bodies if there is close contact with an infected person

Question 14

What part of the body is affected by smallpox?

Answer 14

It causes a rash, fluid-filled blisters and survivors suffer scars from these as well as blindness and limb deformities

Question 15

How was smallpox treated?

Answer 15

• Infected people are given fluids, drugs to control fever and antibiotics to control bacterial infection
• The smallpox vaccine

Question 16

Why was the smallpox vaccine very successful?

Answer 16

Because it was based on the virus’ lack of antigenic mutation (changes to avoid immune response) and highly immunogenic nature of its antigens (produces a very large immune response)

There was no animal reservoir and people were keen to be immunised because of the devastating effects of the disease.

Question 17

What is different about humans involvement with smallpox than other diseases?

Answer 17

Smallpox is the only organism that humans have intentionally made extinct (outside specialist laboratories).

Question 18

What is influenza caused by?

Answer 18

It is caused by a virus of which there are three main sub-groups. Within each sub-group there are many different antigenic types.

(Describing ‘flu A in these flashcards)

Question 19

What part of the body does influenza effect and what are the symptoms?

Answer 19

It infects cells lining the upper respiratory tract causing sore throat, coughing and fever.

Question 20

How is influenza transmitted?

Answer 20

Sufferers spread the disease by droplet infection (aerosol transmission from coughs and sneezes)

Question 21

How is the risk of getting influenza reduced?

Answer 21

1) Quarantine
2) Hygiene e.g discarding tissues
3) Annual vaccination programmes are available but due to the number of types, together with the emergence of new types, they are not always effective.

-Influenza’s mode of spread is difficult to control.

Question 22

How are antibiotics involved with influenza?

Answer 22

Antibiotics are ineffective against influenza and are only used to treat the symptoms of secondary bacterial infection

Question 23

How can pandemics occur as a result of Influenza?

Answer 23

When a new strain of ‘flu appears with new protein on the virus’ surface the human immune system cannot provide adequate protection.

Question 24

How can viruses be pathogenic?

Answer 24

1) Cell lysis when they escape from cells to infect other cells/ organisms
2) Production of toxic substances
3) Cell transformation where they can trigger cells to
become cancerous
4) Suppress the immune system (e.g. HIV)

Question 25

How do viruses make more virus particles?

Answer 25

They use a cells metabolic pathway

Question 26

What is malaria caused by and what is its status?

Answer 26

Malaria is caused by Plasmodium spp., a protoctistan parasite, endemic in some sub-tropical regions.

The disease is caused mainly by two species within which are many antigenic types.

Question 27

How is malaria transmitted?

Answer 27

Female mosquitoes, feeding on blood taken, act as vectors to transmit the parasite to new victims.

Question 28

How does the parasite infect the host?

Answer 28

The organism initially invades liver cells and then multiplies in red blood cells which burst, releasing more parasites

Question 29

What is a symptom of malaria?

Answer 29

severe bouts of fever

Question 30

What is used to prevent transmission of malaria?

Answer 30

1) Prevent biting by use of nets
2) Clothing
3) Insect repellent

Question 31

How can mosquito larvae or adults be killed?

Answer 31

1) They are aquatic so eaten by introduced fish
2) Drainage of breeding sites
3) Spraying of oil on the water surface.
4) The adults are killed with insecticides, with bacterial infections or by sterilisation.

Question 32

Control method for malaria

Answer 32

Drug treatment is available but mainly to reduce the chances of infection.

Question 33

Treatment of malaria and their problems

Answer 33

1) Plasmodium is affected by drugs when outside the cells in the blood but these have limited effectiveness and have side effects; resistance is an increasing problem.

Question 34

Problems with developing a vaccine for malaria?

Answer 34

1) Antibodies also are only effective against the parasite when outside body cells so limiting the target stages for a vaccine
2) Malarial parasite mutates and there are different antigenic types