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England and Wales High Court (Administrative Court) Decisions
You are here: BAILII >> Databases >> England and Wales High Court (Administrative Court) Decisions >> MacDonald, R (On the Application Of) v Secretary of State for Environment, Food And Rural Affairs  EWHC 1783 (Admin) (09 July 2019)
Cite as:  EWHC 1783 (Admin)
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QUEEN'S BENCH DIVISION
Strand, London, WC2A 2LL
B e f o r e :
| THE QUEEN ON THE APPLICATION OF
HELEN JANE MACDONALD
|- and -
|SECRETARY OF STATE FOR ENVIRONMENT, FOOD AND RURAL AFFAIRS
Mr Ned Westaway (instructed by the Government Legal Department) for the Defendant
Hearing date: 6 March 2019
Crown Copyright ©
Mr Justice Murray:
"The Minister may, if he thinks fit, cause to be slaughtered any animal which -
(a) is affected or suspected of being affected with any disease to which this section applies; or
(b) has been exposed to the infection of any such disease." (emphasis added)
Testing of South American camelids for bTB
"A person must not perform a test for tuberculosis on a camelid except with the written consent of the Secretary of State, and a person to whom such consent is given must, as soon as any positive tuberculosis result of such a test is known, report such result to the Secretary of State."
i) Camelid bTB Testing Scenarios Guidance (TN191) ("the Guidance"), of which the version dated July 2018 was included in the hearing bundle; and
ii) Operations Manual: Ancillary Testing in Camelids ("the Operations Manual"), of which the version dated 28 August 2018 was included in the hearing bundle.
i) The Priming Paper noted that the administration of tuberculin to a camelid via a skin test "boosts" the antibody response in a camelid that has been infected with bTB, increasing the sensitivity of a subsequent blood test and thus increasing the chance of identifying an infected camelid.
ii) The Priming Paper surveyed available evidence regarding the effect of priming in connection with blood tests performed on camelids and notes that "[t]he anamnestic boost effect can be observed from 1-2 weeks to several months after tuberculin injection, depending on the type and dose of tuberculin, the host species, stage of infection, format of the antibody test used and other factors".
iii) The Priming Paper recommended a period of 10 to 30 days prior to the blood test for the priming to occur to allow time for the anamnestic boost effect to become established and to ensure that blood samples are taken while the effect is at its peak.
iv) The Priming Paper included the following note of caution, which is relied on by Ms Macdonald:
"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, such as private routine surveillance or pre-post-movement testing. It has not been possible to assess this effect directly in camelids yet, due to lack of samples from skin-tested animals in unrestricted, TB-free herds." (emphasis in original)
v) The Priming Paper qualified that note of caution as follows:
"Even so, analysis of data generated with sera from alpacas on premises with confirmed M. bovis infection in GB (under the conservative assumption/worst-case scenario that all the non-visible-lesion seropositive animals in those herds were false positives) did not suggest that the specificity of the StatPak antibody test was substantially different between animals that undergo prior skin testing and those that do not."
vi) The conclusion of the Priming Paper was:
"In herds with confirmed or with a strong suspicion of M. bovis infection, priming of the antibody TB tests with a tuberculin skin test conducted 10-30 days before blood sampling is essential for optimal performance of those tests, i.e. to maximise the overall sensitivity (probability that an infected animal is classified as positive by the test). For private routine screening or pre-movement testing presumed TB-free herds, skin test priming of the antibody tests is recommended. Although this increases the cost and complexity of testing, it helps identify any undetected infected animals present in those herds without impacting negatively on the test specificity." (emphasis added)
The veterinary risk assessment
"The key conclusion from the probability calculations is that, because of the very high Sp [diagnostic specificity of the test] of the post-import TB test that was applied on the imported alpaca, the PPV [positive predictive value] of the test is also high, i.e. there is a high probability that this animal is truly infected with M. bovis. That is the case even where the assumed (prior) probability of infection with M. bovis in the tested alpaca is considered to be as low as 1% (PPV=74%) or 5% (PPV=94%). The PPV then very quickly reaches 100% once that probability exceeds 5% … ."
