Communicable diseases

• Infectious diseases

  Diseases that are caused by pathogens and can be transmissible between humans or animals to humans
• General points about bacteria

  - Prokaryotic

  - Some are non-pathogenic

  - Sometimes infect the hosts of cells or remain within body cavities or spaces
• What causes tuberculosis?

  Bacteria: Mycobacterium tuberculosis
• What type of species are infected by tuberculosis?

  Mammals
• Transmission of tuberculosis

  Transmit from cows to humans
• Symptoms of tuberculosis

  A chronic cough and bloody mucus, due to poor hygiene and sanitation
• Bacterial meningitis

  Binomial name: Neisseria meningitidis
• What type of species are infected by bacterial meningitis?

  Mammals
• Transmission of bacterial meningitis

  Transmit between humans
• How does meningitis occur?

  Infection of meninges - the membranes of brain and spinal cord

  
  

  Membranes become swollen and damage to the brains and nerves
• Symptoms of meningitis

  Fever, headache, neck stiffness and a characteristic rash
• How does the bacteria of a ring rot affect a plant?

  Infect the vascular tissue and prevent the transport of water and spreads to potato tubers
• Symptoms of ring rot

  Ring of decay in the vascular tissue of a potato tuber or tomato

  
  

  Leaf wilting
• Transmission of ring rot

  In soil, plant debris, contaminated equipment and wash water
• General points about viruses

  - No cellular structure

  - Infect host cells and hijack their machinery to replicate their own genetic material and proteins
• What does TMV stand for and what type of organisms does it affect?

  Tobacco Mosaic Virus and it infects plants
• What are the TMV symptoms?

  A distinctive 'mosaic' pattern of discolouration on the leaves, preventing photosynthesis.
• How can TMV be transmitted?

  Direct contact with leaves infected plants and indirect, like aphids, equipment, water.
• Influenza

  - Virus

  - Infect the cells that line the airways

  - Attack respiratory system
• Symptoms of influenza

  Body aches, fatigue and a high temperature
• How is influenza transmitted?

  Via droplets generated when infected persons cough or sneeze
• Species affected by influenza

  Animals including humans
• What does HIV infect in the body?

  Specific cells of the immune system and compromise the immune response
• What species are infected with HIV and how is it transmitted?

  Humans transmitted via direct transfer of body fluids
• Fungi - general notes

  - Cell walls with central vacuoles

  - Consist of filaments called hyphae

  - Form a network and spread throughout the soil or host
• What type of pathogen is M.fijiensis - black sigatoka?

  Fungi
• What does black sigatoka cause?

  Causes leaf spots on banana plants reducing yield
• Why does black sigatoka reduce yield?

  Spread through leaves of the plant, reducing its ability to photosynthesise, making the leaves die causing black streaks, so the whole leaf dies.
• What type of pathogen is potato's blight?

  Protoctista
• How is potato blight transmitted?

  Via spores - direct
• Signs of potato blight

  - Small dark brown marks on the leaves which quickly increase in size and number

  - Destroys potato and tomato
• Ringworm

  Binomial name: T.verrucosum

  Fungus

  Fungus in the skin with spore causes erupting through skin to cause a rash

  Species affected: cattle

  Transmission direct contact with infected cattle
• Athlete's foot

  Binomial name: T.rubrum

  Fungus

  Growth under skin of feet, especially between the toes

  Species affected: humans

  Transmission: direct contact with items touched by infected individuals
• Malaria

  Binomial name: many types but the most severe is P.falciporum

  Protoctista

  Parasite in blood that causes headache and fever and may progress to coma and death

  Species affected: humans and animals

  Transmission: mosquitoes
• What does autoimmune disease mean?

  When the immune system attacks self-antigens, as they recognise it as foreign antigens.
• Give two examples of autoimmune diseases

  Lupus and rheumatoid arthritis
• Lupus

  - Immune system attacking cells in connective tissues

  - Damages tissues and causes painful inflammation

  - Affect skin and joints as well as organs
• Rheumatoid arthritis

  Immune system attacking cells in joints, causing pain and inflammation.
• Transmission

  Passing a pathogen from an infected individual to an unaffected one
• Two types of transmission

  Direct - organism to organism

  
  

  Indirect - an intermediate is needed, like a vector