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Backgrounder Paper for Sheep Ectoparasiticides

Sheep Ectoparasiticides and the Review

What are they?

Sheep ectoparasiticides are products widely used on sheep in Australia to control or prevent disease and production losses associated with ectoparasite infestation. The Australian sheep blowfly (Lucilia cuprina) and the body louse (Bovicola ovis) are the main ectoparasites of sheep.

The sheep ectoparasiticides review affects 65 products that either:

  • contain one or more of 13 active constituents (alpha-cypermethrin, chlorfenvinphos, cypermethrin, cyromazine, deltamethrin, diazinon, dicyclanil, diflubenzuron, ivermectin, propetamphos, spinosad, temephos and triflumuron) and/or
  • have a claim for treatment of ectoparasites, by any method, in long wool sheep (six or more weeks wool growth).

What are our concerns?

The use of sheep ectoparasiticides can result in significant chemical residues on treated wool. When sheep are handled during wool harvesting and when wool is processed, these residues could have an effect that is harmful to workers or an effect that is harmful to the environment.

The review of sheep ectoparasiticides addresses the following concerns:

  • the occupational health of workers, particularly shearers, who may come into contact with treated wool, primarily during wool harvesting
  • the potential of chemical residues to harm susceptible organisms in the environment, particularly if the chemicals are released in the course of wool processing
  • the potential of chemical residues on treated wool to prejudice Australia’s trade, particularly where overseas wool processing plants discharge scour effluent into river ecosystems.

What are we proposing to do about the concerns?

Occupational health and safety

With respect to occupational health and safety, the APVMA proposes to find that human health risks can be managed by changing sheep ectoparasiticide product labels to prescribe a sheep rehandling interval. The sheep rehandling interval will indicate when people can safely handle treated animals after the sheep have been treated with the ectoparasiticide products which are the subject of the review. These statements range from ‘Do not rehandle sheep until dry after treatment’ to ‘Do not rehandle sheep for 12 weeks’.

Personal protective equipment will be recommended on the product label if sheep must be handled during the sheep rehandling interval.

The Australian environment

With respect to the Australian environment the APVMA proposes to find that the risks can be managed through the application of a ‘wool harvesting interval’ which defines a minimum interval from when the sheep ectoparasiticide product is applied to when the sheep can be shorn. Sheep ectoparasiticides would not be likely to have an unintended effect that is harmful to the environment under current use patterns, provided that the label specifies an appropriate wool harvesting interval.


With respect to trade, the APVMA proposes to find that a change to the label instructions of sheep ectoparasiticide products is needed to provide a clear warning of changes in European Union environmental requirements.

An advisory statement on the label of all sheep ectoparasiticide products will state:

‘Use of this product may result in wool residues that may not comply with European Union environmental quality standards (EQSs) due to be implemented in 2007’.

The APVMA is also considering more than one possible future regulatory approach that may be applied after October 2007, depending on whether a wool residue advice scheme to help manage the trade risk is in operation at that time.

How can interested stakeholders have an input to the review of sheep ectoparasiticides?

The APVMA’s detailed findings are on this website in the APVMA Preliminary Review Findings.

The APVMA invites persons and organisations to submit their comments and suggestions on this Preliminary Review Findings directly to the APVMA. Your comments will assist the APVMA in preparing the Final Review Report and Regulatory Decision. Submissions specifically addressing the areas of concern noted in the Preliminary Review Findings must reach the APVMA by 31 October 2006, by email or by mail to:

Manager Chemical Review Team
Australian Pesticides and Veterinary Medicines Authority
PO Box 6182
For further information please contact (02) 6272 3213 or Fax (02) 6272 3218
(now 02 6210 4700)