Infection and response- Communicable Diseases Flashcards
What is a communicable disease?
A disease caused by a pathogen which can be spread from one person to another/passed between animals or plants
What is a pathogen?
A microorganism which causes disease
How do bacteria cause disease?
Once inside body, they divide rapidly by binary fission.
They kill cells and produce harmful toxins
How do viruses cause disease?
They invade and reproduce inside living cells, leading to cell damage
How can pathogens be spread?
-by air, sneezing,coughing (droplet infection)- flu, tuberculosis are spread this way
-By water, drinking or coming into contact with dirt water - fungal spores in water spread plant disease
-By direct contact, touching contaminated surfaces- bodily fluids,infected plant material left, microorganisms from faeces, kissing
How can the spread of pathogens/ communicable disease be reduced?
-vaccinations
-proximity to others, reducing contact with infected individuals
-hygiene, handwashing, disinfectants, tissues
-removing vectors, use of pesticides
-financial status
Give examples of communicable diseases
Flu, tuberculosis, HIV
Give examples of non communicable diseases
Diabetes, cancer, stroke, heart disease
Why is it especially important to prevent the spread of viral diseases?
Scientists haven’t yet developed cures for many
Name bacterial diseases
Salmonella
Gonorrhoea
Name fungal diseases
Rose black spot
Athletes foot
Name viral diseases
Flu
HIV
Measles
What is measles?
A serious viral disease that can cause blindness and brain damage
Main symptoms are a fever and red skin rash
How is measles spread?
By air- through the inhalation of droplets from coughs and sneezes
What is HIV/AIDS ?
HIV is A virus which attacks and damages immune system until it no longer functions properly
AIDS is the condition resulting from a longterm HIV infection.
There is no cure for either
How is HIV spread?
Direct sexual contact and the exchange of bodily fluids eg blood, breast milk
How can the spread of HIV/AIDS be prevented ?
Use of condoms
Screening of blood transfusions
Not sharing needles
Bottle feeding by HIV-positive mothers
Use of antiretroviral drugs to prevent the development of AIDS
What is Tabcco mosaic virus?
A plant pathogen which causes leaf discolouration when cells are damaged
Affected areas can’t photosynthesise, reducing crop yield
There is not treatment so farmers grow TMV- resistant crop strains to avoid infection
How is tabacco mosaic virus spread?
Contact between infected and healthy plants
Insects may act as vectors which transfer the virus between different plants
What is salmonella?
A type of bacteria found in raw meat, poultry and eggs
If they enter the body, they can affect natural gut bacteria
What are the symptoms of salmonella?
Fever
Abdominal cramping
Vomiting
Diarrhoea
May be fatal in very young or old populations due to risk of dehydration
How can spread of salmonella be limited?
Vaccinating animals intended for consumption
Keep raw meet away from cooked meat
Disinfectant hands and surfaces after contact with raw meat
Thoroughly cook meat
What is gonorrhoea?
A sexually transmitted bacterial infection caused by unprotected sex with an infected individual
Early symptoms- yellow/green discharge from genitals, painful urination
It’s spread can be controlled through the use of antibiotics and using condoms
What is rose black spot?
A fungal disease which causes purple or black spots to develop on rose leaves
Reduces the area of leaf which is available for photosynthesis and causes leave to turn yellow and drop prematurely
How is rose black spot fungus spread?
Fungal spores are spread by the wind and in water
How can rise black spot fungus be treated?
Using fungicides
Destroying infected leaves
What is malaria?
A disease caused by protist pathogens that live in blood
The disease is carried from host to host by an insect vector(mosquito) and the protist enters human bloodstream where they feed
Symptoms- reoccurring fever, temperature, shaking, may be fatal
How can spread of malaria be reduced?
Using insecticides
Using insect nets to avoid bites
Prevent mosquito breeding by removing stagnant water
Antimalarial drugs
What are protists?
Single-celled organisms that: rely on the host for survival, live on or inside other organisms, cause the host organism harm
What is a vector?
An organism that spreads disease, rather than causing it themselves e.g mosquitos
How does the skin prevent pathogens from entering the body? - non specific responses
Acts as a physical barrier
Platelets form scabs after skin is cut to prevent pathogens from entering
Antibacterial secretions which can kill pathogens
Healthy skin flora compete with pathogens and act as an additional barrier
How does respiratory system prevent pathogens from entering body? Non specific responses
Nose- hairs and mucus which trap pathogens
Trachea and bronchi- goblet cells produce mucus that traps dust and pathogens , ciliates cells in trachea then waft mucus from trachea to nose and throat so it can be coughed up
How does the stomach prevent pathogens infecting the body? Non specific responses
Secretes hydrochloric acid- kills any pathogens that could be on food
How do lymphocytes protect us against disease
White blood cells produce antibodies which are complimentary to a specific antigen on a pathogen
The antibodies then bind to the antigen to destroy the pathogen
White blood cells also produce antitoxins that bind to toxins released by pathogens and neutralise them
How do phagocytes protect us against disease?
The phagocyte detects the pathogen, causing it to engulf the pathogen
The pathogen is broken down by the enzymes in the phagocyte and waste material leaves the phagocyte by exocytosis
What are vaccinations?
An injection of a dead or weakened form of a pathogen which stimulates white blood cells to produce complimentary antibodies to the pathogen
They provide immunity and protect us against disease
How do vaccinations work?
