Brought to you by: Camelid Industry Presentation on btb Testing 04/09/2015 1

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Elfrieda Holmes
5 years ago
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The information presented here is the culmination of several years work by a team of individuals from the Camelid Industry working with government.

2 The information presented here is the culmination of several years work by a team of individuals from the Camelid Industry working with government. It has involved collaboration between researchers at Defra performing vital research funded by the Camelid Industry and subsequent negotiations between the Industry (BAS, BLS, BCL & BVCS) and Defra in order to find a workable and agreeable solution to testing for bovine TB in camelids. Testing is still not perfect! But there is now a choice available in TB testing that we hope will satisfy the concerns and fears that surrounded testing a few years ago and also provide us with the possibility to further refine and improve the tests that now exist. Together with biosecurity controls, testing should be used to help us minimise the impact of bovine TB in our Camelids and offer a brighter future for our Community. Claire E Whitehead BVM&S MS DACVIM FHEA MRCVS Camelid Veterinary Services Ltd President, British Veterinary Camelid Society 2

3 Please download and print the following two items and have them ready for the presentation: Scenario document click here Flow chart of the scenario document click here 3

5. Testing for Bovine Tuberculosis 9. The immune response 10. Specificity and Sensitivity 12. Tests now available 27. Boosting (Priming) 31. Consultation 32. Camelid btb testing scenario document 36.

4 5. Testing for Bovine Tuberculosis 9. The immune response 10. Specificity and Sensitivity 12. Tests now available 27. Boosting (Priming) 31. Consultation 32. Camelid btb testing scenario document 36. Serial and parallel interpretation 38. Test performance 41. How to carry out voluntary testing 43. Sure Farm Ltd 46. Sure Farm Ltd statistical package 51. Outline of each testing scenario 60. Contiguous contact and spread/back tracing 61. New legislation 62. Biosecurity 63. Questions and Answers 72. Compensation 73. Support for herds in btb breakdown 4

5 5

6 btb is a complex infectious zoonotic disease - which means it can be passed to humans from animals - caused by the bacterium Mycobacterium bovis (M. bovis). btb is found in the UK and in many mainland European countries. btb is a serious disease that cannot be cured easily in animals. It presents a significant risk to animal health and welfare due to an increasing prevalence of the disease in UK cattle herds and other mammalian species, particularly badgers. It is one member of a large family of Mycobacteria; many others are found in the UK, not all causing significant diseases. btb has been declared a notifiable disease which means that if it is found or suspected it is to be reported to your local office of the Animal and Plant Health Agency (APHA). All camelids can contract btb. 6

7 M. bovis grows at varying rates Clinical signs can be observed quickly or take some time to show A camelids immune responses to M. bovis infection are complicated and variable There are lots of other types of mycobacteria which are very similar to M.bovis and contain a large number of similar genes, between 85 and 100% 7

required both to detect as many infected animals as possible (sensitivity) and to minimise the potential for false positives

8 The large number of bacteria that are very similar to M.bovis and the variable nature of the immune response means that the detection by a test of more than one type of antigen is required both to detect as many infected animals as possible (sensitivity) and to minimise the potential for false positives due to cross reactions (specificity). However understanding the optimum combination of these antigens to maximise both sensitivity and specificity is very difficult and varies between species. 8

Antibodies are found in the blood where they help to fight against bacteria by locking onto the specific antigens so that the bodies defences can destroy

9 Antigens are found in and on bacteria and different bacteria have different antigens attached to them. Antigens stimulate the immune system in a camelid to produce antibodies. Antibodies are found in the blood where they help to fight against bacteria by locking onto the specific antigens so that the bodies defences can destroy them. Once the immune system has created an antibody for an antigen whose attack it has survived, it continues to produce antibodies ready to defend against subsequent attacks from that antigen. Tests based on antigens test the blood sample for antibodies relating to these antigens. 9

Sensitivity of a test: Sensitivity is the proportion of true positives (in this case actually having btb) that are detected by the test being used.

