Pathogens, spread of human disease and control of infection

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  • Created by: Owain
  • Created on: 23-04-14 20:14
What is a pathogen?
A bacterium, virus, or other organisms that can cause disease.
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Are all micro-organisms pathogenic?
No.
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Are micro-organisms pathogens in every area of the body
Yes
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What is an infectious disease?
A disease that may be passed or transmitted from one individual to another.
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What is the meaning of the term carrier?
A person that shows no symtoms when infected by a disease but can pass the disease on to another individual
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What is the meaning of the term resevoir?
The place where a pathogen is normally found. This may be humans or another animal.
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What is the meaning of the term endemic?
A disease which is always present at low levels in an area.
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What is the meaning of the term epidemic?
A significant increase in the usual number of cases of a disease
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What is the meaning of the term toxin?
A chemical produced by a micro-organisms which causes damage to its host
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What is the meaning of the term antigen?
A substance when introduced to the body or tissues induces the formation of antibodies or reacts with them if already present
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What is the meaning of the term antigenic type?
Organisms with the same or very similar antigens on the surface. Such types are sub groups or strains of a microbial species which may be used to trace infections. They are usually identified by using antibodies from serum.
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What is the meaning of the term antibody?
A substance produced by lymphocytes in the presence of a specific antigen and that can combine with the antigen to neutralise, inhibit or destroy it
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What is the meaning of the term antibiotic?
A substance produced by micro-organisms which affect the growth of micro-organsims
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What is the meaning of the term antibiotic resistant?
A micro-organisms which should be affected by an antibiotic, is no longer susceptible to it.
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What are the 8 things you need to know about each pothogen?
Name, Tissues afftected, symptoms, Source of infection, Mode of transmission
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What is the name of the pathogen caused by salmonellosis
Gram negative bacterium
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Describe the bacterium?
Rod shaped bacterium.
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What tissues are affected by the pathogen?
Gut lining
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What are the symtoms of salmonellosis?
Diaarrhoea and vomiting
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Describe 2 ways that the pathogen can be transferred?
Animal slaughter, contaminated food or poor hygiene practise.
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What can happen to this pathogen in storage?
Multiplies during storage.
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Describe 4 ways of reducing the transfer of the pathogen?
Hygienic practices, thorough cooking, cool storage conditions and prevention of contamination from carriers
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How can we trace the source of infection?
Analysis of antigenic types.
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Why do doctors not use antibiotics oftento treat salmonellosis
To prevent a build up of resistance.
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Why is there no vaccine available
There are over 2000 antigenic types.
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What is the name of the pathogen caused by Cholera
Gram negative bacterium
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Describe the bacterium?
Rod shaped
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What tissues are affected by the pathogen?
Gut lining
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What are the symtoms of cholera? What can these symptoms lead to?
Water diarrhoea leading to dehydration and frequentlt death.
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Name one source and carrier of this pathogen
Humans act as reservoirs
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Describe 2 ways that the pathogen can be transferred?
Contaminated water and food
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Describe 3 ways of reducing the transfer of the pathogen?
Hygienic disposal of human faeces, treating drinking water to ensure a clean supply and hygienic preperation of food in order to prevent cross contamination and thorough cooking of food.
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Describe 2 treatments for cholera?
Rehydration and antibiotics.
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Is there a vaccine available, What is the disadvantage of it?
Yes it is used to give temporary protection.
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What is the name of the pathogen that causes TB?
Bacterium
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Why has there been an increase in the number of TB cases recently?
Due to AIDS epidemic and the build up of resistance in bacteria.
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How is TB pathogen transferred?
Spread by airbourne droplet infection when people cough or sneeze.
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Give an example of an environment where TB would spread very quickly?
Spread rapidly in over crowded conditions
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What tissues are affected by the TB pathogen?
Lung and lymph nodes
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What are the symptoms
Persistent coughing, cough up blood and chest pain.
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How is TB treated?
Long course of antibiotics (6-12 months)
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What is the name of the vaccine given to children
Bcg Vaccine
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What type of pathogen causes the flu
Virus
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Describe this type of micro-organism
Made of a central core of RNA, a protein coat and an outer lipoprotein
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How many sub groups does this pathogen have?
3 main subgroups
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What is different about each subgroup?
Different antigenic types
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Which tissue is affected by this pathogen?
Lining of the upper respiratory tract
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What are the symptoms?
Sore throat, cough and fever.
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How is the flu transferred?
Droplet infection when sufferer coughs or sneezes
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How can the spread be prevented?
Prevention is by quarantine and good hygiene
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Why is it difficult to prevent this type of transfer?
Droplet infection is difficult to control
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Why is it not possible to treat flu with antibiotics?
Because it is caused by a virus
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What is the other treatment used?
Vaccination
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How often does this treatment have to be given? Why?
Every year
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Why is this treatment not entirely effective?
New types of flu emerge frequently
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What is the name of the pathogen that causes malaria?
Parasitic protoctistan called plasmodium
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Where is it found in endemic levels?
In tropical areas
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Once the pathogen gain access to the body, where does it go first?
