Benchmarking Australian sheep parasite control practices: a national online survey

Abstract

Context The third Australian national survey on control practices for internal and external parasites of sheep, following similar surveys in 2003 and 2011. Aims To document current parasite control practices and attitudes, measure change and to provide a benchmark against which to assess future practices and attitudes. Methods An online survey emailed to 6460 sheep producers, with a paper version supplied on request. A follow up short survey was conducted to assess non-response bias. Analysis by region and key sheep enterprise. Key results There were 354 and 250 useable responses to the main and short surveys respectively. Mean reported rainfall of 407 mm in 2018 was 27% lower than the average for respondents and >200 mm lower than mean reported rainfall in the previous surveys. The top three methods for worm control over the past 5 years were preventative treatments (74%), preparing clean pastures by spelling paddocks (62%) and treatment on the basis of faecal worm egg count (WEC, 54%). The proportion of respondents using WEC monitoring in 2018 was 40.4%, with a mean frequency of 3.1/year, and this was unaffected by sheep class. The frequency of anthelmintic treatment for ewes and lambs and weaners was 2.1/year. Of the respondents, 36.7% had performed an anthelmintic resistance test in the previous 5 years. The most popular flystrike control methods were timing of crutching (76.4%), preventative chemical treatment (75.9%), timing of shearing (63.1%), mulesing (46.8%) and genetic selection (46.4%). Pain relief was widely used for mulesing ewes (86.6%) and wethers (90.9%). Only 17.3% used Australian Sheep Breeding Values for traits in rams. Most respondents reported ‘evidence of lice’ in the past 5 years (55.8%) and had treated for lice off shears (50.1%), short wool (16.6%) or long wool (6.6%), with only 26.7% having not treated at all in the period. Web-based sources of information on parasite control have become increasingly important. Conclusions Notable changes since the earlier surveys were high rates of pain relief when mulesing, an increase in the use of Australian Sheep Breeding Values for parasite-related traits, an increase in WEC monitoring since 2011 and an increased use of web-based resources. Implications Parasite control remains important for sheep producers and continues to evolve with new drugs and approaches. The surveys highlight the effectiveness of extension networks and identify where more attention is required.

Resistance to dicyclanil and imidacloprid in the sheep blowfly, Lucilia cuprina, in Australia

“…This issue is particularly significant for dicyclanil given its dominance in the flystrike chemical control market. 3 While the likely impact of the in vitro imidacloprid resistance observed in the present study on protection periods for flystrike products is unknown, a comparison of our data with those of Sales et al 5 indicates that the protection period for dicyclanil would likely be significantly reduced for the Walgett strain. Given the current reliance of the sheep industry on insecticidal control of flystrike, there is clearly a need to manage the use of insecticides such that the rate at which resistance develops to the currently-available chemicals is minimized.…”

“…in highlighting the emerging issue of resistance to the currently‐used insecticides in the sheep blowfly. This issue is particularly significant for dicyclanil given its dominance in the flystrike chemical control market 3 . While the likely impact of the in vitro imidacloprid resistance observed in the present study on protection periods for flystrike products is unknown, a comparison of our data with those of Sales et al 5 .…”

“…The insecticides currently used for flystrike control belong to various chemical classes: pyrimidine (dicyclanil), triazine (cyromazine), macrocyclic lactone (ivermectin), neonicotinoid (imidacloprid), synthetic pyrethroid (alpha‐cypermethrin), spinosyn (spinosad) and organophosphates (diazinon, chlorfenvinphos). Dicyclanil dominates the market for flystrike control chemicals, 3 as it provides a much longer period of protection than the other chemical groups (up to 29 weeks for the highest concentration dicyclanil product compared to up to10–14 weeks).…”

The current status and outlook for insecticide, acaricide and anthelmintic resistances across the Australian ruminant livestock industries: assessing the threat these resistances pose to the livestock sector

“…Sales et al 41 conducted an in vivo sheep trial with a highly dicyclanil‐resistant strain and found that flystrike protection periods for dicyclanil‐ and cyromazine‐based products were significantly reduced compared to product label guidelines (for example, label protection period of 18–24 weeks reduced to <11 weeks for dicyclanil). This evidence for resistance impacting on the period of protection of dicyclanil‐based products is particularly significant for the sheep industry given the dominant position of this chemical in the sheep flystrike control market: Colvin et al 42 reported that 40% of producers used this chemical, while Sales 39 found that of those producers who had used chemical recently, 56% had used dicyclanil. Cyromazine, which was also shown to have reduced protection periods when used against a resistant strain by Sales et al, 41 was the second most‐commonly used product according to both Colvin et al 42 at 24% and Sales 39 at 15%.…”

Control of sheep flystrike: what's been tried in the past and where to from here

“…A recent review of current flystrike control practices in the Australian sheep industry found the most commonly used chemical was dicyclanil (40% of producers) followed by cyromazine (24%), ivermectin (12%) and spinosad (12%), indicating a high industry reliance on two structurally related compounds, dicyclanil and cyromazine. 6 However, recent studies have indicated that resistance to these two compounds is emerging in field blowfly populations. Cyromazine was used widely in the sheep industry for over 30 years before Levot 7 reported that larvae recovered from a property in southern NSW showed resistance to this compound, and to dicyclanil to a lesser extent, in in vitro assays.…”