9.1 The evidence presented to the Committee indicated that virtually no one wants to adopt a `do nothing' approach to OJD. That is, there is broad acceptance that the disease should be controlled.1
9.2 Australia is in a peculiarly advantageous position, where the control of a livestock disease is concerned. As a continent it can carry a sufficient population of the livestock involved to provide a large genetic resource. This minimises the need for introduction of new stock. As an island it has exceptionally good barriers to the introduction of disease organisms. The National OJD Program can make use of these advantages and Victoria taps them through this Program.
9.3 A number of strategies to control OJD have been put to the Committee. Broadly they can be described as:
a) reliance on market forces with vendor declaration; 2containment through testing, quarantine, hygiene and zoning;
b) minimisation through on-farm management of infection and expression of the disease; 3quality control and market assurance;
c) eradication through property destocking; 4and
d) eradication through gradual reduction of contamination.
9.4 Adopting one approach to control OJD does not preclude other strategies. Indeed, Dr Kefford, Executive Director, Agriculture, Department of Natural Resources and Environment, advocated the use of a diversity of strategies.5Although determining the distribution of OJD by identifying infected flocks is not strictly an approach to control of the disease, many witnesses to the Inquiry identified this as a necessary step in a control program.
9.5 Specific control techniques that have particular relevance to each of the technical approaches listed above, as well as the determination of distribution and prevalence of OJD, are listed in Table 9.1. In the table the Committee provides an assessment of the adequacy of currently available control techniques to support each approach.
9.6 A technique that is satisfactory for one purpose may not be satisfactory for another.6 For example, in the case of diagnostic tests, if the purpose is to be sure that an animal is infected, then a test that will not return any false positives is required. Even those tests that are stated as 100 per cent specific have a very low risk of returning a false positive.7 This makes a mechanism for verifying results (by repeating the test and/or using more than one type of test) most desirable. If the purpose of the test is to establish freedom from infection, then the test must not return false negatives - that is, it must be very sensitive. It is the risk of false negatives, especially in the first year of infection, that makes establishing freedom from OJD very difficult.8Finding 9.1
An array of technical approaches is feasible. Such approaches are not mutually exclusive but can be used in combination. To ensure that infection does not spread, use of some form of containment approach is required.
9.7 Testing based on trace forward and trace back is an efficient method for identifying infected flocks. However, as the sampling does not have statistical validity, it has limitations as a source of information on the distribution of OJD.9 There is always a possibility that infected flocks will not be selected for testing because the source of infection is a flock that has not been identified.
9.8 Nor can testing based on tracing indicate, within known confidence limits, the prevalence of infected flocks in the State - information that is needed to make rational decisions concerning future control programs. This information can only be provided by random or systematic sampling.10 Abattoir surveillance can be based on a systematic approach to sampling and assess large numbers of animals. Because of this it provides a more reliable method for assessing the distribution of OJD-infected flocks.
9.9 So far abattoir survey in Australia has identified OJD mostly in the localities where it has also been identified by testing flocks at risk.11 These results support the theory that spread of the disease is essentially a product of sheep trading. They also give hope that the main sources of infection have been identified.
