module 7: infectious diseases Flashcards
Identify 6 types of pathogens
Prions, viruses, bacteria, fungi, protozoans, macroparasites
What are the features of prions? What is a disease caused by prions?
They are a type of protein therefore they have no genetic material. It propagates by transmitting the misfolded protein state to other cellular proteins. It is resistant to proteases - which are enzymes that degrade proteins. E.G. Mad Cow disease
What are the features of viruses? What is a disease caused by a virus?
Viruses have a head containing genetic material wrapped in a protein coat then a base and tail which attach to cells. They reproduce by inserting their DNA into a host cell and uses the existing reproduction process. E.G. HIV
What are the features of bacteria? What is a disease caused by bacteria?
Bacteria are unicellular prokaryotes which reproduce by binary fission. They secrete toxins, invade cells and form colonies which disrupt cell function. E.G. E.Coli
What are the features of fungi? What is a disease caused by fungi?
Fungi are eukaryotic and heterotrophic and can be either multi or unicellular. They contain mitochondria and usually reproduce by fragmentation, budding or spores. E.G. oral thrush
What are the features of protozoans? What is a disease caused by protozoans?
Protozoans are unicellular and eukaryotic which can be heterotrophs or autotrophs. E.G. Plasmodium (Malaria)
What are the features of macro-parasites? What is a disease caused by macro-parasites?
Macro-parasites are eukaryotic and multicellular and reproduce sexually with eggs and larvae. E.G. a tick
Investigate the chain of infection of zika during an epidemic
Pathogen - a single-stranded RNA virus (Flavivirus)
Reservoir - an infected person
Point of exit - a mosquito biting an infected person, sexual contact or pregnancy
Transmission - vector transmission (indirect)
Point of entry - infected mosquito biting an uninfected person
New host - the bitten human (or animal)
How was the Zika virus managed and controlled?
It was managed by educating the public, restricting travel and blood donations, installation of mosquito traps and providing advice to avoid sexual transmission with infected person. It was controlled by genetically modifying male mosquitoes to make them infertile, infecting mosquitoes with a parasite so zika cannot replicate and producing antiviral medication.
Name a practical investigation relating to the microbial testing of water or food samples
Comparing microbial growth and number of colonies in chicken including and limited to raw chicken and cooked chicken.
Identify the modes of transmission of infectious diseases
direct contact, indirect contact and vector transmission
How is a pathogen transmitted through direct contact?
There is physical contact between host and a non-infected organism. Physical contact can include: touching, biting, sexual, blood, bodily fluids, open wounds etc. E.G. HIV
How is a pathogen transmitted through indirect contact?
The host and organism have no direct contact with each other and is transmitted by airborne pathogens (i.e. coughing/sneezing), transfer of body tissue, contaminated food/water, vehicle (pathogen moved from one place to another. E.G. Influenza, Gastroenteritis (E.coli)
What is vector transmission?
when pathogens are passed by vectors, such as insects, which carry a disease from person to person. E.G. Malaria
What are the 4 steps of Koch’s Postulates?
- The micro-organism must be present and in abundance in all organisms suffering from the disease
- Micro-organisms must be isolated from the diseased organism, and grown in pure culture
- When a healthy organism is inoculated with the pure culture, it must develop the same symptoms as the original sick organism
- Isolate and re-grow the micro-organism from newly infected organism. If it is identical to the micro-organism cultured in step 2, it has been identified as the cause of the disease.
What are some limitations of Koch’s postulates?
some pathogens cannot be cultured in the lab, some disease are caused by a combination of pathogens, not all organisms infected by a pathogen will develop the disease, ethical considerations
Explain Pasteur’s swan-necked flask experiments on microbial contamination
Pasteur used swan-neck flasks to examine the microbial contamination in broth under two conditions.
Condition 1: swan-neck is left intact and there is no microbial growth. Condition 2: swan-neck is broken, exposing broth to air, and there is microbial growth.
Both broths were boiled at the start to kill existing microbes.
Microbes couldn’t enter Condition 1 due to the shape of the flask not allowing for microbes to move upwards. This disproved the “spontaneous generation” theory and proved the germ theory (all micro-organisms come from pre-existing microorganisms).
Assess the causes and effects of plant diseases on agricultural production
Black spot fungus - strawberries. Results in sunken, brown, circular spots/patches and distorted fruit. Up to 80% yield loss on the field and in the market.
Fire blight bacteria - pears and apples. Results in gray-green appearance at 1-2 weeks after petal fall. The fruit shrivels and goes black and white or amber droplets ooze from the fruit. Can destroy an entire orchard.
