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Australian Sheep Parasite Management Survey 2019 - Worm and Liver Fluke Results


by Alison Colvin, April 2020

In early 2019 Australian sheep producers were asked about their sheep parasite control management practices for the year 2018. The survey, funded by Australian Wool Innovation, was managed by researchers at the University of New England 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, WormBoss, FlyBoss and LiceBoss. Respondents were asked to complete a survey with a maximum of 45 questions which was separated into 5 sections:

1.    Property details
2.    Worms and Liver fluke
3.    Blowfly control 
4.    Lice control 

Location and enterprise results

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

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).

Figure 2: Proportion of Respondents’ Chosen enterprise.
Figure 2: Proportion of Respondents’ Chosen enterprise.

For the first time an attempt was made to measure differences in parasite control practices between different sheep enterprises. Respondents were asked to select an enterprise they would refer to for their answers for questions on parasite control, these are referred to as Chosen enterprise. Most respondents selected Merino x Merino enterprise with the second most popular enterprise being Meat x Meat (Figure 2), those with Merino based enterprises made up 77% of the total respondents.

The average property size was 2733 ha with the highest proportion of enterprise income coming from wool (41%) followed by sheep meat (28%) and cropping (13%) with large variations between Regions. The mean number of sheep DSE managed by respondents was 4971 DSE/ha. About one third of respondents ran cattle in 2018 (34.5%).

Worm results

Worm control techniques and treatments

Most respondents used planned preventative treatments for worm control (74%, lower than in 2011, 87%) with two thirds preparing clean pastures by spelling paddocks (61%, similar to 2011, 62%) and just over half treating on faecal worm egg count (54%, WEC). There were significant differences between Regions but not between enterprises (see Table 2).

Table 2: Proportion of respondents using various techniques and treatments for worm control over the last 5 years (2014-2018) by Region. Coloured cells indicate percentages of respondents that are significantly higher than the national proportion (red) or significantly lower (blue). N= number of responses per Region.
Table 2: Proportion of respondents using various techniques and treatments for worm control over the last 5 years (2014-2018) by Region. Coloured cells indicate percentages of respondents that are significantly higher than the national proportion (red) or significantly lower (blue). N= number of responses per Region.

Faecal worm egg count (WEC) monitoring

The proportion of respondents using WEC increased between 2011 (21%) and 2018 (42%) but was similar to that reported for the 2003 survey (44%). In 2018 the number of WEC monitors per year was 3.1/year for ewes and 3.1/year for lambs and weaners. The number of WEC/year for ewes in 2018 was higher than in 2003 and slightly higher than 2011 (2.6 and 2.9/year, respectively). The number of WEC monitors for lambs and weaners was similar in 2018 to 2003 (3.0/year) but higher than 2011 (2.0/year). There was wide Regional variation in who carried out WEC with national averages being 37% using a private lab, 30% self or employee, 27% using their vet or consultant and 11% using a government laboratory. Respondents in WA were the most likely to carry out WEC themselves (62%) with very few from SA Peninsula (0%) or Wimmera Mallee Murray (15 %) using that option. Private laboratories were popular across most Regions (Central NSW 39%, East Vic 53%, Northern NSW/Qld 50%, SA Peninsula 100%, WA 38% and Wimmera Mallee Murray 35%) except for WA (5%) and Tasmania (22%). Government laboratories were more likely to be used in Tasmania (33%) and Central NSW (25%) than in WA (0%), SA Peninsula (0%), East Vic (7%) and Northern NSW/Qld (13%).

Anthelmintic treatments

Over two thirds of respondents treated their sheep for worms in 2018 (65.8%) and of those who drenched, the frequency of drenching/year was similar across sheep classes (2.1/year for ewes and lambs and weaners, 1.9/year for hoggets and 2.0/year for wethers). These are similar to that reported for the 2017 AWI Merino Husbandry report which found the drench frequency for mixed age ewes was 1.9/year and for young ewes 2.2/year. Similar drench frequencies were reported in the 2003 survey.

Figure 3: Anthelmintic group as a proportion of all anthelmintics used, Nationally. Anthelmintic class abbreviations – AAD: Amino-acetonitrile derivative, BZ: Benzimidazole, ISO: Isoquinolone, LEV: Levamisole, ML: Macrocyclic lactone, OP: Organophosphate, SAL-P: Salicylanilides/Phenols, SPIRO: Spiroindole.
Figure 3: Anthelmintic group as a proportion of all anthelmintics used, Nationally. Anthelmintic class abbreviations – AAD: Amino-acetonitrile derivative, BZ: Benzimidazole, ISO: Isoquinolone, LEV: Levamisole, ML: Macrocyclic lactone, OP: Organophosphate, SAL-P: Salicylanilides/Phenols, SPIRO: Spiroindole.

