Learning Outcomes:
Diseases caused by these major pathogen groups include:
- tuberculosis, tetanus, crown gall of plants
- chytridiomycosis (amphibian chytrid fungus disease)
- malaria, Phytophthora dieback (jarrah dieback is now considered a Protist)
- influenza, Ross River virus, viral diseases of honeybees, Australian bat lyssavirus
Influenza (pp.435-436)
What is it?
Influenza is different from a cold as it is more serious and usually comes on suddenly.
People who have "flu" often feel some or all of these symptoms:
- Influenza is a contagious respiratory illness caused by influenza viruses.
- The viruses infect the nose, throat, and sometimes the lungs.
- It can cause mild to severe illness, and at times can lead to death.
Influenza is different from a cold as it is more serious and usually comes on suddenly.
People who have "flu" often feel some or all of these symptoms:
- fever or feeling feverish/chills
- cough
- sore throat
- runny or stuffy nose
- muscle or body aches
- headaches
- fatigue (tiredness)
- some people (more commonly children) have vomiting and diarrhea
- bacterial pneumonia
- ear infections
- sinus infections
- worsening of chronic medical conditions such as;
- congestive heart failure
- asthma
- diabetes.
- congestive heart failure
- Most experts believe that flu viruses spread mainly by tiny droplets
- Droplets are made when people with flu cough, sneeze or talk.
- Droplets can land in the mouths or noses of people nearby.
- Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose or eyes.
- Thus influenza transmission is both airborne and as indirect contact.
- Approximately 8% of the population will be infected with an influenza virus each year.
- You may be able to spread influenza to someone else before you know you are sick, as well as while you are sick.
- People with influenza are most contagious in the first 3-4 days after illness begins.
- Some adults may be able to infect others 1 day before symptoms develop and 5 to 7 days after becoming sick.
- Young children and people with weakened immune systems, can infect others for an even longer time.
- Incubation period is about 2 days, but can range from 1 to 4 days.
- Get a flu vaccine each year.
- Reduces flu related illnesses
- Reduces and the risk of serious flu complications
- Staying away from people who are sick
- Covering coughs and sneezes
- Frequent handwashing
- Most healthy adults will recover from influenza if given time to rest.
- There are influenza antiviral drugs that can be used to treat flu illness.
- These are typically given to people who are at high risk of serious complications.
Above Influenza information sourced from: https://www.cdc.gov/flu/about/keyfacts.htm
Ross River Virus (pp.436-437)
What is it?
Now Read: https://www.abc.net.au/news/2017-03-09/clinical-trials-for-ross-river-virus-treatment-planned/8339214
- Ross River virus is actually a group of virus called arboviruses
- Arboviruses are arthropod-borne viruses spread by the bite of an infected mosquito
- The virus causes Ross River fever
- Many people who are infected will never develop symptoms.
- Some have flu-like symptoms: fever, chills, headache, aches and pains.
- Some joints can become swollen
- Joint stiffness particulalry in the morning.
- Sometimes a rash occurs on the body, arms or legs and disappears after 7 to 10 days.
- Tiredness or weakness may also occur at times during the illness.
- Symptoms usually develop about 7-10 days after being bitten by an infected mosquito.
- The majority of people recover completely in a few weeks.
- Some experience symptoms such as joint pain and tiredness for many months.
- The virus is spread by certain types of female mosquitoes (males do not feed on blood).
- If they feed on the blood of an infected animal they may become infected.
- The virus then multiplies within the mosquito and is passed to other animals or people when the mosquito feeds again.
- The number of infections tends to peak in the summer and autumn months.
- The virus is not spread directly from one person to another (indirect transmission)
- There is no treatment for Ross River Virus
- Doctors will prescribe medications to ease discomfort.
- There is currently no vaccine against Ross River virus.
- Cover-up with loose fitting clothing when outside.
- Apply mosquito repellent to exposed skin.
- Take care during peak mosquito biting hours (dawn and dusk)
- Remove mosquito breeding sites (e.g. still fresh water) from around the home.
- Mosquito nets
- Mosquito fogging (insecticide)
Now Read: https://www.abc.net.au/news/2017-03-09/clinical-trials-for-ross-river-virus-treatment-planned/8339214
Viral Diseases of Honey Bees (p. 438)
SACBROOD
BLACK QUEEN CELL VIRUS
NOTE: Although not in your syllabus, nosema is mentioned as an associated disease to the above bee viruses. "Nosema apis is a microsporidian, a small, unicellular parasite recently reclassified as a fungus that mainly affects honey bees." - thus a fungal parasitic disease.
