Communicable Diseases

Question 1

What are pathogens?

Answer 1

Microorganisms that cause diease

Question 2

What is a host?

Answer 2

The organism where pathogens live. They create a good habitat for microorganisms to live

Question 3

How do pathogens live?

Answer 3

By taking nutrition from their host which can cause damage in the process

Question 4

What is bacteria?

Answer 4

A type of pathogen belonging to the Prokaryote kingdom. They can reproduce rapidly and once in their host can multiply rapidly.

Question 5

What does bacteria do?

Answer 5

Their presence can cause disease by damaging cells or by releasing waste products and/or toxins that are toxic to the host.
In plants they often live in the vascular tissues and cause blackening and death of these tissues

Question 6

What are some example of diseases caused by bacteria:

Answer 6

~tuberculosis
~bacterial meningitis
~ring rot

Question 7

What does fungus normally do to animals?

Answer 7

Often live in the skin of an animal and where its hyphae which form a mycelium, grow under the skin surface. The fungus can send out specialised reproductive hyphae which grow to the surface of the skin to release spores. Causing redness and irritation

Question 8

What does fungus normally do to plants?

Answer 8

Often lives in the vascular tissue where it can gain nutrients. The hyphae release extracellular enzymes to digest the surrounding tissue which causes decay. Leaves will often become mottled in colour, curl up and shrivel before dying

Question 9

What is some examples of diseases caused by fungus?

Answer 9

~black Sigatoka
~ringworm
~athletes foot

Question 10

What do viruses do?

Answer 10

They invade cells and take over the genetic machinery and other organelles of the cell. They then cause the cell to manufacture more copies of the virus. The host cell eventually bursts, releasing many new viruses which will infect healthy cells

Question 11

What are some examples of disease caused by viruses?

Answer 11

~HIV/AIDS
~Influenza
~Tobacco mosaic virus

Question 12

What do protoctista do?

Answer 12

Usually cause harm by entering host cells and feeding on the contents as they grow

Question 13

What are some examples of diseases caused by protoctista?

Answer 13

Blight (tomatoes and potatoes)

Malaria

Question 14

What is tuberculosis?

Answer 14

It is a disease that affects many parts of the body, killing the cells and tissues, the lungs are most often affected. It is caused by the bacteria Mycobacterium tuberculosis and M.bovis.

Question 15

What is bacterial meningitis?

Answer 15

Infection of the meninges (the membranes that surround the brain and spinal cord) the membranes become swollen and may cause damage to the brain and nerves. It is caused the bacteria Neisseria meningitidis or streptococcus pneumonia

Question 16

What is ring rot (in plants)?

Answer 16

Ring of decay in the vascular tissue of a potato tuber or tomato, accompanied by leaf wilting. It is caused by the bacteria Clavibacter Michiganensis subsp.sepedonicus

Question 17

What is HIV/AIDS?

Answer 17

Attacks cells in the immune system and compromises the immune response. It is caused by the virus human immunodeficiency virus

Question 18

What is influenza?

Answer 18

Attacks respiratory system and causes muscle pains and headaches. It is caused by the virus from family Orthomyxoviridae-‘flu’ viruses

Question 19

What is tobacco mosaic virus?

Answer 19

A disease which causes mottling and discolouration of leaves. It is caused by the virus tobacco mosaic virus

Question 20

What is black Sigatoka (in bananas)?

Answer 20

A disease which causes leaf spots on banana plants reducing yield. It is caused by the fungus Mycosphaerella fijiensis

Question 21

What is blight (tomatoes and potatoes)?

Answer 21

A disease which affects both leaves and potato tubers. It is caused by protoctistan: Phytophthora infestans

Question 22

What is ringworm (cattle)?

Answer 22

Growth of fungus in skin with spore cases erupting through skin to cause a rash. It is caused by the fungus Trichophyton verrucosum

Question 23

What is athletes foot (human)?

Answer 23

Growth under skin of feet- particularly between toes. It is caused by the fungus Trichophyon rubrum

Question 24

What is malaria?

Answer 24

Parasite in the blood that causes headache and fever and may progress to coma and death. It is caused by the protoctistan: Plasmodium falciparum, P.viva, P.ovale, P.malariae

Question 25

What is transmission?

Answer 25

Passing a pathogen from an infected individual to an uninflected individual

Question 26

What is direct transmission?

Answer 26

Passing a pathogen from host to new host, with no intermediary

Question 27

What is indirect transmission?

Answer 27

Passing a pathogen from host to new host via a vector

Question 28

What is a vector?

Answer 28

An organism that carries a pathogen from one host to another

Question 29

What is the life cycle of a pathogen?

Answer 29

~travel from one host to another (transmission)
~entering the hosts tissues
~reproducing
~leaving the hosts tissues

Question 30

What are examples of direct transmission and how can they be prevented?

Answer 30

~direct physical contains e.g. touching some who is infected. This can be prevented by hygiene e.g. washing hand regularly especially after using the toilet
~faecal-oral transmission (usually by eating food or drinking water contaminated by the pathogen) e.g. food poisoning. This can be prevented by washing all fresh food
~droplet infection (pathogen carried in tiny water droplet in the air) e.g. influenza. This can be prevented by covering your mouth while coughing or sneezing
~transmission by spores (which are a resistant stage of the pathogen. Can be carried in the air or reside on surfaces or in the soil) e.g. tetanus. This can be prevented by using a mask

Question 31

What are other factors which affect transmission?

Answer 31

Social factors e.g.
~overcrowding (many people living and sleeping together in 1 house)
~poor ventilation
~poor health
~poor diet
~homelessness
~living or working with people who have migrated from areas where a disease is more common

Question 32

What are direct way plant pathogens and transmitted?

Answer 32

~many pathogens in th soil infecting the plant by entering the roots
~many fungi produce spores which can be carried by the wind (airbourne transmission)
~once a pathogen is inside the plant it may infect the vascular tissue
~when leaves are infected they can shed and carry the pathogen to the soil

Question 33

How does indirect transmission happen in plants?

Answer 33

Often occurs as a result of insect attack. As spores or bacteria become attached to a burrowing insect which attacks an infected. When the beetle attacks another plant the pathogen is transmitted to the uninflected plant.

Question 34

What is the correlation between disease and climate?

Answer 34

Many pathogens can grow and reproduce more rapidly in warm and moist conditions so they are more common in warmer climates. In cooler climates these pathogens may be damaged or killed by the cold weather

Question 35

What is a callose?

Answer 35

A large polysaccharide deposit that blocks old phloem sieve tubes

Question 36

What are passive defences?

Answer 36

These are defences present before an infection and their role is to prevent entry and spread of the pathogen. They include physical barriers and chemicals

Question 37

What are examples of physical defences in plants?

Answer 37

~cellulose cell wall- physical barrier and contains chemical defences that can be activated when a pathogen is detected
~lignin thickening of cell walls
~waxy cuticles- pathogens collect in water so the absence of water is a passive defence
~bark- contains chemical defences
~stomata closure- guard cells close the stomata when pathogens are detected
~callose- deposited around the sieve plates and blocks the flow of the sieve tube preventing a pathogen spreading around the plant
~tylose formation- a tylose is a balloon like swelling or projection that fills the xylem vessel. I plugs the vessel so it can no longer carry water preventing the spread of pathogens