Preamble for WAAVP guideline: Combination anthelmintic products for ruminants and horses

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 anthelmintics.

In 2012, the WAAVP published the following guideline for evaluating the efficacy of anthelmintic combination products targeting nematode infections of ruminants and horses:

Geary, TG, Hosking, BC, Skuce, PJ, von Samson-Himmelstjerna, G, Maeder, S, Holdsworth, P, Pomroy, W & Vercruysse, J 2012, ‘World Association for the Advancement of Veterinary Parasitology (WAAVP) Guideline: Anthelmintic combination products targeting nematode infections of ruminants and horses’, Veterinary Parasitology, vol. 190, pp. 306–16.

We have adopted this WAAVP guideline and provide the following additional guidance to assist applicants conducting trials for the registration of such products in Australia.

This guideline is to be used in conjunction with the APVMA’s Efficacy and Safety Guidelines (Part 8), as well as the following WAAVP and VICH (International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products) guidelines for evaluating the efficacy of anthelmintics:

  • WAAVP second edition guidelines for evaluating the efficacy of anthelmintics in ruminants (bovine, ovine, caprine)
  • WAAVP second edition guidelines for evaluating the efficacy of equine anthelmintics
  • VICH GL7 (Anthelmintics: general)—Efficacy of anthelmintics: general requirements
  • VICH GL12 (Anthelmintics: bovines)—Efficacy of anthelmintics: specific recommendations for bovines
  • VICH GL13 (Anthelmintics: ovines)—Efficacy of anthelmintics: specific recommendations for ovines
  • VICH GL14 (Anthelmintics: caprines)—Efficacy of anthelmintics: specific recommendations for caprines
  • VICH GL15 (Anthelmintics: equine)—Efficacy of anthelmintics: specific recommendations for equines

Because of Australia’s unique environmental and geographical features, farm management practices, animal breeds and parasite burdens and their population dynamics, there are some differences between the WAAVP/VICH recommendations and our recommendations for products that are to be registered in Australia.

The following additional guidance is provided for applicants proposing to register combination anthelmintic products for ruminants and equines in Australia:

  • Because of Australia’s history of parasite resistance selection, we recommend that most of the confirmatory field efficacy work be conducted within Australia under typical farm management practices covering relevant geographical regions.
  • We will apply the same efficacy standards to combination anthelmintic products that we apply to single-constituent anthelmintic products (please refer to our additional guidance information for anthelmintics for ruminants and anthelmintics for non-ruminants). These efficacy standards are summarised in Table 1.
Table 1: Efficacy standards for combination anthelmintic products in Australia
Parasite Host species Claim for treatment/control Claim for persistent effectiveness
Nematodes Sheep and goats >95% >99%
Nematodes Cattle and equines >95% >95%
Liver fluke All >90%  

We encourage you to use these efficacy standards when generating data for combination anthelmintic products for ruminants and equines in Australia. These criteria are usually sufficient to give us confidence in the product’s efficacy in Australia’s unique conditions.

Claims for efficacy against resistant parasite species will need to be demonstrated in the data provided for registration.

If you have efficacy data generated overseas, submit that data at the time of the product registration application.

Geometric versus arithmetic means

In relation to section 4.2 of VICH GL7 (‘Geometric versus arithmetic means’), the geometric mean is appropriate for statistical tests where data are non-normally distributed. However, the geometric mean may underestimate the biological significance of worms in the animals with the highest worm burdens. We consider that the current information on statistics does not support the adoption of geometric means as the sole means of interpreting trial data. If the arithmetic mean for the data provided in efficacy trials shows marked variance from the geometric mean, we may take the arithmetic mean into consideration (that is, we are likely to give more weight to the arithmetic mean when there is variability in the trial data).

The VICH guidelines can also be accessed from the VICH website.

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