Module 7 - Biology - Ruby

Define a Disease

any process or condition that adversely affect the normal functioning of a living thing or parts of a living thing.

• infectious of non-infectious

Define and infectious Disease

caused by an organism or infective agent (called a pathogen) and can be transmitted, either directly or indirectly, from one person to another

Define a Non-Infectious Disease

not caused by a pathogen. Cannot be transmitted from one person to another.

Define Incidence

the number of newly diagnosed cases of a disease

Define Prevalence

the total number of live cases of a disease or proportion of a population that have a disease

Define mortality

Mortality – number of deaths or proportion of a population that die from a disease.

Define Endemic level of disease

the baseline rate (incidence of prevalence) of a specific disease in a certain population

Define Epidemic

a widespread increase in the prevalence of a particular disease (sometimes also called an “outbreak”) above the endemic rate.

Define Pandemic

Pandemic – an epidemic which has spread across multiple countries or continents.

Methods of Disease Transmission? and examples of each?

Direct:

• a disease is passed directly from one human or animal to another human or animal

  • person to person

  • droplet

Indirect:

• a disease is transmitted from person to person - even though the two individuals have not been in contact.

  • fecal-oral

  • airborne

Vector:

• another organism to transfer a disease between individuals - type of zoonotic transmission.

  • insect bite

What are the types of Pathogens?

Living (Cellular Pathogens)

• Bacteria

• Fungi

• Protists

• Macroparasites

Non-living (Non-Cellular Pathogens)

• Viruses

• Prions

When is something a pathogen?

1. Finds favourable conditions for survival and reproduction in the host and is in sufficient numbers to cause disease

2. Is transmittable

What are Prions and how are they transmitted?

Prion:

• They are incorrectly folded proteins

• Convert adjacent brain proteins to the misfolded ‘prion’ form.

• results in holes in the brain → to neurodegeneration and eventually death.

• Composed only of protein and do not contain a nucleic acid.

Transmission:

• Ingestion of infected tissue

• There is concern that plants can take up prions from contaminated soil and that animals that graze on these plants.

• Contaminated:

  • surgical equipment

  • injections from infected animals

  • transplanted tissue or organs.

2 examples of diseases caused by a prion pathogen?

1. ‘Mad Cow Disease’ (BSE)

   • a disease in cattle that humans can catch from eating beef contaminated with brain or spinal cord tissue from an infected cow.

   • can also be caught from a contaminated blood transfusion.

2. Chronic Wasting Disease

   • affects deer/elk/moose

What are Viruses and how are they transmitted?

Viruses:

• Non-cellular so technically not living organisms.

• They can only reproduce and metabolise in a host cells.

  • Attach to the host cell and inject their nucleic acid

  • The cell’s resources are used to copy the viral RNA or DNA and replicate the virus within the host cell.

  • Eventually the viruses burst out of the host cell (killing it) and being released to invade more host cells.

• The structure can vary → they all contain a nucleic acid (either DNA or RNA) enclosed by a protein coat.

• Can affect animals, plants and bacteria.

Transmission:

• Some viruses are airborne

• Some can only be transmitted via bodily fluids (e.g. HIV, ebola).

• Indirectly through contamination of fomites (objects), in some cases through contaminated food, or contaminated blood donations.

• Some viruses can be vector transmitted.

2 examples of diseases caused by a Virus pathogen?

Influenza

• causes fever and chills, sneezing, coughing and a sore throat

• Transmission

  • Airborne droplets – from coughing, sneezing, or talking.

  • Direct contact – touching an infected person (e.g. handshake).

  • Indirect contact – touching contaminated surfaces (fomites).

Ebola

• fever, fatigue, vomiting, internal and external bleeding.

What are Bacteria and how are they transmitted?

Bacteria

• Cellular and living.

• Prokaryotic.

• Able to reproduce quickly through binary fission.

• Most bacteria are not pathogenic and play important roles within organisms.

• Bacteria are the only pathogens which are affected by antibiotics.

Transmission:

• Directly through close contact

• Indirectly through air, contamination of food, water or another object.

2 examples of diseases caused by a Bacteria pathogen?

Salmonella:

• fever, headaches, nausea, vomiting

• ingestion of food or water that has been contaminated with animal faeces

• disease that affects the intestinal tract

Chlamydia:

• painful urination, vaginal discharge, painful sex

What are Protists and how are they Transmitted?

Protists;

• Unicellular eukaryotes

• They reproduce via binary fission.

• Many protozoa do not cause disease

Transmission

• faecal/oral

• Eating contaminated meat

2 examples of diseases caused by a Protist pathogen?

Malaria:

• fever, chills, headache

• Caused by a protozoan called Plasmodium

• First reproduces in the liver cells, then burst out of the liver cells (destroying them) and moving into the red blood cells to reproduce and cause the cells to burst releasing the pathogen into the blood.

• Then if Anopheles mosquito bites this host, the plasmodium (protist) will be transmitted to a healthy person if bitten by this same mosquito.

