Report Bluetongue virus
Bluetongue Virus is a Notifiable Animal Disease. If you suspect Bluetongue Virus you must immediately notify the EAD Hotline on 1800 675 888 (24hrs) or your Local Land Services veterinarian on 1300 795 299 (business hours)
Bluetongue virus (BTV)
All ruminant species are susceptible to infection with bluetongue virus (BTV); however, bluetongue is primarily a disease of sheep. Australia has a recognised BTV zone and monitoring of BTV distribution is undertaken by the National Arbovirus Monitoring Program (NAMP).
Disease information
What is Bluetongue (BTV)?
Bluetongue is an arthropod-borne viral disease of ruminants.
Thirteen bluetongue serotypes have been recorded in Australia (serotypes 1, 2, 3, 4, 5, 7, 9, 12, 15, 16, 20, 21 and 23). BTV-1, BTV-16 and BTV-21 have been detected throughout the endemically (naturally occurring) affected area of NSW. BTV-15 has been detected on the far north coast of NSW in a single year only (2022).
Infection in cattle, although of great epidemiological significance, is usually subclinical (not showing outward signs of disease). The ability to cause disease or virulence of different strains of bluetongue varies significantly.
The disease is most likely to occur in late summer or early autumn due to the build-up of virus numbers in cattle and increasing vector populations with warmer weather.
Clinical disease is an uncommon occurrence in Australian sheep and has never been reported in any other susceptible animal species in Australia. Cases occurred in commercial sheep flocks within the BTV Transmission zone in 2023 and 2024. The mortality rate is very variable in sheep and generally ranges for 0-30% depending on the virus strain and genotype of sheep.
Does BTV affect people?
A zoonotic disease is a disease that can pass from animals to people or people to animals. Bluetongue is not a zoonotic disease and does not infect humans.
How is BTV spread?
Bluetongue virus (BTV) is spread by insect vectors, Culicoides midges, feeding on affected animals. Bluetongue is not transmitted directly between animals.
The distribution of BTV in Australia is associated with the most common and widely distributed vector species, Culicoides brevitarsis. In NSW, BTV transmission occurs regularly on the northern coastal plain to the Hunter Valley, and more irregularly in the northern tablelands, northwest slopes, Sydney basin and south coast regions. This is also known as the Bluetongue Transmission Zone. Link to map of the BTV transmission zone.
What does BTV look like?
Clinical signs may range from mild to severe and typically involve:
- fluctuating fever
- hyperaemia or reddening) and haemorrhages or bruising or bleeding) on oral and nasal membranes
- excess salivation and nasal discharge
- lips and tongue may become swollen, and the swelling may extend over the face and under the jaw
- ulcers develop on the gums, cheek and tongue 5 to 8 days after the onset of fever
- feet lesions may appear towards the end of the febrile period, including reddening and petechial bruising on the coronary band (i.e., at the top of the hoof). The associated pain causes the animals to stand with arched backs and be reluctant to move
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What are the differential diagnoses for BTV in sheep?
- scabby mouth (contagious pustular dermatitis)
- acute photosensitisation
- lameness due to footrot, foot abscess and other foot conditions
- acute infection with Barber’s pole worm (with depression and submandibular oedema)
- facial eczema
- pneumonia
- plant poisoning
- salmonellosis
- sheep pox
- foot-and-mouth disease
- peste des petits ruminants.
What should I do if I suspect BTV?
Bluetongue in sheep, goats and cattle is a notifiable disease in NSW. This means you have a legal duty to report all suspicion of BTV in your animals.
If you suspect BTV, see signs of disease or death consistent with bluetongue in your flock or herd, immediately contact the 24-hour Emergency Animal Disease Watch Hotline, 1800 675 888 or your Local Lands Services District Veterinarian, 1300 295 299.
How is it diagnosed?
Diagnosis is supported by history, clinical signs, confirmation of infection by PCR or virus isolation and the post-mortem finding of haemorrhages in the tunica media at the base of the pulmonary artery (regarded as being characteristic of bluetongue).
There are a range of tests that can be performed on blood (clotted and EDTA), fresh tissue and semen and fixed tissues. Further information around available diagnostic tests and laboratory submission forms can be found at Veterinary Test List.
Highest concentrations of virus in the blood usually occur during the early stage of disease before antibodies develop but virus can be reliably detected for at least 7 to 10 days after the onset of disease and usually much longer when using qRT-PCR.
I have had an endemic, or naturally occurring strain of BTV detected in my flock or on my property. What do I need to know?
Once an endemic strain of BTV is confirmed, the property will be placed under an Individual Biosecurity Direction.
As a precaution the movements of clinically affected sheep will be restricted until the end of the vector season (i.e., the first frosts, or when NAMP testing for the season concludes) to ensure no affected sheep or sheep products leave the BTV transmission zone.
