T3 communicable diseases Flashcards
what is a pathogen
disease-causing microorganism
how do bacteria cause disease
once inside the body, they divide rapidly by binary fission
kill cells and produce harmful toxins
how do viruses cause disease
invade and reproduce inside living body cells, leading to cell damage
give 3 ways in which pathogens can be spread
air - flu, tuberculosis and the common cold are spread by droplet infection
water - fungal spores in water spread plant diseases
direct contact - common in plant diseases and STIs
give 4 ways in which the spread of pathogens can be reduced
hygiene - handwashing, 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 haven’t developed cures for many viral diseases
what is measles
serious viral disease that can cause blindness and brain damage.
main symptoms are fever and red skin rash
how is measles spread
air - inhalation of droplets from coughs and sneezes
what is HIV / AIDS
Hiv - virus which attacks and damages the immune system until it can no longer function properly
AIDs - condition resulting from a long-term HIV infection.
no cure or vaccine
how is HIV spread
direct sexual contact and the exchange of bodily fluids
how can the spread of HIV/AIDS be prevented
condoms
screening of blood for transfusions
not sharing needles
bottle-feeding by HIV-positive mothers
use of antiretroviral drugs to prevent the development of AIDS
what is tobacco mosaic virus
plant pathogen which causes lead discolouration when cells are damaged
affected areas cannot photosynthesise, reducing crop yield
no treatment so farmers grow TMV-resistant crop strains to avoid infection
how is TMV spread
contact between infected and healthy plants
insects may act as vectors which transfer the virus between different plants
what is salmonella
type of bacteria found in raw meat, poultry and eggs
if they enter the body via food poisoning, they can affect natural gut bacteria
symptoms of salmonella food poisoning
fever
abdominal cramping
vomiting
diarrhoea
may be fatal in very young or elderly due to risk of dehydration
how can the spread of salmonella be limited
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
ST bacterial infection caused by unprotected sex with an infected individual
yellow/green discharge from genitals and painful urination
spread can be controlled through antibiotics + condoms
what is rose black spot
fungal disease which causes purple or black spots to develop on rose leaves
reduces the area of the lead which is available for photosynthesis and causes 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 rose black spot fungus be treated
using fungicides
destroying infected leaves
what is malaria
disease caused by protist pathogens
disease is carried from host to host by mosquitoes, and the protists enter the human bloodstream when they feed
fever and shaking, and it may be fatal in some cases
how can the spread of malaria be reduced
using insecticides
using insect nets to avoid bites
prevent mosquito breeding by removing stagnant water
antimalarial drugs
how does the skin prevent pathogens from entering the body
acts as physical barrier
scab formation after skin is cut/wounded
antimicrobial secretions which can kill pathogens
healthy skin flora compete with pathogens and act as an additional barrier
how does the respiratory system prevent pathogens from entering the body
nose - has hairs and mucus which trap pathogens
trachea and bronchi - 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 any pathogens present
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
WBCs produce antibodies which are complementary to a specific antigen on a pathogen
binding of antibodies to antigens causes pathogens to clump together, making them easier to destroy
in case of 2nd infection, 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 inactivated form of the pathogen which stimulates WBCs to produce complementary antibodies to the pathogen
in case of 2nd 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
advantages of vaccinations
eradicate many deadly diseases
many epidemics can be prevented by vaccinations
herd immunity protects those who cannot have vaccinations
disadvantages of vaccinations
not guaranteed to work - might not protect against multiple strains of a pathogen
may have side effects or adverse reactions
what drugs are used to cure some bacterial diseases
antibiotics - they can kill bacterial pathogens inside the body
how do antibiotics work
kill bacterial pathogens inside the body, but do not kill human cells
whilst some 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
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-resistant bacteria
concerning as some types of bacteria are becoming resistant to all known antibiotics, so the diseases cannot be cured
how can we prevent antibiotic resistance
avoid overuse and unnecessary use of antibiotics
finish antibiotic courses - to ensure all bacteria are killed
what effect do painkillers have on infectious diseases
only treat symptoms but don’t kill pathogens
what plant is the heart drugs 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 of mould
Penicillin
what are the 4 qualities of a good medicine
effective
stable
safe
able to be taken in and removed easily
3 main factors 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
drugs is tested at low dose on healthy, then tested on patients and on a larger scale to find the optimum dose
often, 1 group gets placebo and other receive the actual drug, in order to asses efficacy
difference between single-blind and double-blind trial
S: only doc knows whether the patient is receiving the drug or placebo
D: neither patient nor doctor knows
Helps remove bias on the part of the doctor
what is peer review
where the results of drug trials are checked over by scientists knowledgeable in this field