10 Sensitivity of a test: Sensitivity is the proportion of true positives (in this case actually having btb) that are detected by the test being used. In other words, a test with 55% sensitivity means that you will detect 55% of all animals that have disease but that you will fail to detect 45% of animals with disease (45% of those detected will have false negative test results). 10

11 Specificity of a test: Specificity is the proportion of true negatives - in this case the proportion of disease-free animals that are correctly identified as being free of disease by the test being used. In other words, a test with 98% specificity means that you will correctly identify 98% of all animals tested that do not have disease but that 2% of healthy animals will incorrectly test positive (2% of those tested will have false positive test results). 11

12 Detection of infected animals is the key to btb eradication programmes. Diagnostic tests can now be used to ascertain individual and herd btb status, CMI Cell Mediated Immune Response. Considered the primary immunological response to Mycobacterium tuberculosis complex infections SICCT - single intradermal comparative cervical tuberculin Used in a btb outbreak (breakdown) and for EU export and commonly called skin test Serology blood tests looking for antibodies. Enferplex IDEXX Cervid-DPP (replaced StatPak) 12

13 While the use of the Single Intradermal Comparative Tuberculin Test (SICTT) is standardised and well described for cattle (European Commission, 2004) the same is not true for camelids. Generally considered excellent for specificity >99% but poor sensitivity (10-20%) 13

The skin test has proved ineffective in camelids later confirmed to have been infected with btb. Why camelids are particularly poor in responding to the skin test is not understood.

14 The skin test has proved ineffective in camelids later confirmed to have been infected with btb. Why camelids are particularly poor in responding to the skin test is not understood. A final important factor in the use of the test in the camelids is the difficulty in administering the test, particularly in thin-skinned younger animals. There are two types of skins tests now performed by APHA: 1. Comparative - (highest specificity) 2. Single Bovine Tuberculin only - (slightly lower specificity but higher sensitivity) 06/09/

The use of serology for the diagnosis of btb has traditionally been considered of no value as antibodymediated (humoral) responses were thought

15 The use of serology for the diagnosis of btb has traditionally been considered of no value as antibodymediated (humoral) responses were thought to: (a) (b) (c) be slow to develop only occur towards the end stage of the disease process not be present at high enough levels for detection 15

16 Research has shown that antibody activity for different antigens develops at different times during the course of infection. This finding, along with the difficulties of differentiating between species discussed previously, means that use of multiple antigens to detect different antibodies is required. A variety of blood tests using multiple antigens have now been developed so it is now possible to diagnose btb in camelids more accurately 16

17 Easy to perform (take blood) and gives an objective result Cost-effective, quick, can be repeated on the same sample and animal without delay, can be performed by any competent appropriately-equipped lab Responses begin early in infection and tend to increase over time and correlate with pathology (post mortem findings) and shedding of bacteria 17

18 Enferplex seven separate antigens in a multiplex ELIZA format Idexx two antigens mixed together in an ELISA format- MPB83 and MPB70. Cervid-DPP (replacing StatPak) has three antigens, MPB83, ESAT-6 and CFP-10. These are mixed together and used in a snap-test style format such that it produces a test result line similar to a pregnancy test kit. ELIZA: The enzyme-linked immunosorbent assay (ELIZA) is a test method that uses antibodies and colour or light change to identify a specific antigen. 18

The Enferplex test is offered by Sure Farm Ltd for all voluntary testing and APHA for all statutory testing.

19 The Enferplex btb blood test is a serological assay which identifies the presence of antibody to Mycobacterium bovis which causes bovine Tuberculosis (btb). The test was developed and is owned by Enfer Scientific and MV Diagnostics. The Enferplex test is offered by Sure Farm Ltd for all voluntary testing and APHA for all statutory testing. It does this by use of individual antigens antigens are parts of the Mycobacterium which generate antibodies which then bind to the antigen. 19

Test well - viewed from above Ag ID Ag 1 Ag 2 Ag 3 Ag 4 Ag 5 Ag 6 Ag 7 Control Blank RLU 18750 45600 51400 33600 1500 31350 2300 2500 300 There are seven different TB antigens in the test and a

20 Test well - viewed from above Ag ID Ag 1 Ag 2 Ag 3 Ag 4 Ag 5 Ag 6 Ag 7 Control Blank RLU There are seven different TB antigens in the test and a sample of each is placed separately as a spots on the surface of the test well. If an antibody to btb is present in the blood sample, then it will bind to the relevant antigen and the resultant reaction produces a luminescent reaction, the light from which can be measured and quantified as a number of Relative Light Units (RLU). 20

