Macrocyclic lactones Chemical Review

In 1995, the APVMA (formerly the NRA) began a review of macrocyclic lactones (ivermectin, abamectin, moxidectin, doramectin and milbemycin) because of concerns about the possible unintended side-effects of these chemicals on the environment, particularly their potential to adversely affect dung beetle populations and hence dung degradation rates in Australia.

In September 1997, the APVMA released the Macrocyclic lactones draft review report. As part of the review, the APVMA had asked an independent scientific expert from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to review the data and relevant information. The detailed report by Dr John Steele of the CSIRO Division of Animal Production, titled Assessment of the effects of the macrocyclic class of chemicals on dung beetles and drug degradation in Australia (1997), was published as part of the draft report.

The draft review concluded that different products might have different short-term effects and differing toxicities to dung beetle larvae. However, the data available did not indicate that the use of macrocyclic lactones caused long-term effects on dung beetle populations.

The report also noted that for all species of dung beetles there were significant gaps in the data for both short- and long-term exposure to faecal residues under Australian conditions.

In May 1998, the APVMA released the Macrocyclic lactones review final report. The review report was based on information obtained from a variety of sources, including scientific studies and other information submitted by registrants, contributions from members of the public, community and government organisations, and searches of the scientific literature.

Following the review, the APVMA found that there was no clear evidence to indicate that any long-term damage to dung beetle populations was occurring as a result of the use of macrocyclic lactones. However, the APVMA also found that there was not enough information available on any of the macrocyclic lactone products to confirm general label claims of dung beetle ‘safety’.

In the final review report, the APVMA recommended:

• amending product labels to remove general claims that a product is safe to dung beetles, or has little impact on dung beetle populations
• amending product labels to remove claims that products are safe for certain species of dung beetles
• conducting further studies to enable a more complete understanding of the effects of macrocyclic lactones on dung beetle populations and dung degradation rates.