Define the term communicable disease.
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Define the term communicable disease.
A communicable disease is an illness caused by pathogens that can be spread between individuals within a population.
What are pathogens?
Pathogens are microorganisms that cause disease.
True or False?
Only animals can be affected by pathogens.
False.
Plants and animals can be affected by pathogens.
Name the different types of pathogen.
Types of pathogen include:
bacteria
viruses
fungi
protists
How do bacteria cause damage to the body?
Bacteria cause damage to the body by reproducing rapidly and producing toxins which damage tissues.
What are the main ways that pathogens are transmitted?
Pathogens are transmitted through:
direct contact
contaminated water
droplets carried in the air
contaminated food
True or False?
Cooking food thoroughly is a method to prevent the spread of pathogens.
True.
Cooking food thoroughly is a method to prevent the spread of pathogens as pathogens are (usually) killed by high temperatures.
Where do viruses live and reproduce?
Viruses live and reproduce inside living cells of a host organism.
What is measles?
Measles is a viral infectious disease with symptoms including a fever and a rash. It spreads easily and can be fatal if complications arise.
True or False?
Young children are not vaccinated against measles.
False.
Young children are usually vaccinated against measles.
How is measles transmitted between people?
The measles virus is spread by inhalation of droplets (from sneezes and coughs) that contain the virus.
How does HIV cause harm?
HIV can damage the immune system, eventually leading to acquired immune deficiency syndrome (AIDS).
What are the initial symptoms of HIV infection?
The initial symptoms of HIV infection are flu-like symptoms (runny nose, sore throat, achy limbs/joints).
How is HIV transmitted?
HIV is spread by exchange of body fluids, e.g. during sexual contact or when sharing needles. It can also pass across the placenta during pregnancy.
Why do plants infected with TMV have reduced growth?
The ‘mosaic’ pattern caused by the virus discolours the leaves; this affects the growth of the plant due to lack of photosynthesis.
What is Salmonella?
Salmonella is a bacterial pathogen that causes food poisoning; symptoms include:
fever
abdominal cramps
vomiting
diarrhoea
What is the main way that Salmonella infection can spread?
Salmonella enters the human body through ingestion of contaminated food.
True or False?
Proper food hygiene can help prevent Salmonella.
True.
Salmonella bacteria can be found in food prepared in unhygienic conditions. Proper food hygiene can therefore help to prevent Salmonella infection.
What is gonorrhoea?
Gonorrhoea is a sexually transmitted disease (STD) caused by a bacterial pathogen. Symptoms include discharge from the sex organs and pain on urinating.
How is gonorrhoea transmitted?
Gonorrhoea is transmitted through sexual contact.
How can the spread of gonorrhoea be prevented?
Gonorrhoea transmission can be prevented by:
treating infected individuals with antibiotics
the use of barrier contraception, e.g. condoms
What is rose black spot?
Rose black spot is a fungal disease of plants where purple or black spots develop on leaves, which often turn yellow and drop early.
How does rose black spot affect plants?
Rose black spot affects the growth of the plant as photosynthesis is reduced.
How does rose black spot spread?
Rose black spot is spread in the environment by water or wind.
How can rose black spot be treated?
Rose black spot can be treated by using fungicides and/or removing and destroying the affected leaves.
What type of pathogen causes malaria?
The pathogens that cause malaria are protists.
Define the term vector in the context of infectious disease.
A vector is an organism that transfers pathogens from one host to the next.
How do malarial protists infect humans?
Malarial protists infect humans when infected mosquitoes bite. The protists pass from the mosquito saliva into the human blood.
What are the symptoms of malaria?
Malaria causes recurrent episodes of fever and can be fatal.
How is the spread of malaria controlled?
The spread of malaria is controlled by controlling the mosquito vectors, e.g. by:
preventing the mosquitoes from breeding
using mosquito nets to avoid being bitten
What is the role of the trachea and bronchi in non-specific immune defence?
