NEW real-time tests that allow for results in a day rather than weeks will help to detect and identify exotic insects and any Bluetongue viruses they might be carrying, improving Australia’s ability to implement control measures, and protecting overseas market access.

The presence of Bluetongue virus (BTV) in northern and eastern Australia places restrictions on where livestock exports can be sourced. However, surveillance conducted through the National Arbovirus Monitoring Program defines the limits of BTV transmission and provides confidence to gain and maintain access to valuable markets.

The new surveillance tests, funded by red meat levies through Meat & Livestock Australia and NSW Department of Primary Industries, are the work of a team led by Dr Peter Kirkland, senior principal research scientist at NSW DPI’s Elizabeth Macarthur Agriculture Institute, and technical coordinator of the NAMP.

Dr Johann Schröder, MLA’s R&D project manager for animal health, welfare and biosecurity, said improved testing offers many advantages.

“There’s less room for error, especially in the insect identification, and there’s more immediate indication and warning of possible BTV spread,” Dr Schröder said.

“The advantage of quicker diagnosis to producers is that jurisdictions will more quickly be able to institute control measures if a disease threat emerges. Being a viral disease, there is no treatment, other than good nursing. In countries where the disease is endemic, sheep are vaccinated successfully, but at this stage, Australia has not seen the need to establish a vaccine bank.”

BTV is spread by small biting midges known as Culicoides and the NAMP conducts surveillance to monitor distribution of the insects known to be present in Australia and check for the incursion of new species.

BTV is endemic in northern and north-eastern Australia, with the BTV-free zone varying from season to season. However, BTV remains undetected in South Australia, Tasmania and Victoria. While Australia has BTV, it has never had a clinical case of the disease in its commercial livestock populations.

Dr Kirkland said some countries prefer Australian livestock sourced from BTV-free zones, so enhancing testing capability for BTV is an important element to protect market access for Australia’s livestock sector.

“Results can now be obtained for virus detection and identification for several hundred samples in a day, whereas previous methods would usually have taken weeks. We now also have the potential to detect a single exotic midge in a collection of more than 50,000 insects,” Dr Kirkland said.

“With increasing volatility of weather patterns, particularly rising temperatures, southern extension of the distribution of the insects is more likely, threatening sheep populations and rendering large numbers of cattle, sheep and goats ineligible for export.

“During a warm autumn like we’ve had this year, there’s the potential for small pockets of the insects to survive winter, and that gives them a head-start for the next season. Climatic variability is a concern, as just a 2°C change in temperature is predicted to see the insects spread along the entire south coast of NSW and around coastal Victoria.

“It wouldn’t take a large, long-term temperature elevation to totally change the distribution of these insects and significantly reduce our BTV-free zone.”

Dr Kirkland said the new tests not only allow DNA to be extracted from insects for testing, but it can be done in a way that’s non-destructive, leaving their skeletons intact to allow microscopic confirmation of the identification of a species.

“We can also identify what animal an insect has been feeding on. That adds a whole different dimension because it helps unravel if the insects are competent vectors,” he said. “BTV has the greatest impact on Australia’s live animal trade, and in some cases, product as well, and yet the risks can easily be managed, even from the northern infected zones, without presenting a threat to other countries.”

Source: MLA