Topic 10

Question 1

Define the term infectious disease

Answer 1

A disease caused by a pathogen which can be transmitted

Question 2

Define the term non infectious diease [2]

Answer 2

• A disease that cannot be transmitted by direct contact between individuals (lung cancer, sickle cell anaemia)

Question 3

State the binomial name and pathogen type for cholera [2]

Answer 3

• Vibrio cholerae
• bacterium

Question 4

State the binomial names and pathogen type for malaria [5]

Answer 4

• Plasmodium ovale
• Plasmodium falciparum
• Plasmodium malariae
• Plasmodium vivax
• Protoctist

Question 5

State the binomial names and pathogen type for tuberculosis [3]

Answer 5

• Myocbacterium tuberculosis
• Mycobacterium bovis
• bacerium

Question 6

State the pathogen type for HIV/AIDS

Answer 6

Virus

Question 7

What does HIV stand for?

Answer 7

Human immunodeficiency virus

Question 8

What does AIDS stand for?

Answer 8

Acquired immunodeficiency syndrome

Question 9

What causes HIV/AIDS? [4]

Answer 9

1. The HIV virus is transmitted by direct contact with blood, semen, rectal fluids, vaginal fluids and breast milk
2. Attachment proteins bind to complementary CD4 receptor on Th cells
3. HIV particles replicate inside Th cells, killing or damaging them
4. AIDS develops when there are too few Th cells for the immune system

Question 10

How is HIV/AIDS treated?

Answer 10

Taking a combo of antiretroviral drugs prevents HIV replication. PEP can prevent infection after exposure

Question 11

What causes tuberculosis? [4]

Answer 11

1. Transmitted by droplet infection
2. trigger inflammatory response by infecting phagocytes in lungs
3. Infected phagocytes are sealed in waxy coated tubercules so bacteria remain dormant. Primary TB has no symptoms
4. If another factor weakens the immune system, bacteria become active. Secondary TB destroys lung tissue

Question 12

Outline primary treatment of TB

Answer 12

Patients take a combination of antibiotics for several months

Question 13

How is cholera transmitted? [2]

Answer 13

• Fecal/oral transmission
• Ingesting contaminated food or water

Question 14

How is cholera treated? [2]

Answer 14

• Rehydration (fluid and electrolytes)
• Antibiotics

Question 15

Why might incidence and prevalence of communicable diseases change over time? [4]

Answer 15

• Development of vaccines
• Development of treatments (antibiotics)
• Random mutations cause antigen variability in pathogens. Memory cells no longer complementary
• Random mutations result in treatment resistant strains

Question 16

How can spread of HIV be prevented? [6]

Answer 16

• Take PEP or PrEP
• Multi drug treatment
• Use clean needles
• Screen blood donations
• Education on safe sex and the disease
• Use of condoms

Question 17

How can spread of TB be prevented? [4]

Answer 17

• Combination of drugs and vaccines
• Cover mouth and nose when coughing and sneezing
• Quarantine
• Improved sanitation

Question 18

How can transmission of cholera be prevented? [2]

Answer 18

• Education on water sanitation
• Education on contamination of water supply

Question 19

Outline the mode of transmission and infection of the plasmodium spp parasite [2]

Answer 19

• Female mosquitos act as vectors when it transfers saliva to another organism during feeding
• Parasite reproduces asexually in red blood cells in liver causing lysis

Question 20

How is endemic malaria controlled? [3]

Answer 20

• Preventing mosquito bites
• controlling mosquito numbers
• drug treatment

Question 21

Biological, economic and social factors in preventing infectious disease [4]

Answer 21

• Spread faster in densely populated and poorly sanitised areas
• Countries with good healthcare and good education often have less disease
• Social stigma (HIV discrimination)
• Patronage of developed countries (vaccine programs considered suspicious)

Question 22

Pattern of malaria

Answer 22

Generally tropical countries (warm and humid to allow plasmodium to survive). Tend to lack education and healthcare for prevention methods

Question 23

Pattern of TB

Answer 23

Common in developing countries where people live in poorly sanitised cramped conditions

Question 24

HIV/AIDS pattern

Answer 24

Common in developing nations. Lack of access to education in prevention. Lack of healthcare means people go undiagnosed

Question 25

How does penicillin act as an antibiotic? [2]

Answer 25

- Penicillin inhibits the syntheses of the pepdigoglycan wall in bacteria, preventing new cell walls forming. The cell bursts - This class of antibiotic is bactericidal. They work by preventing cell wall synthesis or disrupting protein synthesis

Question 26

Why do antibiotics have no effect on viruses

Answer 26

Work by targeting machinery found in bacteria (prokaryotic cells). Viruses dont have this machinery, meaning they have no effect

Question 27

Why is it important antibiotics do not effect eukaryotes?

Answer 27

Humans are eukaryotic. If antibiotics affected eukaryotic cells they could potentially kill the recipient

Question 28

How does antibiotic resistance occur? [2]

Answer 28

- Spontaneous mutation of bacterial plasmids can occur which may lead to improved tolerance to an antibiotic. These cells are able to survive long enough to divide, increasing the prevalence of the mutation and making the population more resistant to a particular antibiotic. - Resistance can be spread 'horizontally' - the movement of genetic material between unicellular and/or multicellular organisms (conjugation) other than by the 'vertical' transmission of DNA from parent to offspring via reproduction.

Question 29

How can we mitigate bacterial resistance? [8]

Answer 29

- Complete full course of antibiotics - Don't overuse antibiotics - dont use antibiotics in animal feed - reduce contamination in hospitals - aseptic techniques in hospitals - Isolation of infected patients - emphasis on hygiene - reduce use of antibacterial hand gel