Extended response Flashcards

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1
Q

Amphibian chytrid fungus disease

A

Chytridiomycosis disease is caused by a fungus called Batrachochytrium Dendrobatids

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2
Q

symptoms of chytridiomycosis

A

Skin gets thickened and hardens. Respiration becomes difficult because significant gas exchange usually occurs across moist skin under normal conditions. The amphibian can become lethargic. Hind legs extend, and the amphibian becomes sluggish and has no appetite. These symptoms can lead to death.

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3
Q

What is the incubation period of chytridiomycosis

A

2 - 10 weeks. death follows the onset of symptoms within 2-3 days

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4
Q

what are the six steps in the life cycle of chytridiomycosis

A
  1. Zoospores are produced and released from a mature zoosporangium (thallus) discharge tube
  2. Zoospores swim a short distance or are carried by water currents
  3. zoospores encounter a new susceptible host and attach to and penetrate a skin cell. This is the portal of entry
  4. The cells invade the skin, absorbing nutrients. A new zoosporangium develops via asexual reproduction
  5. The zoosporangium matures and zoospores are produced
  6. Chytridiomycosis damages the frog’s skin causing reduced respiration and osmoregulation, leading to death
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5
Q

Zoospores

A

a spore with a flagellum

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6
Q

Flagellum

A

a whip like tail which provides zoospores with locomotion

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7
Q

how is chytridiomycosis transmitted

A

occasionally direct via skin to skin contact. Indirect waterborne and soil transmission is more common. Zoospores are released by infected frogs via a zoosporangium (thallus), then swim through the water to attach to and penetrate the skin of a susceptible amphibian

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8
Q

unique future of chytrid fungus

A

They lack hyphae. Instead they grow a spherical, smooth walled zoosporangium or thallus. Inside asexual reproduction occurs, producing new zoospores. The thallus contains a plug that is removed once the thallus matures, releasing the zoospores into the water

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9
Q

what are the three reasons that this fungus has spread so widely and so quickly

A
  • Virulence of the pathogen (whether it has increased or evolved recently)
  • The environment (whether there are more suitable environmental conditions for the growth and survival of the fungus in its reservoirs)
  • The host (whether there is a reduced resistance to infection in frog populations)
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10
Q

what is the portal of entry

A

Via skin penetration (invades other layer of epithelium)

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11
Q

what is the site of replication

A

Via asexual reproduction inside the thallus (zoosporangium)

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12
Q

what is the portal of exit

A

Via zoospores going from the thallus in the skin of an amphibian into the water

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13
Q

what are the biological issues related to management

A
  • Fungus is temperature sensitive, confined to the relatively cool, wet areas
  • Frog resistance to infection may be reducing by environmental stress (climate change or increased exposure to UV radiation)
  • Vaccines have been tested but no differences in mortality or virulence have been observed
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14
Q

Strategies of prevention and control

A
  1. Efforts aimed at protecting uninfected areas
  2. detect new outbreaks, establish restricted and control areas (quarantine)
  3. Identify and prioritise frog species at risk of extinction
  4. Monitor impacts on frogs, especially populations who recover naturally
  5. Implement hygiene protocols for bushwalking, disinfecting vehicles
  6. Develop a central info storage site to upload and access data
  7. there is no cure
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15
Q

shade map of distribution

A

Eastern Australia (from north Queensland to Melbourne, Victoria)
• South West of Western Australia
• Adelaide
• Tasmania

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16
Q

what are three reasons a species may become threatened due to this disease

A
  • Occupy restricted geographic range
  • small population size
  • Habitat suited to growth of fungus (temperature, rainfall
17
Q

Explain an advantage and a disadvantage of not having a resting stage in the life cycle for this
fungus

A

Advantage: rapid growth/short life cycle. allows pathogen to establish quickly in new area
Disadvantage: adverse conditions, pathogen may not survive

18
Q

what are the diagnostic laboratory tests available to scientists

A
  • Microscopy (direct examination of skin scrapings and immunoperoxidase)
  • PCR
19
Q

State two disadvantages of direct examination of skin scrapings.

A
  • Only small samples of skin can be used without sacrificing the animal
  • Reduced chance of detection in healthy frogs with a light infection
20
Q

State two advantages of using immunoperoxidase

A
  • stains antibodies, used to confirm infection
    Able to detect light infections of the disease
  • Toe clippings can be used, does not require destruction of the amphibian
21
Q

State two advantages of using real-time PCR

A
  • highly sensitive, able to detect light infections of the disease
  • quantitative, indicates level of infection