"a) Summary of the veterinary impact / consequences
The negative consequences of the imported Enferplex TB-positive alpaca being truly infected with M. bovis and remaining alive in the UK would be the eventual development of clinical TB and potential death of the animal after a period that can range from a few weeks to years depending on the rate of progression of infection. In the meantime, the animal could infect other alpacas in the same herd and in other herds. The potential for spread of infection would be increased by the alleged high breeding value of the alpaca and its use as a stud male. Potential spread to other species, including badgers, cannot be excluded, although this risk may be mitigated by certain biosecurity (badger exclusion) measures adopted on this farm.
b) Summary of likelihood
The likelihood of the imported Enferplex TB-positive alpaca being infected with M. bovis (tuberculosis) is high, as demonstrated by the PPV [positive predictive value] calculations [set out in part 5 (risk assessment) of the Veterinary Risk Assessment]." (emphasis added)
i) to proceed with the slaughter of Geronimo without re-testing "as per existing procedures in the APHA Operations Manual and the terms of the voluntary testing scheme developed by Defra, APHA and the camelid industry";
ii) isolate and defer slaughter pending a re-test at the owner's expense, the fate of the animal then to be determined by the result of re-test undertaken "in-house" by APHA; or
iii) isolate and keep the animal under lifetime movement restrictions (if the owner refuses to re-test according to the required APHA protocol).
He set out the advantages and disadvantages of each option, with an accompanying comment, in a further table.
"In light of this, APHA experts recommend that the Enferplex TB positive alpaca imported from NZ should be retested using the higher-sensitivity protocol routinely applied in all government-funded tests of camelid herds in England with confirmed M. bovis infection (and any tracings thereof). This is in order to minimise the risk of false negative results arising from the moderate sensitivity of the available tests:
1. A skin test with PPDB injection 90 days after the pre-export skin test that was conducted in NZ on 31 July. However, if this interval is considered impractical, it could be shortened to between 60 and 90 days (i.e. skin testing could take place from 29 September 2017);
2. If the suspect animal is deemed a reactor to the skin test, it will be removed straight away as a reactor with compensation;
3. If this skin test is negative, APHA will carry out a serology test at the Starcross Laboratory between 10 and 30 days after the tuberculin injection with the owners' [sic] choice of two tests from: two-antigen Enferplex TB, DPP VetTB and IDEXX ELISA. A positive to either (or both) component test(s) will result in the animal being designated as infected with TB and removed with the payment of compensation." (emphasis in original)
i) "PPDB" means PPD produced from M bovis;
ii) "DPP" stands for Dual Path Platform, a quantitative lateral flow antibody test, supplied by a company called Chembio Diagnostic Systems, Inc. under the brand name "VetTB";
iii) "ELISA" stands for enzyme-linked immunosorbent assay, in this case in the form of a test supplied by IDEXX Laboratories, Inc.
The decision to re-test Geronimo
i) The principal basis of her objection was that the protocol was intended for use when there was a herd breakdown, namely, when there were acknowledged incidences of bTB within the herd. In the letter, Ms Macdonald explained that, in her view, it was highly likely that the Enferplex test was a false positive, in that it had measured Geronimo's antibody response to the skin test injection that he had had in New Zealand 21 days earlier.
ii) The skin test involves the injection of tuberculin. The use of the protocol, which required a further skin test injection, would simply replicate the circumstances in which the first suspect Enferplex result had been obtained. She noted that there was no evidence to determine the safety or consequences of repeated injections of tuberculin in healthy camelids. She referred to the policy of the Swedish government since 2015 that, before an alpaca is exported to Sweden, there must be a serological test of the animal carried out before skin testing in order "to avoid possible interactions". She also referred to (and enclosed a copy of ) a "Camelid Industry" presentation dated 4 September 2015 in which it had been said that the anamnestic response has not been confirmed in alpacas.
iii) Ms Macdonald referred in her letter to an extract from the March 2017 version of the Priming Paper that was substantially the same as the first sentence of the extract that I quoted at [29(iv)] above, raising a "potential concern" about the administration of tuberculin to TB-free animals outside "TB breakdown situations", in other words, "the potential induction of false positive results".
iv) Ms Macdonald made some criticism of ELISA serology testing (of which the Enferplex test is an example), saying that it was "not an exact science". She referred to recent examples of "unexpected results at the 3-antigen level" and gave two examples.
v) Ms Macdonald concluded that a proportionate and balanced approach required that the re-test should take the form of an Enferplex test only, without priming.
i) The Secretary of State first noted that in accordance with the protocol agreed by Defra with the British camelid industry bodies, Geronimo should have been removed and slaughtered after he failed the Enferplex 4-antigen test in August 2017. He considered that he was acting in a proportionate and reasonable manner by agreeing to re-test Geronimo, as a matter of exception from the agreed protocol. He reiterated his belief that the Enferplex 4-antigen test has a high degree of specificity, near 100 per cent, so the likelihood of a false positive test was extremely small.