21 Thresholds are set for each antigen spot and if the level of light is above this threshold, a positive reaction is deemed to have occurred. A test where only a single antigen spot reacts to the presence of antibody (Fig. 1) does not mean that the animal is definitely infected because this type of response is seen in animals from TB-free herds and countries. A positive reaction that indicates that the animal is infected is considered to have occurred if two or more of the individual antigen spots react to the presence of antibody (Fig. 2 and 3). Figure 1: Schematic example of test where only one antigen is positive (red) this result would be interpreted as negative to bovine tuberculosis Figure 2: Schematic example of test where two antigens are positive this result would be interpreted as positive to bovine tuberculosis at the two antigen level Figure 3: Schematic example of test where four antigens are positive this result would be interpreted as positive to bovine tuberculosis at the four antigen level To read more about the Enferplex test please click here 21

22 Chembio has developed an innovative diagnostic assay based on the patented DPP technology for tuberculosis (TB) in Cervids. The Chembio DPP VetTB Assay for Cervids is a single-use immuno-chromatographic, rapid test for the detection of antibodies to Mycobacterium bovis in serum of elk / red deer, fallow deer and whitetailed deer. The test is used as an aid in the diagnosis of TB in conjunction with other diagnostic methods. (Chembio.com Aug 2015) To read more about the Cervid-DPP test please click here Designed and developed by the American company Chembio, this test works in a similar way to a pregnancy test kit, whereby the serum (taken from a blood sample) is placed into a paper which at one end is coated with the three antigens mixed together (MPB83, ESAT-6 and CFP-10). If one or more of the antibodies to these antigens are present in the serum they migrate towards the antigens and then cross a line on the paper that turns blue, indicating a positive result. 22

23 Designed and developed by IDEXX, the IDEXX M. bovis antibody test is an enzymelinked immunosorbent assay that uses two TB antigens (MPB83 and MPB70) mixed together for the detection of Mycobacterium bovis (M. bovis) antibody in cattle serum and plasma samples. (Idexx.co.uk - Aug 2015) To read more about the IDEXX test please click here ELIZA: The enzyme-linked immunosorbent assay (ELIZA) is a test method that uses antibodies and colour or light change to identify a specific antigen. 23

24 The AHVLA/BAS study in May 2012 suggested that there was no statistical difference in performance between the available serological tests. Click here to download the study Test n/total % Sensitivity 95% Cl n/total % specificity 95% Cl Stat-Pak 35/ / DPP 30/ / Idexx 36/ / Enferplex* 32/ / Note: The column headed 95% CI shows the range of the sensitivity or specificity with a 95% confidence limit. This tables shows a very large range suggesting that some tests could be better or worse than listed. 24

25 At the 2012 camelid btb forum the Enferplex test was chosen as the preferred test for the following reasons: The advantage of the Enferplex, theoretically, over the other serological tests stems from greater specificity due to a quantitative result (computer-detected light levels as a number RLU) as opposed to the qualitative results (colour change and appearance of a line). Each antigen is analysed separately, as opposed to being mixed. Using the four-antigen cut-off, the Enferplex test is considered on current evidence to achieve, when used in isolation, close to 100% specificity. Furthermore, the sensitivity of the test may have been downgraded inadvertently due to the AHVLA/BAS trial design. 25

26 All the tests have the potential to react to some much rarer forms of mycobacterial infection such as M. microti but the Enferplex test based on numerical results, rather than visual changes and relying on 7 antigens, has the potential to be developed to maximise its sensitivity to M.bovis while making it even more specific so that related infections can be ruled out. 26

Boosting or Priming is when a camelid is injected in the skin with bovine tuberculin with the intention of boosting the levels of antibodies in the blood and therefore increasing the sensitivity of

27 Boosting or Priming is when a camelid is injected in the skin with bovine tuberculin with the intention of boosting the levels of antibodies in the blood and therefore increasing the sensitivity of the three blood tests mentioned before. Bovine tuberculin is a Purified Protein Derivative (PPD) which replicates some of the M. bovis antigen properties. After the skin has been injected, specialised immune cells, called memory cells react to the tuberculin and tell the immune system to produce more antibodies. Theoretically, antibodies cannot be made from the injection of tuberculin alone. The camelid must have encountered M.bovis prior to the injection as the retained memory cells that stimulate antibody production are the result of the body s previous encounter with the live M. bovis bacteria. Injecting bovine tuberculin will not give an animal btb. Click here to download DEFRA s response on priming 27

