27 October 2017
Agriculture Victoria has successfully completed surveillance and sampling activities in cattle herds near Echuca in the temporary bluetongue virus zone in northern Victoria.
Bluetongue Virus 3 November 2017: Frequently asked questions
Media release 27 October 2017: Bluetongue virus surveillance update
Media release 14 October 2017: Temporary bluetongue virus zone change for Victoria
Download the information on BTV surveillance in PDF here.
Download the information on BTV zoning in PDF here.
BTV is endemic in northern and parts of eastern Australia (Figure 1). Whilst the actual virus has not been demonstrated in the Victorian cattle herd, this is the first evidence of recent exposure of livestock to the virus in Victoria.
This surveillance testing is an important step in determining if the recent detection is an isolated case.
There have been 26 serotypes (strains) of the virus detected world-wide to date, with twelve serotypes isolated in northern Australia.
How is the virus spread?
The virus is not spread directly from animal to animal (i.e. is not contagious).
The virus is spread to ruminant animals by biting midges (Culicoides species), i.e. it is an insect-borne viral (arboviral) disease. To date the biting midge Culicoides brevitasis has been considered the most important vector (i.e. insect carrier of disease) of BTV and the distribution of BTV in Australia is largely determined by the distribution of this insect. This insect species is generally limited to the northern areas of Australia and is not present in Victoria.
Infected animals may remain infective (viraemic) for up to a maximum of 60 days. An insect vector spreads the virus through biting a viraemic animal, then transferring the virus to other ruminants.
What species are affected?
Cattle are the most commonly infected ruminant. However, other ruminants including sheep, goats, buffalo, camelids and deer are susceptible to BTV infection.
There has been no evidence of clinical disease in Australian livestock species to date, however the different BTV serotypes can cause varying severity of clinical disease in ruminants as seen in some overseas countries.
Sheep are the most severely affected livestock species and may present with a range of clinical signs. These include depression; swelling of lips, tongue, gums and face; cyanotic (blue) tongue; lameness; unwillingness or inability to stand; pneumonia and/or laboured breathing.
The strain of virus will have an important effect on the clinical expression of bluetongue disease.
Any health concerns in your livestock should be reported immediately to Agriculture Victoria on 1800 675 888 or your veterinary practitioner.
Can the virus spread to humans?
No. Bluetongue virus does not infect people (i.e. is not zoonotic).
Meat and milk is safe to consume. Animals which have been infected do not pose a food-safety issue.
Why the concern?
The presence of BTV can affect access to some international trade markets for cattle, sheep and goats destined for BTV 'sensitive' countries.
Victoria's economy benefits from the export of ruminant livestock and their genetic material (i.e. semen and embryos). This trade depends on a shared confidence between Australia and its trading partners that risks to the animal health status of the importing country can be accurately assessed and properly managed.
BTW surveillance activity
Agriculture Victoria will be undertaking targeted surveillance in a number of northern Victorian cattle herds. Blood samples will be collected for laboratory analysis to determine the extent of exposure to the virus in cattle herds, and for the presence of virus.
Insect trapping activities will also be undertaken on several northern Victorian cattle properties over the next few months to test for the presence of BTV in the Culicoides species present in Victoria.
Figure 1. Bluetongue virus zone map as of 13 October 2017. Yellow = BTV Transmission Zone, grey = BTV Buffer Zone, green = BTV Free Zone. Note the zone of possible transmission and buffer zone in Victoria. Source: National Arbovirus Monitoring Program, 13 October 2017.
A temporary bluetongue virus (BTV) zone has been introduced in northern Victoria on 13 October 2017. The zone was established in response to positive results to routine BTV testing in cattle destined for export. The zone will be in place whilst surveillance activities are undertaken. Results to these activities will assist in determining how and when livestock exports to the countries involved can resume.
What are the BTV zones?
Bluetongue is a viral disease that infects ruminants, including cattle, sheep, goats, camelids and buffalo. A number of BTV serotypes (strains) are present in northern and parts of eastern Australian. These serotypes have not caused clinical disease in commercial Australian livestock to date.
BTV zoning is an internationally recognised means of defining where BTV is present. This is particularly important for the export of livestock internationally. Countries that import significant numbers of livestock from Australia require that they come from BTV-free zones.
The National Arbovirus Monitoring Program (NAMP) monitors the distribution of economically important insect-borne viruses such as BTV. As BTV is spread by insect vectors, the distribution of BTV is likely to vary depending on seasonal conditions. BTV zones change if evidence of BTV is detected in the BTV-free zone. It is imperative to maintain these zones accurately and transparently to protect live animal export markets.
Why is Victoria creating a zone?
Routine pre-export BTV testing recently detected several cattle in a herd in northern Victoria that had been exposed to the virus. Although the cattle showed no clinical signs of infection with BTV, this is the first evidence of exposure to the virus in Victoria.
A temporary BTV zone has been implemented consistent with national arbovirus monitoring procedures.
During this period, surveillance testing will be undertaken to determine the extent of exposure to the virus and, if possible, the initial source of transmission into Victoria.
Where is the BTV zone?
The images indicate national BTV zones following the introduction of a 50 km radius zone of possible transmission around the property of detection, and a further 50 km radius buffer zone, while further investigations are undertaken. Transmission zones are those where there has been evidence of BTV activity within the previous two years. The BTV free zones are where monitoring has found no evidence of BTV activity within the previous two years.
What are the implications of zoning?
The introduction of a temporary BTV transmission zone in Victoria (Figures 2 and 3) means that livestock from within the zone will not be eligible for export to countries that require animals to be sourced from bluetongue free zones.
There are no changes to conditions for moving cattle from this temporary zone to other parts of Victoria, or elsewhere in Australia.
The strains of BTV currently found in Australia are considered to have a very low likelihood of causing disease. No clinical cases of BTV have been observed in commercial herds or flocks in Australia.
No risk is posed by BTV to human health or food safety.
How long is this zoning to be in place?
The temporary BTV transmission zone will be in place for 30 days. The requirement for the zone will be re-assessed when results to surveillance activities have been obtained.
Monitoring will continue under the NAMP with the aim of resuming exports of livestock from this zone as soon as possible.
If you have further questions regarding BTV surveillance, please contact an Agriculture Victoria Veterinary or Animal Health Officer by visiting your local Agriculture Victoria office or telephoning 136 186.
This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.