bio - infectious diseases

pathogen

a disease causing agent that can be transmitted from 1 organism to another

disease

illness/sickness characterised by a set of signs + symptoms

symptoms

a subjective experience felt by a patient

communicable

infectious/able to be transmitted from 1 organism to another

transmission

transport of a pathogen from an infected host or a reservoir to a susceptible host

secretions

body fluids

reservoir

an organism or habitat in which a pathogen can reside + sometimes replicate, prior to entering a susceptible host

outbreak

a sudden inc in no. of disease above usual baseline

vector

an agent that transmits pathogens from 1 host to another

pathogenicity

the capacity of a pathogen to cause disease in a host

resistance

when an infectious agent or toxin is acting on a host, the host has an ability to withstand any adverse effects

susceptibility

the likelihood of developing a disease

incubation period

time between infection and the on set of symptoms

virulence

a measure of the ability of a pathogen to cause severe diseases w/in its host

3 virulence factors that determine pathogenicity of an organism

• adherence + colonisation

• capsules + surface components

• invasion/evasive factors

zoonotic diseases

an infection that is naturally transmitted between vertebrae animals + humans

why is the flu a zoonotic disease

avian/bird flu + swine/pig flu is transmitted from animals to humans

what are the 3 factors that transmission of infectious disease depends on

1. the infectious agent

2. the susceptibility of the host

3. mode of transmission

what is the diff between a micro organism + pathogen

all pathogens are micro organisms but not all m.o are pathogens. pathogens always cause harm but m.o do not

what does it mean a disease can be infectious but not contagious

infectious diseases caused by pathogens but not always easily transmitted to one another. Diseases are a subset of I.D that is highly transmissable

endospore

a tough, dormant structure formed by many species of bacteria to help them resist unfavourable conditions + disperse to new hosts

flagellum

a whip like tail which provides a zoospore or some other motile single cells w/ locomotion

pilus

hair like extensions found on the surface of bacteria which are crucial for bacterial adhesion to host cells + other surfaces, playing a key role in colonisation + infection

bacterial capsule

a slimy layer surrounding the cell wall of some species of bacteria

bacteria

microscopic unicellular organisms that don’t have a nuclear membrane or membrane bound organelles

what is bacteria cell wall made of

peptidoglycan

what are the diseases caused by bacteria

• crown gall of plants

• tuberculosis

structural features of bacteria

• prokaryotic

• unicellular

• flagella for movement

• no nucleus

• lacks membrane bound organelles

• have circular DNA + plasmids

• 1 to 10 micrometres

lytic phase

part of the life cycle of a virus in which viral components are replicated + packaged to form new viruses that lyse the host cell

obligate parasite

an organism that can only survive in another organism

steps to viral replication in eukaryotes

1. attachment virus binds to a protein receptor on surface of the cell

2. entry of virus nucleic acid to host cell via endocytosis

3. viral DNA/RNA enter nucleus of cell

4. Viral DNA/RNA directs the host cell to replicate it + make copies of viral proteins via translation.

5. New viral DNA/RNA and proteins assemble at the host’s cell membrane.

6. new viruses move through membrane. may cause host to die

steps to viral replication in prokaryotes

1. Virus particle binds to the wall of host cell + viral DNA enters the cell’s cytoplasm.

2. Viral DNA directs host cell machinery to produce viral proteins + copies of viral DNA.

3. Viral proteins are assembled into coats; DNA is packaged inside.

4. Tail fibres + other components are added to coats.

5. Host cell undergoes lysis and dies. Infectious virus particles are released.

diseases caused by virus

• influenza A, B + C

• viral disease of honey bees

• ross river virus disease

structural components of a virus

• 30 to 300 nano metres

• contains DNA or RNA

• no membrane bound organelles

• capsid present

• reproduce using host cell

• non cellular

diseases caused by protist

• phytophthora dieback

• malaria

structural characteristics of protist

• eukaryotic

• multicellular + unicellular

• reproduce sexually + asexually

• 2 to 1000 micrometres

zoospore

a spore w/a flagellum

hyphae

a network or bunch of tiny filaments

mycelium

an interwoven mass of hyphae

sporangia

a spore case in which asexual spores are formed

chitin

The polysaccharide that is the main component of fungal cell walls + the exoskeletons of insects + other arthropods

motile

able to move spontaneously without external force

disease caused by fungi

chytridiomycosis

structural characteristics of fungi

• eukaryotic

• cell wall made of chitin

• multicellular + unicellular

• reproduce sexually + asexually

• can be made up of filaments

• macro + microscopic

• has a nucleus

steps to binary fission

1. prior to b.f., chromosome is tightly coiled

2. genetic material in chromosome unwinds, replicates and any plasmids replicate + separate

3. original and replicate chromosomes attach to the cell membrane and are pulled to opposite poles as the cell elongates

4. new cell wall starts to grow. as process commences, cleavage furrow develops in membrane

5. new cell wall fully develops

6. 2 cells seperate via cytokinesis and result in 2 identical daughter cells. chromosome tightly coils again

pandemic

a widespread occurrence of an infectious disease above baseline level over a whole country or the world at a particular time 

epidemic

a widespread occurrence of an infectious disease above baseline level in a community at a particular time. 