Most anthelmintic treatments were given as oral drenches (85%) with smaller numbers as injections (12%) or intra-ruminal capsules (3%). The most popular group of anthelmintics were the macrocyclic lactones (39% of treatments), benzimidazoles (19.5%) and levamisole (17.4%, Figure 3). The use of the newer anthelmintic actives, monepantel and spiroindole (derquantel), was low (both 3.2%), the use of monepantel in the 2011 survey was similar (2.1%). The top three drench actives used were Abamectin (23.6%), Levamisole (17.4%) and Moxidectin (14%) these are the same top three actives used in the 2011 survey.

The majority of drenches given involved a single active (55.4%) followed by triple combinations (21.5%) and double combinations (18.8%). These are very similar to the results of the 2011 survey (single 57%, triple 23%, double 19%). Respondents in Central NSW, Northern NSW/Qld and East Vic were more likely to use combination drenches than the other Regions (Table 3).

Table 3: Number of drench actives used in combination, as a proportion of drenching events across all sheep classes, by Region.  Cells that are significantly higher than the National average are coloured red and significantly lower are coloured blue.
Table 3: Number of drench actives used in combination, as a proportion of drenching events across all sheep classes, by Region. Cells that are significantly higher than the National average are coloured red and significantly lower are coloured blue.

Whilst there had been an increase in the proportion of respondents who conducted a form of drench test over a 5 year period from 2011 (29%) to 2018 (37%) there is still a relatively low proportion of sheep producers conducting drench tests. Only 16% conducted a drench test in an average year of which only 4% used the gold standard method of a Faecal worm egg count reduction test (WECRT). With planned preventative treatments being the most important factor (ranked 3.3/4) when deciding to drench ewes and weaners it is vitally important that producers not only know their drench resistance status but also implement rotation of their drench actives and use combination drenches to slow the development of drench resistance.

It is, however, reassuring to see that results from WEC monitoring were also considered important when deciding to drench ewes (3.2/4) and weaners (3.3/4) which is consistent with the upward trend in the proportion of sheep producers using WEC and the increase in the number of WEC monitors per year. Seasonal weather conditions and time of year were also both considered important when deciding to drench ewes (both 3.1/4) and weaners (3.2/4 season and 3/4 time of year).

Sources of information for Worm control

The WormBoss website was considered ‘important’ by respondents (ranked 2.6/4). The use of WormBoss has increased markedly with 63% of respondents saying they had visited the site of which 28% used the site to make changes to their worm control practices. This is up from 16% visiting in 2011 and only 5% using the site to make changes.

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

Liver fluke

Only 14% of respondents tested or treated for Liver fluke in the years from 2014 to 2018 with large differences between Regions as expected. The Regions with higher rates of Liver fluke testing and treatment were Central NSW (22%), East Vic (21%), Northern NSW (20%) and Tasmania (18%).

Of those respondents testing or treating for liver fluke in the last 5 years (n=39), in an average year 53% tested for Liver fluke with 20% of respondents reporting positive results for a Liver fluke test and 33% had reporting a negative test, 47% did not test. Despite only 20% receiving a positive Liver fluke test in any given year 47% treated for Liver fluke with chemicals.

Over the 5 years from 2014-2018 56% treated for Liver fluke despite only 25% reporting a positive test (65% who conducted a test).

The average number of Liver fluke treatments given per year was 2.0 and was similar across sheep classes. The most commonly used active used to treat Liver fluke was Triclabendazole (40%) used singly, followed by Closantel (21%, see Table 4).

>> More about liver fluke, on WormBoss.

Table 4: Proportion of respondents using different anthelmintics to treat Liver fluke in 2018.
Table 4: Proportion of respondents using different anthelmintics to treat Liver fluke in 2018.

Results from a Liver fluke test was the most important factor when deciding to treat for Liver fluke (rank 3.4/4) followed by ‘Time of year/strategic treatments’ (rank 3.3/4), ‘Appearance or condition of sheep’ (3.0/4), ‘Seasonal weather conditions’ (3.0/4) and ‘After grazing flukey paddocks’ (2.7/4).

Conclusions

Many worm control practices have changed little since the 2003 and 2011 surveys. There was little application of methods for prolonging drench life such as harnessing refugia on pasture by leaving some sheep undrenched, using new drench actives, using Barbervax® in summer rainfall regions or breeding for resistance using ASBV-WEC. However, there was good implementation of grazing management for worm control, particularly the use of preparing clean pastures by spelling paddocks. The usefulness of preparing clean pastures by spelling paddocks is entirely dependent upon the length of the spelling period and the season in which it is used. The methods and timing also vary across regions.

There was an upward trend in the use of WEC monitoring since 2011, despite the dry conditions in the 2018 survey. The top 3 drench actives used were the same in 2018 and 2011 with very low uptake of newer drench actives. There was a small upward trend in respondents conducting drench tests over 5 years, but still low proportions conducting drench tests overall, leaving producers unaware of their drench resistance status.