Communicable Diseases Flashcards
What causes communicable diseases?
pathogens - viruses, bacteria, protists and fungi
What is a communicable disease?
Disease that can be spread to a person from another person
What is a pathogen?
They are microorganisms that cause infectious disease
How do viruses cause disease?
They move into cells and use the biochemistry to make copies of itself. This leads to the cell bursting and releasing all the copies into the bloodstream. The damage and destruction of the cells make the person feel ill
How do bacteria cause disease?
They multiply very quickly dividing by a process called binary fission
How do protists cause disease?
Some of them are parasitic, that live on or inside the host organism. They are often transferred by vectors
How do fungi cause disease?
They can produce spores which can be spread to other organisms.
Can be singles celled or have a body made of hyphae (thread-like structures)
How are pathogens spread?
Direct contact - touching contaminated surfaces
By water - drinking/contact with dirty water
By air - carried in droplets in the air and breathed in
How to prevent pathogens spreading?
- Hand washing
- Disinfectants
- Reducing contact with infected individual
- Removing vectors
- Vaccination
Symptoms of measles: (4)
- Fever and red skin rash
- Lead to pneumonia and blindness
How is measles spread?
The inhalation of droplets from sneezes and coughs.
How do we protect against measles?
Most children are vaccinated against it in the MMR vaccine
What is HIV?
A virus that attacks white blood cells to stop the body’s natural immune system.
How is HIV spread?
Through sexual contact or by exchanging body fluids such as blood.
What are the symptoms of HIV?
Initially, flu-like symptoms.
What is AIDS?
Acquired Immune Deficiency Syndrome - a fatal condition of the immune system caused by HIV, last stage of the HIV infection.
How is HIV treated?
With antiretroviral drugs that stop the virus replicating in the body.
How do we stop HIV turning into AIDS?
Antiretroviral drugs (stop the virus replicating inside the body)
Symptoms of tobacco mosaic virus?
Discoloration of the leaves
The affected part of leaf cannon photosynthesise resulting in the reduction of the yield
How is tobacco mosaic virus spread?
Contact between diseased plants and healthy plants
Vectors such as insects
How is tobacco mosaic virus prevented?
Good field hygiene and pest control
What type of pathogen causes salmonella and gonorrhea?
Bacteria
How is salmonella spread?
Through contaminated food transferring bacteria.
How do we control the spread of salmonella?
Vaccinate poultry against it and good hand washing when preparing meat.
Wash hands and surfaces
Cook thoroughly
Symptoms of salmonella?
Fever Stomach ache Cramps Vomiting Diarrhea
Symptoms of gonorrhea
Thick yellow/green discharge from the vagina/penis
Pain when urinating
How is gonorrhea spread?
Sexually transmitted disease
How is gonorrhea prevented?
Contraception
How is gonorrhea treated?
Penicillin but resistant strains are developing
Symptoms of rose black spot?
Purple/Black spots on leaves of rose plants
Reduces the area of the leaf available for photosynthesis
Leaves turn yellow and drop early
How is rose black spot spread?
The spores of the fungus are spread in water or by wind
How is rose black spot prevented?
Using fungicides
Stripping the plant of affected leaves (then burnt)
How is malaria caused?
Caused by protist pathogens that enter red blood cells and damage them
What are the symptoms of malaria?
Fevers and shaking
How is malaria spread?
Vector is female mosquitoes. The protists reproduce. When the mosquitoes puncture the skin to feed on blood, the protist enter the human bloodstream via their saliva
How is malaria prevented?
Insecticides coated insect nets
Removing stagnant water to prevent vectors from bleeding
Antimalarial drugs to kill parasites that enter the blood
How is the skin a defense system?
Acts as a physical barrier
Produces antimicrobial secretions to kill pathogens
How does the nose have defense systems?
Hairs and mucus in your nose trap particles that could contain pathogens
How does the throat have defense systems?
The trachea and bronchi secrete mucus to trap pathogens.
Cilia beat to waft mucus up so it can be swallowed
How does the stomach have defense systems?
the stomach produces hydrochloric acid to kill pathogens that have made it that far
How do white blood cells attack pathogens?
They engulf them, produce antibodies and antitoxins against them
What is phagcoytosis?
When white blood cells engulf pathogens and digest them. This destroys them, meaning they can no longer make you feel sick
Process of phagcoytosis?
A phagocyte englufs the pathogen. A phagosome is formed after the pathogens are fully engulfed. They pathogen is broken down by lysosomes. Product is released by exocytosis.