Table 9.1: Specific actions/techniques of particular relevance to main technical approach |
||||||||||
|
Action/technique |
Technical approach |
|||||||||
|
Distrib'n and prevalence |
Market forces/ vendor declaration |
Contain-ment |
Minimisa-tion |
Market assurance |
Eradica-tion through destocking |
Eradication through reducing contam'n |
District-based flexible property management |
Exclusion from Victoria |
||
|
Testing and surveillance |
_ |
X |
? |
n/a |
? |
? |
X |
? |
? |
|
|
Flock/sheep identification |
? |
? |
n/a |
n/a |
? |
n/a |
n/a |
_ |
n/a |
|
|
Decontamin-ation |
Quick |
n/a |
n/a |
n/a |
n/a |
n/a |
_ |
n/a |
_ |
n/a |
|
Gradual |
n/a |
n/a |
n/a |
_ |
n/a |
n/a |
? |
? |
n/a |
|
|
Vaccination |
n/a |
n/a |
n/a |
_ |
n/a |
n/a |
_ |
_ |
n/a |
|
|
Containment and exclusion |
At property level |
n/a |
n/a |
? |
n/a |
? |
? |
? |
? |
n/a |
|
Hygiene in sale and transport |
n/a |
n/a |
_ |
n/a |
_ |
_ |
_ |
_ |
_ |
|
|
Reducing prevalence in flock |
Application of good animal husbandry |
n/a |
n/a |
n/a |
? |
n/a |
n/a |
? |
? |
n/a |
|
Treatment |
n/a |
n/a |
n/a |
X |
n/a |
n/a |
X |
X |
n/a |
|
|
Selection for resistance |
n/a |
n/a |
n/a |
X |
n/a |
n/a |
X |
X |
n/a |
|
|
Avoiding reinfection |
Full decontamination |
n/a |
n/a |
n/a |
n/a |
n/a |
_ |
? |
? |
n/a |
|
Alternative stock |
n/a |
n/a |
n/a |
n/a |
_ |
? |
_ |
_ |
n/a |
|
|
Restocking |
n/a |
n/a |
n/a |
n/a |
n/a |
? |
n/a |
? |
? |
|
|
Exclusion of stray or feral animals |
n/a |
n/a |
? |
n/a |
? |
? |
? |
? |
? |
|
|
Control of wash of faeces |
n/a |
n/a |
? |
n/a |
? |
? |
? |
? |
n/a |
|
|
Preserving genetic resource |
Artificial breeding |
n/a |
n/a |
_ |
n/a |
_ |
_ |
_ |
_ |
_ |
|
Identification of uninfected animals |
n/a |
? |
n/a |
n/a |
n/a |
n/a |
? |
? |
n/a |
|
_indicates that available technologies appear adequate; ? indicates that the technology is relevant but may not be adequate at present - more research is needed to provide confidence in its adequacy; X indicates that the technology is inadequate for the approach and there is no reason to believe that it will become adequate in the near future; n/a means that the technology is not relevant to the approach.
9.10 Identifying OJD-infected flocks through abattoir surveillance data requires that the origin of individual sheep can be identified after they are slaughtered and inspected. At the abattoir identification is provided for most lines of sheep by paper work that comes with the truckload of sheep. However, the source of sheep sold through saleyards is not always identified. In addition, there is potential for sheep from different lines to become mixed under the present system.12 From information obtained during its study tour of NSW, the Committee learnt that best use of abattoir survey data will be made when there is a more effective and consistent system for identifying flocks.13 This would ensure the matching of all data collected in the abattoir to the location of the source flocks.
9.11 An improved flock identification system is one challenge that the Committee identified in relation to determining the distribution and prevalence of OJD. The Committee has been led to believe that provision of an adequate identification system is not an insurmountable problem. Another limitation of the test is that it only identifies OJD only after sub-clinical disease is already present and requires the slaughter of the sheep being tested.14
9.12 A further challenge that was raised by Dr D. Picken, Executive Officer, Australian Veterinary Association, is the need for veterinary laboratory facilities to support abattoir surveillance.15 Signs of OJD identified in the abattoir must be confirmed by laboratory examination of the diseased tissues.
Identification of the distribution of infected and OJD-free flocks is a necessary precursor to the successful implementation of most technical approaches to control.
9.13 In assessing the technical aspects of this approach, the Committee assumed no form of regulation other than use of vendor declarations. This is the approach advocated by a number of witnesses to the Inquiry as well as the Yass Rural Lands Protection Board.16
9.14 Representatives of the Australian Beef Association recommended to the Committee that "the notifiable disease status for Johne's disease be removed and that all movement, quarantine and zoning controls be removed".17 These witnesses provided documents describing a program in Wisconsin for management of Johne's disease in cattle - primarily dairy cattle. This depends on a compulsory vendor declaration of the disease status of the flock, with defined levels of assurance - `A' if no animals test positive, `B' if fewer than 5 per cent test positive, `C' if 5 to 15 per cent test positive or the herd is untested. Four per cent of the herd is tested - that is only 16 in a large dairy herd of 400.18 It is then left to the market to determine which animals will change hands.
