communicable diseases quizlet

• What is a pathogen?

  A micro-organism that causes disease. Five groups of organism that can cause disease are fungi, bacteria, protozoa, viruses and worms.
• What is a parasite?

  an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host's expense.
• What are the features of bacteria?

  No membrane bound nucleus or organelles

  Rod-shaped, spherical, comma, spiral and corkscrew
• What are the features of a virus?

  50 times smaller than a bacterium

  Genetic material surrounded by a protein
• What are the features of protoctists?

  Can live in damp conditions or use other organisms as host organisms
• What are the features of fungi?

  • Bodies made of filamentous threads called hyphae
  • Cell walls made of chitin
  • Feed on dead matter (saprophytes) or use host cells
• How do bacteria spread disease?

  they produce toxins which poison or damage host cells
• How do viruses spread disease?

  They spread their genetic material into a host cell, in which a new virus is made and bursts out of the host.
• How do protoctists spread disease?

  They take over the host cell, digest the cell contents and then reproduce
• How do fungi spread disease?

  Digest living cells and destroy them
• Ring Rot


  Caused by clavibacter michiganensis.

  It damages leaves, tubers and fruit.

  It can destroy up to 8-% of the crop and

  there is no cure

  once a field has been infected, it cannot be used for at least two years.
• Tuberculosis


  Caused by mycobacterium tuberculosis and M. bovis.

  TB damages lung tissue and suppresses the immune system.

  TB is curable in people by antibiotics and preventable.
• Meningitus


  Streptococcus pneumoniae or Neisseria meningitidis infect the meninges of the brain, which can spread to the rest of the body and cause septicaemia.

  It mainly affects children and teenagers aged 15-19

  recognised by a blotchy red rash that does not disappear when a glass is pressed against it.

  Antibiotics will cure the disease if delivered early.

  Vaccines can protect against some forms of bacterial meningitis
• Tobacco Mosaic Virus


  A virus that infects 150 plants which damages leaves, flowers and fruit. Symptoms are stunting growth and reducing yields.

  Resistant crop strains are available

  but there is no cure.
• AIDs


  • Caused by HIV
  • this infection is transmitted by body fluids, often during unprotected sex
  • also through cuts and injecting drugs using shared needles.
  • Months or years after the infection of the HIV virus, it becomes active and starts to attack the patient's immune system.
  • There is no cure for HIV /AIDS although many scientists are trying to find one.
• Influenza


  Orthomyxoviridae infects the ciliated epithelial cells in the gas exchange system and kills them, meaning that airways are left open for secondary infection.
• Potato Blight


  Caused by phytophthora infestans.

  The hyphae penetrate host cells, destroying leaves, tubers and fruit. There is no cure but careful management and chemical treatments can be put in place to reduce infection risk.
• Malaria


  Caused by protoctist plasmodium and spread by the bites of Anopheles mosquitoes.

  There is no vaccine against malaria and there are limited cures. Anopheles mosquitoes can be killed by insecticides.
• Black Sigatoka


  A banana disease caused by the fungus mycospharella fijiensis which attacks and destroys the leaves.

  The hyphae penetrate and digest the cells - turning them black.

  If plants are infected it can cause a 50% yield reduction.

  Resistant strains have been developed and fungicides can be used as treatment.
• Athlete's foot


  A human fungal disease caused by tinia pedia

  where the fungus digests the warm mist skin between the toes. Antifungal creams are an effective cure.
• Ringworm


  Trichophyton verrucosum causes grey-white crusty circular areas of skin. There are antifungal creams available to help reduce spread.
• What are the direct ways in which disease can be transmitted through animals?

  • Direct Contact - Kissing and sexual contact (STDs), skin-to-skin contact (athlete's foot) and faeces transmitted on hands (diarrhoea).
  • Inoculation - Through a break in the skin (HIV), from an animal bite (rabies) , through a wound or sharing needles (septicaemia).
  • Ingestion - Consuming contaminated food (amoebic dysentery)
• What are the indirect ways in which disease can be transmitted through animals?

  • Fomites - Objects such as beds and socks (athlete's foot, gangrene)
  • Droplets - Droplets of saliva or mucus can contain pathogens (influenza)
  • Vectors - Animals which carry pathogens (bubonic plague)

  Water - water can act as a vector (diarrhoea)
• What factors affect the probability of catching a disease in animals?

  Overcrowded living conditions

  Poor nutrition

  lack of health services

  poor disposal of waste

  poor immune system
• What are the direct ways in which disease can be transmitted through plants?

  Direct Contact - When a diseased plant comes into contact with a healthy plant (Black Sigatoka)
• What are the indirect ways in which disease can be transmitted through plants?

  Soil contamination - Often diseased plants eave pathogens in the soil. These can infect the next crop. (Ring rot).

  Vectors - Wind, Water, Animals and Humans all can carry pathogens.
• What factors affect the probability of catching a disease in plants?

  Overcrowding of plants

  Poor mineral nutrients

  Damp warm conditions
• How do plants recognise and respond to attacks?

  1. Receptors in the cells respond to molecules from the pathogens, or to chemicals produced when the plant cell wall is attacked.
  2. This stimulates the release of signalling molecules that appear to switch on genes in the nucleus.
  3. This in turn triggers cellular responses, which include:

  • Producing defensive chemicals
  • Sending alarm signals to unaffected cells to trigger their defences
  • Physically strengthening the cell walls