Communicable Diseases

Communicable Diseases

Slide 2

Organisms That Cause Diseases

• Pathogen- a mircroorganism that causes disease.
• Pathogens live in a host, which creates an optimum habitat for the pathogens, by doing so they can cause damage during the process.
• Bacteria, belong to Kingdom Prokayotae, once in a hosts body they reproduce rapidly, they cause disease by damaging cells, or by releasing waste products and toxins. Often live in the vascular tissue.
• Fungi, can affect both plants and animals, its hyphae may form mycelium that grow under the skins surface, and may release spores causing redness and itching. In plants may release extracellular enzymes that cause decay.
• Viruses, invades cells and takes over the genetic machinery and other organelles of the cell, causes the cell to manufacture more copies of the virus, host eventually bursts.
• Protoctista, enter host cell and feeds on the contents as they grow

Pathogen Transmission

• Pathogen life cycle:
• transmission
• entering a hist's tissues
• reproducing
• leaving the host's tissue
• Direct Transmission, through spores, faecal matter, droplet infection and via spores, Factors affecting the transmission: personal hygiene, poor ventilation, poor diet, homelessness, overcrowding, poor health.
• Indirect Transmission, usually through a vector (another organism used by a pathogen to gain entry to primary host).
• Plant Pathogens, can enter directly: through the roots via the soil, or by producing spores via the wind, or when in the plant by infecting the vascular tissue. And indirectly: as a result of insect with spores) attacks by acting as a vector.
• Pathogens can grow and reproduce more rapidly in moist and warm climates= greater variety of diseases.

Plant Defences