28 There is a reported boosting of antibody response (anamnestic response), when the skin test is utilised prior to antibody blood testing in cattle and llamas. [Rhodes et al, 2012] This response has not been confirmed in alpaca. In a herd of 115 alpacas naturally infected with M. bovis in central Spain, the highest proportion of test-positive alpacas that proved to be culture-positive for M. bovis was found when the skin test was used in parallel with serological testing on samples collected 15 to 30 days after a tuberculin injection was administered. The tuberculin consistently improved the sensitivity of the antibody assay for btb. [Bezos et al. (2013)] Bovine tuberculin is the same injection that is used together with Avian tuberculin when the Single Intradermal Comparative Tuberculin Test (SICTT) is performed. This is the common skin test that is also used in cattle when camelids are exported. 28

29 When a camelid is given this injection for boosting purposes the injection site will only be measured if the injection is part of the skin test that is being carried out at the same time. Boosting is compulsory in some situations in scenario 4 where increased sensitivity is desirable in order to remove disease from a herd. It is also highly recommended to be used for pre export testing as it helps protect the export market for camelids and reduces the risk of btb being given to another country. The main concern over boosting is that there is no data to suggest what effect, if any, boosting has on a btb negative camelid. The science and the feedback from the field strongly indicates that the injection of bovine tuberculin, if done correctly, will not affect the specificity of the three blood tests. Because of the slight uncertainty boosting is voluntary in scenarios 1, 2 and 3 where maximum specificity (low false positives) is desirable. Sure Farm, Enfer and MV Diagnostics are in the process of forming a strategy whereby the theory could be tested in a truly negative herd. 29

30 Cervid-DPP to replace Stat Pak In 2014 AHVLA performed, in it s words, a small study comprised of only 15 test-positive camelids, to assess whether the USDA-approved two-antigen band Cervid-DPP serum antibody test (Chembio, USA) was suitable to replace the Chembio STAT-PAK. The Cervid-DPP has the flexibility to be used either as a qualitative test - using the presence/absence of visible bands for either of the antigen bands (MPB83 and ESAT6/CFP10), or as a quantitative test when individual cassettes are inserted into an electronic DPP Reader. AHVLA now APHA will only use the Cervid-DPP test as a quantitative test. When used as a qualitative test in this study the specificity was 85.4% and the sensitivity 60%. 30

31 In 2014 DEFRA opened a btb deer and camelid consultation. Please click here for a copy of the BAS reply to the consultation. In the same year BVCS undertook a survey of camelid owners to gauge their views on btb testing of camelids. To view the results of the survey please click here. 31

The scenario document is the result of three years work headed up by the btb Small Working Group and has been agreed and signed off by the following organisations: DEFRA (Department of Environment,

32 The scenario document is the result of three years work headed up by the btb Small Working Group and has been agreed and signed off by the following organisations: DEFRA (Department of Environment, Food and Rural Affairs) APHA (Animal and Plant Health Agency) BCL (British Camelids) BLS (British Llama Society) BAS (British Alpaca Society) BVCS (British Veterinary Camelid Society) NFU (National Farmers Union) 32

33 This document forms the foundation from which the camelid btb testing protocols that APHA officers in the field MUST follow. It is detailed in their operations manual. Click here to download the scenario document A flow chart which simplifies the scenario document has been created showing each of the four scenarios are represented singly on each page. Click here to download the flow chart 33

34 1. Surveillance 2. Pre Movement 3. Pre Export 4. btb Breakdown a. Suspicion of btb at post mortem examination. b. Spread tracings. c. Back tracings and contiguous contact. Scenarios that are voluntary and owner pays = 1, 2 and 3 Scenarios that are not voluntary (Statutory) and the government pays = 4 34

35 1. Herd Surveillance 2. Pre Movement 3. Pre Export btb blood testing for all of these activities is 100% voluntary. The two possible blood test combinations available are: a) Enferplex b) Combined IDEXX and Cervid DPP (serial interpretation) 35

