3.1 Communicable Diseases Flashcards
Completed | T3 Infection and Response | Physiscsandmathstutor
What is a communicable disease?
An infectious disease that spreads through the transfer of pathogens between animals or plants e.g. flu.
What is a non-communicable disease?
A disease that cannot be transmitted from person to person e.g. cancer.
What are pathogens?
Microorganisms that cause infectious disease.
What are the types of pathogens?
Viruses, Bacteria, Fungi, Protists.
How do bacteria cause disease?
Once inside the body, they reproduce rapidly (binary fission), produce chemicals called toxins, and toxins damage tissues and make us feel ill.
How do viruses cause disease?
They invade host cells and reproduce within it, causing cell damage. Once the virus leaves the cell, it may burst and die.
What are the ways in which pathogens can be spread? (3)
- In the air - flu, tuberculosis and the common cold are spread by [water] droplet infections.
- In water - fungal spores in water spread plant diseases.
- By direct contact - common in plant diseases and sexually transmitted infections.
What are the ways in which the spread of pathogens can be reduced? (4)
- Hygiene - hand-washing, disinfectants, tissues.
- Reducing contact with infected individuals - quarantine.
- Removing vectors - use of pesticides and insecticides, removal of habitats.
- Vaccination.
Why is it especially important to prevent the spread of viral diseases?
Scientists have not yet developed cures for many viral diseases, which cannot be killed using antibiotics.
What is measles?
Measles is a serious viral disease that can cause blindness and brain damage.
What are the symptoms of measles?
The first symptom is often a fever followed by a red skin rash after around 3 days.
How is measles spread?
By air - through the inhalation of droplets from coughs and sneezes.
How are measles prevented?
Vaccination of young children.
What is HIV / AIDS?
- HIV: a virus which attacks and damages the immune system until it can no longer function properly.
- AIDS: the condition resulting from a long-term HIV infection.
How is HIV spread?
- Direct sexual contact.
- Exchange of bodily fluids eg. blood, breastmilk.
How can the spread of HIV/AIDS be prevented? (5)
- Use of condoms
- Screening of blood for transfusions
- Not sharing needles
- Bottle-feeding by HIV-positive mothers
- Lifelong use of antiretroviral drugs to prevent the
development of AIDS
What is salmonella?
A disease caused by ingesting a type of bacteria found in raw meat, poultry and eggs, which causes food poisoning. It may be fatal in very young or elderly individuals due the risk of dehydration.
What are the symptoms of salmonella food poisoning? (4)
- Fever
- Abdominal cramping
- Vomiting
- Diarrhoea
How can the spread of salmonella be limited? (4)
- Vaccinating animals intended for consumption.
- Keep raw meat away from cooked meat.
- Disinfect hands and surfaces after contact with
raw meat. - Thoroughly cook meat.
What is gonorrhoea?
A sexually transmitted disease (STD) caused by unprotected sex with an infected individual.
What are the symptoms of gonorrhoea?
Early symptoms include yellow/green discharge from genitals and painful urination, although it may be symptomless.
How can gonorrhoea be treated?
Antibiotics (no longer penicillin as many strains are resistant).
How can the spread of gonorrhoea be limited?
- Using a condom.
- Getting tested before unprotected sex to kill the bacteria.
What is malaria?
Malaria is a disease caused by protist pathogens which may be fatal in some cases.
What are the symptoms of malaria?
Repeated bouts of fevers and shaking.
How is malaria spread?
Protists (the disease is carried from host to host by mosquitoes, and the protists enter the human bloodstream when they feed).
How can the spread of malaria be reduced? (4)
- Prevent mosquito breeding by removing stagnant
water - Using insecticides
- Using mosquito nets to avoid bites
- Antimalarial drugs
What are insecticides?
Pesticides used to kill insects.
What is tobacco mosaic virus (TMV)?
A plant pathogen affecting many species of plants e.g. tomatoes causing a ‘mosaic’ pattern of discolouration on leaves when cells are damaged, which cannot photosynthesise.
What is the result of tobacco mosaic virus (TMV)?
The discoloured areas cannot photosynthesise, reducing the crop yield and growth of the plant.
How is tobacco mosaic virus spread? (2)
- Contact between infected and healthy plants.
- Vectors (e.g. insects) transfer the virus between different plants.
How can tobacco mosaic disease be avoided?
As there is no treatment, farmers grow TMV-resistant crop strains to avoid infection.
What is rose black spot?
A fungal disease which causes purple or black spots to develop on rose leaves, reducing the area of the leaf which is available for photosynthesis, causing leaves to turn yellow and drop prematurely.
How is the rose black spot fungus spread?
Fungal spores are spread by the wind and in water.
How can the rose black spot fungus be treated?
- Using fungicides
- Destroying infected leaves
What are fungicides?
Chemicals that kill fungi.
What is the role of the non-specific defence system?
To prevent pathogens from entering the human body.
