How likely a Lumpy Skin Disease incursion into Australia remains is subject to debate 12 months after the serious viral disease of cattle and buffalo was first detected in nearby Indonesia.
In the past year LSD has spread across the large islands of Sumatra and Java, moving in a direction towards Australia, with confirmed it had reached east Java reported in December.
The disease can be spread by the movement of livestock and of biting insects.
A key concern for Australia surrounds the increased potential that now exists for LSD to be transported by wind-borne stable flies, mosquitoes, ticks and possibly midges from nearby Java to the Australian mainland, or via “hitchhiker” pests travelling on vessels to Australia.
Some experts such as Indonesian-based Australian cattle veterinarian and market analyst Ross Ainsworth have warned that the chance of LSD reaching Australia from Indonesia is practically inevitable within the next five years.
However, a report recently completed for the National LSD Action Plan, which has been posted without public attention to a page on the Federal Department of Agriculture’s website, suggests the risk is not as high.
The reports quotes the results of epidemiological modelling conducted as part of an assessment of the risk of LSD reaching Australia via non-regulated pathways such as via wind-borne insects.
It says the probability is “lower than previously thought”, and would “depend on the number of insect vectors required to initiate an infection”.
“It matters if it takes more than one insect to start an infection. There is strong scientific evidence that a single insect is unlikely to start an incursion of LSD,” the report states (the report can be downloaded in PDF format from this link).
“Instead, it is very likely that several insects must land on a single animal to begin an infection.
“This is hard to achieve when insects are blown across several hundred kilometres, so it becomes a sensitive parameter in the epidemiological assessment.”
It also mattered where in Indonesia the disease was present, the report stated.
However, it also acknowledges the modelling work underpinning the risk assessment was conducted before the spread of LSD to East Java was confirmed.
“Since the modelling was done, LSD has now been reported in East Java, which is closer to Australia, and windborne dispersal is possible from this region.”
The report notes that the Tiwi Islands and regions east of Darwin to the Cobourg Peninsula are most at risk of windborne incursion, particularly during the northern Australian monsoon season between December and March.
“This information can help to prioritise LSD surveillance activities to look for and quickly respond to outbreaks if they do occur.”
It says the modelling also highlights which group of insects to look at.
Mosquitoes represented a higher risk based on current laboratory studies by leading researchers overseas.
Midges were more likely to be blown across, but there was little scientific evidence yet to show that they spread LSD virus.
The report also notes that key knowledge gaps remain about LSD virus and how it spreads between regions.
For example, it is not known exactly how many infectious insects need to bite an animal to transmit disease.
“Current scientific evidence suggests that multiple insects are required and the modelling results presented here depend on that assumption.
“Another key assumption is that LSD virus does not replicate inside an insect. The virus simply survives on mouthparts of the insects and there is wide consensus in the scientific research on this issue.”
The report has stemmed from high-level “structured expert judgement exercises” which were held in March 2021 and again in March 2022, facilitated by the Centre of Excellence for Biosecurity Risk Analysis.
It says the exercises were discussion-based, using an internationally recognised process, according to the report.
The epidemiological modelling carried out looked at the future rate of LSD incursions under hypothetical scenario where LSD has spread and is endemic throughout South-East Asia, Timor-Leste and Papua New Guinea.
The model examined the windborne entry of insects and infectious insects hitch-hiking on either commercial vessels, returning live export vessels, or vessels moving under the Torres Strait Treaty.
It did not assess the pathway of insects arriving as hitchhikers on commercial airplanes, given the existing control measures and lack of significant cattle populations around international airports.
Insect incursions via Torres Strait Treaty movements were examined, but the risk of LSD being introduced to Australia via this route was estimated “to be negligible”.
The report stated that the parameters used in the modelling were subject to “considerable uncertainty and limitations”.
“It is important to note that while this modelling is not a forecast, it does help us better understand critical points of potential entry pathways and the sensitivity of risk calculations for key parameters like infection rates.
“We now know more as a result of the detailed modelling and this will help us to target research and mitigate the risk of LSD arriving and spreading in Australia.”
But it also said the value of the modelling work was not diminished by the global knowledge gaps about LSD.
“Rather it shows the need for considered judgement of the analysis, including next steps.
“Critically, it provides us with a better understanding of how some of these uncertainties could significantly influence the threat to Australia. This will help us target further work and strengthen Australia’s preparedness.”
For more information about the modelling on the Department of Agriculture website click here
Maybe these expert biosecurity staff discussing the issues are a lot like the UK health minister deciding when they should start another covid scare or LSD scare. How about these experts take their bodies to the affected islands, and do some real research. My first thought would be to: find some affected cattle (trial animals) and some not affected cattle (control group) and run some nutritional assessments, blood sampling etc on the animals to see why the affected animals are affected. Compare the two groups (sets of data) to see what the pre-disposing cause might be. Maybe even undergo a genetic assessment to compare the animals. The science is needed to stop this ridiculous fear campaign going any further. For gods sake, get some real science to compare.
No complacency here
Treat it as a will come and act accordingly now