ii) He did not accept that it was likely that the pre-export skin test three weeks prior to the Enferplex 4-antigen test was the most likely reason for the positive Enferplex test result. He defended the use of priming 10 to 30 days before a serology test by reference to the May 2017 version of the Priming Paper.
iii) The Secretary of State set out his views on the risk of Geronimo having been exposed to bTB in New Zealand, noting that although the bTB situation in New Zealand is "far better" than it is in the United Kingdom, New Zealand was "by no means free from that disease". He added:
"There are still large areas of the country with endemic M. bovis infection in possums (the main wildlife maintenance host), known as 'vector risk' areas, including the North Island [where the farm from which Geronimo was imported is located]. Sporadic bTB breakdowns continue to be recorded even in the low bTB risk ('vector free') areas of NZ in which cattle herds are subjected to routine biennial or less frequent testing."
iv) He noted that he was aware of the policy of the Swedish government, which had a different risk assessment from that of the United Kingdom, and he referred to the position in Norway, which followed the United Kingdom approach.
v) The Secretary of State rebutted the points made by Ms Macdonald about "unexpected results" from Enferplex 3-antigen tests, rejecting the examples given as not relevant.
vi) The Secretary of State considered that Ms Macdonald had not raised any new arguments in her letter of 16 October 2017 that had not been considered by APHA's bTB test and veterinary experts in formulating the protocol set out in the Veterinary Risk Assessment, as communicated to Ms Macdonald on 22 September 2017.
vii) The Secretary of State noted that:
"[I]t is paramount for the credibility of the private TB testing scheme that APHA is seen to apply government disease control policy consistently and fairly to all camelid keepers."
viii) The Secretary of State therefore maintained his position that the re-test protocol, which was intended to stress sensitivity over specificity in order to be confident that a negative test result was truly indicative of Geronimo's being free from M bovis infection before restrictions could be lifted on Geronimo.
"Thank you for sending the data from Geronimo's re-test. I have discussed these with the Enfer team and Neil Watt at SureTest. We note that:-
- There is a response to three antigens, albeit just above cutoff for two of them (Mpb70pep and PPDb) – at this level we expect specificity to be about 97% based on the data held so far.
- The antibody levels and/or numbers of positive antigens have declined, even in the presence of a PPDb boost, which is not suggestive of a progressive disease state
- There has been no response to ESAT6 which is thought to be the most specific antigen for M. bovis.
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."
"If the tests were repeated a third time, and then in the highly unlikely scenario that there was no positive result, our Minister would still not have certainty that the alpaca in question was truly TB-free in light of the two previous positive results."
"Defra is very disappointed to see that Mr Hayton and SureFarm are now casting doubts about the reliability of their own diagnostic test. The upshot of this change of position might well leave Defra with seriously considering withdrawing use of their product as a validated test for camelids because it will become very difficult [to] enforce a positive result in the future whenever a camelid keeper does not like the outcome."
i) No animal (bovine or non-bovine) has ever, since her farm, Nevalea, was established in 1994, tested positive for bTB, despite regular skin testing since 1994, including as part of New Zealand's voluntary bTB testing scheme for camelids, or ever shown to have clinical signs of bTB or, on slaughter, to have been reported as having visible bTB lesions.
ii) Geronimo was bred at Nevalea and kept there until June 2017 when he was removed and placed into quarantine prior to export to the United Kingdom.
iii) Geronimo was used at stud, where he was partnered before export with three female alpacas, all of whom remain at Nevalea, where all tested negative for bTB in August 2018 (along with the rest of the herd). Neither they nor any of their cria (young alpacas) have shown any clinical sign of disease.
i) the Decision is irrational in that the Secretary of State has refused to recognise the scientific and factual evidence to the effect that the test results, in which Geronimo tested positive for bTB, are unreliable; and
ii) in reaching the Decision the Secretary of State has failed to take into account relevant evidence, in particular:
a) the warning from the manufacturer of the Enferplex tests to which Geronimo was subjected that the results are not consistent with the presence of a progressive disease and "should be treated with great caution";
b) the fact that Geronimo, after first testing positive for bTB on 21 August 2017, is still showing no clinical signs of the disease; and
c) the scientific evidence that the "priming" to which Geronimo was subjected could cause false positive results.
