COMMUNICABLE DISEASES, DISEASE PREVENTION, AND THE IMMUNE SYSTEM

What does WHO stand for?

World Health Organization

Define health, according to WHO

a state of complete physical, mental, and social wellbeing and not merely the absence of disease or infirmity

Define disease

bodily disorder / disordered state of an organ/organism

what type of symptoms does disease cause?

can be physical, mental or social

define infirmity

physical/mental weakness

define communicable disease

can be passed on from one organism to another (this can be between the same and different species)

define pathogens

disease-causing organisms

name the pathogens that communicable diseases are caused by?

- virus

- bacteria

- fungi

- protoctista

What are the 11 communicable diseases you need to know about?

- tuberculosis

- malaria

- Athlete's foot

- bacterial meningitis

- Tobacco Mosaic Virus (TMV)

- ring rot

- influenza

- HIV/AIDS

- ringworm

- blight

what organisms does tuberculosis affect?

Animals, typically humans and cattle

which pathogen is responsible for tuberculosis?

bacteria

what are the main symptoms of tuberculosis?

affects many parts of the body, kills cells and tissues, lungs most often affected

what organisms are affected by malaria?

animals, inc. humans

which pathogen is responsible for malaria?

protoctista

what are the main symptoms of malaria?

parasite in blood that causes headache and fever, and may result in a coma and death

What organisms are affected by athletes foot?

Humans

Which pathogen is responsible for athletes foot?

Fungus

What are the main symptoms of athletes foot?

Growth of fungus underneath skin of feet, usually between toes

What organisms are affected by bacterial meningitis?

Humans

Which pathogen is responsible for bacterial meningitis?

Bacteria

What are the main symptoms of bacterial meningitis?

- infection of the meninges become swollen and may cause damage to brain and nerves

- infection could spread to other parts of the body, causing septicaemia and rapid death

- blotchy red/purple rash that doesn't disappear when a glass is pressed against it

What are the meninges?

Membranes that surround brain and spinal cord

What is septicaemia?

blood poisoning

What organisms are affected by tobacco mosaic virus?

Plants

Which pathogen is responsible for tobacco mosaic virus?

Virus

What are the main symptoms of tobacco mosaic virus?

Causes rotting and leave discolouration

What organisms are affected by ring rot?

potatoes and tomatoes (plants)

Which pathogen is responsible for ring rot?

Bacteria

What are the main symptoms of ring rot?

Rings of decay in vascular tissues (xylem and phloem) of a potato tuber / tomato and leaf wilting

What organisms are affected by influenza?

Animals

Which pathogen is responsible for influenza?

Virus

What are the main symptoms of influenza?

Attacks respiratory system and causes muscle pains and headaches

What organisms are affected by black Sigatoka?

Banana plants

Which pathogen is responsible for black Sigatoka?

Fungus

What are the main symptoms of black Sigatoka?

Causes leaf spots on banana plants, reducing yield

What organisms are affected by HIV/AIDS?

Humans

Which pathogen is responsible for HIV/AIDS?

virus

what are the main symptoms of HIV/AIDS?

attacks cells (T-helper cells) in immune system and compromises immune response

what organisms are affected by ringworm?

cattle

which pathogen is responsible for ringworm?

fungus

what are the main symptoms of ringworm?

growth of fungus in skin with spore cases erupting through skin to cause a rash

what organisms are affected by blight?

potatoes and tomatoes

which pathogen is responsible for blight?

protoctista

what are the main symptoms of blight?

affects both leaves and potato tubers

define host?

organism the pathogen lives in/on

which kingdom do bacteria belong to?

prokaryotae

Assuming conditions are ideal, how fast can bacterial cells reproduce?

Every 20 minutes

List two ways that bacterial cells can cause damage to their host

- damage cells

- release waste product/toxins

In plants, why do bacteria often live in the vascular tissue?

That's where water and nutrients are found which bacteria can gain energy from

Define hyphae

Branching filaments of a fungus

Define mycelium

Part of the fungus which reproduces and is made up of lots of hyphae

Define spore

Reproductive cells in plants and fungi.

*LOOK AT HANDOUT NOTES FOR DIAGRAM OF HOW A FUNGUS GAINS NUTRITION FROM ITS HOST

Name three different extracellular enzymes that a fungus would need to secrete in order to gain a range of nutrients

- protease

- carbohydrase

- lipase

List and explain the sequence of events that follows once a virus invades a cell

- viruses invades cell

- virus takes over genetic machinery and organelles of the infected cell (host)

> why zones and enzymes needed to produce copies of virus (diagram on notes)

- causes cell to make lots of copies of the virus

- host cell eventually bursts and many viruses are released that can infect healthy cells

Define retrovirus

Contains RNA not DNA

HIV is a retrovirus. Explain why the virus needs to contain reverse transcriptase enzymes.