9.15 The Committee notes that the circumstances of dairy farming in Wisconsin are considerably different from sheep farming in Victoria. Apart from differences in epidemiology between OJD and BJD, Johne's disease is endemic in Wisconsin and the disease is not `notifiable'.19 The latter circumstance severely limits regulations that can be used in that State to control BJD. The former circumstance suggests that the Wisconsin approach is not effective in reducing the prevalence of the disease.
9.16 The Committee identified the primary technical difficulty with reliance on market forces for control of OJD as the inability of current tests to establish freedom from disease, particularly in the short term. Individual farmers cannot be certain of protecting their flocks from infection if they buy stock.20 While the Committee considers that vendor declarations have a useful role, their value is reduced because of the long time between initial infection and exhibition of symptoms or even a definite blood response.
9.17 The Committee also identified a more human issue with reliance on market forces - that is, the tendency for people to neglect precautions that do not appear to be of immediate urgency to them. An example of this has been identified in relation to Johne's disease in dairy cattle. Bovine Johne's disease has been present in the Victorian dairy herd for many decades and recommendations with regard to its management have been distributed for years.21 A survey undertaken in 1996 to determine the extent to which recommendations were followed showed that Johne's disease was rated as the second most serious disease in importance to dairy farmers. 22 In spite of this, there was a very low level of compliance with recommended control measures, especially among those who had had no direct involvement with the disease.
9.18 Dr R. Gee, keynote speaker at the Sixth International Colloquium on Paratuberculosis concluded that "whether effective intervention will be undertaken by individuals without government action is debatable". 23Dr Prowse concluded that, without an integrated control program, in five to ten years it is likely that most Victorian flocks will have OJD.24In summary, the evidence presented to the Committee suggests that an approach that relies solely on market forces to control OJD is not likely to succeed. However, that does not mean that the market, with some form of vendor declaration, could not have a useful role to play in combination with other strategies. This is the basis of the Market Assurance Program discussed below.
9.19 The Committee received evidence from several eminent researchers that quarantine of infected flocks is necessary to prevent spread of OJD.25 Similar restrictions to trade from suspect properties appear necessary if OJD is to be contained. This is the basis of the National OJD Program.26
9.20 Two broad areas of concern in relation to technical considerations have become evident. The first is ensuring that no infection spreads from the contaminated, or potentially contaminated, property; the second is providing some mechanism by which normal trading can be resumed.
9.21 Containment measures described above, to prevent straying of stock and water transport of faeces, are likely to prove adequate for many situations. The Committee observed how such measures can be tailored to particular farm circumstances during its inspection tours.27 For other properties this might prove more difficult, especially where extensive flooding and overland flow of water is common or existing fences are old.28There appears to be no technical impediment to ensuring that hygiene is adequate to prevent spread of OJD through the transport of sheep, saleyards or the disposal of abattoir waste. The issue is rather one of regulation and enforcement.
9.22 Evidence was presented to the Committee that preventing feral animals from moving across property boundaries could be a more difficult matter.29 Feral goats are a potential threat to containment. 30 More information appears to be needed to determine if feral animals are likely to undermine a policy of containment anywhere in Victoria
9.23 The more vexed issue is that of providing owners of properties under quarantine with a way of returning to normal trading.31 Quarantine can become permanent if there is no way to eradicate the disease or determine that flocks are `clean'.32 Sheep can be sold for slaughter. Destocking may be used to eradicate the disease, but it eradicates the flock as well. For a farmer who does not wish to destock, current tests offer no way to demonstrate conclusively that a whole flock is free of OJD, even if steps have been taken to remove infected animals and decontaminate pastures33 Abattoir surveillance with flock identification offers some promise of improving this situation
9.24 It could be argued that, if a risk-management approach is going to be used for other aspects of OJD control (for example, market assurance), there is no technical reason why it should not apply to release of flocks from quarantine. In essence this is the approach used with `test-and-cull' for bovine Johne's disease.34 A long period of testing would be required. In the meantime, for a valuable flock, artificial breeding could be used to sell genetic material from the flock, or to introduce it to the flock.
