Skip the dip

They've cracked it, after many years – a reliable new sheep lice test that gets around dipping.

A sensitive new laboratory test that can diagnose lice infestations at shearing will be available for wool producers from July.

Researchers who developed the test believe it will be highly economical and give producers confidence not to dip or backline as a precaution.

The test could be used as part of management strategy to eradicate lice from properties and/or reduce chemical usage and hence residues in wool.

The test uses washings from the cleaning of shearers’ combs and cutters.

The washings detect protein from chopped up lice, trapped in grease accumulated on the combs and cutters as lousy sheep are shorn.

The laboratory test is the culmination of many years’ financial investment and co-operative research between NSW DPI, Australian Wool Innovation and CSIRO Livestock Industries.

To be run at Elizabeth Macarthur Agricultural Institute (EMAI), Camden, the test is based on “ELISA” technology.

The EMAI team says the test can pay for itself many times over if producers choose not to dip, or back-line sheep that previously would have been treated “just in case they had lice”.

The test uses samples submitted by or on behalf of producers.

“Proper sample collection is absolutely essential and unless done correctly will invalidate the test results,” the technical officer who developed the test, Paul Young, said.

The kit’s information sheet provides detailed instructions for correct sample collection.

Because of the sensitivity of the test it stipulates all the combs and cutters must be scrupulously clean before use.

A “one sample” kit may be used to collect a single sample from the shearing of a mob of up to 250 sheep.

If a mob contains more than 250 sheep, more than one sample should be collected.
Any number of sample bottles can be provided on request.

To ensure detection of low-level infestations of lice, all combs and cutters used to shear the mob of interest must be washed using the materials provided.
The EMAI team advises producers not to be tempted to sample only some of the mob.

“Sometimes only a few sheep in a mob may be infested,” EMAI technical officer, Narelle Sales, said.

Unless all the comb and cutter washings from the shearing of all of the sheep are included, the samples submitted to the laboratory may not contain any lice protein and the test result would be incorrectly interpreted.

By way of example, NSW DPI biometrician Dr Idris Barchia advised that a mob of 500 sheep of which only five (one per cent) were lousy, would require collection of samples from the shearing of at least 359 of those sheep to be 99pc sure the test would give a positive result.

How the lice test developed

Early in the development of the new lice detection test, NSW DPI technical officer, Paul Young, worked with Dr Wojtek Michalski from CSIRO who produced the monoclonal antibodies that bind with the louse protein.

Mr Young subsequently improved the sensitivity of the test by using minute magnetic polystyrene beads instead of conventional ELISA plates and by using a liquid wash sample instead of bits of solid grease scraped from the combs and cutters. 

“These improvements, combined with the use of other immuno-chemical reagents produced at EMAI, and a colour change reagent, form the framework of a very reliable and sensitive test,” Mr Young said.

More recently Mr Young and fellow technical officer Narelle Sales have re-worked the test procedures including the preparation of samples for use in the test.

The test is complex and time-consuming  but according to Ms Sales, careful processing of the solution containing the material washed from the combs and cutters is a vitally important step to success.

Sampling kits available

Kits containing all the materials needed are available now.

Depending on demand for the service, the kits may be made available from selected NSW DPI and Livestock Health and Pest Authority offices and from selected wool brokers.

Contact Paul Young, paul.young@dpi.nsw.gov.au or Narelle Sales, narelle.sales@dpi.nsw.gov.au, Camden, (02) 4640 6433, for further information or to request a kit.