communicable diseases

What are communicable diseases caused by?

Pathogens

What do pathogens do?

Cause harm through directly damaging tissue or through the release of toxins

What are 4 examples of pathogens?

• bacteria

• viruses

• proctista

• fungi

What kind of diseases are caused by bacteria?

• Tuberculosis

• ring rot

What kind of diseases are caused by viruses?

• HIV/AIDS

• influenza

• tobacco mosaic virus

What kind of diseases are caused by protoctista?

• Malaria

• potato/tomato late blight

What kind of diseases are caused by fungi?

• Black sigatoka

• athletes foot

What/who can Tuberculosis infect?

• humans

• deer

• cows

• pigs

• badgers

How is tuberculosis transmitted?

through airborne droplets and more prevalent where people live in cramped conditions.

How does tuberculosis cause harm?

by damaging lung tissue and suppressing the immune system.

How is tuberculosis cured?

using antibiotics and prevented through vaccination

What does ring rot infect?

• potatoes

• tomatoes

• aubergines

What does ring rot damage?

• leaves

• tubers

• fruit

How is ring rot transmitted?

through infected tubers and micropropagation of plantlets from infected plants

What does ring rot do?

It reduces the crop of the plant and affects the livelihood of farmers

What are viruses classed as?

Non-living and acellular

What does acellular mean?

It is not made up of cells .

Are viruses smaller or larger than bacteria?

smaller

What do viruses consist of?

genetic material (DNA or RNA), a capsid and attachment proteins

What is a capsid?

A layer of protein surrounding the genetic material

Where does viral replication occur?

inside the host cells, and involves the injection of nucleic acid into the cell

What is an example of a virus that infects bacteria?

Bacteriophage

How is HIV transported?

Around the blood until it attaches to a protein on the helper T cells.

What does HIV stand for?

human immunodeficiency virus

What is HIV positive?

When a person is infected with HIV

What is AIDS?

When the replicating viruses in the helper T cells interfere with the normal functioning of the immune system.

What happens when the helper T cells are being destroyed by the virus?

The host is unable to produce an adequate immune response to other pathogens and is left vulnerable to infections and cancer.

How is HIV transmitted?

Through direct contact through sharing/mixing of bodily fluids.

What does the virus influenza infect?

The ciliated cells lining gas exchange surfaces.

Who are at higher risk of getting influenza?

Young children, the elderly and anyone with a lowered immune system

What are some symptoms of influenza?

• headache

• runny or stuffy nose

• sore throat

• aches

• vomiting

• extreme tiredness

• high fever

What is influenza also known as?

The flu

How is influenza transmitted?

By airborne droplets when coughing or sneezing

What does the virus tobacco mosaic virus infect?

Plants, mainly tobacco plants

What does TMV cause damage to?

the leaves, resulting in a mosaic pattern

also damages flowers and fruits

What does the damage from TMV prevent?

prevents the plant from growing

How is TMV transmitted?

When infected leaves touch healthy leaves or gardeners use contaminated tools.

Is there a cure for TMV?

No cure but resistant strains have been developed.

What are protoctista (protista)?

Are eukaryotes that exist as single-celled organisms or cells grouped into colonies.

Are there a lot of protocista that are pathogenic?

Very few are pathogenic, but the few that are cause extremely dangerous symptoms to the hosts they infect.

What are the pathogenic protoctista called?

parasites

How are these parasites usually transmitted?

via a vector, e.g malaria is transmitted by mosquitoes

What is malaria caused by?

Plasmodium

How is malaria spread?

Spread to humans through mosquitoes (vectors)

Does plasmodium reproduce sexually or asexually?

Reproduces both sexually and asexually, within mosquitoes and within human hosts.

How are they passed from mosquitoes to humans?

When mosquitoes bite and take blood from humans.

In humans what does the plasmodium infect?

Infects red blood cells, the liver and the brain

Is there a vaccine or cure?

some preventative medicines, but no vaccine or cure

What are the symptoms of malaria?

• headache

• chills

• sweating

• dry cough

• fatigue

• pain

• fever

• vomiting

What is the protoctista potato blight caused by?

Caused by a fungus-like protoctista

What does potato blight have that enters the plant and causes damage to the leaves and fruit?

Hyphae

how is potato blight transmitted?

By spores which travel on the wind or are transferred by animals and insects from one plant to another.

Is there a cure for potato blight?

There is no cure, but resistant strains have been developed

What is fungi?

eukaryotes that cause many plant diseases.

Are fungi multicellular or single-celled?

Can be either multicellular or single-celled

What are pathogenic fungi?

Parasitic

What do pathogenic fungi release to digests the hosts tissue?

Enzymes

What does black sigatoka infect?

bananas

How does the black sigatoka cause damage?