9.25 Mechanisms are in place to clear flocks identified through tracing or as neighbours of infected flocks, from suspicion. According to Dr B. Kefford:
These use a risk-management framework.. At the outset of the program, a surveillance period of at least three years was adopted and applied to all suspect flocks, which meant many flocks were affected by the surveillance program for up to four years. In 1999, a risk-based approach was proposed by Victoria and agreed nationally. That allowed investigations to be tailored to the circumstances, meaning that some flocks with a low risk of being infected could be cleared from suspicion after one test. It allowed a rapid clearance of many flocks under suspicion, and consequent benefits to the people involved.35As little as one test is used to clear flocks from suspicion. Given that current tests cannot detect early infection, where there is reason to believe that possible infection in a flock would be recent, it seems to the Committee that more one test would be needed.
9.26 In summary, deficiencies in present tests present problems for releasing flocks from quarantine or suspicion. It appears that prolonged testing can overcome these difficulties and better tests in the future will also help to make the approach more satisfactory. It is technically possible to prevent the spread of infection through straying of livestock, though it can be difficult. The potential for most feral or wild animals to cause breakdown of quarantine appears to be low, but there is some apparent risk with feral goats. This could be removed by effective control of the goats. This could be difficult in rugged areas. Preventing the movement of contaminated faeces with overland flow of water could also be difficult in some localities. Containment of OJD through quarantine is probably practical in most locations, but return to normal trade presents problems.
9.27 Under the National OJD Program provision is made for zoning of large areas on the basis of the prevalence of OJD.36 Rules defined in the Standard Definitions and Rules are used to restrict movement of sheep between, and within, zones in such a way as to reduce the risk of spreading OJD from regions of high prevalence to regions of low prevalence. Zoning is considered to be an appropriate way to contain a disease which, as with OJD, is concentrated in limited geographic areas.37
9.28 During its inspection tours of NSW and Victoria the Committee received considerable evidence concerning methods used to minimise the impacts of OJD on production. Both NSW Agriculture and the Department of Natural Resources and Environment currently provide affected farmers with information on how infected flocks can be managed to minimise infection and impacts of the disease.38 A booklet prepared by the Goulburn Rural Lands Protection Board provides guidelines on property management that has been useful in minimising the disease impacts of OJD at the property level, at least in the short term.39For some properties in regions in NSW where OJD is endemic, NSW Agriculture suggests that:
Maintaining the present stock and learning to live with Johne's disease may be the most economically sound option for [some producers] in the short term - provided [they] can control losses from Johne's disease and stop the likelihood of the disease spreading to other flocks ... The importance of co-operation between neighbouring farmers and the value of a group approach to ensure no spread of disease is emphasised by NSW Agriculture. 40From this statement it is evident that a minimisation approach should be combined with a containment approach to prevent spread of OJD.
9.29 As far as the minimisation approach is concerned, the Committee was told of properties, in both Victoria and NSW, where a combination of management activities were being used to minimise the spread and expression of OJD on the property. At least in the short term these appear to be meeting their objectives. What their long-term success will be cannot be determined at this stage. Approaches included:
a) minimising contamination of pastures;
b) reducing exposure of most susceptible animals;
c) removing sheep most likely to be infected; and
d) minimising stress.
9.30 A video called Surviving Ovine Johne's Disease has been produced by NSW Agriculture, describing the experience of one farmer who had successfully reduced losses from OJD by such practices. Some of the techniques used by this farmer were only possible because the property has two shearing sheds, which allowed him to run his property effectively as two enterprises.
9.31 On a Goulburn property inspected by the Committee the owner was able to make use of a period of cropping to decontaminate individual paddocks before introducing lambs on to them for fattening. The locality is suitable for combining prime-lamb, wool and crop enterprises. This allows the owner the flexibility to incorporate a number of practices aimed at minimising pasture contamination into his farming system. He is careful to ensure that his sheep are not put under any stress from poor nutrition or parasites.41Dr J. W. McDonald, private veterinary consultant and former District Veterinary Officer with the Department of Natural Resources and Environment, considers that OJD can be contained, particularly with the assistance of vaccines.42 Measures such as quarantine, voluntary destocking, safe paddocks and vaccination can be combined to contain and minimise the disease.
