Topic 5: Communicable disease

What is our health a state of

physical and mental well-being

What are the main factors that affect how healthy you are

• Diet

• Stress

• Life situations

• Disease

What is a pathogen

A microbe that causes disease

Ways pathogens can be spread

• Air

• Water

• Direct Contact

Describe the difference between communicable and non-communicable diseases

Communicable diseases -

• Caused by pathogens and can be passed on from person to person

Non - communicable diseases -

• cannot be transmitted from one person to another eg, heart disease and arthritis

Bacteria -

(eg tuberculosis/salmonella)

• Large pathogen

• Made of living cells

• Release toxins

• Reproduce by binary fission

Viruses -

(eg aids/cold)

• Very small pathogen

• Not living

• Damage cells

• Live and reproduce inside cells

How do bacteria cause disease

• Reproducing rapidly (cell division)

• Releasing toxins

What is bacteria growth rate affected by

• Temperature

• Available nutrients

• Oxygen levels

• PH

• Water

Why are viruses hard to treat

• They are not killed by antibiotics

• They enter cells to hide from the immune system

How bacteria and viruses make us ill

• Bacteria multiply rapidly by binary fission and release toxins

• Viruses inject their genetic material into host cells, which then makes that cell make new viruses, which then burst out of the cell, which damages it

How the spread of diseases can be reduced or prevented

• Hygiene (hand-washing, clean food prep)

• Vaccination (building immunity)

• Isolation (keeping sick people away)

• Vector control (nets for mosquitoes)

• Lifestyle choices (condoms)

Why communicable diseases spread rapidly following a natural disaster

• clean water supplies + sanitation systems are often damaged

• People live in crowded shelters with poor hygeine, which makes it easier for pathogens to spread

• Health care services are disrupted

Explain why the number of bacteria on an agar plate will eventually stop growing.

They run out of essential nutrients, waste products build up creating a toxic environment ,and oxygen becomes limited, leading to a stationary phase and then a death phase

Explain why it is important to use an uncontaminated culture to investigate bacterial growth

Contamination can lead to inaccurate, unreliable results

Preparing an uncontaminated culture and the rules

• The petri dishes and culture medium must be sterilised before use (eg by heating to a high temperature), to kill any unwanted microorganisms that may be lurking on them

• If an inoculating loop is used to transfer the bacteria to the culture medium, it should be sterilised first by passing it through a hot flame

• After transferring the bacteria, the lid of the petri dish should be lightly taped on to stop microorganisms from the air getting in

• The petri dish should be stored upside down to stop drops of condensation from falling onto the agar surface

Chemicals to stop bacteria growth

• Disinfectant - kills bacteria on surfaces

• Antiseptic - Kills bacteria on skin

• Antibiotics - Kills bacteria inside you

Mealses

Type of pathogen - virus

Symptoms - high fever, cough, runny/blocked nose

Mode of transmission - when a sick person coughs, breathes

How is transmission prevented - vaccination

Treatment - supportive care

HIV

Type of pathogen - virus

Symptoms - fever, sore throat, headaches

Mode of transmission - blood, semen, vaginal fluid, breast milk

How is transmission prevented - condoms, not sharing needles

Treatment - drugs, prep

Salmonella

Type of pathogen - bacteria

Symptoms - diarrhea, fever, abdominal cramps

Mode of transmission - contaminated food + drink

How is transmission prevented - cook at 75 degrees

Treatment - rest, fluids, antibiotics

Gonorrhoea

Type of pathogen - bacteria

Symptoms - burning sensation while peeing, swelling of the genitals

Mode of transmission - unprotected sex

How is transmission prevented - protected sex

Treatment - injection, antibiotics

Athletes Foot

Type of pathogen - fungi

Symptoms - flaky skin, scaly rash, itchy

Mode of transmission - contamination

How is transmission prevented - clean socks, feet

Treatment - creams, sprays, powders

Rose Black Spot

Type of pathogen - fungi

Symptoms - small black spots on leaves

Mode of transmission - release spores

How is transmission prevented - chop of affected leaves

Treatment - chop of affected leaves

Tobacco Mosaic Virus

Type of pathogen - virus

Symptoms - crinkled leaves, mosaic pattern on leaves

Mode of transmission - people touching it + spreading it

How is transmission prevented - don’t touch other leaves

Treatment - chop of affected leaves

Crown Galls

Type of pathogen - bacteria

Symptoms - formation of swelling on plants

Mode of transmission - soils

How is transmission prevented - avoiding the plant, clean soil

Treatment - sanitation, physical removal

Malaria

• caused by

• spread by

• symptoms

• plasmodium

• mosquitoes

• headaches, fever, sweats, chills, dizziness, vomiting

• Why is malaria hard to prevent

• What are the best ways to prevent it

• Mosquitoes are everywhere and can bite you whenever

• Early diagnosis, bite prevention, awarness

How is malaria spread between people

If a mosquito bites someone who has malaria, when they bite another person it passes the malaria to them

Describe similarities and differences between salmonella and gonorrhoea

Human Defences against pathogens

• Tears - enzymes

• Ear wax - filter

• Cilitatmucas (in nose and mouth)

• Saliva - washes mouth

• Skin - barrier, friendly bacteria

• Stomach - PH2, denatured bacteria enzymes

Describe the role of white blood cells in the defence against disease

White blood cells help to defend against pathogens by:

• phagocytosis

• antibody production

• antitoxin production

Phagocytes:

• Track the pathogen down

• Bind to them

• Engulf them

• Destroy them

How does disease damage a plant

Interfering with its vital functions, such as photosynthesis and water transport

what can plant diseases be detected by

• stunted growth

• spots on leaves

• areas of decay (rot)

• growths

• malformed stems or leaves

• discolouration

• the presence of pests

what can plant disease Identification be made by:

• reference to a gardening manual or website

• taking infected plants to a laboratory to identify the pathogen

• using testing kits that contain monoclonal antibodies.

Plant Defenses

Chemical Defences - releasing a chemical to deter a herbivore eg stinging nettle

Physical Defences - a physical barrier that will stop a micro-organism from getting into the plant eg bark

Mechanical Defences - a structure on plants that will deter a herbivore eg mimicry

Describe physical, chemical, and mechanical plant defence responses

Physical defence responses:

• Cellulose cell walls.

• Tough waxy cuticle on leaves.

• Layers of dead cells around stems (bark on trees), which fall off.

Chemical plant defence responses:

• Antibacterial chemicals.

• Poisons to deter herbivores.

Mechanical adaptations:

• Thorns and hairs deter animals.

• Leaves which droop or curl when touched.

• Mimicry to trick animals.

Signs of plant disease to ion deficiency.

• Stunted growth caused by nitrate deficiency

• Chlorosis caused by magnesium deficiency

Calculate the number of bacteria in a population after a certain time if given the mean division time.

Calculate the area of the clear circle around colonies using r²