i) The Secretary of State is relying on the results of two blood tests, the Enferplex tests conducted on 21 August 2017 and 11 December 2017, each of which was preceded by priming by administration of a skin test using bovine tuberculin. In addition, Geronimo had been tested for bTB using a skin test on 9 September 2016. Accordingly, in the 14 months prior to the second Enferplex test, Geronimo had been primed three times. The repeated priming either caused, or is highly likely to have caused, each of the Enferplex tests to have produced a false positive.
ii) The Secretary of State has irrationally "closed his mind" to the increasing body of evidence that demonstrates compellingly that Geronimo is not infected with bTB and that the Enferplex test results are not reliable due to the repeated priming over a 14-month period. As early as 12 April 2016 at a meeting to discuss tuberculosis in camelids between Defra, APHA, the British Alpaca Society and other camelid industry bodies, together with Synergy Farm Health, camelid industry representatives had raised a concern about whether the administration of two or more skin tests during a six month period was causing a build-up of tuberculin in animals that could cause false positives to further blood tests.
iii) The increasing body of evidence includes the following:
a) The evidence of Ms Walker (which I summarised at  above) excludes any realistic possibility that Geronimo contracted bTB in New Zealand, given that there has not been a confirmed or even suspected case of bTB in any animal on the farm since it was established in1994.
b) Geronimo tested negative for bTB on the skin test conducted in New Zealand on 31 July 2017 prior to his importation, on the skin test in the United Kingdom on 13 November 2017 prior to the second Enferplex test and on the DPP blood test on 11 December 2017.
c) Ms 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.
d) Geronimo has been kept in isolation with four (subsequently five) other alpacas since his arrival in the United Kingdom in August 2017. He has been examined twice by a veterinary surgeon who is an expert in camelids, Mr Robert Broadbent, his most recent examination having been on 31 January 2019. Mr Broadbent's evidence confirms that neither Geronimo nor any of his companion animals is showing any clinical signs of bTB.
e) Seven other alpacas imported into the United Kingdom in the same consignment as Geronimo and owned by another alpaca farmer, Mr K Freivokh, were tested for bTB, using skin and serology tests on 21-24 August 2018 and 6 September 2018, respectively, and found to be negative for bTB.
f) Ms Macdonald's expert witness, Ms Mueller, who is independent, has given evidence to the effect that, 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. Ms Mueller also states 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. The Secretary of State's scientific adviser, Dr Shelley Rhodes, who is employed by the Secretary of State and therefore not independent, has acknowledged that evidence on the effect of priming in camelids is "sparse".
g) Mr Hayton of Synergy Farm Health, which developed the Enferplex test, advised Ms Macdonald in his email of 20 December 2017, following the second Enferplex test administered on 11 December 2017, that there is "very reasonable doubt from a clinical and epidemiological perspective as to whether the animal is a true M. bovis positive" and would "highly recommend caution in interpretation of the results".
iv) The Secretary of State is irrationally refusing to permit or order a further re-test of Geronimo and/or other alpacas (for example, Geronimo's companion animals), when that testing would strengthen further the case that Geronimo is not infected with bTB.
"APHA and Defra emphasise that it is also paramount for the credibility of the private TB testing scheme that APHA is seen to apply government disease control policy consistently and fairly to all camelid keepers."
"Allowing a repeat TB positive animal to remain on farm would set a very unhelpful precedent – not just for other camelid keepers, but also for cattle keepers wanting to challenge their positive TB test results. The private camelid TB test scheme will become more difficult to manage and APHA will encounter more resistance when attempting to remove test positive animals in the future on other farms, thus increasing the costs of delivering the policy."
"I maintain my opinion that we lack the evidence base to categorically say that there is no potential for priming to cause artificially elevated antibody levels which may result in a false-positive reaction to serological tests like Enferplex, whether after single or multiple priming."
i) Notwithstanding the evidence of Ms Walker, the possibility that Geronimo was exposed to bTB in New Zealand cannot be excluded. Nevalea is large farm where alpacas are mixed with cattle and other livestock. The Secretary of State has had regard to the evidence of Ms Walker, as can be seen from the correspondence and as reflected in the Decision. But the Secretary of State is not in a position to interrogate the evidence. As noted in correspondence (for example, the letter dated 23 October 2017 from the Government Legal Department to Olephant), the Secretary of State is concerned that in New Zealand bTB surveillance in relation to alpacas is not as rigorous or systematic as it is in relation to cattle, testing is voluntary and based solely on a skin test with a low sensitivity for camelids (meaning a comparatively high risk of false negatives results). Also "vector risk" (that is, the risk of an alpaca being exposed to bTB through contact with a wild animal) cannot be excluded. Accordingly, the evidence of Ms Walker does not take matters much further.
