4.1.1 - Communicable Disease (set A - Pathogens - Including Types Of Pathogens) Flashcards
What are pathogens?
Infective organisms - include bacteria, viruses, fungi and protoctista
What are communicable diseases?
- caused by pathogens (eg bacteria,fungi, viruses ext)
- can be passed from one organism to another or between species
- spread directly from plant to plant
Vectors (eg water or insects) carry pathogens from one organism to another
Outline the type of pathogen - bacteria?
- small portion of bacteria, cause communicable diseases
- prokaryotic cells (no membrane-bound organelles or nucleus)
- classified by basic shape or cell wall
Outline the 2 main types of classification of bacteria?
- basic shape - might be rod shaped (bacilli), spherical (cocci) or spiralled (spiralla)
- cell wall - after staining, gram positive bacteria look purple-blue where as gram negative bacteria appear red
Why is classifying bacteria by their cell wall useful?
The type of cell wall affects how bacteria reacts to different antibiotics (compounds that kill or inhibit the growth of bacteria)
Outline the type of pathogen - viruses?
- non-living infectious agents which invade and take other biochemistry of host cells
- 0.03-0.3 micrometers in length (50 times smaller than bacteria)
- basic structure involves genetic material surrounded by protein
- reproduce rapidly and evolve
Outline the pathogen - Protista?
- group of eukaryotic organisms
- protist which cause disease are parasitic (use people or animals as host organism)
- pathogenic protists may need vector to transfer them to host
- eg - malaria
Outline the pathogen - fungi?
- eukaryotic organisms that are often multicellular
- yeast causes human disease and are single-celled
- fungi are saprophytes (feed on dead, decaying matter) and do no photosynthesise
- can spread rapidly through production of tiny spores
- affect plants by infecting leaves, preventing photosynthesis
Outline how viruses affect the host tissue?
- take over cell metabolism
- viral genetic material gets into host cell and is inserted into the host DNA
- viruses uses host cell to make new viruses which then burst out of the cell , destroying it and infecting others
Outline how protoctista affect the host tissue?
- take over cells and break them open - as new generation emerge (do not take over genetic material of the cell)
- digest and use the cell contents as they reproduce
Explain how toxins damage host tissues?
- most bacteria produce toxins that poison or damage host cells - causing disease
- do this by breaking down the cell membranes, damaging/inactivating enzymes or interfering with host cell genetic material (preventing them dividing
- fungi can produce toxins which affect host cells and cause disease
Outline the plant disease - ring rot?
- bacterial disease of potatoes, tomatoes and aubergines
- caused by gram positive bacterium
- damages leaves, tubers and fruit
- no cure - once bacterial ring rot infects a field it cannot be used to grow potatoes again for 2 years
Outline the plant disease - tobacco mosaic virus (TMV)?
- infects tobacco plants and tomatoes, peppers, cucumbers ext
- damages leaves, flowers and fruit - stunting growth and reducing yield
- resistant crop strands available but no cure
Outline the plant disease - potato blight?
- caused by fungus-like protoctist
- penetrates host cells, destroying leaves, tubers and fruit
- no cure but resistant strains and chemical treatments available
Outline the plant disease - black Sigatoka?
- banana disease
- caused by fungus, which attacks and destroys the leaves - turning them black
- can cause 50% reduction in yield
- treatments can control the spread - no cure
Give 4 plant diseases?
- ring rot
- tobacco mosaic virus (TMV)
- potato blight
- black Sigatoka
Outline the animal disease tuberculosis (TB)?
- bacteria disease
- damages and destroys lung tissue and suppresses the immune system preventing an immune response
- more vulnerable when suffering from AIDS
Outline the animal disease meningitis?
- bacterial infection of the protective membrane on the surface of the brain (meninges)
- can spread to rest of the body causing blood poisoning (septicaemia)
Outline the animal disease HIV/AIDS?
- caused by HIV (virus) which targets T helper cells in the immune system
- destroys the immune system - increasing vulnerability to other infections
- spread through body fluids
- no cure or vaccine but anti-retroviral drugs slow the progress of the disease
Outline the animal disease influenza (flu)?
- viral infection of the ciliated epithelia cells of the gas exchange system - leaves airways open to secondary infection
- three strains A, B and C
- A viruses are most virulent (severe) - classified by proteins on their surfaces
- flu viruses mutate regularly - changes in surface antigens can cause epidemic due to lack of antibodies
Outline the animal disease malaria?
- caused by a protocista (called plasmodium) - spread by the bites of infected mosquitoes (vectors)
- plasmodium parasite has life cycle involving 2 hosts - reproduce inside female mosquito and passed on to people
- invades RBCs, liver and the brain - increasing vulnerability to other infections
- no cure or vaccine but preventive measure available
Outline the animal disease Ring worm?
- fungal disease - affects mammals (eg humans and dogs)
- causes great-white crusty, infections circular areas of skin
- not damaging but can be itchy
Outline the animal disease athletes foot?
- human fungal disease
- form of human ring worm which grows and digests skin between toes - causing cracking and scaling
- can become itchy and sore
- can be cured with anti fungal creams
Give 8 human diseases caused by pathogens?
- Tuberculosis (TB)
- meningitis
- HIV/AIDS
- influenza
- malaria
- ring worm
- athletes foot
Outline the types of transmissions of pathogens between animals?
direct transmission
indirect transmission
Transmission between animals and humans
Outline direct transmission of pathogens - what does it include?
- direct contact - contact with body fluids/skin-to-skin contact
- inoculation - break in skin/animal bite/sharing needle
- ingestion - contaminated food or drink
Outline indirect transmission of pathogens - what does it include?
- formites - inanimate objects (eg bedding or socks)
- droplet infection (inhalation) - droplets of salvia and mucus expelled through sneezes
- vectors - often animals but can be water
Outline 4 factors which increase the transmission of communicable diseases in animials?
- overcrowded conditions
- compromised immune system
- poor disposal of waste - provides breeding sites for vectors
- poor nutrition
Outline 4 factors which increase the transmission of communicable diseases in animials?
- overcrowded conditions
- compromised immune system
- poor disposal of waste - provides breeding sites for vectors
- poor nutrition
Outline direct transmission of pathogens between plants?
Involves direct contact of a healthy plant with any part of diseased plant (eg ring rot or TMV)
Outline indirect transmission of pathogens between plants?
- Soil contamination - infected plants leave reproduce spores from Protista or fungi in soil
- vectors
wind - can carry bacteria, viruses and fungal spores
water - spores swim in the surface film of water on leaves
animals - insects and birds carry pathogens and spores from one plant to another as they feed
Outline 3 factors affecting the transmission of communicable diseases in plants?
- over-crowding - increases likelihood of contact
- damp, warm conditions increase the survival and spread of pathogens and spores
- poor mineral nutrition reduces resistance of plants
