For many herds, 2015 was the third year of tissue tag testing. During discussions with some of our farmer clients lately, there seemed to be some negativity and disillusionment concerning the BVD eradication scheme as many thought it should now be nearly completed, only to hear we are embarking on another year of tissue tag testing.
It is timely therefore to evaluate how the scheme is progressing, what are the next steps and what are the implications of achieving negative herd status (NHS), concerning which many farmers have received text notifications in recent times. Let’s take a brief look at each of these issues in turn.
Progress – A lot done, more to do
To be fair, Animal Health Ireland faced a mammoth task in tackling BVD. The original seroprevalence (proportion of herds showing evidence of exposure to BVD) in Ireland in both beef and dairy herds was close to 100%. This meant that the task at hand was more difficult than in some other countries where seroprevalence before start-up of their schemes, number of cattle movements per lifetime and cattle density were lower.
These factors all contribute to increased risk. However, one of the most significant remaining risks is the retention of persistently infected animals (PIs). There is really no point in assigning culpability to the Government, the scheme organisers or any other body when farmers continue to retain the most risky animal of all on farms adjacent to clean herds or those who are making a genuine effort to become clear.
It would appear to be undesirable to legislate for mandatory removal of PIs in the absence of a support framework and it is beyond the scope of this article to provide a solution to this problem.
However, the bottom line for all farmers is that all PI calves should be culled as soon as possible after they are identified. Apparently, in 2016, herds that retain PI calves for more than seven weeks will be placed under movement restriction (in and out) by the Department of Agriculture (with the exception of PI animals to slaughter), and it is planned that their neighbours and veterinary practitioners will be notified of the increased risk of infection to their herds.
Before the scheme started, approximately 14,000 PI calves were born each year, with most going undetected, often sold and facilitating the ongoing spread between herds. The programme has been quite successful in that it has led to an annual reduction of approximately one-third in the prevalence of infection at both the herd and animal level.
A further benefit has been in preventing the movement of PI animals, preventing spread of infection to other herds. AHI estimates the annual gain to be approximately €50m to the industry. In conclusion, the scheme has been a worthwhile and successful initiative but not without past and indeed future challenges that need to be addressed to bring the completion date of 2020 closer to realisation.
BVD eradication – next steps
For 2016, tissue tag testing of newborn calves will continue in all herds. Data suggests that this is the most cost-effective approach as our national disease prevalence levels are still high enough to justify it. For the years 2017 and beyond, AHI will have to decide on additional strategies/surveillance and test options that might become viable as the prevalence of PIs falls below certain levels. It is proposed that these will be notified to the BVD implementation group at some point in 2016.
Negative herd status (NHS) –
what does it mean for me?
For the majority of herds, 2015 represents their third year of tissue tag testing. Firstly it is important to understand what exactly qualifies a herd for this status. To be classified an NHS herd, the following criteria must be met:
Completion of a minimum of three years of tissue tag testing on calves born into the herd.Existence of a negative BVD status for every animal currently in the herd (on the basis of either direct or indirect results) – in other words, the calf was tested or its dam was tested to give a result indicative of the calf’s status.Absence of any animal(s) deemed to be persistently infected with BVD virus from the herd in the 12 months preceding the acquisition of NHS.Negative herd status (NHS) –
can I lose it?
NHS can be lost if a farmer becomes embroiled in any of the following situations:
1. Purchasing animals of unknown status (unless tested for BVD after purchase, with a negative result).
2. Failing to conduct any testing requested on animals following notification of suspicion of infection with BVD, or animals with empty or invalid results from initial testing.
A PI animal is detected in the herd. How can I minimise the risk of losing NHS or having a BVD breakdown?
Probably the most important message regarding NHS is that while it indicates recent freedom from disease, it may not indicate freedom tomorrow. In other words, if your herd has achieved NHS, it does not mean that you can become complacent as herd BVD control strategies must remain in place that ensure minimisation of risk.
Don’t remove the successful factors that brought you to this point. Biosecurity measures should be maintained, such as maintaining a closed herd, and if this is not possible, implementation of rigid quarantine and testing protocols prior to allowing brought-in animals access to your herd.
A special case worth mentioning is the purchase of pregnant animals which, while not themselves PI, may be carrying PI calves (commonly called Trojan animals). All in-calf animals should be isolated prior to calving and the calf isolated until the tissue tag result is deemed clear. It is advisable to consult your veterinary practitioner for advice on all of the important aspects of biosecurity. One particular aspect of biosecurity worth a mention is vaccination. Farmers often ask vets if it is OK to give up vaccination now that their herd is clear (NHS). However, though your herd may be clear, you do not know the risks that lurk in the environment – neighbouring herds retaining PIs, purchasing Trojan animals, infected equipment entering your farm, etc. If you are currently vaccinating, it is advisable to continue doing so. As stated earlier, don’t remove controls that could be penny wise and pound foolish.
So what is a worthwhile
vaccination regime?
Unfortunately, there is no “one cap fits all” when it comes to generating a BVD vaccination schedule.
Vaccination timing and choice of vaccine are individual farm decisions that should be guided by your local veterinary practitioner.
There are three BVD vaccines on the market – Bovela BVD, Bovidec and Bovilis BVD. A comparison of some of the salient points of difference between these vaccines is given in the table below.
In general, BVD vaccines are administered prior to service to protect the foetus against transplacental infection during the risk period (the first four months of pregnancy). It is important that you consult your local veterinary practitioner for advice concerning the most appropriate approach to vaccination for your herd.