ii) In relation to the evidence from Mr Broadbent that Geronimo is not yet showing clinical signs of the disease and the evidence of Ms Mueller that if he had been exposed to bTB in New Zealand, then it is highly likely that he would by now be in the advanced stages of the disease, the Secretary of State has had regard to this evidence. He accepts Mr Broadbent's evidence, but he relies on his own scientific advisers for the view that clinical signs of bTB may not manifest themselves in a camelid for years after exposure to the disease. He is not bound to accept Ms Mueller's view, which, in any event, Ms Mueller qualified in her original expert report dated 21 September 2018 by saying:
"There are reports of animals without overt clinical signs having visible TB lesions at post-mortem examination. Therefore, the picture is not as clear-cut as one would like."
iii) The Secretary of State has taken a consistent position in relation to this point regarding Geronimo not yet showing clinical signs of the disease. For example, in the Minister's letter of 13 August 2018 to Ms Macdonald, the Minister said:
"Properly validated serological tests, such as the Enferplex test for camelids, are potentially valuable in that they are able to detect disease in the early stages, before clinical signs appear. Given this, it is possible that Geronimo could live for many months or years without signs of ill health … ."
Discussion and decision
"The court must be astute to avoid the danger of substituting its views for the decision-maker and of contradicting … a conscientious decision-maker acting in good faith with knowledge of all the facts."
"A reviewing court should be very slow to conclude that the expert and experienced decision-maker assigned the task by statute has reached a perverse scientific conclusion."
"… in principle the court should afford a decision-maker an enhanced margin of appreciation in cases, such as the present, involving scientific, technical and predictive assessments."
"Judicial review is not … an appropriate set of proceedings in which to determine … complex scientific questions."
"[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 advisors."
Extract from Part 6 of the Veterinary Risk Assessment, referred to at  of this judgment (footnote added)
Argument Counter-argument 1 The alpaca has originated from a farm in NZ that is asserted to have been free from TB continuously for 22 years This animal comes from a very large mixed alpaca and cattle farm in NZ. Although the bTB situation in NZ is better than in the UK, it is by no means a country officially free from TB and there are still high bTB risk areas with endemic M. bovis infection in possums (wildlife maintenance hose), including the North Island of NZ. Sporadic TB breakdowns in cattle herds continue to occur in low risk areas of NZ subjected to biennial or less frequent testing. Additionally, TB surveillance in NZ alpaca herds is not as systematic and rigorous as it is in cattle or farmed herds because camelids are not included in the national bTB eradication strategy and TB testing is voluntary. 2 The animal was skin tested with negative results shortly before export date The tuberculin skin test is difficult to perform and has a low sensitivity in camelids. Used on its own, it has a very low negative predictive value (i.e. negative skin tests are unreliable). 3 Possible interference of the pre-export skin test with the subsequent post-movement antibody test carried out three weeks after tuberculin injection ('priming' effect) There is no evidence that the anamnestic antibody response observed in TB-infected camelids injected or tested with tuberculin also occurs in TB-free animals. The current scientific evidence and the results of field antibody testing carried out in GB in camelids from unrestricted herds adjoining or co-located with infected cattle herds strongly indicates that a prior injection of bovine tuberculin into the skin does not affect the specificity of the antibody tests. See reference no. 3. 4 The animal suffered a degree of stress from flights all the way from NZ and the pre-export quarantine The stress of travel and quarantine would, if anything, have caused immunosuppression and thus a false negative result would have been more likely than a false positive. 5 Other countries, like Sweden, advise against skin testing camelids in the 30 days before the collection of samples for serological TB testing The veterinary authorities in different countries have different risk appetites. The Swedish authorities are willing to sacrifice sensitivity for specificity. by contrast, the veterinary authorities in other countries like Norway do require serological testing to be completed 10—30 days after skin testing, either in the herd of origin or the herd of destination. 6 Re-testing of Enferplex positives is allowed by APHA That is only the case for camelids that give positive results on the more sensitive (but less specific) interpretation of the test, i.e. the two-antigen Enferplex test. However, this is a different situation, in that we are dealing with an alpaca that has given positive antibody responses to four different M. bovis antigens on the highly specific format of the Enferplex TB test. The animal was declared positive by the private lab, which has not acknowledged any errors in the performance of the test.
Note 1 [Reference no 3 is the May 2017 version of the Priming Paper.] [Back]
Note 1 [Reference no 3 is the May 2017 version of the Priming Paper.] [Back]