- Picornavirus causes the disease
- Sacbrood infects adult bees but doesn’t produce symptoms, leaving the bee unaffected
- Spreads through multiple vectors:
- movement of infected hive component between colonies by a beekeeper
- worker bees infecting food sources
- nurse bees infecting larvae through feeding.
- Causes the larvae to turn black and die before reaching pupae stage in their lifecycle.
- Treatments usually include
- re-queening infected colonies
- improving the nutrition of the colonies by providing sugar syrup and pollen.
BLACK QUEEN CELL VIRUS
- This virus has occasionally been recorded to be associated with the death of queen cells
- The virus was thought to be stimulated by lower than ideal temperatures in artificial cell incubators.
- The literature suggests that this virus is closely associated with nosema disease infections.
- Symptoms of the virus include dead queen larvae or pre-pupae after they have been sealed in their cells.
- These dead larvae become dark brown to black in colour
- Spread and distributed through infected Varroa Mites which are tiny parasites
- Varroa Mites live and feed on the haemolymph of adult honey bees and also transfer infection between bees.
- Shortening of bee lifespan leading to colony collapse
- Also transmitted through
- food,
- faeces,
- queen to egg,
- ‘drone’ bee to queen.
- Symptoms recorded in acute infections include
- early death of pupae
- deformed wings
- shortened abdomen,
- discoloration in adult bees
- adult bees can die within 3 days.
- This disease is common in adult bees.
- Symptoms:
- Affected bees tremble,
- tend to crawl about the entrance of the hive
- found climbing onto the stems of grass near the hive
- cluster together on the ground or on grass stems
- abdomens can appear enlarged
- wings dislocated
- hairless, dark to shiny black in colour
- Dysentery (intestinal inflammation) can also be a sign of this disease
- Most of these symptoms are often associated with other aliments including nosema disease or pesticide poisoning
NOTE: Although not in your syllabus, nosema is mentioned as an associated disease to the above bee viruses. "Nosema apis is a microsporidian, a small, unicellular parasite recently reclassified as a fungus that mainly affects honey bees." - thus a fungal parasitic disease.
Australian Bat Lyssavirus (pp.439-440)
What is it?
Treatment:
Transmission:
Prevention:
- Australian bat lyssavirus (ABLV) is a virus that can be transmitted from bats to humans
- It causes serious illness.
- It has been found in four kinds of flying foxes/fruit bats and one species of insect-eating microbat.
- It is assumed that any bat in Australia could carry the virus.
- ABLV is more likely to be found in a sick or injured bat
- Bats that appear healthy may also be infectious.
- Surveys of wild bat populations have indicated less than one percent of bats carry ABLV.
- In sick and injured bats, around 7% have been found to carry the virus.
- ABLV is one of twelve types of lyssavirus which are found around the world.
- ABLV is the only one of these known to occur in Australia.
- ABLV is closely related but not identical to rabies virus which is a usually fatal disease in humans.
- Since November 1996, three people have died as a result of ABLV infection, after being bitten or scratched by bats.
- ABLV infection in humans causes a serious illness
- paralysis
- delirium
- convulsions
- death
Treatment:
- Rabies vaccine given after exposure to ABLV, but before symptoms will prevent the disease.
- Once a person develops the disease there is no specific treatment for ABLV.
- Proper cleaning of the wound reduces the risk of infection.
- If bitten or scratched, immediately wash the wound thoroughly with soap and water for at least five minutes.
- If available, an antiseptic with anti-virus action such as povidone-iodine or alcohol (ethanol) should be applied
- If bat saliva contacts the eyes, nose or mouth, flush the area thoroughly with water for several minutes.
Transmission:
- The virus can be transmitted from bats to humans
- When infected bat saliva enters the human body
- Usually by a bite or scratch, also by getting bat saliva in the eyes, nose or mouth (mucous membrane exposure)
- The virus is also found in the nervous system of affected bats.
- ABLV is unlikely to survive outside the bat or in a dead bat beyond a few hours
- The incubation period is variable. Of the three known human cases of ABLV infection,
- one became ill several weeks after being bitten by a bat
- one became ill more than two years after a bat bite.
- timeframe around exposure of the third case is not confirmed.
Prevention:
- Do not touch bats, even if they are injured.
- Rabies vaccination
- Rabies Vaccine contains killed virus that cannot cause the disease. Stimulates a person's immune system to develop antibodies.
- Human Rabies Immunoglobulin (HRIG) is made from blood donated by people who have been vaccinated against rabies. It is a concentrated form of antibodies against rabies virus.
- Pre-exposure vaccinations in anticipation of coming into conact with bats
- Post-exposure vaccination after exposure to the virus