12.3 TRANSMISSION OF COMMUNICABLE DISEASES Flashcards
1
Q
what are two types of transmission of communicable diseases?
A
- direct
- indirect
2
Q
how can diseases be transmitted directly in animals?
A
- direct contact (contagious diseases)
- inoculation
- ingestion
3
Q
what is direct contact?
A
- kissing or any contact with the body fluids of another person e.g. bacterial meningitis and many sexually transmitted diseases
- direct skin-to-skin contact e.g. ring worm, athletes foot
- microorganisms from faeces transmitted on the hands e.g. diarrhoeal diseases
4
Q
what is inoculation?
A
- through a break in the skin e.g. during sex (HIV/AIDS)
- from an animal bite e.g. rabies
- through a puncture wound or through sharing needles e.g. septicaemia
5
Q
what is ingestion?
A
- taking in contaminated food or drink or transferring pathogens to the mouth from the hands e.g. amoebic dysentery, diarrhoeal diseases
6
Q
how can diseases be transmitted indirectly in animals?
A
- fomites
- droplet infection (inhalation)
- vectors
7
Q
what are fomites?
A
- inanimate objects such as bedding, socks or cosmetics can transfer pathogens e.g. athletes foot
8
Q
what is droplet infection?
A
- minute droplets of saliva and mucus are expelled from your mouth as you talk, cough or sneeze
- if these droplets contain pathogens, when healthy individuals breathe the droplets in they may become infected e.g. influeza, TB
9
Q
what are vectors?
A
- a vector transmits communicable pathogens from one host to another
- vectors are often but not always animals e.g. mosquitoes transmit malaria
- water can act as a vector of disease e.g. diarrhoeal diseases
10
Q
how is the probability of catching a communicable disease increased in animals?
A
- overcrowded living and working conditions
- poor nutrition
- compromised immune system
- poor disposal of waste, providing breeding sites for vectors
- climate change (introduce new vectors and new diseases
- culture and infrastructure
- socioeconomic factors
11
Q
what is direct transmission in plants?
A
- involves the direct contact of a healthy plant with any part of a diseased plant
- e.g. ring rot, tobacco mosaic virus, tomato and potato blight, and black sigatoka
12
Q
what is involved in indirect transmission in plants?
A
- soil contamination
- vectors
13
Q
what is soil contamination?
A
- infected plants often leave pathogens or reproductive spores from protoctista or fungi in the soil
- these infect the next crop
- some pathogens (often as spores) can survive the contamination process so the infection cycle can be completed when contaminated compost is used
- e.g. black sigatoka spores and ring rot bacteria
14
Q
in plants, what are the common vectors of disease?
A
- wind
- water
- animals
- humans
15
Q
how does wind act as a vector of disease in plants?
A
- bacteria, viruses and fungal or oomycete spores may be carried on the wind
- e.g. black sigatoka blown between Caribbean islands
16
Q
how does water act as a vector of disease in plants?
A
- spores swim in the surface film of water on leaves; raindrop splashes carry pathogens and spores, etc.
-e.g. spores of potato blight which swim over films of water on leaves
17
Q
how do animals act as a vector of disease in plants?
A
- insects and birds carry pathogens and spores from one plant to another as they feed
- insects such as aphids inoculate pathogens directly into plant tissues
18
Q
how do humans act as a vector of disease in plants?
A
- pathogens and spores are transmitted by hands, clothing, fomites, farming practices and by transporting plants and crops around the world
- e.g. ring rot survives on farm machinery
19
Q
how is the probability of catching a communicable disease increased in plants?
A
- planting varieties of crops that are susceptible to disease
- over crowding increases the likelihood of contact
- poor mineral nutrition reduces resistance of plants
- damp, warm conditions increase the survival and spread of pathogens and spores
- climate change (increased rainfall and wind promote the spread of new diseases)
20
Q
how can spread of diseases in plants be reduced?
A
- 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 (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