What are the main parts of the non-specific defensive system? (4)
- Skin
- Nose
- Trachea and bronchi
- Stomach
How does the skin prevent pathogens from entering the body? (4)
- Acts as a physical barrier (dead skin hard to penetrate).
- Scab formation after skin is cut/wounded.
- Antimicrobial secretions (sebum) which can kill pathogens.
- Healthy skin flora compete with pathogens and
act as an additional barrier.
How does the respiratory system (nose, trachea and bronchi) prevent pathogens from entering the body? (3)
- Nose: has hairs and mucus that trap pathogens.
- Trachea and bronchi: mucus traps pathogens; ciliated cells waft mucus to the mouth so it can be swallowed.
How does the stomach prevent pathogens infecting the body?
Hydrochloric acid - kills any pathogens present.
What is the role of the immune system?
To attempt to destroy pathogens if they were to enter the body.
What makes up the immune system?
White blood cells (phagocytes and lymphocytes).
How does the immune system help defend against pathogens? (3)
- phagocytosis
- antibody production
- antitoxins production
How does phagocytosis protect us against disease?
White blood cells (phagocytes) ingest and destroy pathogens so they cannot infect more cells.
How does antibody production protect us against disease? (3)
- White blood cells produce antibodies which are
complementary to a specific antigen on a pathogen. - The binding of antibodies to antigens causes pathogens to clump together, making them easier to destroy.
- In the case of a second infection, the correct antibodies can be produced rapidly, preventing the person getting the same disease again.
How does antitoxin production protect us against disease?
Antitoxins bind to toxins released by pathogens and neutralise them.
What is a vaccination? (3)
The process of introducing small quantities of dead or inactivate form of a pathogen which stimulates white blood cells to produce complementary antibodies to the pathogen so that in the case of a second infection, memory cells can rapidly produce the correct antibodies, preventing infection.
What is herd immunity?
When a sufficiently high proportion of a population are immune to a disease (especially through vaccination) meaning the spread of this disease becomes limited.
What are the advantages of vaccinations? (3)
- Many epidemics can be prevented by vaccinations.
- Herd immunity protects those who cannot have vaccinations.
- They have eradicated many deadly diseases eg. smallpox.
What are the disadvantages of vaccinations? (2)
- Not guaranteed to work - might not protect against multiple strains of a pathogen.
- May be side effects or adverse reactions.
What are antibiotics?
Drugs that can be used to kill bacterial pathogens inside the body.
How do antibiotics work?
Antibiotics kill bacterial pathogens inside the body, but do not kill human cells.
Additional: whilst some antibiotics kill a wide range of bacteria, it is important that the right antibiotic is used for specific bacteria.
Why can antibiotics not be used to treat viral diseases? (2)
- They live inside host (human) cells making it difficult to design drugs to kill the virus but not destroy human cells at the same time.
- Viral pathogens have no cell wall, which antibiotics attack.
What is antibiotic resistance?
Antibiotic resistance occurs when mutations lead to individual bacteria being resistant to an antibiotic.
Why is antibiotic resistance a problem?
- Some types of bacteria are becoming resistant to all known antibiotics, so the diseases that they cause cannot be cured.
Additional: The resistant bacteria are able to survive, reproduce and pass on their alleles, leading to a greater proportion of antibiotic-resistant bacteria.
How can we prevent antibiotic resistance? (2)
- Avoid overuse and unnecessary use of antibiotics - eg. antibiotics are often used for viral infections.
- Finish antibiotic courses - to ensure all bacteria is killed.
What effect do painkillers have on infectious diseases?
Painkillers can only treat the symptoms but do not kill pathogens.
What plant is the heart drug digitalis extracted from?
Foxgloves
What drug is extracted from the foxglove plant?
Digitalis
What painkiller originates from a compound found in willow bark?
Aspirin
Where is aspirin extracted from?
Willow bark
What antibiotic was discovered by Alexander Fleming from a type of mould?
Penicillin
What are the four qualities of a good medicine? (4)
- Effective
- Safe
- Stable
- Able to be taken in and removed easily
What three main factors are tested for when developing new drugs?
- Toxicity
- Efficacy
- Dose
What is the first stage of drug testing?
Preclinical testing.
How is preclinical testing carried out?
In a laboratory - uses cells, tissues and live animals
What is the second stage of drug testing?
Clinical testing
How is clinical testing carried out?
The drug is tested at a low dose on healthy volunteers - then tested on patients and on a larger scale to find the optimum dose. Often, one group receive a placebo (not the test drug) and the other group receive the actual drug, in order to assess its efficacy.
What is a placebo?
A tablet of injection with no active drug in.
What is the difference between a single-blind and a double-blind trial?
In a single-blind trial, only the doctor knows whether the patient is receiving the drug or the placebo. In a double-blind trial, neither the patient nor the doctor knows.
What is beneficial about double blind trials?
Double blind trials help remove bias on the part of the doctor in case they pay close attention to those who took the active drug.
What is a peer review?
Where the results of drug trials are checked over by scientists knowledgeable in this field.