36 Some testing both in a voluntary situation (scenarios 1, 2 and 3) and also in some Statutory situations (scenario 4) are carried out using Serial interpretation. Serial interpretation means that both tests used must give a positive result individually in order for the overall result to be positive. For example: Scenario 1 Voluntary herd surveillance testing: Tests used: IDEXX and Cervid DPP Individual Results: IDEXX Positive Cervid DPP Negative Overall Result for Serial Interpretation: Negative Serial interpretation offers higher Specificity (low false positives) but a lower Sensitivity (higher false negatives). 36

37 Only some Statutory situations in scenario 4 are carried out using Parallel interpretation. The reason for this is that Parallel Interpretation offers the greatest sensitivity (lack of false negatives). Parallel interpretation means that only one of the tests used must give a positive result individually in order for the overall result to be positive. For example: Scenario 4 Statutory btb testing to lift movement restriction: Tests used: IDEXX and Cervid DPP Individual Results: IDEXX Positive Cervid DPP Negative Overall Result for Serial Interpretation: Positive Parallel interpretation offers lower Specificity (greater false positives) but a higher Sensitivity (false negatives). 37

38 Enferplex using statistical package: Herds interpreted at 2 and 4 antigen (Ag) level: herds only deemed positive and reported if either positive at 4Ag level or by use of the statistical package if sufficient 2Ag results suggest overwhelming probability of infection at 99.9% Specificity. IDEXX - Cervid DPP running in serial interpretation: Sensitivity 47.6% (CI: not available due to limited data) Specificity 99.5% (CI: ) 38

39 Enferplex 4 antigen interpretation: Sensitivity 55.1% (CI: ) Specificity 99.9% (CI: ) Enferplex 2 antigen interpretation: Sensitivity 66.7% (CI: ) Specificity 96.9% (CI: ) IDEXX - Cervid DPP running in serial interpretation: Sensitivity 40.0% (CI: not available due to limited data) Specificity 99.5% (CI: ) IDEXX - Cervid DPP running in parallel interpretation: Sensitivity 66.7% (CI: not available due to limited data) Specificity 93.0% (CI: ) 39

40 IDEXX - Enferplex 2 antigen interpretation: running in parallel interpretation: Sensitivity 60.0% (CI: not available due to limited data) Specificity 96.7% (CI: ) Cervid DPP - Enferplex 2 antigen interpretation: running in parallel interpretation: Sensitivity 60.0% (CI: not available due to limited data) Specificity 92.0% (CI: ) 40

41 Voluntary btb testing for scenarios 1, 2 and 3 is available to all camelid owners in the UK and Europe. APHA offer a combined IDEXX/Cervid DPP with serial interpretation testing regime. Testing is available via referral to APHA from your vet and has been available since October Sure Farm Ltd offer the Enferplex test using the statistical package. This test has been available since

42 Statutory btb testing for all situations detailed in scenario 4 is administered by APHA. From the 30 th of September 2015 all camelid owners in England will have a choice of what testing regime is used in all situations in scenario 4. APHA officers will still have to carry out a risk and severity assessment when they are notified regarding a farm and scenario 4, however the choice of tests will be the owners decision only. Scotland, Wales and Northern Ireland will run a similar regime but with variants. It is hoped that these countries will soon follow England s regime. The camelid industry has already begun talks with these devolved states regarding this issue. 42

43 43

44 An introduction to the scheme offered by Sure Farm Ltd The scheme has been developed over the last two years in conjunction with DEFRA, APHA, BVCS and representative groups of the Camelid industry. The aim of the scheme is to maintain the integrity and security of the British Camelid Industry health status and thereby increase commercial opportunities for its members including the export of stock to Europe. 44

45 An introduction to the scheme By having animals tested the scheme will seek to clarify the herd or individual animals infection status in relation to bovine TB at the time of testing. It is important to note that this scheme is not an accreditation scheme for btb 45

46 The need for such a statistical approach stems from inherent uncertainty in testing for disease in individual animals. Used for all voluntary scenarios 1, 2 and 3 only. Not used by APHA for scenario 4 btb breakdown testing. At the two antigen level, the specificity of the test is currently estimated as 96.9%. 46

47 For a given herd population size, the package determines the upper bound for the number of animals that could test positive at the two antigen level while the herd would still be considered highly likely to be disease free (because a diseased herd would almost certainly have generated more positives). 47

