4.1.1 Common Pathogens and Communicable Diseases Flashcards
What is a disease?
A disease is an illness or disorder of the body or mind that leads to poor health
Each disease is associated with a set of signs and symptoms
Communicable/infectious diseases are caused by pathogens and are transmissible (can be spread between individuals within a population)
Both plants and animals can be affected by pathogens
What is the difference between infectious and non-infectious diseases?
Infectious disease:
Disease caused by a pathogen that passes from infected individuals to uninfected individuals
Also known as communicable disease
Cholera, HIV/AIDS, malaria, tuberculosis
Non-infectious disease:
Long-term diseases that are not caused by pathogens, Lung cancer, cardiovascular disease, depression, cystic fibrosis, vitamin deficiencies
What type of organisms are pathogens?
Many microorganisms are pathogens including:
Bacteria
Viruses
Fungi
Protoctists
To control disease, it is very important to know what pathogen is causing it
How are Bacteria a pathogen?
Bacteria are a diverse range of prokaryotic organisms
Some bacteria are non-pathogenic (they do not cause any disease or damage) while others are pathogenic
Pathogenic bacteria do not always infect the hosts of cells, they can remain within body cavities or spaces
M. tuberculosis causes tuberculosis (TB) in humans
The bacteria infect the lungs, causing a chronic cough and bloody mucus
It is a disease often associated with poor hygiene and sanitation
M. bovine in cows can also transmit to humans to cause TB
Ring rot diseases in potato plants are caused by bacterial pathogens
The bacteria infect the vascular tissue and prevent the transport of water, causing the plant to wilt and die
The infection spreads into the potato tubers where the vascular tissue is arranged in a ring, producing the characteristic black ring of rot
How are viruses a pathogen?
Viruses do not have a cellular structure
This means they can’t respire, produce ATP, replicate genetic material or synthesise protein
They infect host cells and hijack their machinery to replicate their own genetic material and proteins
The first virus ever discovered was the Tobacco Mosaic Virus (TMV)
TMV infects several plant species
It causes a distinct yellowing of the leaves which produces a mosaic pattern
Three different influenza viruses infect humans to cause the flu
Influenza A, influenza B and influenza C infect the cells that line the airways
They cause a high temperature, body aches and fatigue
Influenza A is the virus that causes the most cases of flu globally
It has a capsid that surrounds 8 single-stranded molecules of RNA
The human immunodeficiency virus (HIV) infects specific cells of the immune system
It is an enveloped retrovirus
The viral enzyme reverse transcriptase produces single-stranded DNA from its viral RNA
DNA polymerase synthesises double-stranded DNA from this single-stranded DNA
The double-stranded DNA is inserted into the host DNA and can remain inactive for many years
Once activated the DNA provirus is used to synthesise new viruses
How are Protoctista a pathogen?
Protists are unicellular eukaryotes
Plasmodium falciparum is a protist that causes severe forms of malaria in humans
The parasite is spread by mosquitoes
Infected individuals experience fever, chills and fatigue
P. infestans causes the infamous potato blight
The pathogen is unusual as it has some fungal characteristics
It is transmitted via spores
The first signs of potato blight are small, dark brown marks on the leaves which quickly increase in size and number
The protist destroys potato and tomato crops leaving them completely inedible
How are fungi a pathogen?
Fungi have a similar structure to plants
Their eukaryotic cells have cell walls and large central vacuoles
However, instead of being made of separate cells, their bodies consist of filaments known as hyphae
These hyphae form a network and spread throughout a host/soil
Fungal diseases are much more common in plants than animals
Athletes foot is a fungal disease that exist on the surface of the skin
Fungal diseases in plants tend to be much more serious and can threaten entire crops
Black Sigatoka is a fungal disease in bananas
It spreads through the leaves of the plant, reducing its ability to photosynthesise
The lack of photosynthesis causes parts of the leaf to die; producing black streaks
Eventually, the whole leaf dies