How do lymphocytes work against antigens?
Produce antibodies. The aim of antibody production is to produce the antibody that is specific to the antigens on the surface of the pathogen. The correct antibody will then reproduce and inactivate/kill the pathogen.
How do lymphocytes work against toxins?
Some pathogens can produce toxins. Lymphocytes produce antitoxins to neutralize the toxins released by the pathogen by binding to them
What are the pros of vaccinations?
- they have helped to control lots of communicable diseases in the UK
- the more people that are vaccinated means that there are fewer people that can pass on the disease this prevents epidemics
What are the cons of vaccinations?
- it doesn’t always work
2. sometimes you can have a bad reaction but it is very rare
How do vaccines work?
- Syringe injects an altered form of the pathogen
- This triggers the immune system to respond
- White blood cells produce antibodies to attack the microbe
- The body now has defenses against this microbe
- The defenses are antibodies in the blood and special memory cells
- If the microbe then attacks the body, the memory cells produce antibodies to attack and destroy them quickly
What is active immunity?
Body creating antibodies to a disease either by exposure to the disease (natural) or by vaccination (artificial)
What is passive immunity?
Comes from antibodies given to you from another organism, for example in breast milk
What do antibiotics treat?
Medicines that treat the cause of the disease
What do painkillers treat?
Medicines which treat the symptoms of the disease
How do antibiotics work?
Cure bacterial disease by killing infective bacteria inside the body. Antibiotics work by stopping bacteria cellular processes such as the production of the cell wall – they affect processes usually only in bacteria so are not harmful to animal cells
Why don’t antibiotics work against viruses?
Viruses reproduce inside cells. They antibiotic would have to kill the cell to kill the bacteria
It is difficult to develop drugs that kill viruses without also damaging the body’s tissues
How is antibiotic resistance developed?
Bacteria have random mutations in their DNA and produce new strains.
Some strains might be resistant to antibiotics, and so are not killed. They survive and reproduce, so the population of the resistant strain rises.
The resistant strain will then spread because people are not immune to it and there is no effective treatment.
How to prevent resistant bacteria?
- Doctors need to avoid the overuse of antibiotics
- Antibiotics shouldn’t be used in non-serious infections or for viral infections
- Patients need to finish the whole course of antibiotics so that all the bacteria are killed and none are left to mutate to resistant strains
Where were drugs originally extracted from? 3 examples
Traditionally drugs were extracted from plants and microorganisms.
- The heart drug digitalis originates from foxgloves helps strengthen heartbeat
- The painkiller aspirin originates from willow, helps fever/inflammation
- Penicillin was discovered by Alexander Fleming from the Penicillium mould
What are new drugs tested for?
Toxicity – does it have harmful side effects?
Efficacy – does the drug work?
Dose – what dose is the lowest that can be used and still have an effect?
What are the stages of drug development?
Preclinical Testing:
- The drug is tested on cells in the lab using cells/tissues
- Computer models used
- Test for efficacy and toxicity
Whole organism testing:
- Tested on animals to see the effect in a whole organism
- Efficacy, toxicity and dosage
Clinical trials:
- Very low doses of the drug given to make sure it is safe in a body
- Test on patients with condition
- Double-blind-study
- Further trials to test the optimum dose
How does double-blind-study work?
The patients are often split into two groups; one given the drug the other given a placebo. Neither the doctor nor the patient knows if the patient is getting the placebo or the active drug
How to culture microorganisms?
- Glass Petri dishes and agar gel must be sterilised before use in an autoclave, or pre-sterilised plastic Petri dishes can be bought (this will kill any bacteria that are present in the solution or on the Petri dishes)
- Pour the sterile agar plates and allow to set fully ( provides the selected bacterium with all the nutrients needed to grow)
- Sterilise the inoculating loop, by heating it in the Bunsen burner flame. (kills any bacteria that are present on the loop)
- Dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate. (this allows the bacteria to spread out and to grow in individual colonies on the agar plate)
- Replace the lid as soon as possible, secure with tape. Label and invert the plate, and store upside down (this stops additional unwanted bacteria in the air contaminating the plate. Do not fully seal the lid, as this will stop oxygen reaching the bacterium, and this may encourage harmful anaerobic bacteria to grow)
- Incubate at a maximum temperature of 25°C in schools and colleges (this reduces the chance of growing harmful pathogens. Hospital laboratories would incubate plates at 37°C (body temperature) to allow quick growth and identification)