• Only transmitted by the Anopheles mosquito Vector

Giardiasis:

• gas, nausea, weight loss.

• Transmitted through contaminated water.

• The pathogen binds to the wall of the bowel, causing a range of digestive issues and interference with absorption of nutrients.

What are Fungi and how are they Transmitted?

Fungi:

• Eukaryotes, unicellular or multicellular.

• Fungi are heterotrophic so will absorb nutrients from their host in order to grow and reproduce.

• Some pathogenic fungi grow on or under the skin, hair and nails. Others can cause severe lung diseases if spores are inhaled.

Transmission:

• transferred via direct contact

• Indirectly → the floor of a public shower

2 examples of diseases caused by a Fungi pathogen?

Athlete’s Foot (Tinea):

• tiny white patches between toes, red skin, sore flake skin

• grow on the floor of a public shower and be transmitted to new hosts with bare feet.

Thrush (Candidiasis):

• naturally inhabit the mucous membranes of the mouth, respiratory tract, digestive system and female reproductive tract (vaginal itching/burning).

• transmitted through direct contact or contact with contaminated bodily fluids.

What are Macroscopic parasites and how are they Transmitted?

Parasites:

• Are multicellular so they are the largest of the pathogen types.

• Endoparasites

  • live inside the host.

• Ectoparasites

  • live outside the body

  • Can cause disease

    • directly by injecting toxins into the blood

    • indirectly as vectors.

Transmission:

• Endoparasites

  • infected individual to pass the eggs in their faeces, which are then ingested by another host through contaminated water or infected soil.

• Ectoparasites

  • can move

2 examples of diseases caused by a Macroscopic parasite pathogen?

Endoparasites

• roundworms, tapeworms and flukes are all worm-like parasites called helminths.

• They attach to the host’s gastrointestinal tract and interfere with digestion and absorption of nutrients.

Ectoparasites

• include parasitic arthopods such as fleas, lice, mites, flies and mosquitos.

• Directly impact the host by benefiting from sucking the blood from their hosts, feed on skin flakes, or injecting toxins, or skin irritation.

• They can also indirectly spread other diseases by acting as vectors.

Whats is Aristotle Theory pertaining to disease?

Spontaneous Generation

• Life is able to arise from nonliving matter if it contained some vital energy

What is Miasma Theory?

That disease and decay were examples of spontaneous generation from “bad air”

What experiment did Pasteurs use to refute spontaneous generation?

Swan Neck Flask Experiment

• The curve of the flask allows exposure to air, but particles (dust and microbes) get trapped in the bottom so they can’t get to the broth

• broth is boiled to kill any lingering microbes

• When the neck of the flask is broken and bacteria can reach the sterile broth, bacterial growth occurred

What can be drawn from Pasteurs experiment?

• Air or the broth itself had no “life force”, but the air did carry microorganisms

• Decay was caused by this microbial contamination of the air and not “spontaneous generation”.

• Spoilage of beer and wine was also due to microbial contamination and developed the process of ‘pasteurisation’ which involves heating liquids to kill microbes. It is still used today in the dairy industry.

• He rescued the silk industry after discovering that a silk worm disease was caused by bacteria.

• Influenced other scientists who introduced antiseptics to hospitals

• his work also inspired Koch to develop a method to determine which specific microbe is responsible for a disease.

What do Koch’s Postulates do and what are they?

statements that can be used to determine if a particular microbe is responsible for a specific diseases. (based on experimental work with anthrax).

A microorganisms is responsible for a disease if:

1. The specific microorganism must be present in every host with the disease

2. The specific microorganism must be isolated from the host and grown in a pure culture

3. A healthy host, when inoculated with the microorganism, must develop the same symptoms as the original host

4. The specific microorganism must be able to be isolated from the second host and identified as the same species as originally cultured.

How did Koch Discover his postulates?

• able to isolate disease causing bacteria from the blood of dying animals

• Compared the blood of sick and healthy animals, sick = microorganisms, heathy = clear

• injecting contaminated blood can transmit microbes

• isolating the microbe and transmitting it caused disease

What did Pasteur use Koch’s discoveries to create?

Pasteur used Koch’s work on anthrax to develop a vaccines for anthrax, cholera and rabies by using an attenuated (weakened) version of the microbe responsible for each disease.

both scientists discoveries laid the foundation for germ theory

What is the problem with agricultural disease, for the industry?

Significant costs:

• reduced productivity

• higher production costs

• negative impacts on international and local trade

• detrimental impacts on the environment and biodiversity

What are Types of Animal Agricultural diseases?

Anthrax:

Caused by bacterium Bacillius anthracis

Can affect a wide range of animal species including humans

Previous outbreaks have caused significant amounts of cattle die.

Spores can survive in deep alkaline soil for many years and grazing animals can become infected

Business costs:

• livestock deaths

• treatment and vaccination costs

• human health risks

Flystrike:

caused by several species of blow flies, most common is Lucilla cuprina.

the flies attacks leave a damaged wound which other flied lay eggs in → maggots then feed on the animals flesh.

