12.3 The Transmission of Communicable Diseases

What do pathogens that cause communicable disease have to be in order to be successful?

have to be transmissible

What does working out how diseases are transmitted from one individual to another allow us to do?

allows us to work out ways to reduce or prevent the transmission of the disease

The two main types of transmission?

direct transmission and indirect transmission

Direct transmission?

pathogen is transferred directly from one individual to another

Indirect transmission?

where the pathogen travels from one individual to another indirectly

The 3 methods of Direct Transmission (animals)?

direct contact, ingestion and inoculation

Examples of direct contact as a means of direct transmission (animals) (3)?

kissing or any contact with the bodily fluids of another person, direct skin-to-skin contact and microorganisms from faeces transmitted on the hands

(Animal) Direct contact: 2 examples of diseases spread through kissing or any contact with the bodily fluids of another person?

bacterial meningitis and many sexually transmitted diseases

(Animal) Direct contact: 2 examples of disease spread through direct skin-to-skin contact?

ring worm and athlete’s foot

(Animal) Direct contact: what diseases are spread through microorganisms from faeces being transmitted on the hands?

diarrhoeal diseases

Examples of indigestion as a means of direct transmission (animals) (3)?

taking in contaminated food or drink, transferring pathogen from the hands to the mouth or from faeces of hands

(Animal) Direct transmission: what 2 diseases are spread through indigestion?

amoebic dysentery and diarrheal diseases

Examples of inoculation as a means of direct transmission (animals) (3)?

breaks in the skin, animal bites or a puncture wound/needle sharing

An example of a disease being transmitted through an animal bite?

rabies

An example of a disease being transmitted through needle sharing/puncture wounds?

septicaemia

The 3 methods of indirect transmission (animals)?

vectors, droplet infection (inhalation) and fomites

What are Fomites?

inanimate objects or materials which can transfer pathogens to a new host

Indirect transmission: 3 examples of fomites?

bedding, socks or cosmetics

Indirect transmission: an example of a disease that is transmitted by fomites?

bedbugs

Indirect transmission: Droplet infection - when are droplets of saliva and mucus expelled from your mouth (3)?

as you talk, cough or sneeze

Indirect transmission: how can the expelling of these droplets transmit a disease?

if these droplets contain pathogens and if healthy individuals breathe these droplets in

Indirect transmission: 2 examples of diseases transmitted through droplets (inhalation)?

flu and TB

Indirect transmission: what do vectors do?

transmits pathogens from one host to another

Indirect transmission: 2 examples of non-animal vectors?

mosquitoes transmit malaria and rat fleas transmit the bubonic plague

Indirect transmission: what else can act as a vector of disease?

water (diarrhoeal disease)

2 examples of communicable disease that can be spread from animals to people?

bird flu strain H1N1 and brucellosis (from sheep)

How to reduce infection rates from animals to people (2)?

minimise any close contact with animals and washing hands thoroughly after any contact with animals

Factors increasing the transmission probability of diseases in animals: what type of conditions make it more likely for diseases to be transmitted?

overcrowded living and working conditions

Factors increasing the transmission probability of diseases in animals: what being compromised makes people more susceptible to disease?

if their immune system is compromised

Factors increasing the transmission probability of diseases in animals: 2 examples of humans having compromised immune systems?

having HIV/AIDS or needing immunosuppressant drugs after transplant surgery

Factors increasing the transmission probability of diseases in animals: what provides breeding sites for vectors?

poor disposal of human waste

Factors increasing the transmission probability of diseases in animals: what does climate disease introduce (2)?

new vectors and new diseases

Factors increasing the transmission probability of diseases in animals: climate change - why does increased temperatures promote the spread of malaria?

as the vector mosquito species is able to survive over a wider area

Factors increasing the transmission probability of diseases in animals: an example of culture increasing transmission?

in many countries traditional health practices can increase transmission

Factors increasing the transmission probability of diseases in animals: 2 examples of socioeconomic factors increasing transmission?

lack of trained health workers and insufficient public warning when their is an outbreak of disease

Factors increasing the transmission probability of diseases in animals: what being poor could lead to an increased chance of getting a disease?

poor nutrition

What is less well developed in plants than animals?

their immune systems

Plants - Direct transmission?

healthy plant in direct contact with any part of an infected/diseased plant

Plants - the 2 types of Indirect transmission?

soil contamination and vectors

Plant indirect transmission - soil: what do infected plants often leave in the soil (2)?

pathogens (bacteria or viruses) or reproductive spores (from Protoctista or fungi)

Plant indirect transmission - soil: what can these pathogens or spores go on to infect?

the next crop

Plant indirect transmission - soil: what can some pathogens (often as spores) survive?

the composting process - so the infection cycle can be completed when contaminated compost is used

Plant indirect transmission - soil: an example of spores that leave infected plants and enter the soil?

black sigatoka spores

Plant indirect transmission: the 4 main vectors?

wind, water, animals and humans

Plant indirect transmission - vectors: 4 examples of pathogens that may be carried by the wind (that is acting as a vector)?

bacteria, viruses. and fungal or oomycete spores

Plant indirect transmission - vectors: 2 examples of how water can act as a vector?

spores swim in the surface film of water on leaves and raindrop splashes carry pathogens and spores

Plant indirect transmission - vectors: what 2 animals carry pathogens and spores from one plant to another as they feed?

insects and birds

Plant indirect transmission - vectors: 3 ways humans act as vectors and transmit pathogens and spores between plants?

by hands, clothing, fomites, farming practices and transporting plants and crops around the world

Factors increasing transmission of diseases in plants: what increases the likely hood of direct contact?

overcrowding

Factors increasing transmission of diseases in plants: what can reduce the resistance of plants?

poor mineral nutrition

Factors increasing transmission of diseases in plants: what type of varieties of plants being planted increases disease?

planting varieties of crops that are susceptible to disease

Factors increasing transmission of diseases in plants: what conditions increase the survival and spread of pathogens and spores?

damp, warm conditions

Factors increasing transmission of diseases in plants: 2 ways climate change increases the spread of disease?

increased rain and windfall promote the spread of disease and changing conditions allow animal vectors to spread to new areas

Factors decreasing transmission of diseases in plants: one way climate change may reduce the spread of disease?

drier conditions may reduce the spread of disease

Preventing the spread of disease in plants: what should you clear as thoroughly as possible?

fields - remove all traces of plants from the soil at harvesting

Preventing the spread of disease in plants: where should you place plants to minimise the spread of pathogens?

leave plenty of room between where plants are placed

Preventing the spread of disease in plants: why can rotating crops help to minimise disease?

the spores of bacteria will eventually die if they do not have access to the host plant

Preventing the spread of disease in plants: what strict practices can minimise disease?

follow strict hygiene practices such as washing hands or washing down machinery

Preventing the spread of disease in plants: what can you control to minimise the spread of disease?

insect vectors