It invades the liver first.
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Where does the pathogen multiply
Multiplies in red blood cell
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how is the pathogen released back into the blood
The red blood cells burst releasing more of the parasites
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What symtoms develop at this stage? why?
Severe fever caused by toxins
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What is the vector of this pathogen
Femail mosquitoes
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How does this vector pick up the pathogen?
By feeding on human blood
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How does this vector transfer the pathogen to another person?
If they bite snother person they inject some saliva to stop the blood clotting, This saliva will contain plasmodium.
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Describe 3 ways we can reduce transfer of Malaria through reducing bites?
1.Hanging nets treated with insectaside 2.wearing protective clothing e.g. long sleeves 3. using insect repellents
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Describe 4 ways we can reduce transfer of Malaria through destroying the vector?
1. Draining swamps where mosquitos lay there eggs 2.spraying the breeding grounds with diesel oil 3.Spraying insecticides on the surface of the swamps to kill the larvae 4.Using biological control
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Why are the problems of using drugs to treat malaria?
They have limited effectiveness and have side effects
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What has the vaccine been difficult to develop?
Resistance is increasing and there are many antigenic types
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Why is the vaccine not very effective?
It is only effective against the parasite when outside body cells
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Why do bacteria have a specific shape?
Due to their rigid cell wall
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What is the name of the chemical that makes up bacteria cell walls?
Bacteria cell walls contain murein
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Describe the structure of this chemical?
They consist of polysaccharide cross linked by amino acid side chains
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Why is the cell wall important for bacteria?
The cell wall protects against osmotic lysis
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Name 2 types of antibiotics and describe them?
Gram positive and Gram negative
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Describe the structural differences between gram positive and gram negative bacteria?
Split into 2 groups according to whether they take up a stain called crystal violet. Gram positive can take up the stain to become purple but gram negaitive do not take up the stain
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Describe how penicillin kills bacteria?
It affects the formation of cross linkages in the bacteria cell wall. The cell walls become weakens and takes up water so it swells. The weak wall cannot withstand the pressure and break
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Why aren't human cells or viruses affectived by antibiotics?
Human cells and viruses do not have a cell walls. Viruses do not have metabolic pathway
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What is a parasite?
Organisms that live on/in other organisms
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Name two groups of parasites and describe the difference?
ECTOPARASITES are specialised to a degree but live outside the body of the host. ENDOPARASITES live inside the body of the host.
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What type of parasite is the pediculus?
Its a headlouse which is an ectoparasite
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Where is it found?
It is found on the scalp of the host
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What does it feed on?
Feeds by sucking blood from the scalp of the host
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How is it transferred?
It can walk from one hair to another so it is transferred by close hair contact
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Describe 3 adaptations of the pediculus?
The 1.eggs are called nits and are laid glued to the base of the hair 2.Produces a large number of offspring 3. The adults have claws on the end of their legs which allow them to attach themselves to the hairs on the head.
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How is pediculis treated?
The use of insectacides and using a fine comb to remove the nits
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What type of parasite is the blood fluke?
Endoparasitic flatworms
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Where is the blood fluke found?
Living in the blood vessels of the intestine or bladder
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What ilness is caused by the blood fluke?
Schistosomiosis
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Descibe the first 3 stages of the blood flukes life cycle?
The larvae are picked up from freshwater and penetrate through the skin of a human when they go fishing or washing. They enter a vein and then pass through the body in the blood stream to the liver. In the liver they mature to adults.
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Descibe the last 3 stages of the blood flukes life cycle?
They enter the capillary network where they feed on red blood cell. Many eggs are produced and are shed in faces or urine. These develop in the snail and the larvae are released into the water to infect human host
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What type of parasite is the ascaris?
Endoparasitic
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How many eggs are produced by the ascaris every day?
200,000 eggs
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How do these eggs pass out of the body?
In the faeces
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How do these eggs gain access to the human beings?
Children become infected after touching the mouth with hands that have been contaminated with the eggs
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How do the eggs get into the blood?
Penetrate the intestine
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Where do the eggs travel now?
To the lungs
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How does the hatched larva get from he small intestine to the lungs?
Pass into blood vessels.
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What type of parasite is the tape worm?
Endoparasitic
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What is the primary host organisms for this parasite
Humans
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What is the secondary host organisms for this parasite
Pigs
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How does the secondary host organisms become infected?
As it feeds in drainage channels contaminated by human faeces
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How does the primary host organisms become infected?
By eating undercooked pork
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Describe 8 adaptations of the tape worm to allow it to survive?
1. It has suckers and a double row of curved hooks to attach to the gut wall
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2.
It has body covering that protects from hosts immune respons
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3.
It has a thick cuticle with inhibitors which stop the digestive enzymes from attacking the host
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4
Simple exretory system and nervous system but most of the body is involved with reproducing
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Very large surface are to volume ratio so it can absorb pre-digested food
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Each segment contains male and female reproductive organs
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Eggs have resistant coats to survive untill consumed by second host organisms
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8
Large number of eggs produced. A mature segment can contain up to 400000 eggs
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