Progressing towards a flystrike vaccine

Scientists from the Department of Primary Industries and Fisheries, Queensland (DPI&F), are unravelling the way blowflies are able to strike sheep without the sheep being able to fight back.

Animals – and people for that matter – are usually able to mount an immune response when they are affected by various germs or parasites. The researchers have found that this is not the case when blowfly larvae (maggots) infect the sheep. In effect, the maggots ‘trick’ the sheep’s immune system into not responding when it is challenged by disease or infection.

Conventional vaccines work by getting the inherent immune response to work faster or more strongly.  These have not succeeded against flystrike because the immune system is effectively being blocked.  Having now identified the molecular factor that prevents the sheep’s immune system from responding, DPI&F scientists now plan to copy this factor and start testing the substance on animals so as to develop a counter-mechanism.

Once the immune suppression can be prevented, the next step would be to determine the strength of the sheep’s immune response, and then to judge whether this immunity needs to be boosted by conventional vaccine technology, such as those immunogens that have been developed in previous flystrike vaccine projects.

The commercial result would see sheep treated in advance so that if a flystrike started, the immune suppression would be prevented and the sheep’s immune system would respond and counteract the effect of the flystrike. This may be all that is needed to prevent the problems associated with flystrike.

The Australian Sheep Industry Cooperative Research Centre has co-funded the research with DPI&F to identify the immunosuppressive substance and sequence the blowfly gene responsible for its production in this quest that could provide the answers needed to develop an effective vaccine against flystrike.

Researcher Dr Terry Tierney (now retired from DPI&F) and technical officer Margaret Commins pioneered the work identifying that the blowfly larvae (maggots) make a substance that blocks the sheep’s natural immune reaction.

This work has been continued by DPI&F staff Dr Tim Mahony, Dr Rebecca Elkington, Dr Merideth Humphries and Ms Narelle Maugeri, along with Ms Commins.