Abstract :
Lucilia cuprina is a blowfly, accidently introduced into Australia about 100 years ago. It
has become the most serious of external parasite issues affecting the Australian wool
sheep industry, currently comprising about 70 million Merino sheep. Sheep blowfly strike
(myiosis) is a cause of significant economic losses through sheep deaths, loss of wool and
productivity, plus interference with management, estimated at AUD 260,000,000 annually.
Of even more concern in recent years, has been an ongoing threat to the marketing of
fine-wool, initiated by animal rights activists objecting to the ‘mulesing’ operation, which
aims, by removing perineal skin, to decrease skin ‘wrinkle’ and to create a bare area that
minimises the risk of blowfly strike. For 80 years, this operation has been used by sheep
farmers to manage blowfly strike and recent estimates were that cessation of mulesing
would result in 7,000,000 sheep affected by myiosis with over 1,000,000 deaths annually.
Pressure by welfare activists on international wool buyers, with threatened boycotts,
resulted in a proposal by Australian Wool Innovations to cease mulesing by 2010, if suitable
alternatives could be found. This proposal proved unachievable, although significant
research progress in managing the issue has been made. An integrated pest management
approach to myiosis control involves crutching (shearing of breech wool prior to periods
of moisture accumulation, such as lambing), timing of shearing (removal of all wool prior
to fly-wave activity), chemical protection (jetting or dipping with acaricides) and genetic
selection against the risk factors of breech ‘wrinkle’ and ‘dag’. Where necessary and for
a short to medium term period, until wrinkle and dag can be genetically minimised, the
surgical alteration of breech conformation to reduce the propensity for accumulation of
moisture in excessive skin of the tail and perineum, is advisable. Mulesing mostly occurs at
‘lamb marking’, a routine procedure performed to improve health management that usually
occurs 6–10 weeks after start of the lambing period. Marking is a complex procedure as
it includes multiple vaccinations, ear tagging or knotching, castration and tail-docking and
where necessary, mulesing. This complexity means there is a labour cost pressure to cease
mulesing or only perform the operation on potential replacement ewes. The whole procedure
is laborious and expensive for farmers, almost never involves veterinarians and, until
recently, no pain management has been provided. In late 2005, a spray-on local anaesthetic
formulation for mulesing, containing lignocaine, bupivacaine, adrenaline) and cetrimide,
has become available in Australia under a licence for use under veterinary supervision. Published
evidence of the efficacy of topical anaesthesia as a practical and affordable method
of pain management at mulesing has resulted in widespread adoption of pain relief for
mulesing. Moreover, we have recently obtained evidence that pain relief is provided for upto 24 h following mulesing. In late 2011, the product achieved registration for sale by veterinarians.
To address international animal welfare concerns with mulesing, we proposed
that, in the period until sheep with the genetics to significantly decrease susceptibility to
myiosis have been more widely dispersed, provision of pain relief during mulesing should
enable breech modification to continue on properties where the sheep genotype requires it
and myiosis incidence warrants it. Investigations are continuing to determine if pre-surgical
treatments with analgesia or other drugs can offer additional pain management and offer
improved welfare benefits. It is noteworthy that a national system of vendor declaration
on the sale of wool to enable wool buyers to potentially select bales from farms using pain
management, has been instituted. Industry reports suggest that routine topical anaesthesia
for pain relief may have been used on 70% of lambs being mulesed in 2011. Australian wool
sheep farmers appear to have readily adopted pain relief at lamb marking, despite the current
lack of a premium price for wool from farms where pain relief is used. Although pain
relief at mulesing currently offers no increase in financial returns to their businesses, recent
trends suggest that a majority of farmers are willing to embrace innovations that provide
welfare improvements in our sheep industry. It is important that international consumers
of wool are made aware that the changing social ethic for animal welfare during invasive
livestock procedures has led to a significant change in attitudes and practice on a majority
of Australian wool sheep farms that remain at considerable risk of cutaneous myiosis.
