New tool in animal disease fight

by 5m Editor
13 October 2004, at 12:00am

AUSTRALIA - CSIRO researchers are investigating whether an ancient arm of the immune system can be used to control livestock animal diseases.

CSIRO Livestock Industries' scientist Dr Tim Doran says a biological phenomenon called RNA interference (RNAi) has huge potential to control, and possibly eliminate, a number of major animal diseases.

"RNAi has existed in plants and animals for millions of years, but scientists only discovered the process and its benefits in the 1990s," Dr Doran says.

"The major benefit of RNAi is that it allows gene-specific silencing - that is, we can 'switch off' targeted genes in the cells of plants and animals."

"This is important as vaccines aren't available to treat many diseases and current chemical treatments are losing their effectiveness as pathogens build up resistance."

"For example, increasingly internal sheep parasites are developing resistance to drenches leading to a decrease in the effectiveness of even the most recent products on the market," he says.

Dr Doran says that by using RNAi to knock out genes across a genome, researchers are able to identify or 'validate' new targets (proteins) for existing drugs. This could potentially eliminate resistant parasites.

By using RNAi, new treatments can also be produced.

Dr Doran says CSIRO Livestock Industries' researchers are using the technique in a bid to develop treatments and vaccines for a range of animal diseases.

"Using RNAi, we're developing treatments against diseases such as avian influenza and Marek's disease in poultry," he says.

Avian influenza swept through 10 Asian countries early this year, resulting in the death or slaughter of millions of chickens and ducks and the deaths of more than 20 people.

Marek's disease is caused by a virus that attacks the chicken's immune system, leaving it open to other infections. The disease costs the world-wide poultry industry about $2,000 million a year.

CSIRO Livestock Industries' researcher Dr Jef Hammond is using RNAi in an effort to control one of the world's most devastating animal diseases, foot and mouth disease (FMD).

"FMD is one of the most infectious animal viruses known," Dr Hammond says. "It can cause debilitating disease in cloven hoofed animals including pigs, cattle and sheep."

While Australia is free from FMD, an outbreak would result in an immediate ban on exports of all livestock, meat and dairy produce. The overall cost of lost markets and rural production is estimated to be $6 billion plus $8 million for each day the outbreak lasts.

Dr Hammond says current FMD vaccines provide varying degrees of protection depending on the dose, the formulation and the species to which they are administered.

Additionally, commercially available FMD vaccines are specific to a particular 'serotype' or strain of the virus.

"An antiviral therapy such as RNAi could be used on a range of animals and virus serotypes," Dr Hammond says.

"RNAi would help stop the virus replicating in all animal species, reducing virus spread. This would be a great benefit in controlling an outbreak of disease."

"If the approach were successful it could be used in place of 'ring vaccination'. Susceptible livestock surrounding infected premises could be given the RNAi treatment, effectively halting disease spread," he says.

RNAi is a key component of CSIRO's biotechnology strategy, with the organisation holding an extensive and growing intellectual property portfolio in the area. CSIRO is developing products for, and with, the plant, livestock, aquaculture, animal biotechnology and biopharmaceutical industries.

Source: CSIRO Australia - 15th September
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