Guest Post | Geronimo: All aboard the express towards scientific reason and compassion.

Guest post by Mark Williams. an independent writer who previously served a decade as a columnist and Editorial Board member of long-running Science magazine.


Geronimo: All aboard the express towards scientific reason and compassion.

The plight of Geronimo the alpaca has captured media attention and gained undeniable public interest. The extensive legal battle, recent international media attention and public outrage centers around his import into the UK and two subsequent positive tests for bovine tuberculosis (bTB).

Animals testing positive for bTB are slaughtered under present UK law yet Helen Macdonald, the veterinary nurse and farm owner responsible for his import, has vigorously challenged those test results claiming they are false-positives, reflect inaccurate science and his proposed slaughter is needless.

The truth is likely that Geronimo’s story has indeed gained widespread attention because he’s a fluffy, goofy-looking character, exuding innocence with an underbite. Crucially, he’s unwittingly surrounded by a compelling David and Goliath narrative featuring a woman fighting a monolithic government to correct a miscarriage of justice.

Yet as many commentators have highlighted, the impact is much wider than one case; from more routine slaughter of cattle, badgers and other animals testing positive for bTB, to the consequent impact on livestock farming and maintaining public confidence in the policy to achieve bTB-free status in the UK. Geronimo’s story doesn’t remove or distract from those issues but instead serves as an important milestone in that scientific, political and public health journey. Regular review of public policy is vital to its success and Geronimo’s gift is the opportunity for public self-reflection, helping us examine whether the current course of action is one we can support in good conscience, whether it is supported by robust science, and whether we are willing to be held accountable for possible decisions resulting from it.

As a long-running dispute, most parties involved seem committed to their opinions. Even if the desire existed, making concessions or deviating from established policy might seem like an unlikely prospect, but the ability to take decisive action to secure an outcome other than Geronimo’s slaughter unquestionably exists. The arguments presented here show why alternatives exist and why avoiding slaughter is the only responsible decision.


Questioning the results.

Broadly summarised, doubt of the positive blood and skin test results in the UK appears to arise from a number of complex, related factors. Geronimo tested positive for bTB using The SureFarm Enferplex test after import to the UK, having been primed with bovine and avian tuberculin on multiple occasions.

The first moment of doubt occurs upon learning Geronimo tested negative for bTB in New Zealand four times shortly prior to entering the UK. A negative result from an overseas test deemed acceptable by the government is a condition of import to the UK. Despite regular testing at the New Zealand farm since being established in 1994, it has seen no cases of bTB. This includes Geronimo’s mates and cria – the alpaca he fathered – continuing to test negative for bTB even after his voyage to the UK. Similarly, no evidence of a bTB outbreak at Geronimo’s current Gloucestershire farm exists either, despite isolating with select animals for his own welfare.

Second, the tests and suitability of the methodology used in testing Geronimo in the UK have been questioned. A High Court judgement1 about the case on 6 March 2019 notes that all parties accept “no test for bTB is infallible”. Significant dispute surrounds the injection of tuberculin to ‘prime’ or ‘boost’ an antibody response prior to conducting the test. Critically examining the claims and science underpinning the performance of tests therefore seems wise.

DEFRA and the UK government argue the Enferplex test is highly sensitive and specific, when primed and unprimed. It is an established, standard method of testing for bTB in cattle yet despite considerable effort from officials asserting this test was suitable for use with Geronimo as an alpaca, its efficacy is distinctly uncertain when used under the conditions in this case.

For instance, DEFRA asserted in a blog post2 on 9th August 2021 that “The accuracy of the Enferplex and the other approved antibody tests for TB in camelids, including alpacas and llamas, were first estimated as part of a peer-reviewed study published in 2012 and were re-evaluated and updated by APHA in March 2018… APHA routinely uses the ‘boosted’ Enferplex and other validated antibody tests in alpacas and llama herds ”.

Despite this, paragraph 84.3.f of the High Court judgement highlights “The Secretary of State’s scientific adviser, Dr Shelley Rhodes…has acknowledged that evidence on the effect of priming in camelids is “sparse”.” Additionally, routinely or repeatedly using a particular methodology in a single case or many cases as DEFRA notes, provides no evidence of its suitability or fitness for use. It is entirely possible to routinely or repeatedly use inappropriate or ineffective methods.

Repeating identical test methodology to seek confirmation of Geronimo’s diagnosis is fundamentally flawed scientific methodology. MacDonald raised an official objection to the repeated use of the same test in a letter dated 16th October 2017, stating it “would simply replicate the circumstances in which the first suspect Enferplex result had been obtained ” (paragraph 45. ii. of the High Court judgement). Consultant Microbiologist Dr David Garner similarly noted in his blog ‘Microbiology Nuts & Bolts’3, “A repeat Enferplex test should not be used as a confirmatory test; it’s bad practice…Using the same test again doesn’t exclude a false positive or cross-reacting test. I would argue that a single positive test, or repeat positives of the same test, does not prove that Geronimo has TB ”.