The role of the trachea and bronchi are to trap pathogens, dirt and dust using ciliated epithelial cells and mucus.
True or False?
Stomach acid is a specific immune defence mechanism.
False.
Stomach acid destroys many pathogens so is a non-specific defence mechanism.
What is the role of phagocytes in the immune system?
Phagocytes engulf and digest pathogens through phagocytosis.
True or False?
The body's response to infection involves antigens recognising antibodies.
False.
The body's response to infection involves antibodies recognising antigens.
What is the role of antibodies in the immune response?
Antibodies attach to antigens on pathogens, binding the pathogens together. This can prevent them from infecting cells, and make it easier for phagocytes to engulf them.
What is the role of antitoxins produced by white blood cells?
Antitoxins neutralise toxins released by pathogens, preventing them from causing harm to the body.
What is the difference between antigen, antibody, and antitoxin?
The difference between antigen, antibody, and antitoxin is as follows:
An antigen is a protein molecule found on the surface of a cell
An antibody is a protein produced by lymphocytes that binds to specific antigens on pathogens
An antitoxin is a protein that neutralises toxins released by pathogens
True or False?
Phagocytes release antibodies as part of their immune response.
False.
Phagocytes carry out phagocytosis to engulf pathogens; they do not produce antibodies.
What is vaccination?
Vaccination introduces dead or inactive pathogens into the body in order to induce immunity.
What role do white blood cells play in vaccination?
White blood cells recognise the antigens in a vaccine and produce specific antibodies.
How does vaccination lead to long-term immunity?
Vaccination leads to long term immunity because when someone is infected again by the same pathogen, white blood cells quickly produce the correct antibodies and the symptoms of infection do not arise.
True or False?
Vaccines increase the likelihood that a pathogen will spread.
False.
Vaccinating a large proportion of a population reduces the likelihood that a pathogen will spread; this is because most people in the population will be immune.
What are antibiotics?
Antibiotics are medicinal drugs that kill pathogenic bacteria.
True or False?
Antibiotics can kill viruses.
False.
Antibiotics do not destroy viruses, so can only be used to treat bacterial infection.
What is antibiotic resistance?
Antibiotic resistance occurs when bacteria survive exposure to antibiotics that would normally kill them or inhibit their growth.
What is the role of painkillers in disease treatment?
Painkillers are used to treat the symptoms of disease but do not treat the source of any infection, e.g. ibuprofen can reduce pain and inflammation but does not kill pathogens.
Why is it difficult to treat diseases caused by viruses?
It is difficult to treat diseases caused by viruses because viruses infect body cells. This means that destroying viruses without damaging body tissue is challenging.
What are some traditional sources of medicinal drugs?
Drugs were traditionally extracted from plants and microorganisms, e.g.
digitalis originates from foxgloves
aspirin originates from willow
penicillin comes from Penicillium mould
How are most new drugs developed today?
Most new drugs are synthesised by chemists in the pharmaceutical industry, although the starting point may still be a chemical extracted from a plant.
What is preclinical drug testing?
Preclinical drug testing is done in a laboratory using cells, tissues, and live animals.
What is the purpose of clinical drug trials?
Clinical drug trials are conducted to test the safety, efficacy, and optimal dosage of new drugs.
What is a double-blind drug trial?
In a double-blind trial some patients are given a placebo, and neither the doctor nor the patient knows whether each patient is receiving the placebo or the active drug.
Define the term placebo.
A placebo is an inert substance given to some participants in clinical trials instead of a true drug. Its role is to eliminate the effects of the brain and expectations on any results.
What is the purpose of testing new drugs on animals?
The purpose of testing new drugs on animals is to see the effect of medicines on a whole organism.
How are clinical trials conducted?
Clinical trials are conducted as follows:
very low doses of the drug are given to healthy volunteers to test safety
patients with relevant medical conditions take part in the trial, often using a double-blind study, to test efficacy and find the lowest effective dose