Module 4: Disease, Transmission & Defences

Viruses and bacteria are both unaffected by antibiotics, while fungi and protoctists are always controlled by vaccines.

Protoctists are prokaryotes like bacteria and so are always susceptible to antibiotics.

Fungi replicate inside host cells like viruses and therefore are solely treated with antivirals.

Bacteria are living cells treatable with antibiotics; viruses are intracellular and often prevented by vaccines; protoctists often need specific drugs and may be vector-borne; fungi are eukaryotic and targeted by fungicides.

Only by causing allergic reactions in the host, never by direct damage.

By photosynthesizing inside host cells and outcompeting host metabolism.

Release of toxins and extracellular enzymes that digest host tissues.

Always by inserting their DNA into host genomes to directly trigger cell lysis.

Ring rot — protoctist that is prevented by vaccination in humans.

Malaria — protoctist (Plasmodium) transmitted by insect vectors.

HIV — bacterium causing lung infection treatable with antibiotics.

Potato blight — virus that infects human lungs.

Socio-environmental determinants like overcrowding, poor sanitation, and suitable climate amplify transmission.

Vaccination levels in plants determine human outbreak risk regardless of human sanitation.

Only the pathogen genome matters; environment has no effect on outbreaks.

Direct transmission is impossible in warm climates.

Human-like fever responses elevating leaf temperature systemically.

Production of antibodies that neutralize fungal spores externally.

Plants using cilia to sweep away microbes from stomata.

Callus formation around an infection site to limit pathogen spread.

Mucus and cilia in respiratory tracts trapping and removing pathogens.

T cell clonal expansion within minutes of first contact.

Antibody production by plasma cells during first exposure.

Photosynthetic skin cells generating defensive oxygen.

Neutrophils produce memory cells that secrete antibodies on second exposure.

Antibodies present antigen to T cells causing fever.

B cells immediately switch into macrophages to phagocytose the pathogen.

T cells recognise antigen on APCs, then undergo clonal expansion to target infected cells.

Eradicating vectors is the only effective measure for all viruses.

Relying solely on antibiotics to stop replication inside host cells.

Vaccination and antivirals, since intracellular viruses are less affected by antibiotics.

Applying fungicides to infected crops to block viral spread.

HIV is a bacterial infection controlled by skin barriers alone.

Antibiotics can reverse HIV infection during asymptomatic stages.

HIV infection does not immediately equal AIDS; disease progression depends on helper T cell depletion and opportunistic infections.

HIV cannot be transmitted until AIDS develops, so asymptomatic people aren't infectious.

Exclusive use of antifungals sprayed across communities.

Quarantining plants while leaving human sanitation unchanged.

Only vaccination campaigns without addressing vector populations or sanitation.

Vector control (insecticides, bed nets), improved sanitation, and access to healthcare and monitoring.