DEFRA also asserted in the aforementioned post that it is incorrect that “Geronimo only tested positive because he was previously primed with injections of bovine TB bacteria”, proceeding to state “The injection of tuberculin does not induce a false-positive antibody response ”.

Karin Mueller, an independent expert witness testifying for Macdonald cast doubt upon this claim. Paragraph 84.iii.f of the judgement notes her testimony that “it is not possible to say, on the current state of scientific knowledge, that priming by injection with bovine tuberculin does not cause false-positive results, and there is some evidence that it may do so”.

A recent letter to the government written by thirteen veterinarians4, including a former senior official at DEFRA, stated “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.”

Even the test’s creator expressed caution about the positive results. At paragraph 51, the High Court judgement records evidence from Alastair Hayton, a Director at Synergy Farm Health, who assisted in developing the Enferplex test. After reviewing Geronimo’s case, he wrote in an email on 20 December 2017 that “there is very reasonable doubt from a clinical and epidemiological perspective… we would continue to highly recommend caution in interpretation of the results ”.

Importantly, Enferplex bTB tests aren’t scientifically validated for this use. While they may be physically used, their efficacy with a multiple tuberculin priming protocol in alpacas hasn’t been established. As a result, claims of the test’s scientific validity here – that they are highly specific and sensitive – are misleading. Dr Eleanor Brown, DEFRA’s Veterinary Head for TB Policy Advice testified 4 to the High Court on 18th August 2021 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” and that the government “did not carry out such a trial in this case “. She also noted “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 “. Consequently, the results are meaningless without evidence or understanding of how multiple primed tests perform in alpacas generally.

In addition to the multiple negative tests and dubious science surrounding the positive tests, further doubt is created by Geronimo’s absence of symptoms from the disease. Mueller’s testimony at paragraph 84.3.f of the High Court judgement suggests symptoms of the disease should have accelerated were he truly positive. She is recorded stating “if Geronimo had been infected with bTB in New Zealand, it is highly likely that he would by now be in the advanced stages of the disease and would be showing clinical signs of it ”.

Similarly, section 5.2.4 of the July 2020 British Veterinary Association policy statement on bovineTB5 states “Llamas and alpacas are susceptible to M. bovis infection, often developing extensive bTB lesions in their lungs and other organs. Clinical signs are predominantly weight loss with later development of respiratory signs, lethargy, anorexia and death. Clinical signs of the disease tend to appear early allowing for rapid containment of infected animals which will limit the opportunity for the spread of infection further.

Geronimo’s complete absence of symptoms after more than four years and regular veterinary checks cannot be conclusive, but it certainly creates further significant doubt of an already questionable finding.


Assessing risk.

The issue of risk is separate to the issues of test result efficacy and accuracy. Reasonable grounds to doubt the positive bTB test results exist but risk is also critical in determining how UK policy is applied. Paragraph 126 of the High Court judgement states “it is possible that Ms Macdonald is correct that the Enferplex test results are false positives. Nonetheless, the two positive results provide strong evidence, to a high degree of certainty, that he is so
infected. Given the contagious nature of bTB and the devastating effect it can have on other animals, bovine and non-bovine, including the risk to humans, the Secretary of State deems it fit to exercise his power to have Geronimo slaughtered

While the risk Geronimo potentially poses should be clearly evidenced, the opposite has consistently emerged in the legal and scientific records. Each of these claims therefore deserves exploration.

First, a risk of bTB to humans does indeed exist, but is minimal. Dr Ricardo de la Rua-Domenech authored a 2005 research paper6 in the journal ‘Tuberculosis’, in which it is stated “Since 1990, only one case has been documented in the UK of confirmed, indigenous human M. bovis infection recently acquired from an animal source. Therefore, for the overwhelming majority of the population, the risk of contracting M. bovis infection from animals appears to be extremely low.

Dr de la Rua-Domenech is a UK Government Veterinary Adviser and Diplomate of the European College of Veterinary Public Health, who wrote the veterinary risk assessment concerning Geronimo on behalf of the government and additionally testified on behalf of the Secretary of State and DEFRA in the High Court proceedings. It therefore seems reasonable to conclude his advice about the risk of zoonotic transmission of bTB to humans would be accepted by the government. Dr de la Rua-Domenech further explained in the same 2005 paper that “ Nowadays the majority of the 7000 cases of human TB annually reported in the UK are due to M. tuberculosis acquired directly from an infectious person ”. The evidence and stance of the UK government advisor shows that minimal risk exists to humans.

It is possible the situation has changed since 2005, of course, however, current guidance7 from the Health and Safety Executive suggests this is not the case. The guidance states “The current risk of bovine TB in humans in the UK is very low, accounting for less than 1% of all human TB cases”. The government’s perceived public lack of concern for Macdonald’s own health or ability to spread infection reinforces the minimal risk to humans.

