Communicable diseases Flashcards
(66 cards)
1
Q
What is a disease?
A
A disorder of structure or function in a human, animal, or plant that produces specific symptoms or that affects a specific location and is not simply a direct result of physical injury
2
Q
What is a communicable disease?
A
A disease caused by a pathogen can be transmitted, directly or indirectly from one organism to another, of the same species or different species
3
Q
What is means of transmission?
A
Movement of pathogens from a reservoir to a susceptible host
4
Q
What is a susceptible host?
A
Individual/member of population at riksk of becoming infected by a disease
5
Q
What is a reservoir?
A
Any person (case or carrier), animal plant, soil or substance in which a pathogen normally lives and multiplies and serves as a source from which other individuals can be infected
6
Q
What is are pathogens?
A
Microorganisms that cause disease
7
Q
What is a vector?
A
A living or non-living factor that transmits a pathogen from one organism to another, e.g. malaria mosquito
8
Q
What type of cells are protists? And what are some examples of diseases caused by protists?
A
single-celled (unicellular) eukaryotes
Examples:
- Malaria
- Potato/tomato late blight
9
Q
What type of cells are fungi? And what are some examples?
A
Eukaryotic unicellular or multicellular organisms
Examples:
- Black sigatoka
- Athlete’s foot
10
Q
What type of cells are bacteria? And what are some examples?
A
Single-celled (unicellular) prokaryotes
Examples:
- Tuberculosis (TB)
- Ring rot
11
Q
What type of cells are viruses? And what are some examples?
A
They are non-living infections agents. It is some genetic material (a single strand of DNA or RNA) surrounded by a protein coat (capsid)
Examples:
- HIV/AIDS
- Influenza
- Tobacco Mosaic Virus (TMV)
12
Q
How do viruses damage the host tissue?
A
- Viruses take over the cell metabolism
- The viral genetic material gets into the host cell and is inserted into the host DNA
- The virus then uses the host cell to make new viruses which then burst out of the cell, destroying it and then spread to infect other cells
13
Q
How do protists damage the host tissue?
A
- Take over cells and break them open as the new generation emerge, but they do not take over the genetic material of the cell
- They simply digest and use the cell contents as they reproduce
14
Q
How do fungi damage the host tissue?
A
- Fungi digest living cells and destroy them. This combined with the response of the body to the damage caused by the fungus gives the symptoms of disease
- Some fungi produce toxins which affect the host cells and cause disease
15
Q
How do bacteria damage the host tissue?
A
- Most bacteria produce toxins that poison or damage the host cells in some way, causing disease
- Some bacterial toxins damage the host cells by breaking down the cell membranes, some damage or inactivate enzymes and some interfere with the host cell genetic material so the cells cannot divide
- These toxins are a by-product of the normal functioning of the bacteria
16
Q
What is ring rot?
A
- A bacterial disease of potatoes, tomatoes, and aubergines caused by the Gram positive bacterium, Clavibacter michiganensis
- It damages leaves, tubers and fruit
- It can destroy up to 80% of the crop and there is no cure
- Once bacterial ring rot infects a field it cannot be used to grow potatoes again for at least two years
17
Q
What are the symptoms of ring rot?
A
- Soft, cheese-like rot of the vascular ring within the tuber
- Vascular ring discolouration
- Internal breakdown and hollowing of the tuber
- The tuber skin may appear sunken, dry, and cracked, with the tuber potentially mummifying
18
Q
What are the means of tranmission of ring rot?
A
- Vascular infection of daughter tubers derived from infected seed
- Contaminated equipment
- Direct contact
- Insects
- Contaminated water
19
Q
What is TMV?
A
- Tobacco Mosaic Virus (TMV) is a virus that infects tobacco plants and around 150 other species including tomatoes, peppers, cucumbers, petunias and delphiniums
- It damages leaves, flowers and fruit, stunting growth and reducing yields, and can lead to an almost total crop loss
- Resistant crop strains are available but there is no cure
20
Q
What are the symptoms of TMV?
A
- Leaf curling and distortion
- Yellowing and chlorosis
- A mosaic pattern of light and green areas on leaves
- Stunted growth
21
Q
What are the means of tranmission of TMV?
A
- Direct contact
- Contaminated soil
- Contaminated tools
22
Q
What is potato/tomato late blight?
A
- A disease caused by fungus-like protist oomycete, phytophthora infestans
- The hyphae penetrate host cells, destroying leaves, tubers and fruit, causing millions of pounds worth of crop damage each year
- There is no cure but resistant strains, careful management and chemical treatments can reduce infection risk
23
Q
What are the symptoms of potato/tomato late blight?
A
- Rapidly spreading rot of leaves, turning them brown and causing them to shrivel and wither
- Brown lesions can also appear on stems
- In potatoes, tubers may develop a brownish rot beneath the skin, potentially leading to complete rot
- Tomato fruits may develop brown patches, leading to a total rot as the disease progresses
24
Q
What are the means of tranmission of potato/tomato late blight?
A
Through wind-blown spores called sporangia
25
What is black sigatoka?
