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10-11 · Infectious Disease and Immunity

10-11 · Infectious Disease and Immunity — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions

5 min read 9 parts Lesson 1 of 21 1 quiz

📚 Cambridge AS & A Level Biology 9700 Hub / Topical Revision
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10-11 · Infectious Disease and Immunity — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Describe the pathogens, transmission and control of cholera, malaria, tuberculosis and HIV/AIDS.Infectious (communicable) disease — it is caused by a pathogen that passes from on…

  • Types of pathogen
  • Direct transmission
  • Cause and spread
  • Distribution
  • Control methods
  • Difficulty

Part 1 of 7Pathogens and infectious disease

Pathogens and infectious disease
Infectious (communicable) disease
  • Infectious (communicable) disease it is caused by a pathogen that passes from one host to another.
Types of pathogen
  • Types of pathogen bacteria, viruses (HIV/AIDS, measles), protoctists (malaria, caused by Plasmodium) and fungi.
    • (cholera, tuberculosis)
Direct transmission
  • Direct transmission contact, droplets, body fluids, or across the placenta.
Indirect transmission
  • Indirect transmission contaminated water or food, or a vector such as a mosquito that carries the pathogen between hosts.

Part 2 of 7Cholera

Cause
  • Cause the bacterium Vibrio cholerae.
Spread
  • Spread by water or food contaminated with faeces.
Effects
  • Effects severe diarrhoea and dehydration.
Control
  • Control clean water, sewage treatment and oral rehydration therapy.

Part 3 of 7Malaria

Cause and spread
  • Plasmodium, spread by the female Anopheles mosquito.
Distribution
  • Distribution it occurs where the climate suits the mosquito.
Control methods
  • Control methods reduce breeding sites, kill larvae and avoid bites.
  • Drain marshes and other unnecessary bodies of water.
  • Stock ponds and ditches with fish that eat mosquito larvae.
  • Use insecticides, insecticide-treated bed nets and repellents.
Difficulty
  • Difficulty mosquitoes lay eggs in even very small puddles, so controlling all breeding sites is practically impossible.
  • Drug resistance and insecticide resistance add to the difficulty.

Part 4 of 7Tuberculosis (TB)

Spread
  • Spread droplets from the coughing or sneezing of an infected person are inhaled by an uninfected person.
Pathogen
  • Pathogen the droplets contain Mycobacterium tuberculosis.
Control
  • Control contact tracing and testing of contacts.
Prevention
  • Prevention the BCG vaccine protects up to 70 to 80 per cent of recipients, though effectiveness decreases with age.
Bovine TB
  • Bovine TB the form passed between cattle and humans is prevented by testing and culling infected cattle and pasteurising milk.
    • (Mycobacterium bovis)

Part 5 of 7HIV/AIDS and socio-economic factors

Spread
  • HIV is a virus passed on by exchange of body fluids: unprotected sex, shared needles and mother to child.
Control
  • Control anti-retroviral drugs, education and safe practice.
Socio-economic status
  • Socio-economic status it affects how HIV is controlled.
  • In high-income countries HIV-positive mothers are advised not to breastfeed.
  • In low- and middle-income countries breastfeeding is more affordable and protects against other diseases such as cholera.

Part 6 of 7More from the specification

1Active immunization as an eradication means
  • Active immunization as an eradication means administering attenuated vaccines stimulates immunological memory, providing an effective public health means to eliminate pathogens.
2Health
  • A state of physical and mental wellbeing.

Part 7 of 7More on this topic

Target
  • Target control is aimed at the vector and at preventing bites.
Bite prevention
  • Bite prevention insecticide-treated nets, repellents and screens.
HeadingWhat to give
PathogenOrganism and type (bacterium, virus, protoctist)
TransmissionRoute, such as water, air, vector or body fluids
SymptomsEffects on the body
TreatmentDrug or other therapy
ControlMeasures that break transmission
TermMeaning
Vector controlReducing the mosquito population to limit malaria.
Contact tracingFinding and testing people exposed to an infected person.
BCG vaccineA vaccine that protects against tuberculosis.
Anti-retroviral drugA drug that slows replication of HIV.
PenicillinaseAn enzyme that breaks down penicillin.
LysisBursting of a cell.

Key terms

TermMeaning
PathogenAn organism that causes disease.
VectorAn organism that carries a pathogen between hosts.
Communicable diseaseA disease that can be passed from one host to another.
Contact tracingFinding and testing people who have been in contact with an infected person.
BCG vaccineA vaccine that protects against tuberculosis.
Oral rehydration therapyA solution of glucose, salts and water that treats dehydration.

Avoid these mistakes

1
Saying all pathogens are bacteria — they include viruses, protoctists and fungi.
2
Saying malaria is spread by all mosquitoes — only the female Anopheles transmits it.
3
Saying TB spreads through water — it spreads by inhaled droplets.
4
Saying HIV spreads by casual contact — it needs direct exchange of body fluids.

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