Sunday, August 12, 2018

Another high profile casualty

Last week, the national press carried the story of a black alpaca called Geronimo, who had failed a blood test for zTB. In our opinion, his owner is fighting the order to slaughter, on some very spurious grounds, not least questioning the validity of the priming skin test.

New owner of this imported animal, Helen Macdonald is quoted as saying that she:
... " voluntarily agreed for Geronimo to have a blood test for TB shortly after he was imported last August. She believes the test came back with a false positive because he had been injected with tuberculin as part of skin tests conducted just before he left New Zealand and also nine months earlier. "
So this alpaca, imported a year ago, was tested in New Zealand, prior to export and previous to that, nine months earlier? No details are available as to exactly what test was used, but if it was just a skin test, then forget it. The Sensitivity of that on alpacas is notoriously bad.

What is also strange about this case, is that the blood test used by Miss. Macdonald on this animal, was our friend, Enferplex -[link] together with a priming skin test. And it was repeated, giving the same result. Positive.

 Now as we explained in that posting, Enferplex with a priming skin test, has a specificity of 97 - 99 per cent. So false positives are very rare. It does however have a low sensitivity (the ability to identify disease) Thus a positive result from Enferplex should be treated with respect.

Geronimo originated in New Zealand, at the Nevalea stud - [link] home to over 700 alpacas, and situated in the Taumarunui region of NZ's North Island. This area is on the edge of a TB hotspot - [link] - Whangamarino - one of the few remaining in New Zealand after years of wildlife control.

New Zealand farmers are keen not to take a foot off that particular pedal, and let incidence of TB rise again. However  Miss Macdonald describes Defra's attitude as 'bullying and intimidation".
In a letter received by Miss Macdonald last Tuesday, Defra’s lawyers gave her seven days to confirm she will have Geronimo put down or they would apply for a warrant to kill the animal. Miss Macdonald last night called for Defra to carry out further tests. She said: ‘If they are sure he has got the disease, it will not hurt them. I have volunteered to pay for it. The problem is they are not listening to anyone because they are arrogant.
This is not the first time alpacas from Gloucestershire have tested positive for zoonotic Tuberculosis. We covered the story of Balthazar - [link] in this 2009 posting. Since then several hundred animals have been slaughtered in the UK and more sensitive tests trialled. Not least the privately funded qPCR test - [link] which screened dead alpacas with great success.

So although we have sympathy for Miss Macdonald, she is on a hiding to nowhere with this fight. As previous owners of alpacas and cattle have discovered.

 More about the alpaca herd and the animal in question, here - [link]