48 This upper bound will be set such that the threshold will only be breached when the confidence level that the herd is truly diseased is reached (herd level specificity set at 99%): i.e., when we can be very confident that disease truly exists in the herd. 48

49 It also determines the number of animals that need to be tested to achieve suitable confidence of freedom from disease. 49

50 In cases where small numbers of animals are tested, a high degree of confidence that all the animals in the herd are disease-free may not be attainable. In these cases, any positive test will need to be treated as potentially a true positive however Defra do plan to repeat test such animals prior to any final decision. 50

51 All herds have the opportunity to adopt routine surveillance provided by an annual whole herd blood test (in herds over 200 head a statistically derived proportion will be acceptable) utilising the Enferplex antibody test (and interpretation using Sure Farm s statistical package) across the UK and Europe. 51

52 Outline of process Owners veterinary surgeon contacts Sure Farm to notify requirement to test Sure Farm send testing kit to owners veterinary surgeon which includes a form TB184, which is sent to the Secretary of state asking permission to carry out private btb testing. Without this form Sure Farm cannot move forward. Sure Farm facilitate the letter. Blood testing is performed Samples dispatched for testing using the Enferplex test Results are analysed using the statistical package and reported to the owners veterinary surgeon 52

53 It is recommended by DEFRA but not mandatory that participants boost (prime) camelids prior to such testing via the use of 0.1ml of an intra-dermal injection of bovine Tuberculin days to promote an antibody response. Priming may offer up to 10% greater sensitivity to the blood test but it will require a second vet visit. 53

54 The process following outcome of testing If animals test negative, no other action required other than to schedule next test in 12 months. If any animals are found test positive: - Where a herd defined as positive at confidence level agreed with DEFRA on the statistical package, then Sure Farm / client s practice will pass the details to APHA and the clients veterinary surgeon who will be informed to notify their local APHA office that the herd is under suspicion of btb. now see scenario 4 of the scenario document. 54

55 The process following outcome of testing If any animals test inconclusive they should be isolated and retested within 30 days of the original test If the animals were not boosted (primed) at the original test, it is recommended that the inconclusive animals are primed with bovine tuberculin 10 to 30 days ahead of the re-test. If the inconclusive animals are negative on the re-test, the herd will be considered clear and will revert to annual surveillance testing. If any positives are found on the antibody re-test then the herd will be deemed as under suspicion of infection now see scenario 4 of the scenario document. 55

The process for testing and reporting will be the same as for herd testing however with regard to the statistical package as there are only likely to be small numbers of animals being tested, any

56 The process for testing and reporting will be the same as for herd testing however with regard to the statistical package as there are only likely to be small numbers of animals being tested, any positive result is likely to be seen as significant and must be re-tested. Likewise given the small numbers the importance of maximising sensitivity is more germane and as such it is recommended by DEFRA but not mandatory that participants boost animals prior to such testing via use of intra-dermal Tuberculin. 56

57 Owners who are exporting must preexport test camelids using the comparative skin test as required by international legislation. It is highly recommended that owners additionally btb blood test all camelids that are being exported. If btb blood testing does occur it must be performed within 30 days prior to the date of export. It is strongly recommend that blood samples are taken 10 days after the skin test to enable the test to benefit from boosting with tuberculin which increases sensitivity. Obviously careful planning will be required to ensure that there is sufficient time for the samples to be processed prior to the export date. 57

58 58

From the 30 th of September the APHA laboratory in Exeter Starcross will be offering the following btb tests for camelids: Enferplex 2 and 4 antigen interpretation.

