CASE NOTES
Australian Wool Innovation Investments And Activities in Sheep Lice Control
Jane Littlejohn (a), Project Manager, Animal Health and Welfare, Australian Wool Innovation and Johann Schroder (b), Program Manager, Animal Health, Welfare and Productivity, Australian Wool Innovation
Posted Flock & Herd August 2009
Abstract
Australian Wool Innovation has invested over $4 million on lice research and lice extension since 2000. The scope of that investment includes detecting lice, detecting insect growth regulator resistance, finding novel drug targets and biological controls, computer modelling of lice control and an electronic decision support system. Responding to concerns in many states, AWI is investing in lice extension in 2009, primarily focusing on training resellers who have broad contact with producers at point of purchase of lice treatments, but including some direct grower training.
The messages will be consistent with those in www.LiceBoss.com.au but will be transformed for broad consumption into simple slogans and pictures, and one page fact sheets. Delivery will be national and the final look of the project will depend upon extension proposals submitted to AWI from the state departments responsible for agriculture.
Introduction
Australian Wool Innovation (AWI) is responsible for facilitating the dissemination, adoption and commercialisation of the results of its investments in research, development and innovation on behalf of Australian woolgrowers and the Australian Government who are its stakeholders. It is charged with improving the efficiency of the wool industry. AWI is accountable to the Government under a statutory funding agreement AWI has a considerable history in lice research having invested over $4 million on lice research and lice extension since 2000. The scope of that investment includes detecting lice, detecting insect growth regulator (IGR) resistance, finding novel drug targets and biological controls, computer modelling of lice control and an electronic decision support system.
Sackett et al., 2006, estimated a $122M cost to the national sheep industry from lice based on prevalences in the high rainfall and sheep/cereal zones of 20% and the pastoral zone of 30%. Lice was the third highest disease cost after internal parasites at $369M and flystrike at $280M. Over the past few months, woolgrowers in Western Australia and Victoria have made it clear to AWI that lice prevalence has reached an intolerable level and have requested more be done to limit its spread. Further consultation has revealed similar concern from NSW District Veterinarians and the NSW Department of Primary Industries (NSW DPI).
Lice prevalence and producers
After consultation nationally, AWI has a sketchy picture of the impact of lice prevalence in 2009. Western Australian producers are fearful of a 80% prevalence and have called on their Government to reregulate. The Victorian Farmers Federation has lobbied their Department of Primary Industries to run an awareness campaign. The NSW Farmers Association has recently received complaints from their regional staff about increasing prevalence and resistance. Tasmanian, South Australian and Queensland governments and state farming organisations have not identified any significant change in their lice situation; however the South Australian department has embarked upon some field day and saleyard control promotion (March 2009).
True lice prevalence is difficult to estimate due to the expense of a physical inspection of sheep or fleeces and in the absence of a widespread fleece testing program. In 2008, Peter James, Queensland Department of Primary Industries and Fisheries (QDPIF), conducted a literature review of lice prevalence for AWI. A benchmarking survey was also done by Ian Reeve and Lyndal-Joy Thompson, University of New England for lice prevalence from 2001 to 2003. A summary of their findings follow in Tables 1 and 2. From these figures there is no noticeable increase.
Table 1: Estimated prevalence pre 2000
Source: Integrated Parasite Management - Sheep, Critical Research Projects, Volume 2, Australian Wool Innovation EC306, 2007
Table 2. Incidence of lice at last shearing (grey text denotes upper and lower 95% confidence limits)
Source: Reeve and Thompson, Integrated Parasite Management in Sheep PRC Benchmarking Survey, A report prepared for Australian Wool Innovation, September 2005
Producer's behaviour surrounding lice infestations has been analysed by Plant 1996 and 1999, Ward and Armstrong, 1998 and Reeve and Thompson 2005 (Table 3).
Table 3 Producer behaviour when treating for lice
The researchers found the treatment rate was two to four fold higher than the lice prevalence rate. Possible reasons for a low risk tolerance to lice include fleece derangement without visual sighting of lice, precautionary treatment due to risky introductions and previous treatment failures. Ward and Armstrong (1998) found that 80% of producers were able to detect their lice infestations when measured against the woolstore test. However, 25% thought they had lice when they did not. The same study found that 94% of producers that did not detect lice treated and only 10 producers that did not detect lice did not treat. The percentage of clean flocks remaining clean recorded by Plant (1996 and 1999) of between 75- 90% could indicate a reasonable level of biosecurity or precautionary use of treatments.
The 1990's data in Table 3, shows that lousy flocks remain lousy reasonably frequently with up to an extraordinary estimated 60% failure recorded by Plant (1999) from 1999 data. This could indicate treatment failure, a high rate of risky introductions or failure to treat. Backliner use is common, with Reeve and Thompson (2005) recording they made up 75% of the mode of treatment.