endemic

A disease that is always present in a population within a geographic area, typically year round

outbreak

A sudden, unexpected inc in the prevalence of a particular disease above the  baseline level for that population 

pathogen for tuberculosis

mycobacteria tuberculosis

entry + exit site for tuberculosis

respiratory system

symptoms for tuberculosis

• ashen skin colour

• lethargic

• bone aches

• headaches

• dec weight + appetite

incubation period for tuberculosis

2 to 8 weeks

latent TB

• strong immune system

• macrophages able to control MTB due to reduction in B.F

• asymptomatic + not contagious

what causes a weak immune system

undergoing chemo, autoimmune disease, malnutrition

life cycle of active TB

1. droplet nuclei containing tubercle bracilli are inhaled + travel to alveoli

2. tubercle bacilli multiply in the alveoli + eventually form lesions called tubercles

3. immune cells form a barrier shell around the tubercle bacilli, called a granuloma

4. Granuloma shell breaks down and the tubercle bacilli escape + release toxins and rapidly multiply, forming more tubercles.

5. infected host coughs or sneezes, sending airborne droplets + aerosols into the air ready to be inhaled

prevention for TB

• early diagnosis, quality control of health + hygiene

• vaccine called bacillus calmette guerin

• separation + good ventilation

• latent TB prescribed treatment to prevent developing active

treatment for TB

• antibiotics course which typically lasts 6 months

• a combo of antibiotics often prescribed to kill whole infection + prevent resistance

• if 6 months does not work, will extend to 2 years

pathogen for crown gall of plants

agrobacterium tumefaciens

plants affected by crown gall

roses, fruit, berry, rapes

life cycle of crown gall

1. bacterial spores released from infected plant galls, moves through water + soil via flagellum

2. transmitted directly by plant to plant contact or indirect by fomite, infected soil

3. bacterium attached to wounded plant as it releases chemicals that attract it. bacterium multiplies

4. bacterium transfers tumour inducing plasmid, which contains genes for uncontrolled growth

5. plant cell genome transfers and is instructed to produce growth hormones. this leads to rapid gall growth

6. galls grow around the plant which leads to stunted plant growth as there is unable to be water transport

7. cycle repeats

prevention against crown gall

• eliminate infected plants

• sterilisation of budding/grafting tools

• redirect run off to reduce soil dispersal

• prevent transferal of infected soils

• do not plant disease infected stock

pathogen for the flu

influenza

symptoms of influenza

• fever

• severe fatigue

• general aches + pains

• lethargic

incubation period for influenza

1 to 4 days

life cycle of influenza

1. infected host sneezes/coughs and airborne containing droplets containing host are inhaled, which they enter in respiratory tract

2. virus attaches to epithelial cells that have viral receptor cells

3. virus undergoes viral replication inside epithelial cells

4. virus released from cells via cough or sneeze

prevention for influenza

• reduce contact w/others

• wash hands, isolate, cough into elbow

• avoid high risk groups e.g pregnant women, young kids

• annual vaccine that contains 2 strains of A + B

treatment for influenza

• antivirals such as oseltamivir

• pain relief medication

pathogen for viral disease of honey bees

deformed wing virus, transmitted by varroa mite

how is deformed wing virus transmitted

vertical transmission from bee to offspring

symptoms of deformed wing virus

• Healthy bees push the infected/sick bees out of the hive 

• Infected bees cannot fly so they walk away from the hive 

• Smaller bee size 

• Swollen abdomen 

• Deformed wings 

incubation of deformed wing virus

death w/in days, if not months. whole colony can die within 1 to 3 years if not prevented

life cycle of deformed wing virus

1. queen bee lays up to 2000 eggs per day in brood cell

2. varroa mites transmit DWV. varroa mite carried by worker bee into hive

3. a few days later mites lay eggs. the first is a male, followed by more eggs that hatch into females

4. mother mite pierces a feeding hole in the bee pupa. before bee hatches + mating occurred, inc in varroa pop’n in hive

5. bee hatches severely diseased + weakened

characteristics of the varroa mite

• deaf + blind

• uses smell sense to locate brood chamber + fine sensory hairs on body

prevention of deformed wing virus

• Routine checks of hives to assist with early infection 

• In the past, 1980's, chemicals used on mites

• Non chemical strategy e.g isolation of queen

• Removing infected drone brood 

• Regular monitoring – using an alcohol wash or sugar shake method will help determine varroa mite numbers 

sugar shake method

1. Collect a sample: A sample of approximately 300 bees is collected from a brood frame, making sure not to include the queen.  

2. Add sugar: The collected bees are placed in a jar with a mesh lid, and powdered sugar (icing sugar) is added.  

3. Shake the bees: The jar is vigorously shaken for about a minute to dislodge the mites.  

4. Separate and count: The sugar is then separated from the bees (e.g., by pouring the contents into a container with water and observing the surface). The mites will float to the surface, making them easier to see and count.  