9.32 NSW Agriculture emphasised the importance of taking account of the characteristics of the individual farm when developing a property-based plan to manage OJD. The Department provides staff to assist farmers in developing such plans.43
9.33 Evidence from a number of producers in Victoria made it clear to the Committee that lack of alternative enterprises, such as cropping, would limit opportunities for minimising pasture contamination while generating an income. Good husbandry practices to minimise stress on livestock can be used on any property.
9.34 No practicable treatment is available for OJD, nor does there appear much prospect of breeding for disease resistance. However, after initial trials, vaccines are likely to be available in the near future. As vaccines are improved, they could provide a means of minimising the impacts of OJD in more heavily infected flocks and, as a consequence, of reducing pasture contamination.
9.35 Techniques on which to base management to reduce losses are being refined through current research under the National OJD Program.44
9.36 In spite of many optimistic reports, the Committee is mindful that farmers attempting to minimise the impacts of OJD have had only a few years experience. It is a characteristic of the disease that it is both slow spreading and can be very variable in its impact. In Victoria, as in NSW, losses have been found to increase with time.45 It cannot be assumed, at this stage, that good management can always prevent such an increase.
Use of a minimisation approach commits the farmer to ongoing management of the disease. It is not applicable, at least in the short term, for farmers aiming at eradication.
9.37 As the Committee described above, some form of vendor declaration concerning the disease status of a flock can be used to provide purchasers with a level of confidence in the stock that they are buying. This allows market forces to play a role in the control of the disease and places responsibility on purchasers to control the spread of OJD. Several experts in animal disease control consider this to be more desirable than placing all responsibility on the owners of infected flocks.46
9.38 Dr L. Denholm, Co-ordinator of the National Abattoir Surveillance Program, explained that quality assurance, as part of a risk-management approach (rather than risk elimination), is becoming more fashionable. However, "while the effectiveness of ... quality assurance programs has been proven for certain diseases such as ovine brucellosis in the stud sheep industry, their general application is less certain, particularly in commercial flocks" where value of individual animals is low or where it is difficult to certify an animal as disease free.47 For any form of vendor declaration or market assurance to be effective, certain technical requirements must be met.
9.39 There are now three levels of assurance offered under the National OJD Program.48 These relate to the level of assurance each gives of freedom from infection. From highest to lowest they are:
a) Vendor Declaration;
b) the Enhanced Vendor Declaration of OJD Status; and
c) the Market Assurance Program.
9.40 The `Vendor Declaration' is a signed statement that, to the best of the vendor's knowledge, there is no reason to suspect that OJD is present in the flock.49 The `Enhanced Vendor Declaration' involves a signed declaration supported by limited testing. Testing may be repeated at yearly intervals to improve confidence that the flock is free of infection.
9.41 The Market Assurance Program, or SheepMAP, a voluntary audited program, requires management to exclude the disease and to have testing by approved veterinarians of a large sample of adult sheep at two-yearly intervals.50 These sheep are identified, usually with an ear tag. The Program is based on negative blood tests of a sample of adult sheep (two years and older) combined with prudent flock management to minimise the risk of introducing infection. This includes restrictions on the introduction of new sheep to the property. The cost of the biennial testing is in the order of $3,000-$4,000 per flock where 400-500 sheep are tested.51 Restrictions on trade required to meet the requirements of `prudent flock management' could add to costs, as they would limit stock purchases and could effectively disallow such enterprises as prime-lamb production that require regular purchase of store sheep.52 There are three levels of MAP - MN1 where the flock has been tested once, MN2 where the flock has been tested at the same standard for a second time, and MN3 where a third test has been applied.53 MN1 status can be maintained by limited testing every two years.
9.42 Prowse considers that the SheepMAP, though it "does not provide absolute certainty that the flock is free of OJD - that is not possible - ... gives ... a high and known level of probability that infection is not present".54Associate Professor Vizard was more cautious concerning the level of assurance provided by SheepMAP.55 According to him:
The market assurance program provides a level of assurance, but people should realise what that level of assurance is ... We can test a certain number of sheep and say there is a 95 per cent chance that the prevalence of disease in this property is 2 per cent or less, which provides some comfort to people ... However, that level of assurance is not good enough to run an eradication program.