AWI suspects that not a lot has changed regarding producer behaviour. Those that can commit resources to fencing, quarantining introductions and flock monitoring will have a greater chance of successful eradication, and those that cannot, will rely on regular treatment at shearing. Backliner use has proved popular as a resource efficient application method. This makes the chemicals that suit this method popular and therefore exposed to resistance mechanisms via incorrect application or frequent dosing.
Recent changes occurring in the producer's environment that may have influenced the calls for action against lice are the suspension of diazinon as a wet dip other than by minor use permit, the creep of IGR resistance, declining terms of trade and labour shortages. These create uncertainty and limitations in the mind of the producer when choosing a lice product (chemical class and application method).
AWI has been approached to fund a survey to determine the current apparent prevalence and lice control behaviours, however AWI is limiting this to an existing commitment to follow up on the Reeve and Thompson (2005) survey.
'Lice sense'
In 2009, AWI will be managing a national 'Lice Sense' extension project focusing on equipping the sales staff of chemical resellers with advice on lice for producers at the point of purchase of lice treatments. This rationale will tap the broad exposure to producers that the public and private advisory sectors do not have and pick up those unable or unwilling to access web based lice resources (eg www.LiceBoss.com.au or state departmental or chemical company websites). It will also more specifically target those producers who believe they have a problem and have decided to buy a chemical to solve it.
The reseller companies have told AWI their staff received reasonable training from chemical companies in the past, however, since the competition for lice treatments has declined, so has this source of training. The large reseller companies however, have proactively invested in their own training programs, with Elders, Landmark and Rural Co all hiring private consultants to conduct regular staff training. 'Lice Sense' will endeavour to add value to this existing relationship.
The project budget is $201,000, to be spent in all states, and as AWI hopes that the resellers will utilise their existing training budget, the project will also extend to direct producer training for existing AWI grower networks and departmental/public extension projects (existing or proposed). The final project description will be influenced by the public sector making proposals to AWI as soon as possible.
AWI wants to ensure that low level messages on lice eradication and prevention are nationally consistent and will focus on creating extension materials with slogans, pictures and one pager fact sheets, as the existing www.LiceBoss.com.au resource has comprehensive higher level materials.
AWI funded research
Worker exposure in wet dips
The wool industry considered the Australian Pesticides and Veterinary Medicine (APVMA) 2000 review of diazinon safety lacked sufficient evidence on submersible cage dipping to warrant label suspension. Thus AWI funded UniQuest P/L, University of Queensland, to conduct an operator safety pilot screening study to investigate the situation in 2007. One operator was studied over 2 replications (days).
Patches for chemical analysis were placed within the operator's protective clothing to assess a normal day's work of mixing chemical, dipping 2200-2500 sheep and cleaning up equipment. The mean total daily exposure was 60- 70 g/hr. At this rate, up to 5000 sheep per day could be caged dipped while maintaining operator safety.
The evidence collected allowed the participating operator sufficient encouragement from the APVMA to proceed with further trials to pursue his minor use permit (current as at February 2009). The precedent has been set for other interested operators to invest in such research.
Other wet dip methods were tested for operator exposure by the National Farmers Federation in 2004, however the results of danger to operators confirmed those of previous studies.
Detecting Resistance to IGRs
The NSW DPI, (Garry Levot) and the Queensland Department of Primary Industries and Fisheries (QDPIF), (Peter James,) produced, respectively, an egg hatch and moulting bioassay for IGR resistance in 2006. The tests are labour intensive, require controlled environment incubators and are slow to perform. They are constrained by the life cycle stage intervals and the lice's notorious inability to survive away from their host. Even if fleece samples can get to the lab quickly enough, the laborious task of picking unhatched eggs or immature lice from wool fibres under the microscope, makes either of these approaches uneconomical and impractical to offer as routine diagnostic techniques. In NSW, testing of fleeces may be specially commissioned by negotiation with Garry Levot who reports that chemical companies are using them infrequently in their investigations into suspected resistance complaints.
The research demonstrated large field strain differences in IGR susceptibility consistent with resistance development and the expected cross resistance between triflumuron and diflubenzuron.
In Shed lice detection test
AWI has an 8 year history of support for the NSW DPI to develop an in shed lice detection test, after it was first mooted by the CSIRO at the FLICS conference in Launceston in 2001. The current project includes a small interest from a commercial partner and aims to reduce the test time to 40 minutes (including washing) and find shelf stable and operator safe reagents. The test is based on previous work by Garry Levot using ELISA, monoclonal antibodies produced in rabbits and purified louse antigen produced by a hybridoma in tissue culture. Production of sufficient antibody immobilisers for the lice antigen and antiserum pose practical obstacles to offering a routine commercial test.