59 From the 30 th of September the APHA laboratory in Exeter Starcross will be offering the following btb tests for camelids: Enferplex 2 and 4 antigen interpretation. IDEXX Cervid-DPP Scenario 4 can be divided into three areas: a. Suspicion of btb b. Spread (forward) tracing c. Contiguous contact or Back tracing For details of what tests are applied by APHA in each situation please see the scenario document and flow chart. 59

60 Spread (forward) tracing is when camelids are traced that have been moved away from the holding currently in btb breakdown. Back tracing is when holdings are traced that have moved camelids to the farm currently in btb breakdown. These are potential herds of origin for the disease outbreak. In both cases, APHA carry out a risk assessment and decide on how far in time to investigate movements, therefore this time will vary from case to case. APHA/DEFRA will however endeavour to complete all tracings within 6 months of the confirmed btb breakdown. Contiguous or dangerous contact is when holdings are deemed close in location to a confirmed btb breakdown. Again, APHA will assess the severity of the contact on a case by case basis. 60

61 Please click here for a summary from DEFRA in regard to the law changes in covering APHA s ability to enter a holding and carry out blood testing if btb is suspected. Please click here for the legislative document. 61

62 Blood testing camelids for btb is not enough to reduce the risk of btb on your farm. Biosecurity measures are essential in reducing the risk of the disease arriving and in some cases leaving your holding. Biosecurity appraisals of your holding can easily be performed by you and your vet. To download a biosecurity checklist please click here For a list of all suitable btb disinfectants please click here For a copy of the BAS biosecurity for shows please click here To view some articles on biosecurity and camelids please click here BLS arrangements are similar 62

It has been said that the voluntary test scenarios (surveillance, pre movement and pre export) will inevitably result in false positive results.

63 It has been said that the voluntary test scenarios (surveillance, pre movement and pre export) will inevitably result in false positive results. Although this is technically true the Enferplex test when read at the 4 antigen level has less that 0.1% risk of a false positive. Any 2 or 3 antigen responses at testing (lower specificity) will be recorded and interpreted in conjunction with the highly advanced statistical package which has been approved by DEFRA. This package will minimise the risk of a false positive interpretation being made and raise the Specificity to approximately 99.9%. Although very rare, it is possible that all of the blood tests could detect other extremely harmful Mycobacterial species that are closely related to M. bovis. However, it is hoped that as the Enferplex test is refined, differentiating between these diseases may become easier. 63

64 If a camelid dies or is tested positive to btb and visible lesions (infection sites) are found at the post mortem examination does APHA always sample the lesion in order to grow and effectively prove btb infection? The answer is no. btb in camelids is still considered to be rare and as a result APHA will generally wish to confirm btb infection by culturing the bacteria after visible lesions are found at a post mortem examination. However, M. bovis and other related diseases such as M. microti are extremely hard to grow in the lab and therefore DEFRA and APHA admit that an inconclusive culture result does not mean that the tested camelid was free of btb infection, it simply means that they were unable to grow it. Many samples from cattle infected in btb endemic areas fail to cutlure in the lab. 64

65 If I have a camelid that tests positive to the btb tests, is slaughtered and no visible lesions are found at post mortem, does this mean that the camelid was not infected with btb? Given the nature of the disease and the differing times it takes to grow and manifest itself with in individual camelids it is highly likely that a lesion does exist in the body but the post mortem examination failed to located the lesion that can be as small as a pin head. When skin test positive but lesion negative cattle were reexamined and effectively bacon sliced lesions were found in over 95% of cases. 65

66 It has been said that the camelid societies are giving a misguided message that the voluntary testing regime is designed to stop the spread of TB. Voluntary tb testing is designed to reduce the risk of spreading the disease and give confidence to domestic and international buyers. It is also used to determine one s own herd health status. There is a concern that having voluntary testing will remove or damage the show circuit and mobile/drive by matings. The testing is voluntary so people can use it if they wish. There is no evidence to suggest that voluntary testing will affect shows or matings. It is up to the individual breeder to carry out a risk assessment which may incorporate bio security measures and/or testing options. The current BAS show bio security guidelines are going to be reviewed by the shows and welfare committee in late 2015 and new guidelines may recommend voluntary testing for shows. 66

67 Do we have to boost (prime) camelids when carrying our voluntary btb blood tests? No. The need for boosting with tuberculin is not compulsory for surveillance (scenarios 1, 2 and 3). It is up to the owner to decide. However, DEFRA and APHA do recommend it as there is some evidence to support that it increases the sensitivity of the blood tests by around 10%. The blood tests were developed without the need for boosting and have significantly higher levels of sensitivity than what is currently available from the skin test alone. Boosting would require a second vet visit when carrying out voluntary testing as the camelid would be injected with bovine tuberculin days prior to the blood test. 67

