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Created page with ''''Epidemiology''' <br>Blowflies are divided into categories depending on their ability to initiate strike *Primary flies are capable of initiating a strike on living sheep. Larv…'
'''Epidemiology'''
<br>Blowflies are divided into categories depending on their ability to initiate strike
*Primary flies are capable of initiating a strike on living sheep. Larvae can penetrate intact skin
**''Lucilia''
**''Phormia''
**''Calliphora spp.''
*Secondary flies cannot initiate a strike. Larvae attack an area already struck or damaged, extending it
**''Calliphora spp.''
**''Chrysomya spp.'' (in warmer climates)
*Tertiary flies attack lesions on carcasses which have become dry
**''Musca''
**''Sarcophaga spp.''
Predisposing factors to flystrike
*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
**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
**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
Blowfly season
*Temperate regions in '''June to September'''
**Mostly in unshorn sheep in June
**Lambs from July to September
*Warmer regions have a more prolonged season due to greater number of blowfly generations
'''Pathogenesis'''
*Severe skin damage
**Larvae lacerate skin with oral hooks and liquefy host tissue by secreting proteolytic enzymes
*Skin lesions are extended and deepened
**Secondary blowfly attack
**Flies attracted to odour of decomposing tissue
*Secondary bacterial infection
*Production losses
**Irritation and distress associated with skin lesions
**Poor weight gain (often the first clinical sign)
*Risk of strike is highest in warm, moist weather
'''Clinical signs'''
*Anorexia
*Listlessness
*Animals standing apart from flock
*Fleece may appear darker, be damp and have a foul smell
'''Control'''
*Prophylactic [[Ectoparasiticides|insecticide]] treatment
**Must kill larvae and remain in fleece to prevent flies from laying eggs
**Applied by spraying, dipping, spray race or jetting
*Insect growth regulators
**Pour-on
**2-4 month protection depending upon the product used
*Effective worm control
**To minimise diarrhoea and therefore soiled fleece
*Crutching to prevent soiling
*'Mule's operation'
**Surgical removal of breech skin in Merino breeds
*Tail docking of lambs
*Proper carcass disposal
**Eliminates fly breeding sites
*Vaccination
**Experimental use against ''Luculia cuprina'' in Australia[[Category:Parasites]][[Category:Flies]][[Category:Myiasis_Producing_Flies]]
<br>Blowflies are divided into categories depending on their ability to initiate strike
*Primary flies are capable of initiating a strike on living sheep. Larvae can penetrate intact skin
**''Lucilia''
**''Phormia''
**''Calliphora spp.''
*Secondary flies cannot initiate a strike. Larvae attack an area already struck or damaged, extending it
**''Calliphora spp.''
**''Chrysomya spp.'' (in warmer climates)
*Tertiary flies attack lesions on carcasses which have become dry
**''Musca''
**''Sarcophaga spp.''
Predisposing factors to flystrike
*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
**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
**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
Blowfly season
*Temperate regions in '''June to September'''
**Mostly in unshorn sheep in June
**Lambs from July to September
*Warmer regions have a more prolonged season due to greater number of blowfly generations
'''Pathogenesis'''
*Severe skin damage
**Larvae lacerate skin with oral hooks and liquefy host tissue by secreting proteolytic enzymes
*Skin lesions are extended and deepened
**Secondary blowfly attack
**Flies attracted to odour of decomposing tissue
*Secondary bacterial infection
*Production losses
**Irritation and distress associated with skin lesions
**Poor weight gain (often the first clinical sign)
*Risk of strike is highest in warm, moist weather
'''Clinical signs'''
*Anorexia
*Listlessness
*Animals standing apart from flock
*Fleece may appear darker, be damp and have a foul smell
'''Control'''
*Prophylactic [[Ectoparasiticides|insecticide]] treatment
**Must kill larvae and remain in fleece to prevent flies from laying eggs
**Applied by spraying, dipping, spray race or jetting
*Insect growth regulators
**Pour-on
**2-4 month protection depending upon the product used
*Effective worm control
**To minimise diarrhoea and therefore soiled fleece
*Crutching to prevent soiling
*'Mule's operation'
**Surgical removal of breech skin in Merino breeds
*Tail docking of lambs
*Proper carcass disposal
**Eliminates fly breeding sites
*Vaccination
**Experimental use against ''Luculia cuprina'' in Australia[[Category:Parasites]][[Category:Flies]][[Category:Myiasis_Producing_Flies]]