Notes on Module 7 Infectious Disease

Resource Description

 

How are diseases transmitted?

• describe a variety of infectious diseases caused by pathogens, including microorganisms, macroorganisms and non-cellular pathogens, and collect primary and secondary-sourced data and information relating to disease transmission, including: (ACSBL097, ACSBL098, ACSBL116, ACSBL117)

A pathogen is an agent which causes disease or illness in a host organism – can only cause infectious diseases (diseases which can be spread from one host to one another

• Pathogens live and reproduce at the expense of host organisms & cause disease by releasing toxins, tissue damage or competing for nutrients
• Infection requires the pathogen to invade, reproduce & elicit a host response

• classifying different pathogens that cause disease in plants and animals (ACSBL117)

Microorganisms – organisms which can only be seen by microscopes, eg, bacteria, fungi & protozoa

Bacteria – prokaryotes which exist everywhere (in and outside of the body). 

The bacteria which is pathogenic can cause many diseases eg, meningitis & cholera

EG of Bacteria – Pantoea Stewartii – found in corn, wilts leaves (restricting growth)

Fungi – eukaryotes – eg yeasts, mould & mushrooms. Fungi can cause disease in

Humans, plants & animals. Fungi can cause Athlete’s Foot 

Protozoa – group of unicellular eukaryotes which cause disease in plants & animals, eg, Trypanosoma Brucei – african sleeping sickness

Macroorganisms – pathogens that are disease causing and can be visible from the naked eye & are either Endoparasitic (living inside of an organism) or ectoparasitic (living outside an organism)

Helminths – group of endoparasitic worms which live and feed on a live host

eg, intestinal worms which prevent the host from absorbing nutrients properly >

Leads to deficiencies in nutrients and a reduction of weight

Non-cellular pathogens – agents which have no metabolism & use the reproductive

mechanisms of the host to reproduce (only made up of nucleic acids, proteins or both)

Viruses – can infect all kinds of organisms & require the cells of their host for

Reproduction. Once the virus is inside, it attaches it’s own RNA or DNA into the

Host’s cells, changing the genetic material which is replicated > increase in virus

Eg – Wheat Streak Mosaic Virus – damaged crops & caused inability to grow

Eg – Vaccination – created to stop spread of influenza, smallpox & measles

• investigating the transmission of a disease during an epidemic
• design and conduct a practical investigation relating to the microbial testing of water or food samples

• investigate modes of transmission of infectious diseases, including direct contact, indirect contact and vector transmission

Direct Contact – when there is physical contact between the host and a non- infected organism, eg through kissing, biting or wound

Indirect Contact – transfer to a new host via a non-living object, eg airborne or contaminated water

Vector – usually the bite of an insect, eg mosquitos or ticks

investigate the work of Robert Koch and Louis Pasteur, to explain the causes and transmission of infectious diseases, including:

• Koch’s postulates
• Pasteur’s experiments on microbial contamination

Koch’s Postulates

• He performed experiments to identify the microorganisms responsible for diseases, his 4 postulates;

1. All diseased organisms must have the microbe causing the disease
2. The microbe must me isolated & grown in pure culture
3. These must be injected into a healthy host who will then show similar signs and symptoms
4. The disease causing microbe extracted from the new host must be identical to the one in the original

Pasteur’s experiments

• He disproved spontaneous generation & identified that microbes were the causes of disease
• His experiment used a beaker, one with a swan neck & one where the broth was exposed to the air, it showed that the one with exposure had grown bacteria & had been contaminated

• assess the causes and effects of diseases on agricultural production, including but not limited to:

• plant diseases
• animal diseases

Plant Diseases

Causes

• drought , lacking nutrient availability or actual pests such as Wheat stem rust – which effects wheat & oats

Effects

• Leads to death of plants, reduces yield farmers can gain from selling plants
• Decreases australian export revenue as they rely heavily on exports

Animal Diseases

Causes

• Can be bacteria, fungi or viral agents
• Eg Avian Influenza – bird flu affecting poultry

Effects

• Deaths of animals, reduces the yield & reduces economic income for the farmer
• Can lead to potential food risks for human consumption – may lead to malnutrition

• compare the adaptations of different pathogens that facilitate their entry into and transmission between hosts (ACSBL118)

Virus – They are able to stick to host cells > can help invade cells & spread around the cell

Bacteria – adhere to substances to prevent ashing by fluids eg urine, & it cannot be washed away which enables bacteria to be stuck

Waterborne – able to colonise & reproduce in water, cannot be destroyed just by boiled water, other methods needed