Over The Horizon

Blowing Away the Blowfly

Massey University scientists hope to halt the destructive spread of the Australian blowfly through genetic manipulation. Molecular Geneticist Dr Max Scott was recently granted $75,000 by Wools of New Zealand to investigate the genetic control of Lucilia cuprina, more commonly known as the Australian blowfly.

The blowfly was first noticed in New Zealand nine years ago at Paparoa. It has since spread through the country and now occupies regions previously assumed too cold for the insect to survive. The fly is responsible for severe fly strike in sheep where eggs are laid on the skin and the resulting maggots destroy large areas of skin, sometimes causing the animal to die.

The flies can be controlled through pesticide application to the wool but chemical residues in the wool complicate farm management because sheep cannot be shorn until recommended withholding periods are met.

Scott predicts the use of pesticides will become less attractive as insecticide resistance increases and European Union countries demand lower levels of chemicals in any greasy wool they purchase. In the long term, control will probably be best achieved by the careful integration of a variety of biological measures.

"It's an extension of some basic work I've been doing for the past few years and now overseas technology developments mean the work should transfer to the blowfly project."

He has genetically altered drosophila insects in the laboratory to establish methods of reducing populations in a controlled way, but up until now the technology has not been available to transfer the methodology to other insects. The breakthrough has come from the Institute of Molecular Biology and Biotechnology in Greece, where scientists have discovered a novel jumping gene. Scott spent two years at the institute from 1990 to 1992.

He plans to integrate DNA into individual fly's chromosomes so the DNA is then passed on to subsequent generations. He is taking advantage of a group of proteins called male-specific lethals, or MSLs. High levels of expression of one of the MSLs causes female drosophila to die.

"We should know within the next 12 to 24 months if the new jumping gene can be used to genetically alter blowfly. After that we would need to determine if expression of the MSLs kills female blowflies. In the long-term, we would try a small field trial which would require regulatory approval. If it works, the genetic control method could potentially be applied to other insects, such as the mosquito -- a major vector for malaria."

Scott is working with AgResearch scientist Alan Heath, who will raise the flies to be used in the study. Heath has studied the flies and methods of control for several years. Australian scientists are also looking at methods to control the pest.