The fungal hyphae cause damage to the leaves, causing them to turn black preventing plant growth. ( as it prevents photosynthesis)

How is black sigatoka transmitted?

By spores from one plant to the next through the wind

What can help kill the fungus?

Fungicides, and resistant strains have been developed

Who does athletes foot infect?

humans

What is athletes foot?

A type of ring worm that thrives in warm, damp regions between the toes

What does athletes foot cause?

Causes the skin to crack and to become scaly, causing itchiness and soreness

How is athletes foot transmitted?

By direct contact e.g wearing the same socks or shoes as an infected person

How is athletes foot cured?

using antifungal creams

How do hot climates make transmission more likely?

Increased heat provides more kinetic energy for chemical reactions and reproduction

How do social factors (poverty/developing countries) make transmission more likely?

Could result in poorer sewage infrastructure, a lack of fresh water and food, poorer sanitation and overcrowded living quarters. Medicines and vaccines may aslo be less readily available to prevent the spread.

What are the two different types of transmission?

• direct transmission

• indirect transmission

In direct transmission what consists of direct contact?

touching, kissing, contact with cuts in skin and sexual contact

In direct transmission what consists of inoculation?

animal bites, sharing needles and cuts in skin

In direct transmission what does ingestion consist of ?

drinking and eating contaminated water and food

In indirect transmission what are vectors?

Usually animals that pass the pathogen to humans, such as mosquitoes transmitting malaria.

In indirect transmission what is droplets?

Pathogens transmitted in droplets of water e.g saliva and mucus expelled when sneezing

In indirect transmission what are Fomites?

Dirty bedding, socks and cosmetics are examples of inanimate objects that can carry and transmit pathogens

What is examples of direct contact between plants?

ring rot, tobacco mosaic virus, black sigatoka and blights

In indirect transmission in plants what is contaminated soil?

Pathogens and their spores can remain in the soil and infect the roots of subsequent plants.

In indirect transmission in plants what are vectors?

Wind, water, animals and humans can all carry pathogens and spores from one plant to another.

What do plants have instead of blood and an immune system to help with responses to pathogens?

• barriers to prevent entry, such as bark or waxy cuticles

• antibacterial chemicals and proteins as a defence against bacterial infections. Can repel insects (vectors) and kill pathogens

• Physical defences to prevent pathogens from spreading between their cells such as producing callose

What are the two lines of defence that animals have against pathogens?

• primary (non-specific)

• secondary

How does skin act as a barrier against pathogens?

It contains skin flora (healthy microorganisms), which outcompete pathogens for space and resources on the skin.

How does blood help as a response to pathogens?

Blood clots will form if the skin is cut to form a new barrier

How do mucous membranes act as a response to pathogens?

Mucus membranes line many body tracts. The mucus produced traps pathogens and the cilia sweep the mucus away from the lungs.

How does lysozymes act as a response to pathogens?

Lysozymes are hydrolytic enzymes which digest pathogens.

What explosive reflexes force pathogens out of the body?

sneezing, coughing, vomiting.

How does inflammation act as a response to pathogens?

inflammation will occur in localised areas where damage to cells is detected. It causes the area to become red, hot, sore itchy and swollen. When cells are damaged, this triggers mast cells to release histamines and cytokines.

How do histamines act as a response to pathogens?

Histamines cause blood vessels to dilate and therefore more blood is flowing in this area. Increases temperature from blood can kill pathogens. Histamines also make the walls of blood vessels more permeable so more white blood cells can be delivered to the site of damage.

How do cytokines act as a response against pathogens?

They attract phagocytes which can engulf and destroy pathogens

What phagocytes travel in the blood and squeeze out of capillaries to engulf and digest pathogens?

What is this process known as?

macrophages and neutrophils

Known as phagocytosis

What is stage 1 of the process of phagocytosis?

1. Damaged cells and pathogens release cell-signalling chemicals (cytokines) that attract the phagocytes to the site of infection.

What is stage 2 for the process of phagocytosis?

2. An opsonin protein can attach to pathogens to mark them and make it easier for neutrophils and macrophages to engulf them.

What is stage 3 of the process of phagocytosis?

3. phagocytes have receptors which can attach onto chemicals on the surface of pathogens.

What is stage 4 of the process of phagocytosis?

4. The phagocyte then engulfs the pathogen into a vesicle to create a phagosome.

What is stage 5 of the process of phagocytosis?

5. Within the phagocytes, there are lysosomes which contain hydrolytic lysozyme.

What is stage 6 of the process of phagocytosis?

6. The lysosome fuses with the phagosome to expose the pathogen to the lysozyme. The lysozyme hydrolyses the pathogen and any soluble useful molecules are absorbed into the cytoplasm of the phagocyte

What is stage 7 of the process of phagocytosis?

7. The phagocytes will present the antigen of the digested pathogen on their surface, they are then called antigen-presenting cells.