Equine Influenza - Communiqué to Queensland Veterinarians
From Ron Glanville, Chief Veterinary Officer, Queensland
We are now two months into the equine influenza response in Queensland and NSW. This has been a very trying time for everyone, yet much has been achieved. Now that we have better knowledge of the way this disease operates within our environment, confirmation of many aspects of the disease’s epidemiology, and reasonable supplies of vaccine it is timely to give you an update on the current situation and where we see the response heading.
Current situation
The map below shows the distribution of infection in eastern Australia since the response commenced on 25 August. The positive thing about this map for Queensland is that EI is still contained within the Red Zone in the SE corner of the State. However it only shows part of the story.
The next map below shows the number of new infected premises reported in the last week. While we are still seeing significant numbers of new infections, they are largely within existing clusters and some clusters such as those around Warwick have largely ‘burnt’ themselves out – the numbers or density of susceptible horses has dropped below that needed to maintain the disease. We do not expect to see any more new IPs at Goondiwindi or Milmerran.
The most significant recent new infection is in the Samford Valley, however we are now able to respond to new “outliers” such as this more aggressively using strategic vaccination – more on that later.
The Estimated Dissemination Rate (EDR) graph above shows that the ratio has fallen just below one for Queensland as a whole and for the Rosewood – Minden cluster, well below for Warwick, but above one for the Tamborine cluster and the Brisbane cluster, that includes Samford and Pine Rivers.
We are aware that some level of under-reporting is likely, influencing these figures, but the trend is probably still valid. Some over-reporting is also possible.
Values of EDR that are less than one on a consistent basis indicate that the epidemic is being brought under control. Values of EDR rising above one indicate that the epidemic is continuing to spread and is not being brought under effective control
Where to from here?
There remains a strong commitment both in Queensland and NSW to eradicate this disease. The EI containment & eradication strategy continues to be based on:
• Movement Controls & Biosecurity
• Vaccination buffer zones
• Strategic Vaccination (infection suppression)
• Surveillance
• Infected Premises Controls
• Information & Education
The most significant development is the availability now of reasonable supplies of ProteqFlu vaccine. The view nationally now is that we should only use this type of vaccine if possible, for the following reasons:
· Efficacy – it produces very good immunity, with protective levels from as early as two weeks after the first dose. The following graph shows typical development of immunity in an average horse. Note that individual horses will vary depending on their individual circumstances. This vaccine produces a much quicker immune response than other EI vaccines. This is a vital attribute in an eradication context.
· It is also possible to distinguish between infection and vaccination through serology. This will assist in the future with ‘proof of freedom” work and movement testing.
Of course, no vaccine is 100% effective and significant challenge may still lead to infection – but with milder signs, less virus produced and shedding for a shorter period. While generally beneficial, these attributes of the virus will have to be managed to ensure that infections do not go unnoticed.
This development now enables us to take a much more aggressive approach to eradication of EI through:
· Vaccination buffer zones. A number of you would already be involved in implementing the large vaccination buffer zone around the Red zone. . This zone exploits areas of generally low horse density and is designed to stem outwards spread should infection occur near its boundary. We have now started on an inner buffer to further isolate areas of the red zone that do not have infection. See maps below and DPI&F website for further details.
· Strategic vaccination. We are now in a position to commence strategic vaccination aimed at stopping spread out from existing clusters or new clusters. For example we have commenced vaccination in the northern part of the Samford Valley and will work back towards to new cluster to limit its spread. We will also be looking for significant populations of non-infected horses near existing clusters to protect them and limit further spread.
· Suppression vaccination. There has now been enough vaccine allocated to vaccinate 30,000 horses within the performance & pleasure horse sector. This will do a number of things, including assisting with implementation of protocols to allow limited horse events to recommence, possible in January. However it will also mean that infection will be significantly suppressed in and around the existing clusters, especially around Minden-Rosewood and Tamborine. We are already seeing a similar effect through vaccination of thoroughbred breeding farms around Beaudesert and Toowoomba.
You will also see vaccine used for what we call “business risk mitigation”, such as vaccination of horses in Victoria to protect the Spring Racing Carnival. These are decisions made at the national level in full consultation with industry.
Influenza viruses do not survive well in the environment when conditions of high temperatures and high relative humidity occur. Human and avian influenza epidemics decline markedly when the season changes. We expect that same to be true of equine influenza now that warmer, more humid weather has arrived. So this is a crucial time in which to attack the epidemic. It is more important than ever to ensure that on-property biosecurity is maximised.
With the expected decline in the epidemic and the imminent availability of vaccine, horse owners would be ill-advised to abandon efforts to protect their horses or, of course, to intentionally expose them to the virus.
How long will this last?
For those of us who have been involved in this response, we have been astounded at how contagious this virus is, and how easily it can be spread. Despite this, there are promising signs and with the more aggressive use of vaccination, we now have an aim to have the epidemic largely under control by Christmas (i.e. an EDR approaching zero). This may be seen as a brave call, and we are likely to get further cases into 2008, but I firmly belief this is achievable if everyone plays their part.
A possible progression of changes to zone status follows.
Current
December 2007
March – April 2008
June – July 2008
We are already working on protocols to allow movements to recommence within these new zones so that industry can start to get back on its feet. This is a difficult balancing act as movement of horses will always bring the risk of disease spread. However it is essential otherwise we will not have an industry, owing to the economic effects of movement restrictions.
So, everyone who is contributing to this response, hang in there. I believe it is one of our greatest ever disease control challenges, but we have shown many times before that disease eradication is achievable with appropriate and sustained effort. The strategy to date has worked. The disease has been contained within a small area of Queensland, defences to outward spread have been shored up, and progress is being made.
Thanks you for all your efforts to date.
