Module 7

Causes of Infectious Disease

100

A non-infectious disease is caused by a?

Pathogen

200

Name the three ways infectious diseases spread and an example of each. 

Direct: STI, passing of fluids, droplets from cough and sneeze

Indirect: contaminated food, airborne, contaminated objects. 

Vectors: mosquito bites, flea bites. 

300

Outline how Pasteur's experiments on microbial contamination explains the causes and transmission of infectious diseases. 

Louis Pasteur’s experiments on microbial contamination fundamentally reshaped our understanding of infectious diseases by demonstrating that specific microorganisms, rather than miasmas or spontaneous generation, are the causative agents of diseases. His work with swan-necked flasks disproved spontaneous generation by showing that microbes from the environment contaminate sterile substances, proving that life does not arise spontaneously but from existing organisms. Pasteur's studies on fermentation and spoilage revealed that particular microbes are responsible for these processes, leading to the germ theory of disease. He further established that diseases are transmitted through these pathogens, which can spread via direct contact, contaminated food, water, or surfaces. His development of pasteurization and vaccines highlighted practical methods for preventing microbial contamination and disease, laying the foundation for modern microbiology and public health practices.

400

What is a cause and effect of an animal or plant disease on agricultural production? 

Foot-and-Mouth Disease (FMD)

Overview:

• Pathogen: Caused by the Foot-and-Mouth Disease Virus (FMDV), which is a member of the Picornaviridae family.
• Hosts: Primarily affects cloven-hoofed animals such as cattle, sheep, goats, and pigs.

Impact on Agriculture:

• Economic Losses: FMD can lead to severe economic losses due to decreased productivity (such as reduced milk and meat production), high mortality rates in young animals, and the cost of controlling and eradicating outbreaks.
• Trade Restrictions: Outbreaks often result in trade restrictions and export bans, as countries may prohibit the import of livestock and livestock products from infected regions, impacting international markets.
• Control Measures: Control strategies include vaccination, quarantine, and culling of infected animals, all of which incur significant costs and can disrupt agricultural operations.

Late Blight

Overview:

• Pathogen: Caused by the oomycete pathogen Phytophthora infestans.
• Hosts: Primarily affects potatoes and tomatoes, but can also impact other Solanaceae family members.

Impact on Agriculture:

• Economic Losses: Late Blight can cause devastating crop losses, reducing yields and quality of potatoes and tomatoes. It leads to significant economic losses for farmers and the agricultural sector.
• Crop Management: The disease can spread rapidly under favorable conditions (cool and wet weather), requiring frequent fungicide applications to manage. This increases production costs and can contribute to environmental concerns due to pesticide use.
• Food Security: In severe outbreaks, Late Blight can threaten food security, especially in regions heavily reliant on potatoes as a staple crop.

500

Write a method for microbial testing of food samples. 

Correct method format. 

Responses to Pathogens

100

What are two types of immune defenses?

Non-specific innate (passive) and specific adaptive (active)

200

List come physical responses to a pathogen. 

Vomiting, diarrhoea, cell death, increased urination and wound healing. 

300

List at least 3 examples of first lines of defense. 

Skin, mucous membranes, skin secretion, tears and mucous membrane

400

List and describe 3 chemical defences against infection 

Urine: urine's alkaline conditions are ideal for phagocytes which help with UTIs.

Sebum and sweat: Keeps pH of skin at 5.5, and Lysosomes secreted in sweat lyses or break down bacterial cell walls.

Saliva: Has antimicrobial molecules in it (immunoglobulin A (IgA) and lysozyme)

Tears: Has antimicrobial properties (IgA) 

Gastric (stomach) secretions: The highly acidic environment discourages the growth and survival of microbes. Also since the duodenum (first past of first intestine) has a very high pH, this sudden change in pH cannot facilitate pathogen survival.

Inflammation 

500

Evaluate a response of a named Australian plant to a named viral or fungal pathogen.

Example provided. 

Immunity

100

The 'foreign' molecules that the immune system uses to differentiate between self and pathogens are called. 

