Christensen is concerned about the failure of the industry to control and eradicate bovine tuberculosis (bTB). He says: “There is a combination of factors, but a key challenge is a lack of decent testing of the animals in our herds. The current tests are unable to accurately identify those at an early stage of the disease, before they become infectious, so that they can be removed.
“The other main concern is the lack of a vaccine. I am proactive about herd health and vaccinate my cattle against a range of other diseases, so if there was an effective vaccine for bovine TB I would use it.”
Actiphage® is a new rapid blood or milk test for the mycobacteria that cause bovine TB, Johne’s Disease and human TB. It identifies live mycobacteria and so can distinguish between vaccinated and infected animals, a pre-requisite for a vaccine.
Actiphage is currently available as a non-validated test, licenced by the APHA for use in herds with a chronic breakdown, but PBD Biotech, the company developing Actiphage, has recently raised funds to take it through World Organisation for Animal Health (OIE) validation.
Christensen welcomes this development: “I welcome the diversity of tests coming forward – although I’m no expert, I expect they will all have a role in some capacity – the more we’ve got, the better because then we can tailor the tools to each on-farm situation.”
The official skin test measures the immune response that develops after an animal has been exposed to bTB. This response takes time to develop and it is known that up an average of 20-25% of TB-infected cattle can be missed by one round of skin testing using standard interpretation – leaving a reservoir of disease in the herd.
Actiphage can be used to retest those animals where there has been some reaction to the skin test but not sufficient for them to be classified as positive and culled. Christensen sees promise in this approach.
“We’ve had animals that are not officially inconclusive but there’s been some bovine TB reaction. We’ve used Actiphage to test those animals, and then made a decision about the animals based on those results.
“Actiphage told us that those animals were carrying bTB, so those animals were then removed from the herd.
“However, the problem at the moment is that if you use Actiphage to make the decision to cull then you don’t get any compensation – so we lost the value of the cows.”
The hope within the industry is that through validation by OIE it will be possible to use Actiphage in parallel with other tests, to increase knowledge about the disease.
Christensen continues: “Once Actiphage is accredited by the OIE I presume then that those cattle would be included in the compensation scheme – if a farmer is proactively seeking to reduce disease level in their herd, it is only fair and right that they be compensated for that.
“With better information about the progression of the disease it might be possible to develop a management strategy based on the information that a test can give. For instance, we could proactively remove animals before they became infectious and thus reduce the overall disease pressure in the herd – but all that is yet to be proven, which is why the validation is so important.
“Another unknown is the risk to the calves of cows that have tested positive. An accurate and reliable diagnostic would allow us to test the offspring from TB reactors and see if they were carrying the disease. With more information you could develop a strategy – perhaps to use through targeted application with certain animals to get greater information about their TB status.”
Actiphage can be used as a blood test by a vet but also as a milk test, and Christensen sees considerable potential for using a milk test for quality assurance.
“The primary function of Actiphage requires the vet to take a blood sample, whereas a milk test potentially becomes a parlour-side test, which, as farmers, we can do ourselves – and at that stage it becomes potentially more relevant. We may be able to do it on a more regular basis as a screening test.”
Actiphage can detect all mycobacterial diseases, including Johne’s Disease which has been found to survive the pasteurisation process.
“The Johne’s test interests me,” says Christensen. “It is possible to have animals in the herd that show up as carriers for the disease but never develop clinical signs of Johne’s. I am sceptical about the current Johne’s testing, and more accuracy on that would be helpful.
“It is all about getting greater information to improve the accuracy of decision making, to make better decisions, and to be much more proactive in the way we manage disease, so that we can get on top of infections before they get on top of us.”