9.43 The limitations of current tests have been one of the issues most frequently raised with the Committee in relation to market assurance for OJD. Discovery of OJD in flocks that have earlier achieved MN1 status supports this concern.56 In light of the deficiencies in tests, particularly for recently infected flocks, several witnesses questioned the value of the Program.57Reliable flock identification is also necessary for any quality-control program. As indicated above, this is the subject of current developments. As it is in the interests of those involved that identification should be maintained, this is not likely to be a significant problem. Artificial breeding can allow introduction of new genetic material without compromising the program.
9.44 Exclusion of any source of infection, be it stray stock, feral animals or faeces washed on to the property or carried on trucks, must be avoided. The Committee has identified that this could present some problems. The exclusion of stray stock can be particularly difficult for most farmers. Exclusion of feral animals or flood-borne faeces will be a particular challenge on some properties.
9.45 Cost of testing may restrict application of SheepMAP to stud flocks, while any less-rigorous program appears to the Committee to offer very limited assurance to purchasers.58 At the same time, if all stud flocks where to be tested to MN3 status, this should offer the industry a considerable improvement in the potential to restrict the spread of OJD.
9.46 Eradication can be at the national, State, regional, district or farm level. Whatever the scale, the evidence presented to the Committee indicated that the key is breaking the infection cycle.59According to Dr I. D. Wardrop, long-time consultant in the livestock industry, technical requirements for a sound disease control/eradication program are:
a) Well-understood epidemiology - the basis for identifying where the infection cycle can be broken;
b) accurate diagnostic tests - a necessary prerequisite to removing sources of infection; and
c) management techniques, drugs or vaccines that will lead to either a cure or prevent spread of infection to clean animals.60Additional requirements raised in many submissions include the need for good knowledge of the distribution and prevalence of the disease.61
9.47 The Committee notes that not all these criteria were present as far as bovine tuberculosis was concerned, particularly in the early years of the eradication program. The program still succeeded, but it took several decades and cost a very large amount of money (see Chapter 3).
9.48 The key technical issues that the Committee identified in relation to an eradication program for OJD, especially at a large scale, are:
a) incomplete information on distribution;
b) deficiencies in available tests;
c) incomplete knowledge of the spread of the disease and ways to prevent this;
d) incomplete knowledge concerning requirements to decontaminate pastures under a range of conditions;
e) potentially several species at risk - sheep, goats, alpacas and possibly cattle and deer; and
f) methods for retaining the genetic resources in flocks. 62A wide range of opinions was expressed to the Committee concerning the feasibility of eradication. Dr J. W. McDonald, private veterinary consultant and former District Veterinary Officer with the Department of Natural Resources and Conservation, believes that OJD will prove too difficult to eradicate regionally.63 Prof. R. Hirst, Veterinary researcher from James Cook University, agrees.64Others point to the apparent reduction in prevalence of the disease in Victoria as a result of the Victorian OJD Eradication Program, the peculiar advantages of an island continent and past success with other diseases as evidence that eradication over large areas is probably technically feasible.65
9.49 An alternative view was put to the Committee that a clear picture of the distribution of OJD might allow regional or district eradication in some localities and endemic-disease approach in others - that is, containment and on-farm minimisation where eradication appears to be impractical.66 It was further proposed that:
While we are reducing the level of infection ... it makes good sense to define disease-free regions and protect them as safe sources for restocking infected regions which are cleared.67The issue then becomes - what are the technical options for eradication?