Antigens

200

Identify the correctly matched immune cell type and function:
A. B-cells: Attack infected host cells

B. T cells: initiate the inflammatory response

C. Antibodies: recruit other immune cells to the site of infection

D. Macrophages- Phagocytose pathogens 

D

300

Describe the role of inflammation in the immune response. 

The inflammatory response is part of the second-line of defense and involves the body increasing the delivery of immune cells to the site of infection. Blood vessels around the site of infection. Blood vessels around the site dilate to increase blood flow, and become permeable so while blood cells can migrate from the blood stream into the tissue space.

400

Plot a graph to illustrate a person's antibody production over time following a primary exposure, and then a secondary exposure to a pathogen. Label the time points for primary and secondary exposure.

Correct graph drawn and labelled. 

500

With use of a diagram, explain the process of clonal selection and outline its importance to the adaptive immune response.
(Clonal selection is the theory that specific antigen receptors exist on lymphocytes before they are presented with an antigen due to random mutations during initial maturation and proliferation.)

- states clonal selection is important because it leads to antigen-specific immune response. 

- states clonal selection occurs both for T and B cells

- notes that the starting population of naive T and B cells are highly variable with different antigen affinities

- stating selection occurs based on antigen affinity

- noting that rapid multiplication leads to the generation of clones with the same good antigen affinity

- states the clones differentiate into effector cells (plasma or memory B cells, and killer, helper, suppressor, or memory T cells.)

- explaining that for B cells, memory cells and plasma cells are generated, and for T cells killer, helper. memory, and suppressor T cells are generated. 

- has a clear diagram showing the steps involved. 

Prevention, Treatment and Control

100

List 2 procedures that can be employed to prevent the spread of diseases. 

hygiene practices – quarantine – vaccination, including passive and active immunity– public health campaigns – use of pesticides – genetic engineering

200

Which of the following is a correct statement:

a) antivirals are used to destroy viruses
b) The rapid evolution of viruses impacts the effectiveness of antivirals.
c) Antibiotics can block the ability of a virus to invade host cells
d) Antibiotics and antivirals share the same mechanism of action

B

300

Xyella fastidiosa is a bacterial plant pathogen, transmitted by an insect vector called leafhoppers. This pathogen and insect are not present in Australia, but if it were to arrive here, it is predicted to severely impact Australian citrus, grape, olive, peach and plum industries along with our native plan species. You are employed by the Department of Agriculture to develop a strategy proposal to minimise the risk of X.fastidiosa poses to Australia.
Describe 2 strategies which could be implemented to prevent the arrival of this pathogen and insect into Australia. 

1. Restrict imports of plants an animals from affected countries to prevent the pathogen or vector from entering our shores. Since Australia is an island, this type of quarantine method is effective. 

2. Public awareness campaigns to warn travelers about bringing contaminated products to Australia. 

400

Jean has visited her GP and has been diagnosed with the flu due to the infection with the Influenza virus. Jean has asked for an antibiotic prescription.

Explain what will happen if she is given antibiotics. 

Antibiotics are used to treat bacterial infections, and since Jean is infected with a virus, the antibiotics will not assist in her treatment. However, if she takes the antibiotics good bacteria will be attacked and it may lead to antibiotic resistance due to increased exposure to antibiotics to bacteria.

500

There has been an outbreak of a newly identified infectious disease. A vaccine has been developed against the causative pathogen and is currently being distributed and administered as a strategy to manage the spread of this disease.
Evaluate the use of vaccines to prevent the spread of an outbreak. 

Vaccines are a substance used to stimulate immunity to a particular infectious disease or pathogen, typically prepared from an inactivated or weakened form of the causative agent or from its constituents or products. They are vital in controlling the spread of infectious diseases, stopping then from infecting new hosts. Since vaccinated individuals will have a strong, rapid immune response to a pathogen, the pathogen will be unable to multiply much before being defeated by the immune system. Thus, by minimising the pathogen, there is a decreased chance of transmission to another host. Another benefit of vaccines is that they provide herd immunity where a significant portion of the population is vaccinated, so it is hard for pathogens to spread with few susceptible individuals. This is crucial for protecting new borns, the elderly, and the immunodeficient who cannot be vaccinated.