For many herds, 2015 was the third year of tissue tag testing. During discussions with some of our farmer clients lately, there seemed to be some negativity and disillusionment concerning the BVD eradication scheme as many thought it should now be nearly completed, only to hear we are embarking on another year of tissue tag testing.
It is timely therefore to evaluate how the scheme is progressing, what are the next steps and what are the implications of achieving negative herd status (NHS), concerning which many farmers have received text notifications in recent times. Let’s take a brief look at each of these issues in turn.
Progress – A lot done, more to do
To be fair, Animal Health Ireland faced a mammoth task in tackling BVD. The original seroprevalence (proportion of herds showing evidence of exposure to BVD) in Ireland in both beef and dairy herds was close to 100%. This meant that the task at hand was more difficult than in some other countries where seroprevalence before start-up of their schemes, number of cattle movements per lifetime and cattle density were lower.
These factors all contribute to increased risk. However, one of the most significant remaining risks is the retention of persistently infected animals (PIs). There is really no point in assigning culpability to the Government, the scheme organisers or any other body when farmers continue to retain the most risky animal of all on farms adjacent to clean herds or those who are making a genuine effort to become clear.
It would appear to be undesirable to legislate for mandatory removal of PIs in the absence of a support framework and it is beyond the scope of this article to provide a solution to this problem.
However, the bottom line for all farmers is that all PI calves should be culled as soon as possible after they are identified. Apparently, in 2016, herds that retain PI calves for more than seven weeks will be placed under movement restriction (in and out) by the Department of Agriculture (with the exception of PI animals to slaughter), and it is planned that their neighbours and veterinary practitioners will be notified of the increased risk of infection to their herds.
Before the scheme started, approximately 14,000 PI calves were born each year, with most going undetected, often sold and facilitating the ongoing spread between herds. The programme has been quite successful in that it has led to an annual reduction of approximately one-third in the prevalence of infection at both the herd and animal level.
A further benefit has been in preventing the movement of PI animals, preventing spread of infection to other herds. AHI estimates the annual gain to be approximately €50m to the industry. In conclusion, the scheme has been a worthwhile and successful initiative but not without past and indeed future challenges that need to be addressed to bring the completion date of 2020 closer to realisation.
BVD eradication – next steps
For 2016, tissue tag testing of newborn calves will continue in all herds. Data suggests that this is the most cost-effective approach as our national disease prevalence levels are still high enough to justify it. For the years 2017 and beyond, AHI will have to decide on additional strategies/surveillance and test options that might become viable as the prevalence of PIs falls below certain levels. It is proposed that these will be notified to the BVD implementation group at some point in 2016.
Negative herd status (NHS) –
what does it mean for me?
For the majority of herds, 2015 represents their third year of tissue tag testing. Firstly it is important to understand what exactly qualifies a herd for this status. To be classified an NHS herd, the following criteria must be met:
Completion of a minimum of three years of tissue tag testing on calves born into the herd.Existence of a negative BVD status for every animal currently in the herd (on the basis of either direct or indirect results) – in other words, the calf was tested or its dam was tested to give a result indicative of the calf’s status.Absence of any animal(s) deemed to be persistently infected with BVD virus from the herd in the 12 months preceding the acquisition of NHS.Negative herd status (NHS) –
can I lose it?
NHS can be lost if a farmer becomes embroiled in any of the following situations:
1. Purchasing animals of unknown status (unless tested for BVD after purchase, with a negative result).
2. Failing to conduct any testing requested on animals following notification of suspicion of infection with BVD, or animals with empty or invalid results from initial testing.
A PI animal is detected in the herd. How can I minimise the risk of losing NHS or having a BVD breakdown?
Probably the most important message regarding NHS is that while it indicates recent freedom from disease, it may not indicate freedom tomorrow. In other words, if your herd has achieved NHS, it does not mean that you can become complacent as herd BVD control strategies must remain in place that ensure minimisation of risk.
Don’t remove the successful factors that brought you to this point. Biosecurity measures should be maintained, such as maintaining a closed herd, and if this is not possible, implementation of rigid quarantine and testing protocols prior to allowing brought-in animals access to your herd.
A special case worth mentioning is the purchase of pregnant animals which, while not themselves PI, may be carrying PI calves (commonly called Trojan animals). All in-calf animals should be isolated prior to calving and the calf isolated until the tissue tag result is deemed clear. It is advisable to consult your veterinary practitioner for advice on all of the important aspects of biosecurity. One particular aspect of biosecurity worth a mention is vaccination. Farmers often ask vets if it is OK to give up vaccination now that their herd is clear (NHS). However, though your herd may be clear, you do not know the risks that lurk in the environment – neighbouring herds retaining PIs, purchasing Trojan animals, infected equipment entering your farm, etc. If you are currently vaccinating, it is advisable to continue doing so. As stated earlier, don’t remove controls that could be penny wise and pound foolish.
So what is a worthwhile
vaccination regime?
Unfortunately, there is no “one cap fits all” when it comes to generating a BVD vaccination schedule.
Vaccination timing and choice of vaccine are individual farm decisions that should be guided by your local veterinary practitioner.
There are three BVD vaccines on the market – Bovela BVD, Bovidec and Bovilis BVD. A comparison of some of the salient points of difference between these vaccines is given in the table below.
In general, BVD vaccines are administered prior to service to protect the foetus against transplacental infection during the risk period (the first four months of pregnancy). It is important that you consult your local veterinary practitioner for advice concerning the most appropriate approach to vaccination for your herd.
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