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Australian Sheep Parasite Management Survey 2019 - Lice Results


by Alison Colvin, June 2020

In early 2019 Australian sheep producers were asked about their sheep parasite control management practices for the year 2018. The survey was conducted by Dr Alison Colvin, Professor Stephen Walkden-Brown and Dr. Ian Reeve from the University of New England and was supported by Australian Wool Innovation Limited and followed previous surveys of the years 2003 and 2011. The results of the survey will ensure that research, advice and information can be tailored to producers at a regional, state or national level, addressing the issues that are currently of greatest importance.

Survey process

A link to the survey was emailed to the Australian Wool Innovation Ltd (AWI) email list and links were available on the AWI website (wool.com) and the ParaBoss suite of websites: paraboss.com.au, wormboss.com.au, flyboss.com.au and liceboss.com.au). Respondents were asked to complete a survey with a maximum of 45 questions which was separated into 5 sections:

1.    Property details
2.    Internal parasites
3.    Blowfly control
4.    Lice control  (this article)

Table 1: Number of respondents to the main survey by Region.
Table 1: Number of respondents to the main survey by Region.

Location and enterprise results

The response rate to the survey was lower than in previous years with a total of 354 usable responses returned with a further 250 responses to the short, 5 question survey used to measure non-response bias. There were 575 responses for the 2011 survey and 1365 responses to the 2003 survey. The reduced response rate may have been due to severe and continuing drought experienced by a large part of the country in 2019, survey fatigue in respondents, length of the questionnaire and presentation of the survey on an online platform. The responses to the short, 5 question survey confirmed that the responses to the main survey were a good representation of Australian sheep producers with very few differences in responses between the two.
Figure 1 shows the distribution of the respondents sorted by postcode into Meat and Livestock Australia (MLA) Reporting Regions (Region). The largest number of respondents came from Central NSW (83), Wimmera Mallee Murray (79) and Northern NSW/Qld (Table 1). 

Figure 1: Location of survey respondents within MLA Reporting Region.
Figure 1: Location of survey respondents within MLA Reporting Region.

The mean age of respondents was 57 years with a range of 27-92 years, this is higher than in 2003 (51 years) and 2011 surveys (56 years). The mean reported rainfall in 2018 (407mm) was significantly lower than the mean average annual rainfall of respondents (557mm).

Lice results

Evidence of lice

Respondents were asked to summarise their yearly lice detection and treatment methods over the period 2014– 2018. On average 31% reported evidence of lice each year during this period (14% live lice seen, 17% sheep seen rubbing and 0.1% lice detected by lab test). This was slightly lower than the 38% annual detection rate reported in 2011. The proportion of respondents reporting evidence of lice in at least one year during this period was 56%, again somewhat lower than the 68% reported in 2011. The mean number of years evidence of lice was reported was 1.0 year within the 5-year period (2014–2018), although the range was 0 (no evidence of lice in any year) up to 5 (evidence of lice every year). This suggests that, on average, when lice infestations are detected they are treated successfully and do not generally persist in the years after treatment.

Treatment of lice

Despite 31% of respondents detecting lice annually on average, 73% treated for lice in an average year with most applying the lice treatment off shears (50%, Figure 2). Similarly only 56% reported evidence of lice at least once from 2014-2018 but 88% treated for lice over the same period. Respondents treated for lice an average of 2.9 years out of 5 with Northern NSW/Qld treating 3.6 years and Tasmania treating less frequently at 1.6 years out of 5. These data indicate that preventing lice infestations is still a major strategy for producers as it was for those in the 2011 survey where 78% treated at least once over 5 years.

Figure 2: Proportion of respondents giving lice treatment by timing of treatment in an average year.
Figure 2: Proportion of respondents giving lice treatment by timing of treatment in an average year.

Respondents’ preferred method of application of chemicals was backliner/spray on, on both short wool (74%) and long wool (60%) with low numbers using other application methods (Short wool: 1.4% hand jet, 9.3% plunge dip, 1.4% cage dip, 5.0% electrodip, 0.7% jetting race and 7.9% shower dip; Long wool: 8.4% hand jet, 8.6% plunge dip, 8.6% cage dip, 8.6% electrodip, 2.9% jetting race and 2.9% shower dip). Backliner application is an easy and quick method of treatment application, however, care must be taken to apply the chemical correctly to ensure even coverage over the sheep and application must be within 24 hours to 7 days after shearing depending on product specifications. This method of application can also contribute to the development of resistance to chemicals due to the risk of incorrect application or under-dosing.

Neonicotinoids have overtaken insect growth regulators (IGR) as the active ingredient predominantly used for off shears/short wool treatments (imidacloprid 40%, thiacloprid 11%) with only 4% using IGR in 2018 compared to 47% in 2011.

For long wool treatments, spinosad was still a clear favourite (58%) but down in use from 2011 (74%) followed by ivermectin (25%). Only 8.4% of respondents suspected resistance to a lice product (down from 26% in 2011), 50% of those suspected resistance to insect growth regulators, 29% to synthetic pyrethroids, 16% to organophosphates and 6% to neonicotinoids. Rotation of actives (21%) was the most common important change that producers made to their lice management in the last 5 years.

Farm Biosecurity

Respondents were very clear that introduction of lice through fences or from purchased sheep was considered a major factor causing lice control problems in their flock, it was ranked 3.8/4 for importance and was a recurring theme in the comments. Multiple flock treatments or not treating the whole flock at the same time and incomplete mustering were also reported as important factors in recurring infestations (3.4/4). However, only 21% of respondents applied a quarantine lice treatment when introducing sheep into their flock, although 82% isolated sheep for at least 2 weeks and 65% requested an animal health history from seller. Biosecurity on farm is vital for lice prevention and includes maintaining boundary fences, treatment and inspection for lice of introduced sheep, whole flock treatment and complete mustering of the flock for treatment. The LiceBoss website has information on sheep lice and biosecurity.

Sources of information for lice control

The LiceBoss website was considered ‘somewhat important’ by respondents (ranked 2.4/4). The use of LiceBoss has increased significantly with 57% of respondents saying they had visited the site and 20% using the site to make changes to their flystrike control practices compared with 13% visiting in 2011 and only 3% using the site to make changes.

The LiceBoss website has a range of tools and information including:

Overall the survey results indicate an ongoing reliance on chemicals for lice control, with neonicotinoid insecticides assuming a dominant role in off shears/short wool treatments. Producers appear to be relatively unconcerned about insecticide resistance in lice. Lice detection rates are slightly lower but treatment rates are slightly higher than in the previous survey in 2011. Use of a quarantine lice treatment for introduced sheep was low although there was greater usage of other biosecurity practices. There was a major increase in use of the LiceBoss web site in this survey relative to the 2011 one.