Treatments/preventions:

• removing tails

• shearing

• chemical treatments

Same economic impacts..

What are Types of Plant Agricultural diseases?

Citrus Canker:

Caused by the bacterium Xanthomonas citri

The bacteria forms lesions on stems → leaves and fruit die back

high economic impact to the farmers and the government who lose tree plantations

Potato Moth:

Phthorimaea operculella

Destructive pest of potatoes in NSW → can also interfere with tomatoes, tamarilloes and eggplant

caterpillars feeds on leaves and tubers

Insecticides used to kill caterpillars and stop moths laying eggs

infestations can severely affect crops and productivity.

Define an Adaption

Adaptations are structures, behaviours or physiological responses that help an organism to survive and/or reproduce in its environment.

to successfully establish an infection a pathogen must…

1. enter the host

2. multiply in host tissues

3. resist or not stimulate host defence mechanisms

4. damage the host

In order to colonise a new host the pathogen must…

1. Exit original host

2. be transmitted to another host either directly or indirectly

3. repeat the steps to establish infection in new host.

Bacterial Cell Adaptions

1. Varied Transmission Route

   eg: air, water, food, bodily secretions

2. Attachment to surfaces

   surface adaptions to attach to other cells (fimbriae/glycoalyx)

3. Rapid Reproduction

   rapid multiply in/on host

4. Mobility

   some have flagellae to allow greater mobility.

Methods of entry of prions? and an adaption that aids in entry?

Oral route

•Prions can enter a new host via the gut .

Nasal Cavity

•Small amounts might be inhaled and infect the host.

Skin

Can enter the body through open lesions to skin.

Prions are able to retain their infectious properties in soil for long periods of time.

Protein can “adapt” and change shape to the most infectious form for a particular host cell in the absence of a nucleic acid

How do prions suppress host immune system?

They invade specialized white blood cells found in the lymph nodes and spleen and replicate and eventually invade nervous tissue.

Methods of entry of Viruses? and 3 adaptions that aids in entry?

Adaptations:

1. Entry via receptor mediated endocytosis

Spikes which usually cover Viruses cause the host cell to form a vesicle bringing the virus into the host.

Eg influenze

2. Fusion:

Use their spike proteins to bind to host cells surface proteins, "tricking" the host cell to fuse its membrane, allowing the virus to enter.

3. Entry via Genetic Injection
Use surface proteins to attach then inject their genetic information.

Similarities and Differences of Viruses to other pathogens

Similar to bacteria and fungi, they have to stick to their host cell prior to invasion

Differences: → Surface proteins on capsid or envelope adhere to the host cell

Do Viruses suppress the host immune response?

Due to high rate of mutation, their surface proteins can change so host immunity – specific memory  B and T cells against one strain are ineffective against new strains of the same virus

Bacteria Similarities and Differences

Similar to viruses and fungi they have to stick to their host cell prior to invasion

Differences → Chemicals called adhesins or Pilli and Fimbria stick to the host cell.

Bacterial cells can also stick together forming a biofilm, which aids adhesion.

Do Bacteria suppress the host immune response?

Release of chemicals destroy or suppress the hosts immune defences.

→ so do Bacteria, fungi and macroparasites

distinguishing adaptation of bacteria to aid in entry to host

Bacterial cells can stick together forming a biofilm.

Biofilms are inherently highly antibiotic resistant.

An adaption of protozoa that benefits them in infecting hosts.

Some protozoans can conceal or change their surface antigens, which delays detection by the immune system

Fungi Similarities and differences…

Similar: to bacteria and viruses, they have to stick to their host cell prior to invasion

Differences:

Cell wall or capsule molecules permit adhesion to cells

An adaption of fungi that benefits them in infecting hosts.

Some fungi can produce chemicals which suppress the host immune system.

Difference of macroparasites

Specialised mouth to attach to the host (internally or externally)

An adaption of macroparasites that benefits them in infecting hosts.

Some macroparasites (e.g. ticks and hookworms) secrete molecules that supress the host immune response

many have specialised mouth parts which hook onto the hosts skin eg: ticks

Prion Adaption for Transmission

Prions are able to retain their infectious properties in soil for long periods of time.

Viruses Transmission Adaption

able to live in a range of bodily fluids which enable them to be transmitted through the blood and other bodily fluids

Bacteria Transmission Adaption

horizontal gene transfer where bacteria can share genetic information

→ This paired with their high mutation rate allows for beneficial mutations to be shared.

• eg antibiotic resistance

These large colonies of resistant bacteria are more difficult for the host to destroy, giving bacteria more time for the infected host to pass on the pathogen.

Protozoa Transmission Adaption

Transmitted through food + water

• have adaptations enabling them to survive and replicate outside a host and are well adapted to move through water.

Fungi Transmission Adaption

fungi that cause tinea and ring worm can thrive anywhere that is warm and moist so they can be transmitted through direct contact or indirectly

Macroparasite Transmission Adaption

vary widely

• Ticks have adaptations that enable them to detect animals´ breath and body odors, or by sensing body heat, moisture, and vibrations.