Some movements may still be allowed on a case-by-case basis as determined by NSW DPIRD (e.g., sheep direct to slaughter or low risk movements within the existing BTV zone). Movement restrictions will cease at the end of the transmission period (usually July).
It is important that owners and managers of affected sheep and/or their private veterinarians continue to liaise with their Local Land Services District Vet (DV) during this period so that they can work with you in a mutually beneficial manner that protects your farm and the region’s livestock industry.
No ruminants or their products will be eligible for international export from confirmed infected properties during the transmission period. (e.g., cattle, goats, sheep and their products) due to the requirements of importing countries.
There is no treatment for the virus, but supportive therapy may assist the animals whilst recovering – discuss this with your private veterinarian. Protection from insect bites may be helpful but may not be practical. If cattle are present on the same farm, separating sheep and cattle may assist in reducing midge activity on the sheep.
Other key information and resources
Prevention and management
National freedom from BTV is not possible. There is no treatment for the virus, but supportive therapy may assist the animals whilst recovering – discuss this with your veterinarian. Vaccines are available overseas and can be used to protect susceptible animals against clinical disease if a need arises.
Protection from insect bites using insecticides and/or repellents may be helpful but may not be practical in substantially reducing transmission of BTV in most circumstances. If cattle are present on the same farm, separating sheep and cattle may assist in reducing midge attack on the sheep.
What is the National Arbovirus Monitoring Program (NAMP)?
The National Arbovirus Monitoring Program (NAMP) monitors the distribution of economically important insect-borne viruses of livestock and their vectors. NAMP specifically monitors bluetongue virus, Akabane and bovine ephemeral fever. It provides a system for detection of any new strains of bluetongue virus and any change in distribution of these viruses within Australia.
Why does NAMP monitor for arboviruses?
Some countries that import live sheep, goats and cattle are concerned about the presence of bluetongue viruses in Australia. These countries require ongoing assurance that livestock imported from Australia are free of these viruses. NAMP provides the necessary evidence on which to base these assurances.
NAMP provides a bluetongue early warning system, enabling the detection of incursions of exotic strains of bluetongue virus (BTV) and vectors (Culicoides species biting midges) that have the potential to adversely affect livestock production in Australia and trade through surveillance within the bluetongue transmission zone.
In addition, NAMP assists producers and exporters to manage risk by detecting changes in seasonal distribution of vectors and showing the likelihood of arboviruses affecting stock in particular areas.
For more information about the NAMP and arbovirus monitoring, impacts to export trade and markets, see Animal Health Australia’s https://animalhealthaustralia.com.au/maintaining-access-to-arbovirus-sensitive-markets/.
How does NAMP operate in NSW?
NAMP carries out its disease monitoring in two ways:
- Sampling and testing for antibodies in sentinel cattle
- Trapping insects to check for the presence of insect vectors.
NSW Department of Primary Industries and Regional Development (NSW DPIRD) officers take blood samples from sentinel cattle at strategic sites in NSW regularly to detect the presence of bluetongue, Akabane and bovine ephemeral fever. They sample young cattle after weaning and then sample the same animals during and after the time when insect vectors are expected to be active, and transmission of the virus is likely to occur, to examine whether they have been exposed to the virus(es). The NSW DPIRD Animal Health and Plant Laboratory at Elizabeth Macarthur Agriculture Institute analyses the samples and refers all samples where bluetongue virus is suspected to the Australian Centre for Disease Preparedness (ACDP) in Geelong.
Seasonal and environmental factors influence the distribution of the viruses and their vectors. Traps are set to collect insect vectors at selected sites in NSW. Entomologists examine the contents of the traps for the presence of the specific insects that can spread the viruses of interest to NAMP.
Resources
- Animal Health Australia’s AUSVETPLAN Bluetongue Disease Strategy: https://animalhealthaustralia.com.au/download/1622
- Bluetongue virus zone map: https://namp.animalhealthaustralia.com.au/public.php
- Veterinary Testing for Bluetongue: Veterinary Test List
- Bluetongue virus - Veterinary sampling key list DOCX, 76.06 KB
- BTV clinical cases presentation (Dr Heidi Austin, North West LLS)
- Primefact - PUB24/358 - Bluetongue virus in sheep – Information for producers PDF, 343.11 KB
- Primefact – PUB24/309 – Bluetongue virus in sheep – Information for Private Vets PDF, 409.29 KB
Reporting animal biosecurity emergencies
Some animal pests and diseases, or residues in animal products or stock feed can have serious consequences for trade, production or human health. By remaining vigilant and acting quickly if you suspect a significant animal pest, disease, or residue you may be able to prevent these consequences. Don’t delay! Contact Local Land Services or ring the 24 hour hotline: