When we compile VetWatch we include a range of topics, animal species and industries so that there will be something of interest for everyone in our wide readership.

Today, we feel that we should deviate from that approach to bring you our first ever special edition of VetWatch that is focused only on avian influenza and specifically on high pathogenicity (HPAI) H5N1 clade 2.3.4.4b.

This is not the same high pathogenicity avian influenza subtype that was recently detected in Victoria (H7N3, H7N9) or NSW and the ACT (H7N8).

HPAI H5N1 clade 2.3.4.4b has caused ongoing outbreaks of serious disease in domestic poultry, wild birds, and wild and domestic mammals since 2021. Cases have been reported in North and South America, Europe, Asia and Africa, and most recently, Antarctica and its islands. There have also been occasional reports of human cases.

Australia / Oceania is the only continent free from HPAI H5N1 clade 2.3.4.4b, but wild migratory birds will be returning to Australia from the north between now and November. Once here, some of those birds continue southward to visit Antarctica, then return to southern Australia to breed.

Consequently, we are currently facing an extended period of very high risk during which this deadly virus could enter, then potentially establish in our wild bird populations. The effects of such an incursion in Australia are unknown but some species such as black swans and emus may be particularly badly affected. We may also see sea mammals, local carnivores (cats, dogs, foxes), omnivores (brush-tailed possums) and iconic species like quolls and Tasmanian devils impacted.

In this special edition, we are pleased to bring you the latest information about the virus from experts Dr Michelle Wille from the University of Melbourne, Dr Helen O’Brien from the Department of Health and Dr Claire Harrison from Wildlife Health Australia. We also provide links to further information or to resources that you can use in your practice and can share with owners and wildlife rescuers and carers, to help them understand the risk and be better prepared.

Finally, as a reminder, you must report any suspected cases of HPAI, and the best way to do that is to call the 24/7 Emergency Animal Disease Hotline on 1800 675 888.

Reporting sickness and mortality events in domestic or wild animals or birds, or in sea mammals, is vitally important and will allow us to evaluate the need for diagnostic testing or other investigation

Thank you for your ongoing contribution and assisting Agriculture Victoria in protecting Victoria’s agricultural industries and wildlife.

Dr Graeme Cooke
Chief Veterinary Officer (CVO) Victoria

Dr Michelle Wille1,2 

1. Centre for Pathogen Genomics, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity
2. WHO Collaborating Centre for Refence and Research on Influenza, at the Peter Doherty Institute for Infection and Immunity

Email: michelle.wille@unimelb.edu.au

Over the last months avian influenza has been heavily featured in the Australian media, with stories focussing on both the domestic HPAI H7 outbreaks as well as the looming threat of HPAI H5N1.

What is avian influenza?

Avian influenza comprises a large diversity of different subtypes and pathotypes, each with different characteristics, risk profiles, and consequences. Subtypes refer to the different haemagglutinin (HA) and neuraminidase (NA) proteins found on the outside of the virus: there are 16 different HAs and 9 different NAs found in birds which can mix and match, and are reported in combination: e.g. H5N1, H7N9. The vast majority of avian influenza viruses are low pathogenicity avian influenza (LPAI) which circulate in wild bird populations, including here in Australia, and cause no clinical disease in wild birds (although may cause mild disease in chickens). When subtype H5 and H7 (exclusively) jump from wild birds in poultry, they may evolve to become highly virulent, causing significant disease and death in poultry. These lethal viruses are referred to as high pathogenicity avian influenza (HPAI) viruses.

Global situation of HPAI H5N1

The Victorian and New South Wales HPAI H7 outbreaks that occurred this year, did so amid growing concerns about the arrival of an overseas strain of HPAI H5N1. HPAI H5N1 clade 2.3.4.4b is responsible for an ongoing global panzootic (i.e. animal pandemic), and the risk, response strategy and implications of HPAI H5N1 are vastly different compared to the recent HPAI H7 outbreaks.

While HPAI H5N1 viruses have been around for decades, mostly circulating in Asian poultry, in 2021 a number of key changes in the virus sparked a panzootic. The number of outbreaks in wild birds and poultry rapidly increased in Europe starting in 2020, followed by massive global expansion commencing in 2021. In late 2021 the virus arrived in North America. It entered North America on at least three occasions – twice over the Atlantic Ocean and once across the Pacific Ocean. Approximately one year later, in late 2022, the virus entered South America. Approximately six months after arriving in South America, it was detected on the southern tip of the continent – a journey of 6000km, leaving a trail of destruction behind. About a year later, in October 2023, the virus was first detected on South Georgia Island, and in February 2024, it was confirmed on the Antarctic Peninsula. Oceania is the only part of the planet free from HPAI H5N1.

To date, this virus has infected >350 species of wild birds and >50 species of mammals. It’s not just the breadth of species affected, the virus is having catastrophic consequences for some species. For example, within a 3 week period, 40% of Peruvian Pelicans in Peru died due to HPAI – that’s almost 1 in 2 Pelicans in Peru that died due to this virus. In Argentina,  ~18,000 Southern Elephant Seals died, almost all being 1-2 weeks old, prompting concerns about mammal-to-mammal transmission in seals. Beyond wildlife, over 130 million chickens were culled globally in 2022 due to this virus. In the USA alone, over 100 million chickens have been culled since January 2022. In the USA HPAI H5N1 has now been found in over 195 dairy herds across 14 states. The virus causes generally mild and transient disease in dairy cattle, and the infection occurs largely in the mammary glands causing extremely high levels of virus in milk. Fortunately pasteurisation appears to work effectively, but to date at least 4 dairy workers have been infected. Cattle have infected cats living in dairy sheds, as well as other livestock on farms, including llamas and poultry, creating an extremely complex situation. Because the virus is now being maintained in wild birds, poultry, cattle, and other mammalian species, the standard approach to control (i.e. culling of poultry), is ineffective in eradicating this virus.

In contrast the enormous number of cases in animals, there have been remarkably few human cases due to HPAI H5N1 clade 2.3.4.4b. Most human cases due to HPAI H5Nx (including all clades) have been in poultry workers, those with infected backyard birds, people who work in or regularly visit live poultry markets, or dairy workers (in the USA). A recent quadripartite risk assessment reiterated that the risk to the general public was low, but for occupationally exposed workers the risk was low to medium with high uncertainty.

Risks and consequences to Australia

Given the change in epidemiology of HPAI H5N1, the substantial global spread, and large numbers of outbreaks, the risk of this virus has increased. A recent risk assessment indicates overall risk is considered high, with moderate uncertainty. This is based on a moderate increase in the likelihood of entry and exposure of HPAI with a significant increase in the consequence of HPAI incursions.

The most likely route of virus introduction is with long distance migratory birds, with a moderate risk, albeit high uncertainty. Migratory shorebirds and seabirds arrive to Australia in the millions each spring, so although we do not know which year it will arrive, it is most likely to arrive in spring. The virus may also arrive with nomadic duck species found in the Australio-Papuan region, but only if HPAI H5N1 clade 2.3.4.4b is present east of the Wallace line. A third pathway, not included in the risk assessment, but discussed in a recent OFFLU report is via the Antarctica. At present, cases are along the Antarctica Peninsula – thousands of kilometres from Australia, and arguably too distant for a bird or mammal to travel within the infectious window. This route of introduction may become more relevant if/when outbreaks in Antarctica are occurring in the region directly south of Australia and New Zealand.

The consequences of viral introduction into Australia will be substantial. The consequences to poultry are assessed as high with moderate uncertainly. The consequences to wild birds are assessed as catastrophic . I would argue that given the catastrophic consequences to wild animals, globally, it’s unlikely that the outcome of virus arrival to Australia will be any different.

What are we doing?

In Australia we have a National Avian Influenza in Wild Birds (NAIWB) surveillance program: state and territory laboratories as well as research laboratories undertake avian influenza surveillance in wild birds to monitor and characterise LPAI viruses in wild birds, and maintain fit-for-purpose diagnostic tests and national laboratory diagnostic capacity and capability. In addition to the long-standing surveillance program run by the NAIWB, researchers have been sampling incoming long distance migratory birds each spring since 2022 in response to the threat of HPAI H5N1. In spring 2023 >800 samples were collected from incoming shorebirds captured in Broome, Exmouth, King Island, and Western Port Bay and seabirds on Philip Island and Lord Howe Island. Our 2024 program will begin in October, coinciding with the arrival of these birds. We are grateful to all the organisations and jurisdictions for their support of this work. 

We, of course, will need your help in monitoring for HPAI in Australia. It is critical that sick or dead birds be reported via the Emergency Animal Disease Watch Hotline: 1800 675 888

Useful resources:

• Advice for people who encounter sick or dead wild birds
• Advice for bird banders, wildlife rangers and researchers
• Advice for veterinarians and other animal health professionals
• WHA website
• Michelle Wille’s Avian Influenza Resources

Dr Claire Harrison
Senior Project Officer
Wildlife Health Australia (WHA)
Email charrison@wildlifehealthaustralia.com.au
wildlifehealthaustralia.com.au

Since 2021, a new strain of HPAI, H5N1 clade 2.3.4.4b, has caused ongoing outbreaks of disease in poultry, wild birds and wild mammals in all geographical regions except Oceania (which includes Australia and New Zealand). HPAI H5N1 clade 2.3.4.4b has not been detected in Australia. Mortalities have been observed in a wide range of wild species, seen as individual bird deaths and mass mortalities, and individual and mass mortalities in marine mammals. The current global situation means an increased level of risk to Australia via migratory birds from the northern hemisphere and local non-migratory movements of infected wildlife.

More information and resources on HPAI and wildlife are available on the WHA website HPAI incident page.
HPAI topics include:

• general HPAI advice and information from WHA (e.g. a Fact Sheet on AIV and Australian wild birds, HPAI advice targeted for particular stakeholder groups (including what to look out for and how to report), technical advice, videos and a communications guide)
• WHA HPAI and wild animals in Australia - risk mitigation toolboxes for wildlife managers and wildlife care providers
• national and international HPAI guidelines from government agencies
• other relevant information and resources (e.g. human health, communications materials).

WHA HPAI resources which may be particularly useful for veterinarians include:

• Advice for veterinarians and other animal health professionals
• Risk mitigation toolbox for wildlife care providers
• Fact Sheet: Avian Influenza in wild birds in Australia
• National Wildlife Biosecurity Guidelines

Dr Helen O’Brien
MB BCh BAO, MSc, FAFPHM
Acting Deputy Chief Health Officer (Communicable Disease)
Department of Health
Email: helen.o’brien@health.vic.gov.au

Avian influenza (AI) does not usually infect people, but rare cases of human infection have occurred with some AI viruses. Humans can be exposed to the virus through contact with infected birds, including with their respiratory secretions and faeces, or contaminated environments. Since 1997, more than 900 sporadic human cases of H5N1 have been reported globally, which is relatively few compared to the wide circulation of the virus. There is no evidence that the H5N1 strains of avian influenza circulating globally can be spread easily from human to human.

In the small number of AI cases that have been reported around the world, symptoms have included fever, respiratory symptoms, conjunctivitis, fatigue, diarrhoea and headache, which may occur 1-10 days following exposure. Rare complications include pneumonia and encephalitis. While some cases of H5N1 have resulted in death, most infections with clade 2.3.4.4b have resulted in conjunctivitis or mild respiratory symptoms.

Although the risk of avian influenza transmission to humans is very low, it's important to protect yourself and your staff when working with potentially infected birds (or animals). A wide range of bird species can be infected by AI, and they may be asymptomatic or show only mild clinical signs when infected, therefore it’s important to take precautions.

To minimise risk to yourself, adhere to strict hygiene protocols when handling any birds. Always wash your hands and arms thoroughly with soap and warm water after handling birds or contaminated materials. Hand sanitiser (60-90% ethanol) can be used as a supplement but should not replace thorough handwashing.

When working on affected properties or when in contact with potentially infected birds or contaminated materials, make sure to wear the appropriate personal protective equipment (PPE):

• Fluid-resistant coveralls, and depending on activities, waterproof apron
• Respiratory mask (N95 or P2)
• Protective eyewear (goggles) and face shield
• Waterproof footwear
• Head cover or hair cover
• Gloves

Ensure that PPE is removed properly to avoid self-contamination. All reusable and non-disposable PPE should be cleaned and disinfected after every use with a detergent then disinfectant that will kill influenza viruses.

Seasonal flu vaccination is recommended for everyone aged 6 months and over. It does not protect against avian influenza virus infection however it can help prevent the mixing of avian influenza and seasonal influenza viruses, which can lead to new mutated viruses that could spread rapidly. This is particularly important for those who handle sick birds or poultry during their work.

If you or your staff develop symptoms consistent with AI after contact with birds suspected to be infected, contact your healthcare provider to arrange for testing. Remember to wear a mask and call ahead before attending for testing.

Useful resources:

• What Causes Bird Flu Virus Infections in Humans | Bird Flu | CDC

Dr Rachel Gibney
Agriculture Victoria
Email: rachel.gibney@agriculture.vic.gov.au

Avian Influenza (AI) is a highly contagious viral infection of birds. The disease is caused by either high pathogenicity or low pathogenicity strains. Pathogenicity refers to the ability of the virus to cause disease in poultry; high pathogenicity avian influenza viruses (HPAI) can cause severe clinical signs and high mortality (up to 100%) in domestic poultry (chickens) and turkeys. Low pathogenicity avian influenza viruses (LPAI) can result in some mortality, but often present with few or no symptoms.

Wild birds are considered the natural host for LPAI. Certain water birds act as reservoirs of influenza viruses by carrying the virus in their intestines. Infected birds shed the virus in saliva, nasal secretions and faeces. Avian influenza viruses spread among susceptible birds through contact with contaminated nasal, respiratory, and faecal material from infected birds.

Good biosecurity practices remain essential to reduce the risk of disease. Poultry owners should be vigilant for signs of disease especially where multiple mortalities occur in poultry, or many birds are sick. Care should be taken to maintain poultry in isolation from wild birds.

Between May and 24 June 2024, Victoria experienced an outbreak of HPAI H7N3 on 7 properties in the Meredith/Lethbridge area, and HPAI H7N9 on one property near Terang. In total, approximately 1.3million birds died or were depopulated during these outbreaks. Destruction and disposal activities have been completed on these properties, with decontamination and restocking activities still underway. NSW and ACT concurrently experienced outbreaks of HPAI H7N8, which were unrelated to the Victorian outbreaks.

Ongoing movement restrictions (figure 1) for poultry and poultry products, and surveillance activities in both poultry and wild birds is continuing to contribute to achieving Australia’s proof of freedom status. For more information on this response, visit Agriculture Victoria’s Avian Influenza webpage.

Figure 1. Restricted (red) and Control (pink) areas for HPAI in Victoria at 6 September 2024.

HPAI H5N1 clade 2.3.4.4b is having severe impacts on the health of poultry, wild birds and biodiversity. It is estimated that over 200 million poultry have died or been depopulated as part of response activities since 2021.

H5N1 has caused the death of entire flocks of birds and is devastating to the poultry and associated industries internationally and has led to increased price in poultry products including eggs and meat in some countries.

Infected birds will experience fever and respiratory problems leading to death in a matter of hours or days.

HPAI should be considered as a possible cause if a flock or group of birds become ill very quickly – progressing from normal to severe illness or death within 24 to 48 hours.

All bird species are thought to be susceptible to HPAI H5N1 clade 2.3.4.4b.

Clinical signs of HPAI may include:

• sudden death
• respiratory distress/breathing difficulties
• swelling and purple discoloration of the head, comb, wattles and neck
• coughing, sneezing, or rasping respiration
• rapid drop in feed intake, water intake and egg production
• typical “sick bird” signs – ruffled feathers, depression, closed eyes
• diarrhoea
• nervous signs (occasionally seen).

Gross Pathology:

• Peracute deaths: minimal gross lesions may be observed, consisting of dehydration and congestion of viscera and muscles.
• Subacute deaths: In birds that die after a prolonged clinical course, petechial and ecchymotic haemorrhages occur throughout the body, particularly in the larynx, trachea and proventriculus and epicardial fat, and on serosal surfaces adjacent to the sternum. There is extensive subcutaneous oedema, particularly around the head and hocks. The carcase may be dehydrated. The pancreas, liver, spleen, kidney and lungs can display yellowish necrotic foci. The air sacs may contain an exudate. The spleen may be enlarged and haemorrhagic.

Reporting suspicion of HPAI:

• Avian influenza (AI) is a notifiable disease, and veterinarians who know of or suspect the presence of avian influenza MUST report it IMMEDIATELY to Agriculture Victoria.

You can do this by immediately calling the all-hours Emergency Animal Disease Hotline on 1800 675 888.

Investigating suspect cases of HPAI:

• The Victorian Significant Disease Investigation (SDI) Program aims to boost Victoria's capacity for the early detection of diseases such as HPAI by subsidising the cost of investigating significant diseases. Where there is a genuine suspicion of an HPAI outbreak, the department will lead the disease investigation and cover the cost of the investigation.
• Further information on the SDI program can be found at Agriculture Victoria SDI program.

Sample collection and diagnosis:

• Agriculture Victoria will advise on samples required, sample transport requirements and any additional activities required.
• Samples requested may include:

                 - oropharyngeal and cloacal swabs -plain, sterile swabs transported in viral transport                       media (VTM)

                 - a range of post-mortem tissues.

• All samples and carcasses must be stored at 4° C prior to submission.

For more information

• On the Significant Disease Investigation program can be found at Agriculture Victoria SDI program
• Agriculture Victoria’s Avian Influenza webpage.
• Bird flu (avian influenza): how to prevent it and stop it spreading - GOV.UK (www.gov.uk)
• Bird flu (avian influenza): housing your birds safely - GOV.UK (www.gov.uk)
• Bird Flu | Bird Flu | CDC
• Avian influenza (bird flu) - DAFF (agriculture.gov.au)
• Avian Influenza | Animal and Plant Health Inspection Service (usda.gov)

Dr Nicole McLaughlin
Agriculture Victoria
Email: nicole.x.mclaughlin@agriculture.vic.gov.au

Feline infections with H5N1 clade 2.3.4.4b have been reported globally since the initial case was identified in France in December 2022. This case involved a cat living near an infected duck farm. Four days after the ducks on the farm were depopulated, the cat was presented to a veterinarian with symptoms of lethargy and mild hyperthermia. The cat's condition deteriorated, with pronounced neurological symptoms and dyspnoea, leading to euthanasia four days later. Since 2023, additional cases have been confirmed in Poland, Italy, the USA, Canada, and South Korea, as shown in Figure 1 below.

Figure 2. Emergency Prevention System (EMPRES) global disease information map (Empres-i (fao.org) accessed 04/09/2024)

The incubation period in cats is brief, with clinical disease often observed 2–3 days after infection. Infections in felines have most commonly been reported in animal shelters, rural settings such as farms, and private lands.

Reported clinical signs include:

• Neurological signs: seizures, ataxia, circling, absent menace reflex, and absent pupillary light response
• Respiratory signs: dyspnoea and oculonasal discharge
• Ocular signs: blindness and chorioretinitis
• Non-specific signs: lethargy, anorexia, pyrexia, weight loss, and death
• The overall case fatality rate among RT-PCR confirmed feline infections, based on a recent systematic review, is estimated at 67%. Subclinical infections have also been reported.

Feline infections are believed to result from bird-to-feline transmission. Infected cats have been associated with  the consumption of dead pigeons, chickens, or other birds including wild birds, as well as contaminated raw chicken meat. Notably, two domestic farm cats in Texas, USA, were reported to have been fed raw colostrum and milk from AIV-infected dairy cattle.

High pathogenicity H5N1 has not been detected anywhere in Australia yet, so there is currently no risk of infection for cats living in Victoria. This could change quickly if or when H5N1.2.3.4.4b arrives. If cases are confirmed in wild or domestic birds, or in other species locally, the following measures are recommended:

• Keep cats indoors to prevent hunting and ingestion of wild birds.
• Avoid feeding raw poultry meat (cooked or commercially available pet foods will still be safe for cats).
• Increase testing of cats with severe respiratory or neurological signs, particularly those with a history of hunting or exposure to avian influenza virus infections during outbreaks among poultry or farm animals.

Testing
Influenza A PCR and further sequencing to determine subtype and pathogenicity:

• Deep pharyngeal and nasal swab in acute stages of the disease 
• Port mortem tissues – brain, lung and liver

Note: Swabs for virology testing should be submitted in Viral Transport Medium (VTM).  If VTM is not available, swabs should be placed in 2ml sterile saline. Do not send dry swabs.

Subsidies may be available for investigation of unusual disease events in small animals through the Significant Disease Investigation (SDI) program, including where there is  unusual manifestation of disease or initial investigation fails to establish a diagnosis. 
To discuss whether your case may be eligible contact your local veterinary officer on 136 186.

Reporting 
Avian influenza is a notifiable disease under the Victorian Livestock Disease Control Act, 1994.
Notifiable disease when suspected by owners, veterinarians or laboratories must be reported within a defined time frame to Agriculture Victoria. High pathogenicity avian influenza is an exotic disease and must be notified immediately. 

To notify call the Emergency Animal Disease Hotline on 1800 675 888 (24 hours a day, every day of the year).

Information on notifiable diseases can be found at Notifiable diseases | Animal diseases | Biosecurity | Agriculture Victoria

Further reference material can be found here:

• https://www.woah.org/en/document/qa-avian-influenza-in-cats/
• Bird Flu in Pets and Other Animals | Bird Flu | CDC

Dr Cathy Bunter
Agriculture Victoria
Email cathy.bunter@agriculture.vic.gov.au

Given the recent high pathogenicity avian influenza (HPAI) outbreak involving multiple poultry properties in southwest Victoria this year, it is important to differentiate between this disease and the disease currently being experienced in USA dairy cattle since March 2024.

The strain of HPAI involved in recent outbreaks in USA dairy cattle is a specific strain called HPAI H5N1 2.3.4.4b. Cattle and a small number of cats have been infected in the USA 2024 cases. Fortunately, there have been very few cases of human disease reported globally usually in humans with close contact with infected birds.

HPAI H5 viruses have never been detected in Australia in wild birds, poultry or livestock.

The two strains of HPAI virus currently detected in the Avian Influenza outbreak in southwest Victoria are H7N3 and H7N9 (Australian lineage) - distinctly different strains of the Influenza A virus causing disease and high mortality limited to poultry.

The disease was first detected in late March 2024 on a dairy farm in Texas. An observant veterinary surgeon visiting the property began thinking there may have been a link between the drop in milk production that some of the cows in the herd were experiencing and the death or seeming disappearance of some of the farm cats who had been drinking the cows’ milk. She sent samples of cows’ milk and histology samples from some of the cats to her pathology colleague in a neighbouring state. The samples tested positive for a bird flu virus never before seen in cattle - Influenza A H5N1.

Whilst the initial HPAI cases in dairy cattle in Texas and Kansas have been confirmed to be via wild bird exposure it is important to note that detections in 12 other US states (Michigan, Idaho, New Mexico, Ohio, North Carolina, South Dakota, Colorado, Minnesota, Wyoming, Iowa, Oklahoma and California; see Table 1) have occurred because of interstate movement of dairy cows. Many of the impacted properties received dairy cattle from one of the first Texas cases prior to the initial confirmation of infection.

Whole genome sequencing (WGS) analysis suggests an initial single spillover event of the virus from wild birds to dairy cattle, most likely occurring in the Texas panhandle in December 2023 when there appears to have been a spillover from a high local environmental load in wild birds and a unique jump into cattle which has thus far only been witnessed in the USA. Further analysis via ongoing genetic testing and epidemiology supports the likelihood that this event has occurred because of a single introduction into dairy cattle (novel host) followed by onward transmission.

To reduce the risk of further spread of the HPAI H5N1 virus via dairy cattle movement, the USDA Animal and Plant Health Inspection Service (APHIS) issued a Federal Order on April 24, 2024, requiring premovement testing for lactating dairy cattle moving interstate and mandatory reporting of positive influenza A test results in livestock.

Older, lactating dairy cows appear more susceptible initially presenting with a significant drop in milk production, loss of appetite and a low-grade fever. More severely affected cows may produce thick, concentrated, colostrum-like milk and rarely respiratory signs including a clear nasal discharge. Animals recover with supportive treatment- there is no report of mortality.

The disease has not been detected in beef cattle. A group of alpacas were detected positive in late May 2024 but there was no recorded mortality.

There is no true indication that the cows are actively shedding the virus, but the USDA have identified spread of the disease between cows within the same herd and spread between dairies associated with cattle movements. It is highly likely that mechanical transmission is occurring via milk droplets in suction cups or on dairy workers clothes or gloves. The spread between dairy farms is likely multi-factorial with spread via cattle movement, vehicles, equipment and humans all implicated

Tests on blood samples, nasal swabs and milk have shown that the most reliable sample with the highest sensitivity is milk. The virus appears to actively replicate in the udder. USDA APHIS have reported that they did find HPAI in a lung tissue sample from a cull dairy cow with no clinical signs, but this appears to be a rare finding.

Pasteurisation kills the virus, so it is recommended that people do not consume raw milk or raw milk products.

Cases among humans in direct contact with infected animals are possible but the current risk to the public remains low.

Up to this point in time there have been four associated cases in USA dairy workers. Three workers experienced a very mild conjunctivitis after accidentally having milk contact their eyes whilst the third human case experienced the more typical symptoms of acute respiratory illness associated with influenza virus infection. US dairy workers have been advised to wear appropriate PPE to reduce the risk of exposure to the virus.

Private practitioners with cases in cattle where clinical signs are consistent with H5N1 and that cannot be explained by other causes, may qualify under the Victorian Significant Disease Investigation (SDI) Program.

Clinically significant signs include:

• Significant drop in milk production
• Anorexia
• Fever
• Thickened, colostrum-like milk
• (Rarely) Respiratory signs with a clear nasal discharge

Samples required:

1. Milk- in a plain, sterile container is the sample of choice
2. Whole blood (EDTA)
3. Serum for serology
4. Nasal swabs

Veterinarians should contact their local district vet or the Emergency Animal Disease hotline on 1800 675 888 to discuss as appropriate. Agriculture Victoria will arrange sample submission where cases meet submission criteria.

AgriBio (the Victorian state laboratory) will perform testing or coordinate sample packaging and consignment for delivery to CSIRO-ACDP, if needed.

For more information about the subsidies for significant disease investigations and reporting, contact Animal Health and Welfare staff at your nearest Agriculture Victoria office or the Customer Service Centre on 136 186.

For further information visit

• Agriculture Victoria avian influenza webpage.
• Avian influenza virus type A (H5N1) in U.S. dairy cattle | American Veterinary Medical Association (avma.org)
• Current H5N1 Bird Flu Situation in Dairy Cows | Bird Flu | CDC

So, what can do NOW?

• Become better informed – find information sources; bookmark key webpages; stay updated on the situation.
• Plan and prepare - put the EAD hotline number in your phone; gather PPE and learn how to ‘don and doff’ safely; put together an H5N1 biosecurity plan for the site (practice, wildlife shelter) and exercise activating it; use the WHA risk mitigation toolboxes as a guide.
• Be alert for signs - of avian influenza in commercial and domestic poultry, and wildlife; report suspected cases.

An outbreak of the HPAI clade 2.3.4.4.b would likely be detected first in wild birds, wild marine mammals, domestic poultry or commercial poultry. Include avian influenza in your differential diagnosis list for any unusual disease outbreaks or mortality events.

• Information for veterinarians - DAFF (agriculture.gov.au)
• Advice for veterinarians and other animal health professionals
• Avian influenza - Information for vets_July 2024.pdf (nsw.gov.au)
• Australian Veterinary Association | Personal Biosecurity (ava.com.au)
• Avian influenza materials for veterinarians (ava.com.au)
• Avian influenza | Poultry diseases | Animal diseases | Biosecurity | Agriculture Victoria

In December 2023, Agriculture Victoria delivered a webinar to vets providing an overview of:

• The Victorian Government Emergency Animal Disease (EAD) Preparedness Program
• Biosecurity threats and current risk status
• What a biosecurity response is like in Victoria
• The potential role of vets in an EAD response
• How Agriculture Victoria will work with vets during the preparedness phase, and any response to an EAD event
• How will vets be engaged/contracted
• Training opportunities

The recording is available at https://rise.articulate.com/share/D31ul9L-0O82LyixDFma36pqfpxJr-K8#/