Communicable Diseases
12.1 Animal and Plant pathogens
12.1 Animal and Plant Pathogens
- Communicable diseases are caused by pathogens. 12.2 animal and plant diseases
- Usually spread within a species but can also spread 12.3 the transmission of communicable diseases
between species.
- Vector ~ Anything that carries a pathogen 12.4 plant defences against pathogens
- Parasite ~ An organism that lives on another host 12.5 Non-specific animal defences against pathogens
organism.
12.6 the specific immune system
Bacteria:
- Prokaryotes do not have membrane bound 12.7 preventing and treating disease
organelles.
- Releases toxins that damage cells and the immune system responds to that giving you symptoms.
- Classified in two ways:
o By shape – rod shaped (bacilli), spherical (cocci), comma shaped (vibrio), spiralled (spirilla),
corkscrew (spirochaetes)
o By cell walls – gram positive bacteria look blue/purple under a light microscope e.g., MRSA. Gram
negative bacteria appear red e.g., E. coli
- Some bacteria have flagella to help them swim. Others make slime so they can ooze over surfaces.
Fungi:
- Eukaryotic (yeast is single celled)
- Can’t photosynthesise
- They are saprophytes, feed on dead and decaying matter, some are parasitic and feed on living plants
and animals.
- Reproduce in spores which can spread huge diseases.
- Often affect leaves of plants, stopping them photosynthesising and killing the plant.
- Some fungi make long threads of cells called hyphae (what makes mould look fuzzy).
- Grows best in acidic conditions.
- Infections mostly affect plants.
Viruses:
- Smallest type of pathogen
- Not living according to MRS GREN.
- DNA or RNA surrounded by protein.
- Once a virus has got into another creature’s cell and used it to make new copies of itself, the cell
bursts, and the new virus copies get shot off into the cells next door.
- Retroviruses affect T lymphocytes which leads to Kaposi’s sarcoma which is a pattern of opportunistic
infections.
- There are 4 types of viruses: helical, polyhedral, spherical and complex
- Can be caught off animals and can be found on surfaces,
- Can infect every living thing but tend to be picky about what type of cells they infect.
- Bacteriophages (virus that destroy bacterial cells)
o Virus attaches to cell surface.
o Viral DNA is injected into the cell; the coat of the virus remains outside.
o Nucleic acid is replicated in host cell.
o New protein coats are synthesised within the host cell.
o Mature virions are assembled within the cell.
o Cell ruptures releasing mature virus particles.
Protists:
- Eukaryotic, can be one celled or in colonies.
- Only a small amount of Protoctista act as pathogens, these are parasitic and use people or animals as a
host.
, - They often require a vector.
- Can be found in polluted water.
- Replicate by taking over cells.
- E.g., malaria (vector, mosquito), sleeping sickness (vector, tsetse fly) and giardia (water)
12.2 Animal and Plant Diseases
Plant Diseases:
- Ring rot
o Bacterial disease of potatoes, tomatoes and aubergines.
o Caused by gram positive bacteria Clavibacter michiganensis.
o Damages leaves, tubers and fruit, can destroy 80% of the crop, no cure.
o Once infected a field cannot be used for 2 years.
- Tobacco Mosaic Virus (TMV)
o Virus of tobacco plants and 150+ species including tomatoes, peppers, cucumbers, petunias and
delphiniums.
o Damages leaves, flowers and fruit, reduces yields, stunts growth and leads to an almost
complete crop loss.
o Resistant crop strains available but no cure.
- Potato Blight
o Caused by fungus-like Protoctista Phytophthora infestans.
o Penetrate host cells, destroys leaves, tubers and fruit.
o No cure, but resistant strands and chemical treatment can reduce infection.
- Black Sigatoka
o Banana disease caused by fungus Mycosphaerella fijiensis.
o Attacks and destroys the leaves.
o Hyphae penetrate and digest cells turning leaves black.
o 50% yield reduction.
o Fungicide can control speed, no cure, resistant strains are being developed.
Animal Diseases:
- Tuberculosis (TB)
o Bacterial disease of humans, cows, pigs, badgers and deer.
o Caused by Mycobacterium tuberculosis and M. bovis.
o Damages lung tissue and suppresses immune system making them more vulnerable to other
diseases.
o Curable by antibiotics and preventable by improving living conditions and vaccination.
- Bacterial Meningitis
o Bacterial infection of meninges in the brain (Streptococcus pneumoniae or Neisseria
meningitidis).
o Can spread to the rest of the body causing blood poisoning and rapid death.
o Mainly affects young children and 15-19 years.
o Blotchy red/purple rash which does not disappear with a glass pressed against it is a symptom
of septicaemia (blood poisoning).
o 10% die, 25% of recovered have permanent damage.
o Antibiotics cure if delivered early, vaccines protect.
- HIV/AIDS (human immunodeficiency virus) (acquired immunodeficiency syndrome)
o Targets T helper cells in immune system making it more vulnerable to other diseases such as
TB, pneumonia and cancer.
o Can affect humans and primates.
