2.8 Immunology

• What is a ‘pathogenic’ organism?


  An organism that has the ability to cause damage to a host.
• What is an ‘infectious’ disease?

  A disease that can be transmitted between individuals.
• Define carrier.


  An infected individual that is asymptomatic but can spread the disease.
• What is the disease reservoir?

  The environment (host) in which an infectious pathogen is found.
• Define endemic.

  A disease that is ever-present in an area.
• Define epidemic.


  A rapid rise in the incidence of a communicable disease at a local or national level.
• What is a pandemic?

  An epidemic that occurs worldwide, affecting a large number of individuals.
• Define vaccination.


  The deliberate exposure of an individual to non-pathogenic forms, antigens or products of pathogens to provide artificial active immunity.
• What is an antibiotic?


  A chemical or compound produced by a living organism that kills or prevents the growth of bacteria.
• What is an antigen?


  A chemical present on the surface of a cell that induces an immune response.
• Define antibodies.


  Immunoglobulins produced by B-lymphocytes in response to a specific antigen, triggering an immune response.
• What are antibiotic-resistant bacteria?

  Bacteria that mutate to become resistant to an antibiotic, survive and reproduce very rapidly, passing on their antibiotic resistance.
• Define vector.


  A living or non-living agent that transmits a pathogen between organisms.
• What is a toxin?


  A substance produced by a pathogen that causes damage to its host.
• What are antigenic types?


  Organisms that possess the same or similar antigens on their surface, e.g. strains of a bacteria.
• How are antigenic types usually identified?


  Using antibodies from serum.
• What is a host?

  The organism from which a pathogen or parasite obtains nutrients and/or shelter.
• Give some examples of bacterial infections.

  Cholera and Tuberculosis.
• What is cholera?


  A disease caused by strains of the Gram negative bacterium, Vibrio cholerae, the toxins of which cause severe diarrhoea leading to dehydration.
• How is cholera spread?

  Fecal/oral transmission and ingesting contaminated food or water.
• How is cholera treated?

  Rehydration (fluid and electrolytes) and antibiotics.
• What is tuberculosis?


  A bacterial disease, caused by Mycobacterium tuberculosis and M. bovis, that damages lymph nodes in the lungs and neck, and weakens the immune system.
• How is tuberculosis transmitted?

  Airborne droplet transmission.
• Describe the methods of tuberculosis prevention and treatment.

  Prevention - BCG vaccination of children; Treatment - extensive course of antibiotics.
• Give some examples of viral infections.


  Influenza and Smallpox.
• How is the influenza virus transmitted?

  Droplet infection and contact with contaminated surfaces.
• What tissue is affected by influenza?

  Upper respiratory tract.
• Describe the symptoms of influenza.

  Headache, coughing and sneezing, sore throat, vomiting, fever, muscular and joint pain; may cause secondary bacterial infections.
• How is influenza treated?

  Quarantine, antiviral medication, antibiotics for secondary bacterial infections, and management of symptoms, e.g. painkillers.
• What is smallpox?


  A disease caused by the virus Variola major that affects the skin and multiple other organs.
• How is smallpox spread?

  Droplet transmission and bodily fluids.
• Describe the symptoms of smallpox.


  Symptoms include a headache, fever, and pockmarking of the skin.
• Describe how smallpox has been eradicated.

  Due to a successful vaccination program.
• What properties of the smallpox virus made its eradication possible?

  Little variation in antigens, low rate of antigenic mutation, immunogenic nature of antigens, and no animal reservoir.
• Give an example of a protoctistan infection.


  Malaria.
• Name the malarial parasite.

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

  The female mosquito acts as a vector when it transfers saliva to another organism during feeding; the parasite reproduces asexually in red blood cells in the liver, causing lysis

  
• What is the rate of antigenic mutation in the context of antigens?

  Low rate of antigenic mutation
• What is the immunogenic nature of antigens?


  Antigens have the ability to provoke an immune response
• What is the significance of having no animal reservoir in relation to antigens?

  It indicates that the disease does not have an animal host