Communicable Diseases Flashcards
Specification reference: 4.1.1
Communicable diseases
Caused by an infective organisms known as pathogens. These can be passed from one organism to the other.
Pathogens
microorganisms that cause disease
Vectors
Carry pathogens from one organism to another. Vectors are involved in a number of plant and animal diseases.
What are the common vectors
Water and Insects
Bacteria
-Prokaryotic (don’t have a membrane bound nucleus organelles)
How is bacteria classified
- By the basic shape
2. By the cell walls
Bacteria Basic Shapes
- Bacilli (rod shaped)
- Cocci (spherical)
- Vibro (comma)
- Spirillum (spiral)
Bacteria cell walls
There are two types of cell walls, with different structures and react differently to gram staining.
Gram Positive Bacteria
Cell walls look purple-blue under the light microscope (MRSA)
Gram Negative Bacteria
Cell walls look red under a light microscope (E.Coli)
Why is Gram standing useful?
The type of cell wall affects how bacteria react to different antibiotics
Antibiotics
A compound that kills/inhibits the growth of bacteria
Viruses
Non living infectious agents
0.02-0.3um in diameter
Basic structure of a virus
Some genetic material (DNA,RNA) surrounded by a protein.
Function
-Viruses invade living cells, where the genetic material of the virus takes over the biochemistry of the host cell to make more viruses.
How are viruses successful pathogens?
-Viruses reproduce rapidly and evolve by developing adaptations to their host
Pathogenic
Viruses are pathogenic and can cause disease in every other organism
Bacteriophages
- Viruses that attack bacteria
- They take over the bacteria cells, use them to replicate and destroy bacteria at the same time
How can Bacteriophages be used?
They can be used to identify and treat some diseases .
Medical scientists consider viruses as parasites
Protoctista
- Group of eukaryotic organisms with feeding methods
- They include single celled organisms + cells grouped in colonies
- Protists that cause disease are parasitic
Parasitic
Use people or animals as their host organism
Pathogenic protists
Need a vector to transfer them to their hosts (malaria + sleeping sickness). Or they may enter the body directly with the use of water (giardia)
Fungi
- Eukaryotic organisms that are often multi-cellular ( yeast which cause thrush is single-celled)
- Fungi can’t photosynthesis and digest their food extracellularly before absorbing nutrients
Fungi are saprophytes as …
they feed on the dead and decaying matter
Pathogenic fungi …
which are parasitic cause communicable diseases because fungal infections often affect the leaves of a plant (stopping them from photosynthesizing so they die)
How do fungi reproduce?
They reproduce by producing millions of spores which can spread over large distances.
Spores spreading over large distances is an adaptation because…
Spores can spread rapidly and widely through crop plants
How do pathogens work?
- Damage Host cells directly
2. Produce toxins which damage host cells
How viruses attack and damage host cells?
-Viruses take over the cell metabolism. The viral genetic material gets into the host cell and is inserted into the host DNA
How viruses attack and damage host cells?
- Viruses take over the cell metabolism. The viral genetic material gets into the host cell and is inserted into the host DNA
- The virus then uses the host cell to make new viruses and hen burst out of the cell, destroying it and then spread to infect other cells
How does a bacteriophage destroy a bacteria cell.
- Virus attaches to a host cell
- Insertion of a viral nucleic acid
- Replication of viral nucleic acid
- Synthesis of a viral protein
- Assembly of virus particles
- Lysis of host cells
How do some bacterial toxins damage the host cells?
- They break down the cell membrane
- Some damage or inactivate enzymes
- Some interfere with host cell genetic material so the cells can’t divide
Toxins are a byproduct of normal functioning bacteria
Some fungi produce toxins
What are the plant diseases caused by pathogens
- Ring Rot
- TMV (Tobacco mosaic virus)
- Potato Blight
- Black sigatoka
Animal diseases
- TB
- Bacterial meningitis
- HIV/AIDS
- Influenza (flu)
- Malaria
- Ring worm
- Athletes foot
Ring Worm (Fungi)
- A fungal disease affecting mammals
- Different fungi infect different species
- In cattle ring worm is caused by verrucosum
- It causes a grey-white, crusty infectiois circular areas
Ring Rot
- Bacterial disease
- Found in potatoes, tomatoes etc.
- Caused by the Gram positive bacterium
- Damages leaves, tubers and fruit
- Once ring rot affects a field crops cant be grown for another 2 years
TMV
- Virus
- Infects tobacco plants and other species (tomatoes)
- Damages leaves flowers and fruit
- Resistant crop strains can be made - no cure
Potato Blight
- Fungus like protocists oomycete
- The hyphae penetrates host cells, destroying leaves, tubers and fruit
- Resistant strains are used along with chemical management - no cure
Black sigatoka (Fungi)
A banana disease caused by a fungi which attacks and destroys the leaves.
- The hyphae penetrates and digests the cells so they turn black
- Resistant strains are made + fungicides are made
TB
- Bacterial disease cause by M.bovis
- Tb damages + destroys lung tissue + suppresses the immune system.
- TB is curable by antibiotics + preventable by vaccinations + standards
Bacterial Meningitis
- Bacterial Infection of the meninges of the brain (protective membrane of the brain) which can spread to the rest of the body causing septicemia (blood poisoning) + death
- Affects aged 15-19
- Symptom of septicemia: A blotchy red/purple rash appears
HIV/AIDS
-Targets T Helper cells in the immune system
-Damages the immune system so they are more open to more diseases
-
Malaria
- Caused by a Protoctista + is spread by anopheles mosquitoes
- Plasmodium
Athletes Foot
- A human fungal disease caused by a human form of ringworm
- It grows and digests the worm moist skin between toes
- Causes cracking and scaling (itchy)
- Antifungal creams are effective
What are the two main types of transmission?
Direct and indirect transmission