68 Is there a fully agreed protocol in place. From the 30th of September 2015 the protocol for the voluntary and statutory tests will be implemented fully by APHA and DEFRA. The baseline protocol is available and is called the scenario document and flow chart. The APHA field manual is currently being updated by DEFRA and APHA to accurately reflect the scenario document. Are the camelid societies imposing the tests? The BAS, BLS, BCL and BVCS are not imposing the tests but are reacting to the majority of the membership who would like the option of using the best tests if they so wish in the three voluntary scenarios which are: Herd surveillance Pre movement Pre export In scenario 4 (confirmed btb breakdown infection) the tests are imposed by law by APHA. 68

69 Is biosecurity the only way to reduce the risk of btb? Biosecurity measures are fundamental in helping prevent the entry of the disease onto a holding. Voluntary testing offers another string to the bow to preventing the disease either arriving or leaving a holding and it can be used to check the TB status of a herd if the owner has a concern. Voluntary testing also helps prevent TB being exported into Europe and therefore it helps protect our export market. There is a fear that if a positive camelid is found during voluntary testing the owner will be subjected to stringent skin and blood tests by APHA. From the 30 th of September all camelid owners in England who are faced with scenario 4 btb breakdown, will have a choice of what blood tests are used on their camelids. Owners will be able to chose two of the three blood tests offered by APHA which will include the Enferplex test. This choice will give owners the highest rate of specificity and sensitivity and which will greatly lower the risk of false positive results. 69

70 Will I be able to use the Cervid-DPP (previously Stat Pak) and IDEXX tests to test my alpacas voluntarily? Yes. The tests alone are available for all voluntary testing scenarios (1, 2 and 3) by veterinary referral to APHA. DEFRA and APHA are not currently planning on launching their own voluntary btb testing scheme in the same way that Sure Farm Ltd are. 70

71 How can I reduce the risk of getting btb in my herd? There are three areas where you can reduce the risk of into your herd: a. Implement tight biosecurity measures b. Carry out a whole herd blood test to obtain disease status c. Blood test camelids before you move them onto your farm d. Minimise contact with stock outside of your holding 71

72 Currently there is statutory compensation for all camelids that are slaughtered by APHA as a result of btb. The current figure stands at 750 per head in England. The BAS feel that this figure does not represent the true and fair value of alpacas in the UK and subsequently have been working together with The Anderson s Centre to formulate a report detailing fairer alpaca compensation. The BLS are conducting a similar review. This report is almost complete and therefore will be available for members comment shortly. DEFRA have advised the camelid industry that the government is now asking for comment in regard to compensation and that the industry needs to have a report ready for submission by the 20 th of November Click here for the Call for Views Page 72

73 The BAS have a number of contacts that can offer advice and some support to owners affect by btb. For contact details please click here The TB Support and Research Group also offer a support and advice network. For contact details please click here The TB Advisory Group offer advice and support for farmers affected by btb. For contact details please click here For llama support please contact Tim Crowfoot on timcrowfoot@btinternet.com or

74 The detection of btb in camelids and most mammals is an extremely complex task that has many challenges. These new serological blood tests are a huge development in the fight towards btb eradication but at the same time they do have their limitations and are not guaranteed to detect all positive animals (sensitivity). As the tests are used more widely in the camelid industry there will teething problems that one would expect from any new regime. APHA and Sure Farm are determined to work through all issues that may arise in the field and will endeavour to refine and increase the quality of the tests now available. No other livestock sector currently offers voluntary btb testing so this is new territory for England. The camelid industry should be congratulated for working together to come up with a workable and pragmatic regime for voluntary and statutory testing. This new regime signifies the btb fightback within the camelid industry and will be the catalyst for the expansion of the domestic camelid industry and the increase in export sales as buyers grow in confidence to buy from btb tested herds. Thank you for your time 74

75 All of the regional group representatives have been fully briefed on the docucument you have hopefully just read. If you have any questions please feel free to contact your regional group representative or us at the BAS here: or call Sue on Sue will be able to direct your enquiry to the appropriate person. For llama owners: 05/09/

Camelid btb Testing Scenarios

Camelid btb Testing Scenarios Scenario 1: (Voluntary) Camelid owners undertaking voluntary routine btb surveillance as part of a scheme promoted by the industry and endorsed by Defra. Farm veterinarian referral for blood testing package