communicable diseases

• Communicable diseases

  1. Caused by pathogens including bacteria, viruses, protoctista, and fungi

  2. Cause harm through directly damaging tissue or releasing toxins
• Examples of diseases caused by pathogens

  • Tuberculosis
  • Bacterial meningitis
  • Ring rot
  • HIV
  • Influenza
• Prokaryotic cells

  • Classified by shape or cell wall
  • Shapes include rods, spherical, comma, spiraled, corkscrew
  • Cell walls determine if bacterium is gram-positive or gram-negative
• Tuberculosis is caused by Mycobacterium tuberculosis or Mycobacterium bovis, infects humans, deer, cows, pigs, badges, damages lung tissue, suppresses the immune system, can be cured with antibiotics, and prevented through vaccination
• Bacterial meningitis is caused by Streptococcus pneumoniae or Neisseria meningitidis, infects the brain, spreads quickly causing septicemia, can result in death, can be cured with antibiotics if diagnosed early, and some forms can be vaccinated against
• Ring rot is caused by Clavibacter michiganensis, infects potatoes, tomatoes, aubergines, damages leaves, tubers, and fruit
• Viruses

  • Non-living, acellular, smaller than bacteria, consist of genetic material, capsid, attachment proteins, replicate only inside host cells
• HIV consists of a capsid, core with RNA and reverse transcriptase, envelope made of host cell membrane lipids, attachment proteins, attaches to host's helper T cells, fuses with helper T cell membrane, RNA and reverse transcriptase enter host cell, reverse transcriptase copies virus's RNA into DNA, DNA moves to host cell's nucleus, transcribed to create viral proteins, new virus particles are made, HIV positive means infected with HIV, can develop into AIDS
• HIV leads to AIDS when replicating viruses interfere with immune system, destroys helper T cells, affects immune response to infections and cancer, can result in death
• When enough Alpha T cells have been destroyed


  It affects the immune system's ability to respond to infections and cancer cells, leading to AIDS
• AIDS results in death due to the destruction of the immune system
• Influenza can be caused by orthomixoviridae
• Influenza infection

  1. Infects ciliated cells in gas exchange surfaces, such as the bronchi

  2. Can result in harmful secondary infections like pneumonia caused by bacterium infecting the Airways
• Young children, elderly, and individuals with a lowered immune system are more at risk of severe symptoms and death from influenza
• Tobacco mosaic virus infects tobacco plants, causing damage to leaves and sometimes flowers and fruits
• Destruction of leaves by tobacco mosaic virus affects photosynthesis and prevents plant growth
• Scientists have developed resistant plant strains against tobacco mosaic virus
• Protoctista are eukaryotes that exist as single-celled organisms or colonies
• Pathogenic protoctists are extremely dangerous and cause severe symptoms in the host
• Pathogenic protoctists are usually transmitted through vectors, such as mosquitoes
• Malaria is caused by Plasmodium, a type of protoctista, and is transmitted by mosquitoes
• Plasmodium infects red blood cells, liver, and brain in humans
• There are preventative medicines for malaria, but no vaccine or cure
• Potato blight is caused by Phytophthora infestans, a fungus-like protoctista
• Phytophthora infestans causes damage to leaves and fruit of potatoes and tomatoes
• There are resistant strains of plants developed against potato blight
• Fungi are eukaryotes that mainly cause diseases in plants
• Pathogenic fungi release enzymes to digest host tissue and feed off it
• Black Sigatoka is caused by Mycosphaerella fijiensis, mainly infecting bananas
• Ringworm is caused by Trichophyton verrucosum and infects many mammals, including humans
• Athlete's foot is caused by Tinea pedis and mainly infects humans, thriving in warm, damp regions
• Direct transmission of pathogens includes contact, inoculation, and ingestion
• Indirect transmission of pathogens includes vectors, droplets, and fomites
• Hot climates can increase pathogen transmission due to faster reproduction rates
• Social factors like poverty can impact pathogen transmission due to lack of infrastructure and resources
• Medicines and vaccines may be less available in poorer areas, affecting pathogen prevention and treatment
• Modes of transmission in animals

  • Direct contact
  • Indirect transmission vectors
  • Droplets
  • Fomites
  • Animal bites
  • Sharing needles
  • Cuts in the skin
• Modes of transmission in plants

  • Direct
  • Indirect
• Plants' responses to defend against pathogens

  • Barriers to prevent entry like bark and waxy cuticles
  • Production of antibacterial chemicals and proteins
  • Repelling insects
  • Physical defenses to prevent pathogen spread between cells
• Primary lines of defense in animals against pathogens

  • Non-specific responses regardless of the pathogen
  • Skin as a physical barrier
  • Skin Flora providing benefits
  • Blood clots forming temporary barriers
  • Mucous membranes producing mucus
  • Ciliated cells sweeping mucus out
  • Lysozymes digesting pathogens
  • Sneezing, coughing, vomiting
  • Inflammation causing redness, heat, soreness, itchiness, and swelling