12.1 Animal and Plant pathogens
12.1 Animal and Plant Pathogens
- Communicable diseases are caused by pathogens. 12.2 animal and plant diseases
- Usually spread within a species but can also spread 12.3 the transmission of communicable diseases
between species.
- Vector ~ Anything that carries a pathogen 12.4 plant defences against pathogens
- Parasite ~ An organism that lives on another host 12.5 Non-specific animal defences against pathogens
organism.
12.6 the specific immune system
Bacteria:
- Prokaryotes do not have membrane bound 12.7 preventing and treating disease
organelles.
- Releases toxins that damage cells and the immune system responds to that giving you symptoms.
- Classified in two ways:
o By shape – rod shaped (bacilli), spherical (cocci), comma shaped (vibrio), spiralled (spirilla),
corkscrew (spirochaetes)
o By cell walls – gram positive bacteria look blue/purple under a light microscope e.g., MRSA. Gram
negative bacteria appear red e.g., E. coli
- Some bacteria have flagella to help them swim. Others make slime so they can ooze over surfaces.
Fungi:
- Eukaryotic (yeast is single celled)
- Can’t photosynthesise
- They are saprophytes, feed on dead and decaying matter, some are parasitic and feed on living plants
and animals.
- Reproduce in spores which can spread huge diseases.
- Often affect leaves of plants, stopping them photosynthesising and killing the plant.
- Some fungi make long threads of cells called hyphae (what makes mould look fuzzy).
- Grows best in acidic conditions.
- Infections mostly affect plants.
Viruses:
- Smallest type of pathogen
- Not living according to MRS GREN.
- DNA or RNA surrounded by protein.
- Once a virus has got into another creature’s cell and used it to make new copies of itself, the cell
bursts, and the new virus copies get shot off into the cells next door.
- Retroviruses affect T lymphocytes which leads to Kaposi’s sarcoma which is a pattern of opportunistic
infections.
- There are 4 types of viruses: helical, polyhedral, spherical and complex
- Can be caught off animals and can be found on surfaces,
- Can infect every living thing but tend to be picky about what type of cells they infect.
- Bacteriophages (virus that destroy bacterial cells)
o Virus attaches to cell surface.
o Viral DNA is injected into the cell; the coat of the virus remains outside.
o Nucleic acid is replicated in host cell.
o New protein coats are synthesised within the host cell.
o Mature virions are assembled within the cell.
o Cell ruptures releasing mature virus particles.
Protists:
- Eukaryotic, can be one celled or in colonies.
- Only a small amount of Protoctista act as pathogens, these are parasitic and use people or animals as a
host.
, - They often require a vector.
- Can be found in polluted water.
- Replicate by taking over cells.
- E.g., malaria (vector, mosquito), sleeping sickness (vector, tsetse fly) and giardia (water)
12.2 Animal and Plant Diseases
Plant Diseases:
- Ring rot
o Bacterial disease of potatoes, tomatoes and aubergines.
o Caused by gram positive bacteria Clavibacter michiganensis.
o Damages leaves, tubers and fruit, can destroy 80% of the crop, no cure.
o Once infected a field cannot be used for 2 years.
- Tobacco Mosaic Virus (TMV)
o Virus of tobacco plants and 150+ species including tomatoes, peppers, cucumbers, petunias and
delphiniums.
o Damages leaves, flowers and fruit, reduces yields, stunts growth and leads to an almost
complete crop loss.
o Resistant crop strains available but no cure.
- Potato Blight
o Caused by fungus-like Protoctista Phytophthora infestans.
o Penetrate host cells, destroys leaves, tubers and fruit.
o No cure, but resistant strands and chemical treatment can reduce infection.
- Black Sigatoka
o Banana disease caused by fungus Mycosphaerella fijiensis.
o Attacks and destroys the leaves.
o Hyphae penetrate and digest cells turning leaves black.
o 50% yield reduction.
o Fungicide can control speed, no cure, resistant strains are being developed.
Animal Diseases:
- Tuberculosis (TB)
o Bacterial disease of humans, cows, pigs, badgers and deer.
o Caused by Mycobacterium tuberculosis and M. bovis.
o Damages lung tissue and suppresses immune system making them more vulnerable to other
diseases.
o Curable by antibiotics and preventable by improving living conditions and vaccination.
- Bacterial Meningitis
o Bacterial infection of meninges in the brain (Streptococcus pneumoniae or Neisseria
meningitidis).
o Can spread to the rest of the body causing blood poisoning and rapid death.
o Mainly affects young children and 15-19 years.
o Blotchy red/purple rash which does not disappear with a glass pressed against it is a symptom
of septicaemia (blood poisoning).
o 10% die, 25% of recovered have permanent damage.
o Antibiotics cure if delivered early, vaccines protect.
- HIV/AIDS (human immunodeficiency virus) (acquired immunodeficiency syndrome)
o Targets T helper cells in immune system making it more vulnerable to other diseases such as
TB, pneumonia and cancer.
o Can affect humans and primates.
