Changes

*Secondary flies cannot initiate a strike. Larvae attack an area already struck or damaged, extending it

Blowfly strike is a serious disease worldwide in sheep of all ages. It is caused by 'blowflies' laying eggs in damaged areas of skin. Larvae then hatch and eat the skin causing severe and debiliatating disease. The disease can also occur in rabbits and is incredibly distressing to rabbit owners.

**''Calliphora spp.''

**''Chrysomya spp.'' (in warmer climates)

*Tertiary flies attack lesions on carcasses which have become dry

Blowflies are divided into categories depending on their ability to initiate strike. Primary flies are capable of initiating a strike on living sheep and larvae can penetrate intact ski. These are ''Lucilia, ''''Phormia and ''''Calliphora spp. ''Secondary flies cannot initiate a strike. Larvae attack an area already struck or damaged, extending it. ''Ca''''lli''''phora spp. and ''''Chrysomya spp.'' (in warmer climates)are examples of these. Tertiary flies attack lesions on carcasses which have become dry; ''Musca and ''''Sarcophaga spp. ''cause this.

**''Musca''

**''Sarcophaga spp.''

*Temperature -Temperature in the spring will determine when the overwintering larvae hatch and high temperature and humidity will create a microclimate in the fleece, attracting adult flies to lay eggs.

*Temperature  

**Temperature in the spring will determine when the overwintering larvae hatch

**High temperature and humidity will create a microclimate in the fleece, attracting adult flies to lay eggs

*Rainfall

*Rainfall- Persistent rainfall will make the fleece microclimate attractive to adult flies. Females lay eggs after the rain cease. Breeds with long, fine wool are the most susceptible.

**Persistent rainfall will make the fleece microclimate attractive to adult flies. Females lay eggs after the rain ceases

**Breeds with long, fine wool are the most susceptible

*Host susceptibility  

*Host susceptibility - This is increased when putrefactive odours develop on the fleece due to bacterial decomposition of organic matter following soiling with urine or faeces, such as in cases of diarrhoea, caused by worms or other alimentary tract diseases. Merino sheep have a narrow breech area with excessive wrinkling making them more susceptible to soiling. A narrow opening of the penile sheath in rams and wethers may result in accumulation of urine and increase blowfly strike in this area. Also, cuts during shearing, fighting and barbed wire will also increase the incidence of blowfly strike.

**This is increased when putrefactive odours develop on the fleece due to bacterial decomposition of organic matter following soiling with urine or faeces

**Merino sheep have a narrow breech area with excessive wrinkling making them more susceptible to soiling

**A narrow opening of the penile sheath in rams and wethers may result in accumulation of urine and increase blowfly strike in this area

**Cuts during shearing, fighting and barbed wire will also increase the incidence of blowfly strike

<br> '''Pathogenesis'''  

*Temperate regions in '''June to September'''

*Severe skin damage  

 

 

*Severe skin damage

**Larvae lacerate skin with oral hooks and liquefy host tissue by secreting proteolytic enzymes

**Larvae lacerate skin with oral hooks and liquefy host tissue by secreting proteolytic enzymes

*Skin lesions are extended and deepened

*Skin lesions are extended and deepened  

**Secondary blowfly attack

**Secondary blowfly attack  

**Flies attracted to odour of decomposing tissue

**Flies attracted to odour of decomposing tissue

*Secondary bacterial infection

*Secondary bacterial infection

*Production losses

*Production losses  

**Irritation and distress associated with skin lesions

**Irritation and distress associated with skin lesions  

**Poor weight gain (often the first clinical sign)

**Poor weight gain (often the first clinical sign)

*Risk of strike is highest in warm, moist weather

*Risk of strike is highest in warm, moist weather

*Anorexia  

*Anorexia

*Listlessness  

*Listlessness

*Animals standing apart from flock

*Animals standing apart from flock

*Fleece may appear darker, be damp and have a foul smell

*Fleece may appear darker, be damp and have a foul smell

*Prophylactic [[Ectoparasiticides|insecticide]] treatment  

*Prophylactic [[Ectoparasiticides|insecticide]] treatment

**Must kill larvae and remain in fleece to prevent flies from laying eggs  

**Must kill larvae and remain in fleece to prevent flies from laying eggs

**Applied by spraying, dipping, spray race or jetting

**Applied by spraying, dipping, spray race or jetting

*Insect growth regulators

*Insect growth regulators  

**Pour-on

**Pour-on  

**2-4 month protection depending upon the product used

**2-4 month protection depending upon the product used

*Effective worm control

*Effective worm control  

**To minimise diarrhoea and therefore soiled fleece

**To minimise diarrhoea and therefore soiled fleece

*Crutching to prevent soiling

*Crutching to prevent soiling

*'Mule's operation'

*'Mule's operation'  

**Surgical removal of breech skin in Merino breeds

**Surgical removal of breech skin in Merino breeds

*Tail docking of lambs

*Tail docking of lambs

*Proper carcass disposal

*Proper carcass disposal  

**Eliminates fly breeding sites

**Eliminates fly breeding sites

*Vaccination

*Vaccination  

**Experimental use against ''Luculia cuprina'' in Australia

**Experimental use against ''Luculia cuprina'' in Australia

[[Category:To_Do_-_Kate]]

[[Category:To_Do_-_Kate]]