The enzyme convert RNA to DNA

Define transmission

Passing a pathogen from an infected individual to uninfected individual

Define direct transmission

Where a disease is passed directly from one organism to another

What are examples of direct transmission?

- Droplet infection (sneezing/coughing over someone)

- sexual intercourse (HIV)

- touching an infected person (Athlete's foot)

Define indirect transmission

Where a disease is passed on via an intermediate

What are examples of indirect transmission?

- air (influenza)

- water (cholera)

- food (salmonella)

- vector (other organism) (malaria)

Define vector

An organism that carries a pathogen from one host to another

*DIAGRAM ON HANDOUT

What does plasmodium cause and how is it transmitted between animals?

Plasmodium causes malaria and is transmitted between animals by the female Anopheles mosquito

What are the different factors that affect disease transmission in animals?

- overcrowding

- Poor ventilation

- homelessness

- lack of education

- Poor health/lowered immune system

- Poor diet

- travel

- climate change

What are the two ways plant pathogens can be transmitted?

Direct and indirect

What does direct transmission in a plant mean?

Contact between a healthy plant with any part of a diseased plant

What are the four ways of indirect transmission in a plant?

- soil

- air/water

- insects/birds

- humans

Explain how soil is a form of indirect transmission in a plant

Pathogens enter roots

Explain how air/water are a form of indirect transmission in a plant

Pathogens can be carried in the wind. Fungi produce spores which can be carried in the wind and water.

Explain how insects/birds are a form of indirect transmission in a plant

Pathogens can attach themselves to insects which are eating plants

Explain how humans are form of indirect transmission in a plant

Pathogens dispose, are transmitted by hands, clothing, machinery, and transporting crops

State the different factors that affected disease transmission in plants

- planting crops that are susceptible to disease

- overcrowding

- Poor mineral nutrition

- damp and warm conditions

- climate change

Define necrosis

Deliberate cell suicide

What happens when a plant tissue becomes diseased?

necrosis - it will get sealed off and sacrificed

What are the physical barriers plants have against the attack of pathogens?

- waxy cuticle of leaves

- tree bark

- cellulose cell walls

- lignin

- stomata can close

- callose

What is callose?

A polysaccharide of beta glucose that can get deposited in the plasmodesmata of cells that are under attack as well as old phloem sieve tubes and tylose blocks xylem vessels

Explain the chemical barriers plants have against the attack of pathogens

- antimicrobial chemicals:

> destroy cell membranes of pathogens

> inhibit growth of pathogens

- some chemicals are toxic to insects so reduce the chance of infection via insect vectors, alkaloids and tannins (e.g. of toxic chemicals)

- some chemicals repel insects

- some chemicals are present before infection but others are made when an infection has been detected (this is and energy-saving mechanism)

what are primary defences?

those that prevent pathogens entering the body

what are non-specific defences?

prevent entry of all pathogens (engulf many different pathogens)

List the examples of primary, non-specific defences you need to know

- skin

- tears and sweat

- sebum

- mucus and cilia

- HCl in stomach

- nasal hairs

- most secretions contain lysozyme

- expulsive refluxes

what is skin?

tough, dead outer layer made of keratin

what is sebum?

oily substance that inhibits growth of pathogens

what does lysozyme do?

(enzyme that) destroys cell walls of bacteria and fungi

what is a fungi cell wall made up of?

chitin

what is a bacterial cell wall made up of?

peptidoglycan

What are examples of expulsive refluxes?

coughing, sneezing, diahorrea

why are expulsive refluxes a good primary non-defence?

sudden expulsion of mucus / gut / bowel contents will carry with it the pathogenic microbes

*CLOTTING DIAGRAM ON NOTES HANDOUTS***

define inflammation

swelling and redness of tissue caused by infection

what is a mast cell?

type of wbc that releases histamine

explain what histamine causes?

- vasodilation: blood flow to area of infection is increased

- capillary walls become more permeable to wbc's and proteins and increase production of tissue fluid causes swelling/oedema

- excess tissue fluid drains into the lymphatic system taking some pathogens with it

*MORE CLOTTING DIAGRAM ON HANDOUTS***

what is a secondary defence?

when a pathogen enters the body

what are the 2 types of white blood cells?

phagocytes and lymphocytes

what are the 2 types of phagocytes?

neutrophils and macrophages

fill in the gaps.

WBCs recognise pathogens as ___1____ and will destroy them.

This is bc the pathogen is covered by ___2___ (special protein / glycoprotein molecule)

1. foreign

2. antigens

what are the protein molecules found in blood plasma called?

opsonins

what do opsonins do?

attach to foreign antigens to help phagocytes destroy the pathogen