Research into flystrike vaccine will continue despite mixed results after four years

Australian Wool Innovation has poured millions of dollars into efforts to development a vaccine against flystrike over the past four years.

Growers want to stop mulesing if a vaccine could be developed.

About half of all Australian wool growers still mules their sheep to help prevent fly strike.

At the same time, research into a long-held dream of being able to sidestep the expensive chore of shearing through biological defleecing of sheep is continuing.

Neither project has found the solution yet.

The four-year flystrike vaccine research project undertaken by CSIRO is about to end.

AWI tipped in a further $650,000 in funding in 2021 to try and fast track development of a vaccine after launching the project with $2.5 million in 2018.

It has been estimated AWI's investment in breeding for flystrike resistance related RD&E projects since 2005 has reached around $10 million.

AWI has today repeated its enthusiasm for a vaccine as a "game changer for the wool industry".

"But it is a high-risk project with no guarantee of success," AWI's general manager of research Bridget Peachey said.

AWI says there are still "significant hurdles to navigate" although much had been learned in the first four-year stage.

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With help from the University of Melbourne research into the blowfly genome, CSIRO researchers have tested more than 50 candidate proteins and prototype vaccine formulations.

Researcher say the mostly likely prototype vaccine used six key proteins which were produced using insect cell culture.

A second prototype vaccine using proteins obtained directly from blowfly larvae was also developed.

Serum from vaccinated sheep was fed to blowfly larvae and tested in the lab which found the trial vaccines achieved up to a 75 per cent reduction in blowfly larval growth.

But out in the field this was found to be about 25pc.

Researchers said the results from the lab trials demonstrated the sheep immune response to the trial prototype vaccines resulted in high levels of antibody production.

Those antibodies were evident after the initial dose but were boosted by a second dose "at which point the effect on stunting larval growth was demonstrated in the lab to be greatest".

Antibody levels were found to last up to six months, but effectiveness was found in the lab to reduce after two months.

CSIRO flystrike vaccine project leader Tony Vuocolo said: "Much more work must be done to extend the period of efficacy and translate these encouraging findings to actual on-sheep on-farm efficacy.

"The laboratory environment where blowfly larvae can be directly fed vaccinated sheep serum under controlled and defined conditions is markedly different to the conditions larvae encounter in the field."

Testing over the past 18 months have moved to field trials where the vaccine was directly tested on sheep.

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Researchers say this has presented "significant challenges" in the performance of the prototype vaccines.

To date the best result recorded on sheep has been a 25pc reduction in larval growth.

"Disappointingly, the field results are not yet enough to reduce the risk of flystrike for woolgrowers," Ms Peachey said.

"An important strategic imperative for AWI is to invest in these high-risk projects, that, if successful offer a high return for woolgrowers, however, as we have seen with the flystrike vaccine project, this challenging research doesn't always provide an easy pathway to the solution."

CSIRO scientists are now reassessing their initial results and formulating strategies to produce better antigens, refine approaches to vaccine formulation and optimise vaccine delivery.

They hope this will provide the best chances of producing an effective immune response at the skin where the larvae and sheep interact.

Back in March, AWI chairman Jock Laurie said the biological defleecing dream was still alive but had similar challenges.

Mr Laurie said work "is progressing well" on research into defleecing with the University of Adelaide.

AWI last year invested $1.4 million into a three-year research project with the university.

Researchers hope to isolate a compound which can create a weak point in the wool fibre, making it easier to remove the fleece.

Mr Laurie urged growers to remain optimistic.

He said researchers are confident in about in 18 months "we should have a clearer picture of what the story is" in regards to biological defleecing.