A new development for this test is the use of magnetised nanoparticle polystyrene beads to fix the immobilisers during washings which increased the test sensitivity 33 fold in wool grease samples spiked with ground up lice (Levot pers. com. 2009). Field validation of this new platform is being conducted by NSW DPI independently of AWI.
The test is only applicable to comb and cutter debris from shearing not crutching due to the lack of lice found on the crutch and their aversion to daggy wool (Levot pers.com. 2009). As lice infestations are not uniformly spread throughout a mob, the number of grease samplings per run may have an affect on sensitivity.
The test will have the benefit of confirming the absence of lice in non rubbing mobs which is a difficult scenario for producers to diagnose. This peace of mind will reduce chemical use and the potential for spread of resistance.
Biological lousicide
Diana Leeman, of QDPIF, has funding from AWI to pen trial Metarhizium fungal spores as a biolousicide. Previous work showed that spores germinate after ingestion or contact with the cuticle, invade the louse (nymph to adult stages) and rapidly kill it - depending on the spore count, this can occur within a matter of hours. Lice were undetectable at 3 weeks post treatment and the spores remain viable up to 14 weeks after application. Submersible cage dipping and hand jetting pen trials with spores in an oil and water suspension are near completion.
A commercial company is being approached for the product development phase. The benefits of nil chemical residue and low risk of resistance make the product attractive.
Ecdysone receptor blocker
The hormone, ecdysone is important in the moulting process of lice and other arthropods. It is the principal hormone controlling development and reproduction of all insects, however it does not occur in any vertebrate. Using molecular biology, each insect's ecdysone receptor can be characterised by species thus an ecdysone blocker has the potential to be the most environmentally friendly of agents. Order-specific ecdysone receptors have been found for insects such as Helicoverpa (cotton boll worm), white fly, aphids, lice and sheep blowfly.
The CSIRO has expertise with ecdysone in plant pests and has developed fluorescence polarising screening technology and x-ray crystallography to determine the atomic structure of the ligand binding domain. AWI funded CSIRO Molecular and Health Technologies researchers, Ron Hill and his team, characterised the sheep louse receptor, cloned it, scanned their in-house chemical libraries for blockers and found them.
The next step available is for CSIRO to approach a commercial partner, with a view to using the cloned receptor as a screening tool in their drug discovery efforts.
www.LiceBoss.com.au
LiceBoss is a web based decision support tool of integrated parasite management advice. It is funded by AWI and created and kept current by the expertise of departmental staff around Australia. It helps producers or their advisors to decide whether to treat or not in both long and short wool scenarios, find the source of infestation and design a biosecurity plan, design a treatment strategy for lambing ewes, assess products and application methods, estimate wool residues and determine causes of rubbing other than lice. It is available from AWI, free to wool levy payers and at $5.00 fee to others.
Conclusion
AWI's investments in lice control over the recent past cover diagnosis, lousicide application, biosecurity and extension of this message which has essentially remained unchanged for decades. This is unlikely to change, even should novel lousicides be released on the market. AWI's efforts into the foreseeable future will aim at achieving producer adoption of knowledge already available, but which may have become forgotten or crowded out, either by the availability of convenient and effective chemicals, or the demands of other activities in a mixed farming enterprise. AWI will endeavour to lever its investment through the involvement of other stakeholders whose ultimate aim is the effective control of sheep lice.
References
- Armstrong B and Ward M (1998) Queensland Lice Report, Survey of Queensland wool lots at the Yennora Wool Selling Centre, Sydney. Project Report Q099006. Sheep and Wool Institute, Department of Primary Industries, Queensland
- Brightling A (1989) Evaluation of strategies for control of sheep lice (Damalinia ovis) with an epidemiological model Australian Veterinary Journal 66:55-58
- James PJ and Riley MJ (2004) The prevalence of lice on sheep and control practices in South Australia Australian Veterinary Journal 82(9):563-567
- Plant JW (1996) National survey of relationship between pesticide residues in wool and pesticide usage on farm, Final Report. International Wool Secretariat
- Plant JW (1999) Pers comm to S Williams
- Plant JW and Dawson K (1999) Sheep ectoparasite treatments in New South Wales - 1989 to 1997. In Proceedings of the Australian Sheep Veterinary Society, Hobart, 1999 (Ed. B Besier) 105-111. (Australian Veterinary Society: Indooroopilly, Qld.)
- Reeve I and Thompson L-J (2005) Integrated Parasite Management in Sheep PRC Benchmarking Survey, A report prepared for Australian Wool Innovation, September 2005
- Sackett D, Holmes P, Abbott K, Jehpcott S & Barber M (2006) Assessing the economic cost of endemic disease on the profitability of Australian beef cattle and sheep producers (final report). Sydney: MLA. April 2006
- Ward MP and Armstrong RTF (1999) Prevalence and clustering in louse infestation in Queensland sheep flocks Veterinary Parasitiology 82:243-250