Regards
Ron
From Ron Glanville, Chief Veterinary Officer, Queensland
We are now two months into the equine influenza response in Queensland and NSW. This has been a very trying time for everyone, yet much has been achieved. Now that we have better knowledge of the way this disease operates within our environment, confirmation of many aspects of the disease’s epidemiology, and reasonable supplies of vaccine it is timely to give you an update on the current situation and where we see the response heading.
Current situation
The map below shows the distribution of infection in eastern Australia since the response commenced on 25 August. The positive thing about this map for Queensland is that EI is still contained within the Red Zone in the SE corner of the State. However it only shows part of the story.
The next map below shows the number of new infected premises reported in the last week. While we are still seeing significant numbers of new infections, they are largely within existing clusters and some clusters such as those around Warwick have largely ‘burnt’ themselves out – the numbers or density of susceptible horses has dropped below that needed to maintain the disease. We do not expect to see any more new IPs at Goondiwindi or Milmerran.
The most significant recent new infection is in the Samford Valley, however we are now able to respond to new “outliers” such as this more aggressively using strategic vaccination – more on that later.
The Estimated Dissemination Rate (EDR) graph above shows that the ratio has fallen just below one for Queensland as a whole and for the Rosewood – Minden cluster, well below for Warwick, but above one for the Tamborine cluster and the Brisbane cluster, that includes Samford and Pine Rivers.
We are aware that some level of under-reporting is likely, influencing these figures, but the trend is probably still valid. Some over-reporting is also possible.
Values of EDR that are less than one on a consistent basis indicate that the epidemic is being brought under control. Values of EDR rising above one indicate that the epidemic is continuing to spread and is not being brought under effective control
Where to from here?
There remains a strong commitment both in Queensland and NSW to eradicate this disease. The EI containment & eradication strategy continues to be based on:
• Movement Controls & Biosecurity
• Vaccination buffer zones
• Strategic Vaccination (infection suppression)
• Surveillance
• Infected Premises Controls
• Information & Education
The most significant development is the availability now of reasonable supplies of ProteqFlu vaccine. The view nationally now is that we should only use this type of vaccine if possible, for the following reasons:
· Efficacy – it produces very good immunity, with protective levels from as early as two weeks after the first dose. The following graph shows typical development of immunity in an average horse. Note that individual horses will vary depending on their individual circumstances. This vaccine produces a much quicker immune response than other EI vaccines. This is a vital attribute in an eradication context.
· It is also possible to distinguish between infection and vaccination through serology. This will assist in the future with ‘proof of freedom” work and movement testing.
Of course, no vaccine is 100% effective and significant challenge may still lead to infection – but with milder signs, less virus produced and shedding for a shorter period. While generally beneficial, these attributes of the virus will have to be managed to ensure that infections do not go unnoticed.
This development now enables us to take a much more aggressive approach to eradication of EI through:
· Vaccination buffer zones. A number of you would already be involved in implementing the large vaccination buffer zone around the Red zone. . This zone exploits areas of generally low horse density and is designed to stem outwards spread should infection occur near its boundary. We have now started on an inner buffer to further isolate areas of the red zone that do not have infection. See maps below and DPI&F website for further details.
· Strategic vaccination. We are now in a position to commence strategic vaccination aimed at stopping spread out from existing clusters or new clusters. For example we have commenced vaccination in the northern part of the Samford Valley and will work back towards to new cluster to limit its spread. We will also be looking for significant populations of non-infected horses near existing clusters to protect them and limit further spread.
· Suppression vaccination. There has now been enough vaccine allocated to vaccinate 30,000 horses within the performance & pleasure horse sector. This will do a number of things, including assisting with implementation of protocols to allow limited horse events to recommence, possible in January. However it will also mean that infection will be significantly suppressed in and around the existing clusters, especially around Minden-Rosewood and Tamborine. We are already seeing a similar effect through vaccination of thoroughbred breeding farms around Beaudesert and Toowoomba.
You will also see vaccine used for what we call “business risk mitigation”, such as vaccination of horses in Victoria to protect the Spring Racing Carnival. These are decisions made at the national level in full consultation with industry.
Influenza viruses do not survive well in the environment when conditions of high temperatures and high relative humidity occur. Human and avian influenza epidemics decline markedly when the season changes. We expect that same to be true of equine influenza now that warmer, more humid weather has arrived. So this is a crucial time in which to attack the epidemic. It is more important than ever to ensure that on-property biosecurity is maximised.
With the expected decline in the epidemic and the imminent availability of vaccine, horse owners would be ill-advised to abandon efforts to protect their horses or, of course, to intentionally expose them to the virus.
How long will this last?
For those of us who have been involved in this response, we have been astounded at how contagious this virus is, and how easily it can be spread. Despite this, there are promising signs and with the more aggressive use of vaccination, we now have an aim to have the epidemic largely under control by Christmas (i.e. an EDR approaching zero). This may be seen as a brave call, and we are likely to get further cases into 2008, but I firmly belief this is achievable if everyone plays their part.
A possible progression of changes to zone status follows.
Current
December 2007
March – April 2008
June – July 2008
We are already working on protocols to allow movements to recommence within these new zones so that industry can start to get back on its feet. This is a difficult balancing act as movement of horses will always bring the risk of disease spread. However it is essential otherwise we will not have an industry, owing to the economic effects of movement restrictions.
So, everyone who is contributing to this response, hang in there. I believe it is one of our greatest ever disease control challenges, but we have shown many times before that disease eradication is achievable with appropriate and sustained effort. The strategy to date has worked. The disease has been contained within a small area of Queensland, defences to outward spread have been shored up, and progress is being made.
Thanks you for all your efforts to date.
Regards
Ron
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