9.50 Total property destocking is still the eradication approach espoused by the Department of Natural Resources and Environment and the Victorian Farmers Federation. According to Dr P. Bailey, Director, Quality Assurance:
Our knowledge ... [indicates] that the only way to effectively eradicate the disease from a property is to totally destock the property for two summer periods.68Researchers in other countries, and also in NSW, consider that gradual decontamination of pastures is a technically feasible alternative to destocking, although this has yet to be confirmed conclusively.69
9.51 The Committee was provided with evidence that the destocking of the whole property need not be done in one step. Mrs B Vickers, whose NSW property the Committee inspected, used a longer period of destocking.70 Mrs Vickers destocked half her property for two summers. During this period she sought out a source of low-risk replacement sheep with which to restock at the end of the decontamination period. She used artificial insemination with the new flock to preserve the genetics from the section of the flock that had, at this stage, not been slaughtered. She then destocked the second half of her property. This approach, which is now also being adopted by at least one producer in Victoria, takes longer than whole-property destocking.71 However, as Mrs Vickers explained, it allows the quality of the flock to be preserved and provides some income during the period of decontamination.
9.52 The Committee identified a number of technical issues relating to the effective use of destocking for eradication. First among these is the adequacy of available tests. Doubts have been raised concerning their accuracy, at least under the level of quality control applied during the Victorian OJD Program, in determining that flocks are definitely infected.72 The available evidence indicated that current tests can provide this information with a high level of confidence, provided more than one test is used, blood tests are verified by autopsy and histopathological examination and there are strict procedures for quality assurance and accountability in place.73 Accountability procedures requested by witnesses include opportunity for retesting and reassessment of tests by independent technicians.74 Quality control relates to identification of individual animals as well as laboratory procedures. At present it appears to the Committee as not always adequate, in spite of the "chain of evidence" that is in place.75
9.53 It also appears to be important to producers for them to have an estimate of the prevalence of infection in their flocks if they are to make an informed decisions concerning destocking. This information has not been provided routinely under the Victorian OJD Program. However, there appears to be no technical difficulty presented by currently available tests to the providing of a meaningful report to producers. The main requirement would be that an adequate sample of sheep be tested to represent each type of sheep within the flock, particularly each age group. The main barrier to doing this would be cost rather than technical considerations. The focus under past practices has been to focus on those animals most likely to be infected (the `tail' of the flock) to minimise testing costs.76 This approach is efficient for identifying infection but will not indicate prevalence in the whole, or other segments of the flock.
9.54 The lack of sensitivity of available tests is also a problem for eradication by destocking, as it introduces the risk of reinfection during restocking. Even if the 95% confidence claimed for SheepMAP flocks is accurate, some producers see a 5% risk of reintroducing infection with a new flock as unacceptable when large numbers of animals must be introduced, as at restocking.77
9.55 The Committee also identified some problems with the decontamination process. Prowse considers the main advantage of the destocking approach is its speed relative to other approaches - decontamination of a property may be achieved in fifteen months.78 This, as the Committee noted earlier, is still a long time compared with that required to eradicate other diseases where destocking is used, although it is a much shorter period than the 10-20 years required to eliminate infection by gradual reduction of contamination. As indicated above, work is under way to determine if this time can be reduced in some circumstances and where two summers may not be sufficient for decontamination. At the level of on-farm management, more detailed information is needed on the effects of environmental factors on the length of time that pastures need to be destocked to achieve decontamination. In the mean time it the evidence available to the Committee suggests that two summers' destocking is probably adequate for most locations.
9.56 Reinfection through alternative stock is a matter of concern, but can, technically, be prevented. Preventing reinfection via feral animals may present more difficulty in some locations. The risk generally appears to be low but not insignificant. Results of on-going research are needed to clarify this matter. It should be possible to prevent reinfection from faeces washed on to a property in many, but not all localities.
9.57 Retaining the genetic resource in a flock through artificial breeding is technically possible.
9.58 In summary, limitations of current tests, and factors that pose risks of reinfection, have been presented to the Committee as providing the main technical difficulties with a destocking approach.
9.59 Rather than eliminate the infection from a property within two years, some have proposed that eradication could be achieved by gradually `winding down' contamination. As with eradication by destocking, this approach depends on ultimately breaking the cycle of infection.79 By contrast with destocking, it aims to do this gradually by progressively reducing pasture contamination, reducing the prevalence of infection within flocks and increasing the number of properties that are free of infection.
