Animals other than cattle are considered to be dead-end hosts and not important in the ongoing spread of the cattle disease.
“There is no scientific evidence that non-cattle species can act as a source of infection to cattle,” Gwyn said.
He expressed concern the matter continues to be raised given it has potential to unnecessarily heighten farmers’ anxiety.
“Our firm view is the transfer of M bovis from non-cattle to cattle is not of material concern,” Gwyn said.
He was responding to a blog posted last week by Lincoln University Professor Keith Woodford that suggested there is extensive overseas evidence M bovis can transfer between species and infect sheep, goats, pigs, deer and even poultry.
Woodford’s blog said the implications had not been considered in the M bovis response.
Gwyn said MPI has, throughout the response, regularly reviewed academic literature regarding the likelihood of other species contracting and spreading the disease.
“We have not found any published information that provides evidence that non-cattle species infected with M bovis can spread the disease.”
MPI has carefully reviewed the blog and the scientific evidence Woodford examined.
“In this instance it seems that Professor Woodford has unfortunately overstated and misconstrued the scientific evidence in this blog entry.
“If Professor Woodford has information he thinks we have not uncovered from our extensive literature review we would be pleased for him to provide it to us.
“We will continue to review and consider any new evidence that comes to light,” Gwyn said.
MPI has acknowledged there have been rare occasions when M bovis has been reported to have caused other animal species to become infected and sometimes sick.
Published case reports include infections in pigs, sheep, goats, deer and chickens.
However, they are rare events that require the non-cattle animals to be exposed to very high amounts of M bovis and also likely needs them to have other reasons for being susceptible, such as having reduced immunity to disease in general because of stress or other factors.
Despite some industry speculation that MPI is pegging back on its eradication decision, Gwyn said it remains focused on eradication.
“Our priority is to contain and eliminate the disease from the places where it is detected.
“Other species are not a priority in this response because there is no evidence that there is a substantial risk of them spreading the disease and hindering the eradication effort,” Gwyn said.
Meantime, a Technical Advisory Group report highlights the variation in opinion within TAG about the likelihood of success of eradication.
Four TAG members now believe, given the number of new infected properties and notices of direction, that logistically and economically eradication is no longer achievable or economically rational.
Six believe eradication is technically achievable given that while the scale of the job has increased substantially, the epidemiology does not appear to have changed.
But significant caveats exist, including concern about the rate of ongoing new infection and serious concerns about ongoing social licence and personal impacts of eradication.
The report says TAG has been cautious about the number of undetected IPs for some time and remains concerned over the likely number of unrecorded young stock movements that might have occurred.
While no new clusters have been found TAG noted there has been no surveillance outside of the trace forward process, beyond bulk milk testing.
As all the IPs have been found as a result of high-risk traces and most other routes of transmission are not being actively pursued there is insufficient data to define whether other transmission routes have occurred.
“The documents provided to TAG do not provide sufficient information for detailed analysis of the epidemiology of the modelling approach.
“Inferences from unvalidated predictive models should be viewed with caution,” the report said.
TAG said it has concern the impacts of an eradication campaign might be greater than the benefits given the concerns over support from within the industry for an ongoing campaign and the fatigue being experienced by farmers and MPI staff.
There are 43 active infected properties including five new sheep and beef farms notified in the past week.