5. Assess infestation: The number of mites found in the sample is used to estimate the overall mite infestation level in the hive.  

alcohol washing method

1. Gather materials:  You'll need a Varroa mite testing kit, methylated spirits or isopropyl alcohol (at least 70% concentration), a container to shake the bees into, a container for the alcohol wash, and a way to filter the alcohol (like a fine mesh or cloth).  

2. Locate the queen and exclude her: The alcohol wash will kill the bees in the sample, so it's crucial to find and remove the queen from the frames you'll be using.  

3. Collect a bee sample: Shake bees from a brood frame (or frames) into a container. Aim for about 300 bees

4. Wash the bees: Pour the alcohol into the container with the bees, shake vigorously for a set time (e.g., 60 seconds), and then strain the alcohol through a filter.  

5. Count the mites: Examine the filter for mites. If present, they will be visible as small, brown, oval-shaped insects.  

6. Repeat the wash: Repeat the washing process a few times (e.g., two or three times) to ensure most mites are dislodged.  

7. Record results: Note the no. of mites found and consult recommended treatment guidelines for your area.  

 

vector for ross river virus

Aedes Vigilax

incubation for ross river

1 to 3 weeks

life cycle for ross river

1. RRV circulates/resides in blood of marsupial reservoir. does not replicate

2. mosquito takes blood feed containing viruses from marsupial

3. virus replicates. virus finds receptors on mosquitos epithelial cells. virus moves to salivary glands

4. mosquito chooses target via smell + heat. injects saliva containing virus into host bloodstream. primary replication occurs in skeletal muscles

5. Human-mosquitohuman/marsupial transmission is unlikely but possible.

prevention for ross river

• protective clothing

• insect repellent

• reduce exposure

• dec stagnant water

treatment for ross river

• no cure

• no vaccine

• pain relief medication

pathogen for chytridiomycosis

chytrid fungus

transmission of chytrid

• zoospores released into water (indirect), in which they are motile. therefore transmitted in contaminated H2O

• direct, frog to frog contact

• humans transfer spores via movement

impacts of chytrid fungus

• disrupts gas exchange by dec O2 in + CO2 out, which effects cellular respiration (dec ATP/energy, inc lethargic behaviour)

• dec in moisture, disrupting osmoregulation and the skin hardens + sloughs off

• electrolytes unbalanced which disrupts homeostasis + nervous system

• neurological issues: dec O2 to brain, lack of movement, legs splayed/unusual posture

step 1 to life cycle of chytrid

zoospores are motile + aquatic, they possess a flagellum + chitin cell wall and move in soil + H2O. spores can remain dormant in unfavourable conditions. they target keratin as a food source

step 2 to life cycle of chytrid

zoospores invade epidermal layer of skin which is high in keratin. it matures into filament + mycelium, absorbing nutrients. mycelium develops into zoosporangiums which release more zoospores, which can be transmitted directly or indirectly + is highly infectious

step 3 to life cycle of chytrid

zoosporangium produces zoospores asexually

step 4 to life cycle of chytrid

zoospore swims to new host. highly infectious

prevention + treatment of chytrid

• no cure

• dec human spread (tyres, shoes)

• dec illegal frog trading

• monitor effects of climate change on species no. + health

• disrupt chytrid life cycle

• dec soil + H2O transfer between env’t

• monitor no. in frog species

pathogen for dieback

Phytophthora cinnamoni

symptoms of die back

• leaves wilt, turn yellow

• retention of dry foilage

• darkened root colour

• decline in yield

• stunted growth

incubation period for die back

months to years

dieback life cycle for favourable conditions

1. healthy roots become infected. grows rapidly from tips to whole root system

2. gains moisture + nutrients from host root cells. zoospore develops into a cyst which produces a tube that invades the root cell + develops into mycelium. plant starts to suffer. dec ability to transport nutrients + H2O. damages vascular tissue

3. after 2 to 3 days, mycelium will produce sporangia. asexual reproduction.

4. in warm + moist conditions, zoospores are released into soil

5. zoospores penetrate the roots of a healthy host plant

dieback life cycle for unfavourable conditions

1. healthy roots become infected. grows rapidly from tips to whole root system

2. gains moisture + nutrients from host root cells. zoospore develops into a cyst which produces a tube that invades the root cell + develops into mycelium. plant starts to suffer. dec ability to transport nutrients + H2O. damages vascular tissue

3. after 2 to 3 days, mycelium will produce chlamydospores + await favourable conditions. asexual reproduction.

4. chlamydospores survive unfavourable cold + dry conditions in soil/dead plant material.

5. when conditions are favourable, they are activated and release zoospores

6. zoospores penetrate the roots of a healthy host plant

description of chlamydospore

• long living tough structures

• long term, non motile

prevention against die back

• map the presence of die back

• quarantine or destroy all infected plants

• spray fungicides on infected soil

• use impermeable materials on roads to prevent run off

• clean vehicles before entering die back free zones

pathogen that causes malaria

plasmodium falciparum

vector for malaria

anopheles mosquito

incubation period for malaria

10 to 15 days