Scottish Bovine Viral Diarrhoea eradication scheme: consultation on phase five responses

Proposal 6 - Notification of herds from which PIs originate

PIs are born infected with BVD, being the calf of a PI dam or a dam that was transiently infected with BVD during pregnancy. Studies show that PIs are born when their mothers are infected in the interval between 18 and 120 days of pregnancy. Thus, a PI can only be born if there was a PI in the herd, or the pregnant female was otherwise exposed to BVD, during the risk period of the pregnancy.

Where a PI is identified on a holding other than the holding of birth or the holding(s) where the risk period of pregnancy took place, restrictions are currently only placed on the holding of residence, even though the holding(s) of pregnancy risk period may have had a BVD risk at the time the PI was developing in utero, and the holding of birth (if different) will have experienced BVD exposure when the PI calf was born. Depending on the testing being carried out, BVD infection on the holding(s) of pregnancy risk period and birth may not have been recognised, posing an on-going risk to those herd(s) and potentially to cattle on neighbouring farms.

We consulted on adding a new requirement that will track PIs back to their herd(s) of pregnancy risk period and birth. We asked: regardless of where and when a confirmed PI is identified, should the holding(s) where the dam was resident during days 18-120 of pregnancy be recognised as BVD "not negative"? And should the same apply to the holding of birth (if different)?

Question 16: Should the holding where the dam was resident on days 18-120 of pregnancy and the holding of birth be automatically given a "not negative" status as soon as the PI is identified? If so, what would we need to consider in order to avoid penalising holdings that have already carried out BVD investigations?

69% of respondents agreed with the proposal to change the status of a holding to "not negative" where a PI has originated. 17% of respondents did not agree with the proposal and 11% respondents were unsure if the status should change to "not negative".

Figure 17: Should the holding where the dam was resident on days 18-120 of pregnancy and the holding of birth be automatically given a "not negative" status as soon as the PI is identified?

Respondents who agreed with this proposal thought it was a sensible decision to take as the source of the infection should be investigated. Where an investigation had already been carried out on the farm of pregnancy, there was strong support for not taking further action. Respondents agreed that the holding of birth should be able to avoid the "not negative" status if a full investigation had been carried out since the movement of the PI from the holding. One respondent suggested that it should be possible to lift the "not negative" status almost immediately where a vet confirms that a full investigation has been carried out, because there should be evidence of it on the ScotEID database.

A more cautious approach was advised by some respondents who advised that the source of infection may not have come from the holding of pregnancy. An in-calf female can be infected during transport or when moving through a mart. 19% of respondents pointed out the complexity of imposing and administering the proposed restrictions accurately and fairly on the holding(s) of pregnancy.

9% of respondents thought that imposing the proposed restrictions on the herd of pregnancy would be unfair. Some respondents who disagreed with the proposal suggested alternative solutions, rather than placing automatic restrictions without first considering the individual circumstances of the herd. One suggested that a notification could go to the holding and the holding's private veterinary surgeon, which should trigger an immediate investigation on the holding without changing the status straight away.

Question 17(a): When tracking a PI back to their herd of birth, should this be restricted to confirmed PIs ( i.e. those that have had a second positive antigen result at least 3 weeks after the first sample)?

70% of respondents supported the proposal that only confirmed PIs should be tracked back to their herd of birth. 23% did not agree and 3% were unsure.

Figure 18: When tracking a PI back to their herd of birth, should this be restricted to confirmed PIs?

The respondents who agreed with this proposal recognised that restrictions based on transient BVD infection would be meaningless and unfair. They thought it would therefore be essential to confirm PI status. Those who gave feedback on the timescale for imposing restrictions on the herd of pregnancy felt that 3-6 weeks should be granted to the keeper of the suspect PI (virus positive animal) before imposing restrictions on the herd of pregnancy. The period of 3-6 weeks would allow confirmatory testing to take place. However, if confirmatory test results were not received within the set time frame, then restrictions on the herd of pregnancy could be triggered.

23% of respondents supported changing the status of the herd of pregnancy to "not negative" on the first antigen positive result. A further 4% supported changing the status to "not negative" for animals that died (or were killed) before a confirmatory re-test could take place. These respondents felt that the lowest risk option would be to act on the initial positive test. Some respondents pointed out that the status would change to "not negative" on suspicion and BVD "negative" if the re-test shows that the animal is not a PI.

Question 17(b): If so, it may result in less confirmatory testing: are you concerned about this?

Views on this proposal were mixed. 31% of respondents were concerned that there might be less confirmatory testing, 36% were not concerned and 20% were not sure.

Figure 19: If tracking a PI back to their herd of birth is restricted to confirmed PIs, are you concerned about less confirmatory testing?

64% respondents provided comments on this question.

Amongst those that were concerned, 14% of respondents felt confirmatory testing should be mandatory due to the potential implications for other herds. One respondent raised a concern that waiting for confirmatory testing would introduce delays, and suggested that a rigid time scale would need to be put in place for a mandatory secondary test. In the absence of a confirmatory test, a number of respondents thought that the animal should be considered a PI, with restrictions imposed on the herd(s) of pregnancy.

Responses from those who were not concerned about lack of confirmatory testing centred on trusting the keeper to "do the right thing" by re-testing and/or removing suspect PIs from their herd. One respondent pointed out the advantage to keepers of a negative confirmatory test is that it will change their herd status from BVD "positive" to "negative", therefore keepers would not be deterred from carrying out confirmatory testing. Another respondent felt that it was better to encourage early removal of PIs.

One respondent who was not concerned about lack of confirmatory testing said that the scheme should concentrate on the prompt removal of PIs from the herd. Other "unconcerned" comments (7% of respondents) pointed out the onerous nature of the proposed restrictions, both for the herd of pregnancy, and for enforcement agencies. One stated "It is unlikely that the lack of backward tracing to date has been a substantial problem therefore we should avoid substantially increasing the burden on herds".

Question 18: When tracking a PI back to their herd of birth, would this be better handled as an advisory matter e.g. by sending a letter to the holding(s) concerned. Possibly copied to their vet?

50% of respondents agreed that tracking a PI back to their herd of birth would be better handled as an advisory matter. 36% did not agree and 11% were unsure if this was the best way to manage the process.

Figure 20: When tracking a PI back to their herd of birth, would this be better handled as an advisory matter?

Respondents who agreed with an advisory approach generally thought that it would be fairer as the holding of birth may have already carried out an investigation. Respondents who commented placed considerable emphasis on using "tracking back" in a proportionate way, given potential uncertainty over the location where infection occurred and the possibility that the herd(s) of pregnancy had undertaken BVD testing and investigation since the BVD animal moved off the farm. There was significant support (27% of respondents) to include the private veterinary surgeon in any advisory correspondence sent to the farmer.

Concerns raised by respondents who did not support this proposal varied. There was concern that advisory letters have little effect and would be ignored by the recipients. Some respondents were keen to make PI tracing mandatory and not treat it as an advisory matter, in order to demonstrate that we are committed to eradicating BVD from Scotland. Respondents were also keen to ensure that there was some follow up action on the herd of birth and wanted mandatory investigation of the source of the BVD infection.