23 Aug 2021
Thirteen MRCVS and a former member co-author open letter casting doubt on Defra’s approach to handling bTB broadly, and raising reservations on alpaca’s positive diagnosis.
Joshua Silverwood
Job Title
Geronimo the alpaca.
An open letter by a group of senior members of the RCVS expresses “grave concerns” over the Government’s handling of Geronimo the alpaca.
Thirteen members of the RCVS, and one former member, have co-authored an open letter casting serious doubt on Defra’s approach to handling bTB.
The letter was penned by a collection of eminent vets – including Iain McGill, director of the Piron group; Andrew Knight, professor at the University of Winchester; and former vet Paul Torgerson, professor of veterinary epidemiology in Zurich – among others.
The letter reads: “We write as Members of the RCVS to express our grave reservations about the safety of Defra’s ’positive’ bovine tuberculosis (bTB) diagnosis for Geronimo the alpaca, belonging to [RVN] Helen Macdonald.
“It is our professional opinion that the diagnosis in Geronimo’s case is unsafe, and may well represent a false positive, due to the fact that Geronimo had been repeatedly ‘antibody boosted’ (or primed) five times in his lifetime – with four injections of bovine tuberculin and one of avian tuberculin in the run-up to the final Enferplex blood test, which confirmed the ‘positive’ diagnosis of ‘suspicion of disease’.
“One of the developers of the Enferplex test, veterinary surgeon Alastair Hayton, stated1 that Geronimo’s Enferplex results were ‘not suggestive of a progressive disease state’, and that ‘given these observations, and that there is very reasonable doubt from a clinical and epidemiological perspective as to whether the animal is a true M bovis positive, then we would continue to highly recommend caution in interpretation of the results’.
“Defra bTB scientist Ricardo de la Rua Domenech stated2 that: ‘The negative impact of the administration of tuberculin on the specificity of antibody tests in TB-free animals (i.e. the likelihood of false positive results) is a potential concern when antibody tests are used outside TB breakdown situations.’
“In 2020, 199 camelids were killed following a ‘positive’ diagnosis by skin or blood tests involving prior administration of tuberculin3. Of 56 submitted for postmortem examination, only 4 had postmortem evidence of bTB, and successful culture of bTB was only achieved in 7 of the 35 animals where this was attempted.”
The letter continues: “Notwithstanding that bTB cases sometimes have no visible lesions, and that bTB may sometimes be hard to culture, these data indicate a very low specificity.
“Defra bTB scientist Eleanor Brown stated4 to the High Court on Thursday 18 August that a ‘bespoke randomised field trial’ would be needed to evaluate whether repeated injections of tuberculin gave rise to a significantly higher proportion of positive antibody (Enferplex, DPP or IDEXX) test results in TB-free animals than in ‘non-primed’ (non-boosted) TB-free animals from the same herds.
“Dr Brown went on to confirm that ‘APHA did not carry out such a trial in this case’.
“Defra officials have claimed4 that the specificity of Enferplex in alpacas is more than 99%. This may be true for the validated Enferplex test used as a stand-alone test without antibody boosting (priming).
“However, the specificity of Enferplex for alpacas that have been multiply primed with tuberculin is simply unknown and the test is unvalidated when used in this way.”
On Geronimo’s sentence, they say: “Under section 34 of the Animal Health Act 19815, the secretary of state has the power to commute Geronimo’s death sentence to one where he is reserved for observation and treatment, whereby his immune responses may be non-invasively studied by a range of tests, remaining, as he is currently, in isolation at Ms Macdonald’s farm.
“We could learn a great deal from Geronimo were he to be compassionately studied, but very little from his death. We believe Geronimo’s case shines a light on the shortcomings of the current bTB testing policy, and gives an opportunity for a comprehensive review of the bTB testing and control policy, based on science and for the health and well-being of farmers, cattle, alpacas, badgers, the environment and the public.
“Given the mental anguish that Helen Macdonald has had to endure these past four years, and the publicity surrounding the case, we would urge secretary of state for Defra George Eustice and his team to discuss matters with us and Ms Macdonald to find a way out of this impasse.”
