Defra has not been able to conclusively confirm that Geronimo the alpaca had bovine tuberculosis (bTB).
The stud alpaca was propelled into the spotlight after a four year long battle between his owner, Helen MacDonald, and Defra.
Geronimo was euthanised on the Wickwar farm on south Gloucestershire, on August 31.
He had twice tested positive for bTB in 2017 but, since the animal showed no symptoms, Ms Macdonald fought a lengthy legal battle around the accuracy of the tests, that ultimately she lost.
Shortly after midnight (December 9) the Animal and Plant Health Agency (APHA) issued its announcement.
It said that in September, an initial post-mortem examination revealed the presence of TB-like lesions which underwent further testing to determine the source of infection.
However, this morning APHA said it "has confirmed that it was not possible to culture bacteria from tissue samples taken at post-mortem examination, meaning that it will not be possible to carry out Whole Genome Sequencing in order to try to understand how the alpaca caught the disease.
"This does not mean the animal was free of bTB infection because it had previously twice tested positive using highly specific, validated and reliable tests."
Chief veterinary officer Christine Middlemiss said: "This animal tested positive for bovine tuberculosis on two separate occasions using highly specific tests.
"Due to the complexity of the disease, further testing has not enabled us to use Whole Genome Sequencing to try to understand how the animal became infected in the first place.
"Our sympathies remain with all those with animals affected by this terrible disease which devastates farmers’ livelihoods.
"It is important to remember that infected animals can spread the disease to both animals and people before displaying clinical signs, which is why we take action quickly to limit the risk of the disease spreading."
bTB is an infectious disease of cattle and other mammals. It is one of the most significant animal health challenges that England faces - in 2020 alone, more than 27,000 cattle had to be slaughtered to curb its spread.
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