- A banana disease caused by mycosphaerella fijiensis, which attacks and destroys the leaves
- The hyphae penetrate and digest the cells, turning the leaves black
- If plants are infected it can cause a 50% reduction in yield
- Resistant strains are being developed
- Good husbandry and fungicide treatment can control the spread of the disease but there is no cure
26
What are the symptoms of black sigatoka?
- Dark streaks and spots on leaves, starting as small, reddish-brown flecks on the underside of leaves
- These spots then grow, darken, and may develop grey centers and yellow margins, leading to leaf death and reduced production. Affected leaves may also fold at the edges.
27
What are the means of tranmission of black sigatoka?
- Through both spores and infected plant material
- Short-distance spread occurs via rain-splash and wind dispersal of conidia, while long-distance spread happens through the movement of infected leaves, nursery stock, and fruit
28
What are the symptoms of TB?
- Persistent cough lasting more than 3 weeks
- Coughs that produce mucus or blood
- Fever
29
What is TB? And what are the effects?
- An infectious bacterial disease of humans, cows, pigs, badgers and deer
- Damages and destroys lung tissue and suppresses the immune system, so the body is less able to fight off other diseases
30
How is TB transmitted?
- Through the air when someone with active TB of the lungs or throat coughs, sneezes, or sings, releasing tiny droplets containing the bacteria into the air
- Another person nearby can inhale these droplets and become infected
- Prolonged and close contact with someone who has active TB is necessary for transmission
31
How can TB be cured/prevented?
- Curable by antibiotics
- Preventable by improving living standards and vaccination
32
What is bacterial meningitis? And what are the effects?
- A bacterial infection of the meninges of the brain (protective membranes on the brain surface) which can spread to the rest of the body causing septicaemia (blood poisoning) and rapid death
- About 10% of people infected will die
- Up to 25% of those who recover have some permanent damage
33
What are the symptoms of bacterial meningitis?
- Blotch red/purple rash that does not disappear when glass is pressed against it (for blood poisoning)
- Sudden high fever
- Severe headache
- Vomiting
- Stiff neck
34
How is bacterial meningitis transmitted?
Through respiratory secretions, particularly through close contact e.g. coughing, sneezing and kissing
35
How can bacterial meningitis be cured/prevented?
- Antibiotics will cure the disease if delivered early
- Vaccines can protect against some forms of bacterial meningitis
36
What is HIV/AIDS? And what are the effects?
- HIV is the virus that targets T-helper cells in the immune system
- AIDS is the most advanced stage of HIV infection where the immune system is severely compromised (HIV causes AIDS)
- It gradually destroys the immune system so affected people are open to other infections, such as TB, pneumonia and some types of cancers
- HIV stands for Human Immunodeficiency Virus, and AIDS stands for Acquired Immunodeficiency Syndrome
37
What are the symptoms of HIV/AIDS?
- Early HIV infection may present as a flu-like illness with fever, sore throat, and rash
- Later stages, or AIDS, involve severe illnesses like pneumonia and opportunistic infections due to a weakened immune system
38
How is HIV/AIDS transmitted?
- Through exchange of bodily fluids containing the virus (during intercourse or through sharing needles)
- Can occur from mother to child during pregnancy, childbirth or breastfeeding
39
How can HIV/AIDS be cured/prevented?
There is no cure or vaccine but anti-retroviral drugs slow the progress of the disease
40
What is influenza? And what are the effects?
- A viral infection of the ciliated epithelial cells in the gas exchange system
- It kills them leaving the airways open to secondary infection
- Fatal for those with chronic illnesses
41
What are the symptoms of influenza?
- Fever or feeling feverish/chills
- Cough
- Sore throat
- Body/head aches
- Fatigures
42
How is influenza transmitted?
- Through respiratory droplets released when an infected person coughs, sneezes, or talks
- These droplets can be inhaled directly by others nearby or can land on surfaces, allowing the virus to spread through indirect contact if someone then touches their eyes, nose, or mouth after touching a contaminated surface
43
How can influenza be cured/prevented?
- There is no cure
- The vulnerable are vcaccinated every year to protect against everchanging strains
44
What is malaria? And what are the effects?
- Caused by a protist
- It invades the red blood cells, liver and the brain
45
What are the symptoms of malaria?
- Fever
- Chills
- Sweating
- Headache
- Fatigue
- Muscle aches
- Anemia
- Seizures
46
How is malaria transmitted?
- The parasite that causes the disease is spread by the bite of infected mosquitoes
- The Plasmodium parasite has a complex life cycle with two hosts - mosquitoes and people
- They reproduce inside the female mosquito
- The female needs to take two blood meals to provide her with protein before she lays her eggs - and this is when Plasmodium is
passed on to people
47
How can malaria be cured/prevented?
- There are no vaccines and limited cures
Preventative measures can be used:
- Killing the mosquitoes (vectors) with insecticides
- Removing the stagnant water where they breed
- Mosquito nets, window and door screens
- Long clothing can prevent biting and spreading of the disease
48
What is ring worm? And what are the effects?