-A vaccine contains a dead or weakened form of the pathogen
-When injected into body it stimulates white blood cells to produce complementary antibodies to the pathogen that bind to antigens causing pathogen to be destroyed
- in the case of a second infection, memory cells remember the specific type of antibody for the pathogen so more antibodies are produced very quickly to prevent illness. This is immunity
What is immunity?
Having specific antibodies to fight against a disease meaning you can’t become infected
What is herd immunity?
When a sufficiently high proportion of a population are immune to a disease(through vaccination)the spread of the disease is limited
What are the advantages of vaccinations?
They have eradicated many deadly diseases- smallpox
Many epidemics can be prevented by them
Herd immunity protects those who can’t have vaccinations
What are the disadvantages of vaccinations?
Not guaranteed to work- might not protect against multiple strains of a pathogen
May be side effects or adverse reactions
What drugs are used to cure some bacterial diseases?
Antibiotics- can kill bacterial pathogens inside body
How do antibiotics work?
Kill bacterial pathogens inside body but don’t kill human cells
They prevent the cell wall forming and preventing DNA replication therefore preventing binary fission
And example of an antibiotic is penicillin
Why can antibiotics not be used to treat viral diseases?
As they have no effect since viruses live index the host’s cells
Viruses live inside out cells meaning antibiotics can’t destroy the virus without damaging healthy cells surrounding it
Is also difficult to develop drugs that would kill the virus without destroying the body’s tissue
What is antibiotic resistance?
Occurs when random genetic mutations lead to individual bacterial cells having features which mean it can’t be killed with an antibiotic( is antibiotic resistant)
These bacteria are able to survive, reproduce and pass on their alleles to a greater proportion of antibiotic resistant bacteria
Is concerning as some types of bacteria are becoming resistant to all known antibiotics so diseases they cause can’t be cured
How can we prevent antibiotic resistance?
Avoid overuse and unnecessary use of antibiotics
Finish antibiotic course- ensures all bacteria is killed
Why can’t pain killers cure infectious diseases?
As they don’t kill the pathogen they only treat symptoms and numb the pain
Name a strain of bacteria that is resistant
MRSA
Why don’t antibiotics attack our own cells?
As our cells don’t have cell walls
Also may use specific enzymes
Where do we get drugs from?
Plants and microorganisms
Laboratories
Mould/fungi
What drugs were extracted from plants and microorganisms
-Aspirin originates from willow
-Antibiotic penicillin originates from penicillium mould
-heart drug digitalis extracted from fox gloves
What did Alexander Fleming discover?
Penicillin
What are the qualities of a good medicine?
Effective
Safe
Stable
Able to be taken in and removed easily
What must drugs be developed and tested for?
-tested to establish required doses
-tested for efficacy- do they prevent or cure the disease, can they successfully be taken in and removed from body
-checked that they are safe-tested for toxicity and to ensure there are no side effects
What are the stages involved in drug development?
Research- researchers target a disease and develop ideas for treatments
-pre-clinical trials- drugs are tested on living cells,tissues and organs.drugs are tested to check for toxicity and efficacy
-pre-clinical trials(part 2)- drugs are tested on animals to check to whether there are any side effects
-clinical trials- a very low dose is tested on animals small number of healthy human volunteers
-clinical trials- then tested on a small number of patients suffering from the disease to check the drug treated the disease and to find the optimum dose
-clinical trials- drug is tested on a larger number of patients and control groups are compared to experimental groups
What are the different methods of human trials?
Blind trials- volunteers don’t know which group they are in so don’t know if they are receiving the drug or placebo but the researcher/doctor does
Double blind trials- neither the doctor or patient knows what group the patient is in
Placebos- control group is given a fake drug which has no effect on body
Random allocation of participants- participants are grouped randomly
What are the advantages and disadvantages of different methods for human trials?
Blind trials- disadvantage- researcher could be biased leading to unreliable results
Double blind trials- advantage- more reliable results as there is no bias, disadvantage- more complex to prepare and organise
Placebos- advantage- removes psychological improvements, disadvantage- some doctors don’t think it’s fair and view it as unethical as doctor is lying
Random allocation of participants- advantages- prevents bias, range of ages,genders,health and lifestyles, disadvantage- still a chance of similar groupings
What drug affected new born babies limbs?
Thalidomide
How was penicillin discovered?
By accident
Fleming left bacterial plates growing and came back to discover they were killed by a natural mould
How did they know penicillin worked?
There were large zones of inhibition
What is medicine?
A chemical substance that is used in the diagnosis, cure, treatment and prevention of disease
What is a drug?
A substance taken into the body that modifies or affects chemical reactions in the body
What is a peer review?
Where the results of drug trials are checked over by scientists knowledgeable in this field
Describe the life cycle of a virus
The virus attached to the cell and invades it
-in the cell viral DNA is copied
-virus then reproduces rapidly in the cell to make hundreds of thousands of copies of itself
-this causes cell to burst which releases virus particles
-virus then enters the blood and can attach onto healthy cells and infect them
-cycle continues
What did Edward Jenner realise?
Milkmaids didn’t get small pox as they had already caught a weaker version from the cows, making them immune to small pox
Describe the life cycle of a mosquito
-Mosquitos saliva contains the parasite
-Mosquito bites the host causing them to become infected
-sporozoite is released into the hosts blood from the saliva. The sporozoite then travels to the liver infected liver cells
-sporozoite multiplies to become thousands(merozoites). The infected blood cells burst releasing merozoites into the blood
-mosquito feeds on the blood so it becomes infected
-the infected mosquito then bites another person
