Blow flies

Question 1

Name the three important spp of Bot flies.

Do these exhibit facultative or obligate myiasis?

Answer 1

• Greenbottle - Lucilia sericata (pictured; most common in UK)
• Blackbottle - Phormia terranova
• Bluebottle - Calliphora spp
• facultative myiasis

Question 2

What are the main hosts for blow flies?

Describe their general morphologic features.

Answer 2

• sheep mainly (also rabbits)
• fairly large and robust - ~1cm long
  *

Question 3

Describe the general life cycle of Blow flies.

How many generations per year do bot flies produce?

Answer 3

• adults lay eggs on fleece
  
  • attacted to odor - wounds, feces on fleece, necrotic areas
• larvae penetrate hide (enzymes and hooks)
• larvae emerge and drop to the ground, burrow into soil, and pupate
• adults live about 1 month
• 3-4 generations per year

Question 4

What is the difference between a primary and secondary blow fly?

Answer 4

• primary - can initiate a strike on living sheep
• secondary - cannot initiate strike. Attack areas of existing strike or damage

Question 5

What is the pathologic significance of blow fly infestation?

What percentage of sheep farmers in the UK report blow fly strike?

Answer 5

• very irritating lesions
• interruption of grazing and loss of condition
• secondary bacterial infection (can lead to septicemia)
• 80% of UK sheep farmers report cases of strike

Question 6

What are some factors affecting the presence of strike?

Answer 6

• Temp - >9C for pupal development
• Climate and rain - warm wet conditions ==> wool rot, which attracts flies
• breed - fine wool breeds more susceptible to wool rot (body strike). Horned sheep more susceptible to horn strike. Wrinkled or narrow breech (breech strike).
• soiling (D++) - breech and tail strike
• wounds - horned breeds fighting, injuries from barbed wire//bushes//etc (poll and body strike)
• foot lesions - foot rot

Question 7

What are some ways to limit blow fly strike in sheep?

Answer 7

• pour-ons, dips
• prevent D++
• clip wool around breech
• tail docking
• shearing
• use polled breeds
• remove any carcases

Question 8

What is the economic significance of blow fly strike in sheep?

Answer 8

• most prevalent ectoparasite-mediated disease affecting sheep in the UK
• severe strike can kill
• wool is downgraded
• reduction in repro potential and lamb crops
• increased time to market for lambs
• reduced leather quality