6.2 Flashcards
what are bacteriophages
viruses that attack and destroy bacteria
when do viruses cause symptoms of disease
when they lyse
some viral protein coats act as a toxin
how are viruses specific to particular tissues
due to the presence of antigenic markers on the surface of host cells, each type of virus can only bind to particular antigens
what is an epidemic
a higher than average number of people are infected with a disease in a particular area or country
what is a pandemic
a higher than average number of people are infected with a disease across a number of countries
what are the 3 main strains of influenza and which is most deadly
A,B & C
A is the most deadly
what are the subsets of these influenza strains named by
specific antigenic markers e.g. H1N1
define mode of transmission
the different ways a pathogen is spread from one host to another
what are the 3 main ways influenza is spread
droplet infection
contaminated surfaces
contact with feces or mucous
what is a zoonotic infection
an infection in a person caused by a pathogen that can cross the species barrier from other animals
define mode of infection
the way a pathogen causes infection
what is influenzas mode of infection
infects ciliated epithelial cells of respiratory system, viral RNA reaches nucleus, new viral particles made, cell lyses
how does influenza kill
death of ciliated epithelial cells of trachea and bronchi when cell lyses leaves airway open to severe secondary bacterial infections
what is the pathogenic effect
the symptoms of disease a pathogen causes
what are the symptoms of influenza
fever, shivering & sweating, loss of appetite. aching muscles, painful joints
why is influenza so hard to treat
it is an RNA virus therefor it is more prone to mutation so it is constantly monitored for emergence of new flu strains
what are fungi cell walls made of
chitin & glucans
what is a hyphae
a thread-like fungal structure that is a single unit of mycelium
which fungus threatens wheat & barley crops
stem rust fungus (Puccinia graminis)
how is stem rust fungus transmitted
spores from infected wheat plants/berberis are carried to young crops by the wind infected plants left in the soil
how does the stem rust fungus infect plants
-spores land on host & need water to germinate
-hypha emerges from spores & penetrated the stomata
-the hypha secretes enzymes which digest cells & nutrients
-hyphae branches to form mycelium that feeds & grows
what is a mycelium
a fungal body made up of a mass of thread-like hyphae
what are the signs of stem rust fungus
rusty red pustules break through epidermis of the stem which eventually goes black and the crop becomes blackened
how does the stem rust fungus effect the crop and their impacts
-absorbs nutrients from plant reducing yield
-breaks epidermis, harder to control transpiration, less efficient metabolism, drys out plant
-mycelium grows in vascular tissue, absorbing water & nutrients
-weakens stem, more likely to fall over, less effective harvesting
state 5 ways of controlling stem rust
-bigger spaces between plants reduces moisture, increases distance to travel
-reduce use of fertilizers
-early maturing crops (avoid time of max spread)
-remove wild berberis (interrupt life cycle)
-use fungicides (expensive)
what are protozoa
unicellular
eukaryotic
organisms
how is malaria transmitted
transmitted to a human host by a female anopheles mosquito vector
describe the mode of infection for malaria
the malaria parasite enters the blood by a female anopheles mosquitos
it then travels to the liver until the next stage
it will then re-enter the blood and invade red blood cells and begin to reproduce asexually
at regular intervals (48-72 hours) the parasite bursts out of the red blood cells destroying them
it then goes on to infect more red blood cells
this continues in cycles
some of the parasites become gametocytes and are taken into a female anopheles mosquito during a blood meal
describe the symptoms of malaria (long term & short term)
fever, sweating, shaking, muscle pains and headaches
long term liver damage and a reduction in the number of red blood cells which leads to weakness, anemia and eventually death
how is the plasmodium parasite (malaria) well adapted for survival
- it can take advantage of more than one host
- it can survive dormant for a long time without moving to a new host
- spends most of its time inside the liver or red blood cells therefor it is hidden from the immune system so it cannot be destroyed
- it takes a long time to kill the host therefor there are many opportunities for it to be passed on
what is an endemic disease
one in which the active disease or pathogen that causes the disease is constantly present in a particular country or area
what are the issues with trying to treat endemic diseases
- often widespread so difficult to track down and remove sources of infection
- requires cooperation of a large population to eradicate
- expensive
what are the treatments of malaria
there are drugs (quinine, chloroquinine, artemisinin) that kill the parasite and prevent it returning but they are only effective of they are taken soon after infection
it is advised to take anti-malarial medicines in advance so that the pathogen is destroyed before it can infect the host
often a combination of drugs are used as the parasite develops resistance
why is malaria so hard to treat/prevent
it hides from the immune system and antigens on its surface are constantly changing
what is the most effective way of preventing malaria
controlling the vector (mosquitos)
how can you reduce contact with mosquitos
- have mosquito screens on doors and windows
- sleep under mosquito nets
- use insect repellents and insecticides
- cover as much skin as possible
where does the lifecycle of an anopheles mosquito mainly take place
in water
how can mosquito breeding be prevented
- remove possible breeding sites (ponds, old drink cans etc)
- proper disposal of sewage
- biological control (seeding local water sources with organisms that feed on mosquito larvae)
- chemical control (spraying local water sources with pesticides)
what are the issues with the methods of preventing the spread of malaria
social implications - people must be persuaded to change their behavior
economic implications - requires substantial economic investment
ethical implications - reservations about vaccines, consent in medical trials, spraying insecticides will affect other insects
