WAAVP guideline for lice and sheep keds on ruminants

The World Association for the Advancement of Veterinary Parasitology (WAAVP) is a not-for-profit organisation for scientists who study the parasites of non-human animals. The guidelines, developed by the international expert working groups of the WAAVP, assist in the international harmonisation of standards and procedures for the evaluation of veterinary parasiticides. The WAAVP guidelines for evaluating the efficacy of ectoparasiticides on ruminants aim to standardise the minimum set of data that should be submitted to demonstrate the efficacy of new ectoparasiticides for use on or in ruminants.

The APVMA has adopted the WAAVP guidelines for evaluating the efficacy of ectoparasiticides on ruminants to assist registration holders in the conduct of regulatory trials. The APVMA notes that in some instances the WAAVP guidelines advise consultation with the regulator. We also recognise that because of Australia’s unique environmental and geographic parameters, parasite burdens and their population dynamics, farm management practices and animal breeds, there are some differences between the WAAVP guidelines and the APVMA’s recommendations for efficacy trials for products to be registered in Australia. Therefore, applicants should conduct efficacy trials within Australia under typical farm management practices covering relevant geographical regions and the following additional guidance is provided to assist you in conducting these trials. If you follow this additional guidance, your data should generally be sufficient for the APVMA to assess its confidence in the product’s efficacy given Australia’s unique conditions.

This preamble refers to the following World Association for the Advancement of Veterinary Parasitology (WAAVP) guideline: Holdsworth, PA, Vercruysse, J, Rehbein, S, Peter, R, Letonja, T & Green, P 2006, ‘World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines for evaluating the efficacy of ectoparasiticides against biting lice, sucking lice and sheep keds on ruminants’, Veterinary Parasitology, vol. 136, pp. 45–54.

1. Lice species

In Australia, efficacy studies in sheep should use Bovicola ovis as the target parasite species.

2. Claims and level of efficacy for lice

The WAAVP guidelines refer generally to a ‘lice eradication/elimination’ claim (100 per cent) and a ‘lice management’ claim (95 per cent). For clarity and consistency in new and existing registered products, the APVMA uses the term ‘eradication’ for an ‘eradication/elimination’ claim, and the term ‘control’ for a ‘lice management’ claim.

2.1. Eradication

This claim is only applicable to products applied off-shears or in short wool. ‘Eradication’ is defined as: ‘Elimination of all live lice and viable eggs from treated animals, as determined by inspection of sheep 52 weeks after treatment.’

2.2. Control

For products used off-shears and in short wool, ‘control’ is defined as: ‘Elimination of all live lice and viable eggs from treated animals, as determined by inspection of sheep 20 weeks after treatment.’

For products used in long wool, ‘control’ is defined as: ‘Reduction of the lice population by more than 95 per cent after 90 days (or less as supported by data) in sheep examined in pen and field trials’.

For products used in long wool, if you present unequivocal evidence of a reduction in fleece damage caused by the lice at any time, then the 95 per cent figure may be modified. The term ‘aids in control’ would apply.

2.3. Terminology:

  • off-shears: within 24 hours after shearing
  • short wool: at least 24 hours and up to 6 weeks after shearing
  • long wool: at least 6 and up to 43 weeks after shearing.

3. Field trials for lice

The World Association for the Advancement of Veterinary Parasitology guidelines provide general advice on field trials in section 3.4.3, and specific considerations for field trials for sheep in section 4.2. As additional guidance, for products used on sheep off-shears or in short wool, the APVMA recommends that five studies be conducted, with mob sizes of not less than 300 and ideally at least 500 sheep, for at least 20 weeks. Three of these trials should be conducted with fine-wool merinos. Fine-wool merinos are defined as having wool less than 20 µm (microns) in diameter. A mob is defined as all the sheep treated with the test product being maintained together at all times throughout the trial period. At least 25 tagged tracer sheep should be included in each mob.

For products used on sheep in long wool, the APVMA recommends six studies (two each at three, six and nine months), three of which (one per wool length) should be conducted in fine-wool merinos, with mob sizes not less than 300 and ideally at least 500 sheep, for 20 weeks or until next shearing (whichever occurs first). At least 25 tagged tracer sheep should be included in each mob.

4. Lice counts

For determining the level of infestation of biting lice in sheep, the World Association for the Advancement of Veterinary Parasitology guidelines specify examination of 40 sites (partings), about 10 cm wide, in total per animal or 80 sites (partings), about 5 cm wide, per animal. The sites should be spaced so that they are representative of the full area of the body covered by the fleece on each side of the sheep. In addition, the APVMA recommends that you divide the examination sites equally on each side of the animal, that is, 20 (10 cm) or 40 (5 cm) sites should be examined on each side of the body (total = 40 (10 cm) or 80 (5 cm) sites). Furthermore, the APVMA recommends that you distribute the number of partings on each side of the body equally between the neck, shoulder, withers, rump and flank, that is, 4 (10 cm) or 8 (5 cm) partings at each location on each side of the body.

5. Level of lice infestation

The World Association for the Advancement of Veterinary Parasitology guidelines specify that sheep in field studies should have at least a moderate infestation of lice (30 lice per animal) at the pre-treatment examination. The APVMA also recommends that sheep in field studies should have at least a moderate infestation of lice at the pre-treatment examination; however, the APVMA defines the level of infestation as follows:

  • low infestation: less than 1 louse per 10 cm parting
  • moderate infestation: 1 to 5 lice per 10 cm parting
  • heavy infestation: more than 5 lice per 10 cm parting.

Therefore, sheep with a moderate infestation would have at least 40 lice per animal (based on 40 x 10 cm partings).

6. Persistency studies for lice

For persistent efficacy studies in sheep, the World Association for the Advancement of Veterinary Parasitology guidelines recommend infestation with 50 lice on the shoulder and/or flank. The APVMA finds this recommendation to be unclear, that is, the total could be 50 or 100 lice. To clarify, the APVMA recommends infestation with 50 live lice on the right shoulder and right flank (total = 100). The APVMA also recommends that the studies be conducted in merinos.

7. Wool or hide damage

Given the importance of the wool and cattle by-product industries to Australian commerce, it is recommended that applicants collect and submit data on wool staining or damage, hide or skin damage, or damage to animal products.

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