Chapter 12 Communicable Diseases Flashcards
What are the different types of pathogens?
Bacteria
Viruses
Fungi
Protoctista
What are the different modes of action used by pathogens to cause disease?
Pathogens can damage the host tissues directly or produce toxins which damages the host tissues.
How do viruses cause disease?
The viral genetic material is inserted into the host cells DNA. The virus then uses this host cell to make new viruses which burst out of the cell, destroying it and spreading the infection to other cells.
How does protoctista cause disease?
Protoctista take over the cells, breaking them open as the new generation emerge, however they do not take over the genetic material of the cell.
Instead the Protoctista digest and use the cell contents as they reproduce.
How does fungi cause disease?
Fungi digests living cells and destroys them.
However, some Fungi may also produce toxins that also affect the host cells.
How does bacteria cause disease?
Produce toxins that can damage host cells either by breaking down the cell membrane, inactivating enzymes or interfering with the host cells genetic material so the cell cannot divide.
What type of pathogen causes Tuberculosis?
Bacteria (affects humans and animals)
What type of pathogen causes Ring rot?
Bacteria (affects potato and tomato)
Caused by the Gram positive bacteria
What type of pathogen causes HIV/AIDS?
What is the effect of the pathogen?
Virus
The virus destroys the immune system so individuals become vulnerable to secondary infections
What type of pathogen causes Influenza?
Virus
What type of pathogen causes Tobacco Mosaic virus?
What is the effect of the pathogen?
Virus
The Tobacco plant leaves become damaged resulting in stunted growth
What type of pathogen causes Malaria?
Protoctista (carried by mosquitoes which act as vectors)
What type of pathogen causes Potato/ Tomato blight?
Protoctista
What type of pathogen causes Black Sigatoka?
What is the effect of the pathogen?
Fungi (affects Banana)
The fungi destroys the leaves
What type of pathogen causes Athletes foot?
Fungi
What is a vector?
Carries a pathogen spreading the disease from one organism to another
What type of pathogen causes Bacterial Meningitis?
What is the effect of this pathogen?
Bacteria
Affects the brain but can spread to the rest of the body causing blood poisoning and if left untreated death.
What is the effect of Influenza?
A viral infection which affects the Ciliated epithelial cells in the gaseous exchange system. It kills them and leaves the airways open to secondary infection.
It can rapidly mutate ——> new strains causing epidemics as there are no antibodies available.
New vaccination are constantly needed to be made.
What measures could be put in place to prevent the spread of Malaria?
Caused by a Protoctista which is spread via the mosquito which acts as the vector.
Preventative measures can be put in place to control the vector, using mosquito nets, insecticides and removing stagnant water to reduce breeding.
What is direct transmission?
The pathogen is transferred directly from one individual to another
How can pathogens be directly transmitted between animals?
Direct contact
Inoculation
Ingestion
Give some examples of direct contact
Kissing
Direct skin-to-skin contact
Sexual transmission
Contact with bodily fluids
Give some examples of Inoculation
Through broken skin
Animal bite
Through a puncture wound or sharing needles
Give some examples of ingestion
Consuming contaminated food or drink
Transferring pathogens to the mouth from the hands
What is indirect transmission?
A pathogen that is transmitted indirectly from one individual to another
How can pathogens be indirectly transmitted between animals?
Fomites
Droplet infection
Vectors
Give some examples of Fomites
Inanimate objects such as bedding, socks, cosmetics can transfer pathogens
Give some examples of droplet infection
Droplets of saliva and mucus which are expelled from the mouth when talking, coughing or sneezing.
These droplets can spread to healthy individuals if inhaled
Give some examples of vectors for animals
Other animals/ insects
Water
What factors can affect the transmission of communicable diseases in animals?
-Overcrowded living and working conditions
-Poor nutrition
-Compromised immune systems
-Poor disposal of waste
-Providing breeding sites for vectors
-Climate change (this can introduce new vectors and new diseases)
-Culture and infrastructure
-Socioeconomic factors- lack of trained health professionals and insufficient public warning.
How can pathogens be directly transmitted between plants?
Pathogens are spread between plants when a healthy plant comes into direct contact with a diseased plant.
How can pathogens be indirectly transmitted between plants?
Soil contamination
Vectors
Give some examples of soil contamination
Infected plants often leave pathogens or reproductive spores from Protoctista or fungi in the soil which can then infect the next crop.
Give some examples of vectors that transmit disease between plants
Wind- bacteria, viruses or spores can be carried in the wind between plants
Water- Raindrops can carry pathogens and spores
Animals- insects and birds carry pathogens and spores between plants
Humans- pathogens and spores can be transmitted by hands, clothing, farming practices and transportation.
What factors can affect the transmission of communicable diseases in plants?
- Planting varieties of crops that are susceptible to disease
- Overcrowding increases the risk of contact
- Poor mineral nutrition
- Damp, warm conditions increase the survival and spread of pathogens and spores
- Climate change- changing conditions allow animal vectors to spread disease and changing rainfall and wind promote transmission.
What are physical defences in plants?
Barriers that prevent microorganisms from entering plant tissue
What are chemical defences in plants?
Substances secreted by the plant that kill microorganisms
How do plants respond to attack from pathogens?
Receptors in the cell walls respond to chemicals that are produced when the cell wall is attacked or chemicals produced by the pathogen.
Receptors respond by releasing signalling molecules which switch on genes in the nucleus
This triggers cellular responses:
- either the production of defensive chemicals which trigger defences in unaffected cells
- or by physically strengthening cell walls.
What are the physical defences of a plant?
-Waxy cuticle which acts as a barrier and prevents pathogens from coming into direct contact with epidermal cells
-Cell walls composed of cellulose
-Production of Callose
Describe the role of Callose
Callose provides a physical barrier within plants to prevent the spread of a pathogen.
Callose is deposited between the cell walls and cell membranes next to infected cells, as well as depositing itself in the plasmodesmata of adjacent cells to the site of infection to prevent further spread.
Lignin can then be added to Callose in order to strengthen the barrier formed.
Callose also blocks the sieve cells of the phloem reducing spread of the pathogen around the plant.
What are the Chemical defences of plants?
-Insecticides
-Insect Repellents
-Cyanide
-Antibacterial compounds
-Anti fungal compounds
-Anti-oomycetes
How do Insecticides work in plants?
Plants naturally produce chemicals (such as nicotine or caffeine) to kill off insects as well as insect eggs and their larvae.
How does insect repellent work in plants?
Insect repellents repel the insect vector that carry disease, for example extracts that come from lemon grass repel mosquitoes.
How does the production of cyanide work in plants?
Plants can make chemicals that can be broken down to produce cyanide compounds when the plant is under attack.
How do antibacterial compounds work in plants?
Plants produce antibacterial chemicals compounds that kill off bacteria such as phenols (antiseptics)
How do anti-fungal compounds work in plants?
Plants produce chemicals that kill fungi by producing enzymes such as chitinase which breaks down the chitin cell wall of Fungi.