Second, bTB is highly infectious to other animals, but the circumstances of Geronimo’s case also mitigate that concern, if it exists. Paragraph 84.iii.c of the High Court judgement highlights Macdonald “has never had any other suspected or confirmed case of bTB on her farm and has excellent biosecurity measures (a fact not disputed by the Secretary of State), including badger-proof fencing”. At paragraph 36, Dr de la Rua-Domenech also confirms the risk of transmission “may be mitigated by certain biosecurity (badger exclusion) measures adopted on this farm”. As a result, the proven history of the farm and it’s biosecurity measures is accepted to protect other animals from bTB infection. The longstanding lack of challenge of this point by the government suggests it concurs these measures are effective. Macdonald has curiously been prohibited from seeking bTB tests for other animals at her farm until after Geronimo’s proposed slaughter. This evidence shows risks to other animals posed by Macdonald’s farm is therefore also minimal.

Third, whilst only a recent concern, no risk of bTB transmission from alpaca to cattle has been documented. In the policy statement from July 2020, the British Veterinary Association wrote “Historically, camelids were seen as spillover, dead-end hosts posing a negligible risk in the bTB epidemiology…. it is important to note there has been no documented spread of the disease from camelids to cattle ”. This evidence shows there is currently no established risk posed to cattle by Geronimo.

Fourth, to be clear about the absence of risk from Gerinomo, paragraph 3 of the High Court judgement very plainly explains “ Geronimo is currently in isolation, and it is common ground that he therefore currently poses no risk to human or animal health.” As such, both the Government and Macdonald accept the absence of risk to humans and other animals, even if Geronimo was infected with bTB.

There is consequently both significant doubt of the positive bTB test results and the acceptance by all parties that even if the positive tests are correct, Geronimo poses no risk of infection to other animals or humans. It seems easy to argue that slaughtering any animal in those circumstances is nonsensical.


The power to decide

In light of dubious test results and no risk to others, the only remaining argument for Geronimo’s slaughter is that it follows an established process. Blind adherence to policy generally leads to blunt and ineffective action, but there is clear advice, precedent and authority to make a decision other than slaughter.

Paragraph 38 of the High Court judgement notes Dr de la Rua-Domenech’s suggested actions in the veterinary risk assessment, written prior to the second positive test. Specifically, it suggests plausible actions include: i) proceeding with Geronimo’s slaughter, ii) isolating Geronimo and deferring slaughter pending a re-test, or iii) isolating and keeping Geronimo under lifetime movement restrictions. It is therefore clear that even to the government’s own advisor, isolating and permanently prohibiting Geronimo’s relocation to a new farm is a possible and acceptable outcome.

Paragraph 116 of the High Court judgement also notes Justice Murray’s recognition that “Judicial review is not … an appropriate set of proceedings in which to determine … complex scientific questions” and that “[On] public health issues which require the evaluation of complex scientific evidence, the national court may and should be slow to interfere with a decision which a responsible decision-maker has reached after consultation with its expert
”. As Secretary of State for Environment, Food and Rural Affairs, George Eustice therefore has ultimate power to decide Geronimo’s fate. Strictly following an established process isn’t required when alternative options and the authority to pursue them exist.

Indeed, paragraph 109 of the High Court judgement recognises “There is nothing improper about the Secretary of State bearing in mind broader policy considerations. The Secretary of State’s approach to this case has not been blindly dictated by the protocols set out in the Guidance and the Operations Manual ”. This publicly demonstrates legal recognition of the ability to make rational, informed decisions outside the normal protocol.

Eustice even firmly established this ability to authorise exceptions to protocol by ordering Geronimo’s second test in order to provide reassurance of the results to Macdonald. Now Eustace can reassure the UK public and those following Geronimo’s case internationally, by demonstrating that Britain is led by reason and compassion, rather than strict adherence to blunt policy and demands for Geronimo’s slaughter which is deeply questioned by the science of the case and expert scientists and veterinarians.

Summarising this approach, the thirteen veterinarians very succinctly wrote in their letter “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 ”.


A complex argument, summarised.

The potential for false-positive results is accepted by all parties. Geronimo tested negative before import and no bTB outbreak has ever been observed at either the UK or the New Zealand farm. This use of the bTB tests and methodology have been identified to be inappropriate, scientifically flawed or leading to questionable results by a number of experts, including the test’s creator. A large group of veterinarians have also urged caution about trusting the allegedly positive results. All parties accept Geronimo poses no risk to humans or other animals, while one of the government’s own advisors previously suggested isolation and restricted movement as an alternative to slaughter.

Exceptions to the routine process have been firmly established both generally and in this case, but the Secretary of State has the unique authority to deviate from this with good cause, which is clearly present here. Slaughtering Geronimo bears a very significant risk of undermining confidence in UK policy, strategy and environmental leadership, whilst professional veterinarians have strongly suggested compassionately studying Geronimo would lead to far greater and wider benefits for science and public health.

There is plainly a civic and moral duty to proceed with caution and compassion by ensuring Geronimo remains alive. Proceeding with his slaughter given the current facts can only reflect blind bloodlust or highly improper use of political power. Geronimo, Macdonald, researchers, businesses and all farmers and livestock who have first-hand experience of bTB are owed the most accurate and reliable information about the disease.


Killing Geronimo is irrational and amoral. Possessing a legal ability to do so, in no way makes it right.