Topic 6.5-6 Other pathogenic agents, controlling endemic disease

Question 1

Define endemic

Answer 1

Disease occurs routinely in a geographical area

Question 2

Define epidemic

Answer 2

Temporary rapid increase in incidence of disease in a geographical area

Question 3

How is the influenza virus transmitted?

Answer 3

• Droplet infection
• Direct contact with mucus containing virus
• Zoonotic infection: contact with animal waste
• Contact with fomites (infected surfaces)

Question 4

Outline the mode of infection of influenza

Answer 4

1. Injects viral RNA into ciliated epithelial cells
2. Viral RNA hijacks cell biochemistry to produce new virions (viral particles)
3. Cell lysis releases virions

Question 5

What pathogenic effects does the influenza virus have?

Answer 5

Headache, coughing and sneezing, sore throat, vomiting, fever, muscular/ joint pain.

Symptoms last roughly 5-7 days.

Question 6

How is influenza treated?

Answer 6

• Antiviral medication
• Antibiotics treat secondary bacterial infection
• Management of symptoms e.g. pain killers

Question 7

How is stem rust fungus transmitted?

Answer 7

• Windborne spores
• Host crops (cereal crops and Berberis) leave infected fragments in the soil

Question 8

Outline the mode of infection of stem rust fungus

Answer 8

• Presence of water enables spore to germinate and produce hyphae which enter through stomata
• Enzymes e.g. cellulase digest plant cells so fungus can absorb nutrients as it grows into mycelium and surrounds tissues

Question 9

What pathogenic effects does stem rust fungus have?

Answer 9

• Depletes nutrients
• Weakens stem
• Plant loses control of transpiration rate (reduces photosynthesis)
• Pustules on epidermis release more spores when they burst

Question 10

Give the binomial name of the stem rust fungus on wheat crops

Answer 10

Puccinia graminis

Question 11

Name the malarial parasite

Answer 11

Plasmodium spp.

(a type of single-celled Protozoan)

Question 12

Outline the mode of transmission and infection of the Plasmodium spp. parasite

Answer 12

Female Anopheles mosquito acts as vector when it transfers saliva to another organism during feeding.

Parastie reproduces asexually in red blood cells in liver, causing lysis.

Question 13

What pathogenic effects does Plasmodium spp. have?

Answer 13

Paroxysm, liver damage, anaemia caused by damage to red blood cells, shaking, headaches, sweating, muscle pain.

Question 14

How is endemic malaria controlled?

Answer 14

Preventing mosquito bites: mosquito nets, insect repelllent.

Controlling mosquito numbers: pesticide, chemical treatment of standing water and sewage, introduction of predators for mosquitoes.

Drug treatment: combination of quinine, chloroquinine, artemisinin.

Question 15

Suggest the ethical and social implications of controlling endemic malaria

Answer 15

• Treatments must be evidence based to reduce saftey concerns
• Difficulty to obtain informed consent if knowledge of medical trial is poor
• Using insecticide kills other organisms

Question 16

Suggest social and economic implications of controlling endemic malaria

Answer 16

• Expensive to implement, especially since many affected countries have low GDP
• Opportunity cost: money could be spent on other initiatives e.g. malnutrition
• Preventative measures require change of customs

Question 17

Suggest the practical difficulties of controlling endemic malaria

Answer 17

• Widespread endemic
• 2 hosts involved
• High antigen variability
• Parasite enters host cells, which shields it from immune response

Question 18

Explain the role of the scientific community on controlling malaria

Answer 18

• Develop and test evidence-based treatments
• Develop accurate diagnostic tools to avoid overuse of expensive drugs