6.5 Flashcards
why are viral infections often specific to particular tissues?
bc of the presence/absence of ANTIGENIC MARKERS on surface of host cells - each type of virus can only bind to particular antigens on host cells
what is influenza virus?
= flu - respiratory disease that can be fatal
- v short incubation period (= time bw exposure + symptoms)
- mutates frequently so can overcome immune response of body
what are the modes of transfer of influenza? 4
- droplet infection
- direct contact w animal droppings/ virus filled mucous from nose
- surfaces contaminated w virus
- skin contact w viral filled mucous
what is the mode of infection of influenza?
- infects ciliated epithelial cells of respiratory system!
- viral RNA reaches nucleus of host cell + takes over biochemistry -> new viral particles
- cell lyses - viruses released
- body reaction to lysis of cells -> symptoms of disease
- death of epithelial cells of trachea + bronchi - airways are open to infection eg secondary bacterial infections
who is most likely to die of flu?
- v young w no prior immunity
- elderly = weakened immune system
- those prone to asthma/heart disease
what is the pathogenic effect of influenza?
- fever - shivering + sweating
- loss of apetite
- aching muscles + painful joints
- sever headaches, sore throats
- shortness of breath
what is stem rust fungus?
a fungus that threatens wheat + barley crops, called Puccini gram inis
- damages human food supply!
how is stem rust fungus transmitted?
- spores from infected wheat plants are carried to young crop by the wind
- infected by parts of infected plants left in soil after harvest
what is the mode of infection of stem rust fungus
- when spores land on host plant they need water to germinate
then thread like hypha emerge from spore and penetrate stomata of leave/stem
fungus enters internal tissues of plant
hypha secretes enzymes (Cellulase) - digest plant cells -> these nutrients absorbed into fungus
hyphae branch form a mycelium - feeds + grows
BEST GROWTH TIME: hot + wet leaves
what are the pathogenic effects of the stem rust fungus
- absorbs nutrients from plant - less growth - less yield
- pustules break epidermis - difficult to control transpiration
- mycelium grows into vascular tissue- absorbs water + nutrients
- weakened stem - plants fall over in heavy winds/rain
what is malaria and its parasite?
- plasmodium spp. = parasite of blood + resp for malaria
transmission of malaria?
- by an Anopheles mosquito vector
- when it takes a blood meal - transmission occurs in both directions
what is the mode of infection of malaria
- enters blood of human -> straight to liver
- remains there then released into blood
- parasite invades RBC + reproduces asexually 0 burst RBCs - destroying them - infecting more RBCs
pathogenic effect of malarial parasite?
- flu like symptoms - fever, shaking, sweating muscle pain headache
- long term damage to liver
what is the life cycle of malaria parasite
1) infected female anopheles mosquito takes blood meal - transmits malarial parasite to person
2) parasites travel to liver
3) parasite released from liver -> blood 0 invade RBCs
4) Ps reproduce asexually - burst out RBCs - destroying them
5) P transmitted to mosquito when taking blood meal
how is plasmodium spp adapted
- can survive in dormant form for a long time
- spends most time in liver/RBCs - hidden from immune system - cant be destroyed
