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Immunology and Disease (Diseases (Influenza (Antigenic types are different…
Immunology and Disease
Diseases
Cholera
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Transmission
- It's endemic in parts of the world
- Contaminated food or water
- People become carriers and reservoirs of disease
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A disease reservoir is the long term host of a pathogen with few/no symptoms and can be a source of disease outbreak
Effects
- V. cholerae produces a toxin in the small intestine that affects the chloride channel proteins (CFTR)
- Water and many ions aren't absorbed into the blood
- Patient has severe, watery diarrhoea, causing dehydration and a fall in blood pressure
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Prevention
- Good hygiene and sanitation
- Better sewage treatment, water purification (e.g. boiling water), safe food handling, regular hand washing
- Vaccine provides temporary protection for those at high risk of dying
Treatment
- Water and ions are replaced by giving patients electrolytes
- Bacteria are treated with antibiotics
Tuberculosis (TB)
Causes
Caused by the bacillus bacterium, Myobacterium tuberculosis
Effects
- Patients have tubercles/nodules of dead and damaged cells in the lungs
- Chest pain and cough up phlegm containing blood
- Infect lymph nodes in the neck, which swell
- People lose their appetite and develop a fever
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Prevention using BCG
- BCG (Bacillus of Calmette and Guerin) vaccine given to babies and u16s at high risk.
- Provides 75% protection for 15yrs.
- Made from a weakened strain of similar bacterium, M. bovis
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Smallpox
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Transmission
- Virus is inhaled
- Virus is transmitted in saliva
- Close contact with infected people
Effects
- Enters small blood vessels in the skin, mouth and throat and is dispersed around the body
- Causes a rash and fluid-filled blisters, leaving scars on survivors
- Blindness and deformities
- 60% of infected die
Treatment
- Fluids and drugs control fever and pain
- Antibiotics control bacterial infections
- Vaccine made from live Vaccinia virus, similar to smallpox has been very effective at preventing and treating it so virus is now extinct
Influenza
Causes
- Influenza virus infects many species e.g. birds
- Immune system can't protect against it, causing a pandemic
A pandemic is an epidemic over a wide area, infecting many countries
Structure of the virus
- Contains 8 strands of RNA as its genetic material
- Surrounded by a phospholipid envelope from the host's cell membrane
- Envelope contains antigens that are spikes on the surface of the virus: Haemagglutinin (H) helps virus enter host cell, Neuraminidase (N) helps virus leave the host cell
An antigen is a molecule that causes the immune system to produce antibodies against it. They can be formed inside the body e.g. bacterial toxins
Effects
Virus attacks mucous membranes, especially in the upper respiratory tract, causing sore throat, cough and fever
Transmission
- Inhaled from coughs and sneezes
- Mucous protects the virus
- Survives better in dry air and UV light so higher risk in winter than summer
- From animal reservoirs e.g. pigs
An animal reservoir is a source of new infection produced when an animal virus mutates and can infect humans
Prevention
- Regular hand washing
- Tissues for coughs and sneezes
Treatment
- Annual vaccines
- Quarantine
Antigenic types are different individuals of the same pathogenic species with difference surface proteins, generating different antibodies
Antigenic Drift
- No RNA proofreading enzymes
- After each replication, every new viron has a new mutation
- Gradual change of surface proteins
- Annual vaccines needed
Antigenic shift
- RNA strands recombine, making new virus types
- Can cause epidemics
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Malaria
Causes
- Caused by the protoctistans, Plasmodium falciparum and P, vivax
Is malaria endemic, epidemic or pandemic?
- Endemic in some sub-tropical regions
- Epidemic during wet seasons
- Can be pandemic