3.1 Communicable diseases Flashcards
What is a communicable disease?
A disease caused by a pathogen which can be passed between animals or plants e.g. flu
What is a pathogen?
A disease-causing microorganism e.g. bacteria.
How do bacteria cause bacteria?
Once inside the 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 body cells, leading to cell damage
What are three ways in which pathogens can be spread.
By air - flu, tuberculosis and the common cold spread via droplet infection.
By Water - fungal spores in water spread plant diseases..
By direct contact - common in plant diseases and STI’s
Ways in which the spread of pathogens can be decreased.
Hygiene - handwashing, disinfectants
Reducing contact with infected individuals - quarantine.
Vaccination
Why is it especially important to prevent the spread of viral diseases?
Scientists have not yet developed cures for many viral diseases.
What are measles?
Measles is a serious viral disease that can cause blindness and brain damage. The 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 the immune system until it can no longer function properly.
AIDS is the condition resulting from a long term HIV infection. There is no or vaccine for HIV/AIDS
How is HIV spread?
Direct Sexual contact and the exchange of body fluids e.g. blood breastmilk
How can the spread of HIV/AIDS be prevented?
- Use of condoms
- Screening of blood for transfusions
- Not sharing needles
- Bottle-feeding by HIV-positive mothers
What is tobacco mosaic virus?
A plant pathogen which causes leaf discolouration when cells are damaged. Affected areas cannot photosynthesise, reducing the crop yield. As there is no treatment, farmers grow TMV - resistant crop strains to avoid infection
How is tobacco 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 via food poisoning, they effect natural gut bacteria.
What are the symptoms of salmonella food poisoning?
- Fever
- Abdominal cramping
- Vomiting
- Diarrhoea
Maybe fatal in very young or elderly populations due to the risk of dehydration.
How can the spread of salmonella be limited?
- Vaccinating animals intended for consumption
- Keep raw meat away from cooked meat
- Disinfected hands and surface after contact with raw meat
- Thoroughly cook meat
What is gonorrhoea?
A sexually transmitted bacterial infection caused by unprotected sex with an infected individual.
What is rose black spot?
A fungal disease which causes purple or black spots to develop on rose leaves. It reduces the area of the leaf which is available for photosynthesis causing it to eventually die.
How is 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 is malaria?
a disease caused by protist pathogens. The disease is carried from host to host by mosquitoes, and the protists enter the human bloodstream when they feed. Symptoms include fever and shaking, can be fatal in other cases
How can the spread of malaria be reduced?
- Using insecticides
- Using insect nets to avoid bites
- Prevent mosquito breed by removing stagnant water
- Antimalarial drugs
How does the skin prevent pathogens from entering the body?
- Acts as a physical barrier
- Scab formation after skin is cut/wounded
-Healthy skin flora compete with pathogens and act as an additional barrier
How does the respiratory system prevent pathogens form entering the body?
- Nose: has hairs and mucus which trap pathogens/
- Trachea and bronchi: have mucus that traps pathogens. Ciliated cells move mucus to the mouth so it can be swallowed.
How does the stomach prevent pathogens infecting the body.
Secretes hydrochloric acid - kills pathogens present
How does phagocytosis protect us against disease?
White blood cells ingest and destroy pathogens so they cannot infect more cells.
How does antibody protection protect is against diseaase?
White blood cells produce antibodies which are complementary to 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?
Contains a dead or inactive form of the pathogen which stimulates white blood cells to produce complementary antibodies to the pathogen. In the case of a second infection, memory cells can rapidly produce the correct antibodies and prevent illness.
What is herd immunity?
If a sufficiently high proportion of a population are immune to a disease, the spread of this disease will be limited
What are the advantages of vaccinations?
- They have eradicated many deadly diseases e.g. smallpox
- Many epidermis can be prevented by vaccinations
- Herd immunity protects those who cannot have vaccinations
What are 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?
Antibodies - they can kill bacterial pathogens inside the body.
How do antibodies work?
Antibodies e.g. penicillin kill bacterial pathogens inside the body, but do not kill human cells. Whilst some antibodies kill a wide range of bacteria, it is important that the right antibodies is used for specific bacteria
Why can antibodies not be used to treat viral diseases?
Antibiotics have no effect on viral pathogens as they live inside the host’s cells. Therefore, it is difficult to design drugs that would kill the virus and not destroy human cells at the same time.
What is antibiotic resistance?
occurs when mutations lead to individual bacteria being resistant to an antibiotic. These bacteria are able to survive reproduce and pass on their alleles, leading to a greater proportion of antibiotic - resistance bacteria. This is concerning as some types of bacteria are becoming resistant to all known antibiotics, so the diseases that they cause cannot be cured.
How can we prevent antibiotic resistance?
- Avoid overuse and unnecessary use of antibiotics - e.g. antibiotics are often used for viral infections.
- Finish antibiotic courses - to ensure al bacteria is killed.
What effect do painkillers have on infectious diseases?
Painkillers can only treat symptoms but do not kill pathogens.
What plant is the heart drug digitalis extracted from?
Foxgloves
What painkiller originates from a compound found in willow bark?
Aspirin
What antibiotic was discovered by Alexander Fleming from a type a mould?
Penicillin
What are the four qualities of a good medicine?
- 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
How is preclinical testing carried out?
In a lab - uses cells, tissues and live animals
How is clinical testing carried out?
Uses healthy volunteers and patients. Firstly the drugs is tested at a low dose on healthy people - then tested on patients and on a larger scale to find the optimum dose. Often, one group receive a placebo and the other group receive the actual drug, in order to assess its efficacy.
What is the difference between a single-blind and double-blind trial?
In a single blind trial, only the doctor knows whether the patients is receiving the drugs or the placebo.
In a double-blind trial, neither the patient nor the doctor knows. Double blind trails help remove bias on the part of the doctor
What is peer review
Where the results of drug trails are check over by scientists knowledgeable in this field.