A fungal disease affecting mammals including cattle, dogs, cats and humans
49
What are the symptoms of ring worm?
- A red, ring-shaped rash that can be itchy and scaly
- The rash may appear on any part of the body, including the scalp, where it can also cause patchy hair loss
- It is not damaging but looks unsightly
50
How is ring worm transmitted?
Primarily transmitted through direct skin-to-skin contact with an infected person or animal, or indirectly by contact with contaminated objects or surfaces
51
How can ring worm be cured/prevented?
Antifungal creams are an effective cure
52
What is athlete's foot? And what are the effects?
- A human fungal disease
- It is a form of human ring worm that grows on and digests the warm, moist skin between the toes
53
What are the symptoms of athlete's foot?
- Itching, burning, or stinging between the toes or on the soles of the feet
- It causes cracking and scaling, which is itchy and may become sore
54
How is athlete's foot transmitted?
Through direct contact with an infected person or contaminated surfaces
55
How can athlete's foot be cured/prevented?
Antifungal creams are an effective cure
56
How does HIV infect a cell?
- HIV is a retrovirus
with RNA as its genetic material
- It contains the enzyme reverse transcriptase, which transcribes the RNA to a single strand of DNA to produce a single strand of DNA in the host cell
- This DNA interacts with the genetic material of the host cell
57
What is direct transmission?
Immediate transfer of the pathogen from host/reservoir to susceptible host
58
What is indirect transmission?
Pathogen is transferred or carried by an immediate item, organism or process to a susceptible host
59
What are the ways in which a disease can be directly transmitted between animals?
- Direct contact => sex/kissing, skin-to-skin, microorganisms from faeces transmitted onto hands
- Incoulation => through break in skin during sex (HIV/AIDS), animal bite, puncture wound, sharing needle, blood transfusion
- Ingestion => taking in contaminated food or drink, or transfering pathogens to the mouth from hands
- Transplancental => mother to foetus e.g. HIV
60
What are the ways in which a disease can be indirectly transmitted between animals?
- Formites => inanimate objects such as bedding, socks or cosmetics can transfer pathogens e.g. athlete's foot
- Droplet infection (inhalation) => minute droplets of saliva and mucus are expelled from your mouth as you talk, cough and sneeze and inhalation of the droplets may result in infection
- Vectors => a living or non-living factor that transmits a pathogen from one organism to another, e.g. malaria mosquito
- Water => it can act as a vector for disease, e.g. diarrhoeal disease carried in water
61
What are the factors affecting transmission of communicable diseases in animals?
- Overcrowding in living/working conditions
- Poor nutrition (lowered immune system)
- A comprimised immune system, including having HIV/AIDS
- Poor disposal of waste and lack of sewage system, providing breeding sites for vectors
- Climate change can introduce new vectors and diseases
- Culture and infrastructure. In many countries traditional medical practices can increase transmission e.g. application of non-sterile ointment to open wounds
- Socioeconomic factors such as lack of trained healthworkers, underfunded healthcare system and insufficient public warning when there is an outbreak of a disease
- No or incomplete immunisation
- Lack of public awareness/education
62
What are the ways in which a disease can be directly transmitted between plants?
This involves direct contact of a healthy plant with any part of a diseased plant
63
What are the ways in which a disease can be indirectly transmitted between plants?
- Soil contamination => infected plants often leave pathogens or reproductive spores from protist or fungi in the soil which can infect the next crop
- Wind => bacteria, viruses and fungal spores may be carried in the wind
- Water => spores swim the in the surface film of water on leaves and raindrop splashes carry pathogens and spores
- Animals => insects and birds carry pathogens and spores from one plant to another as they feed e.g. aphids
- Humans => pathogens and spores are transmitted by hands, clothing, formites, farming practices (through farm machinery) and by transporting plants and crops
64
What are the factors affecting transmission of communicable diseases in plants?
- Overcrowding increases likelihood of contact
- Poor mineral nutrition reduces immunity/resistance to diseases so the plant won't be as robust
- Damp, warm conditions increase the survival and spread of pathogens and spores
- Climate change e.g. increased rainfall and wind promote spread of diseases, changing conditions allow animal vectors to migrate to new areas, drier conditions may reduce the spread of disease
- Monoculture
- Planting varities of crops that are susceptible to disease
65
How can the spread of communicable disease be prevented in plants?
- Leave plenty of room between plants to minimise the spread of pathogens
- Clear fields as thoroughly as possible - remove all traces of plants from the soil at harvesting
- Rotate crops - the spores or bacteria will eventually die if they do not have access to the host plant
- Follow strict hygiene practices - measures such as
washing hands, washing boots, sterilising storage
sacks, washing down machinery, etc
- Control insect vectors
66
How can the spread of communicable disease be prevented in humans?
- Hand washing => regular hand washin is the single most effective way of preventing the spread of many communicable diseases
- Improvements in living and working conditions e.g. reducing overcrowding, ensuring good nutrition
- Disposal of both bodily and household waste effectively