9.60 Both Dr. B. Allworth and Dr. L. Denholm consider that eradication of OJD from a property may be achieved in some circumstances, without total destocking, by use of property-based control measures that lead to reduction of pasture contamination could reduce contamination to the point where the disease cannot sustain itself.80As indicated above, vaccination over a long period may achieve this, though this is yet to be confirmed conclusively. Otherwise circumstances that allow a diversity of management options within the property will be a prerequisite. The Committee outlined the steps advocated to reduce pasture contamination in an earlier section. If a producer is able to implement the required practices and avoid reinfection it appears likely that progressive eradication of OJD is technically feasible.
9.61 However the Committee has identified several difficulties with the approach. These difficulties are:
a) the long time frame needed to establish conditions under which the approach can work;
b) the long period required to achieve de-contamination of pastures, during which time containment would be necessary;
c) lack of applicability to properties that do not have options for alternative enterprises such as cropping; and
d) inadequate testing procedures to establish that eradication has been achieved.
9.62 Issues associated with avoiding reinfection would be similar to those for eradication by destocking, except that the problems of ensuring that flocks for restocking are `clean' would be removed.
9.63 Where a diversity of enterprises is limiting, it may be possible to eliminate contamination one paddock at a time, as described above. Depending on the nature of the property and the farmers operation, this may be possible to undertake without removing animals from the property. If uninfected animals can be identified, these could then be moved to the decontaminated paddocks. Identifying uninfected animals remains difficult, although use of prolonged testing of small groups or individual animals (as described in the preceding chapter) appears to be a technically feasible way to do this. The main barriers appear to be the long time, perhaps ten years, required to decontaminate a property by such an approach. The approach has yet to be tested.
9.64 An alternative to attempting to deal with control across the whole State in a uniform manner could be to `wind back' infection on a regional or district basis. Farmers might choose any control option that does not lead to spread of infection. Containment of the disease would be essential, and so all control techniques relevant to that approach would be required for farmers who chose not to destock. Control techniques used to minimise the impacts of the disease would also be relevant to these farmers.
9.65 Technically, flexibility would also be constrained by the physical circumstance of the property in relation to neighbouring properties. For example, where the topography of the land would make it impossible for a farmer to ensure that contaminated faeces could not be carried to a neighbouring farm, the farmer could not choose a minimisation approach with containment.
9.66 Dr. G. Neumann, Director, Animal Health Australia, considers that zones could be much smaller than those presently defined under the National OJD Program. He suggests that they could be based on realistic trading areas, allowing contraction of `control' and `residual' areas as new areas are shown to be free of OJD.81 Smaller `zones', or districts have been used as the basis of footrot eradication in both NSW and Victoria (see Chapter 3). The Committee could see no technical difficulty with zoning at any scale apart from that of establishing freedom from infection and controlling the movement of stock. Abattoir surveillance may overcome this difficulty.
9.67 Some groups of farmers could choose to actively pursue a status of `free' zone for their district. In order to achieve this status reasonably rapidly, eradication by destocking would be the most likely method used. Techniques to confirm the district's freedom from infection and exclude any new introduction of infection would then be needed. Abattoir surveillance with good flock identification could be used for the former. Exclusion of infection would require restrictions of animals introduced to the district to those that had been identified as uninfected - particularly those from other zones identified as free of infection and flocks tested under the Market Assurance Program. New genetic material could be introduced by artificial breeding techniques as well as by introducing new sheep. Control of feral goats would appear to be a sensible precaution in some districts.
9.68 Before all properties in the district were identified as free of infection, control techniques to prevent property reinfection would be needed, such as barriers to contamination at property boundaries and care with hygiene connected with sale and transport of animals. Once the district was determined to be free of OJD, exclusion techniques would only be of major importance for those properties at the margins of the district. These margins could be placed against natural barriers to infection such as catchment boundaries and land not used for grazing.
9.69 For instance, most sheep producers in the forest-enclosed Ensay valley have been involved in the Victorian OJD Control Program and there has been widespread testing, with infected properties mostly destocked and decontaminated. Like all district-based OJD management areas, on going surveillance and monitoring would be required to confirm that the district remained free of OJD.
9.70 Other groups of farmers could chose another objective, say to live with the disease and would adopt techniques to contain and minimise the disease.
9.71 Where and individual farmer does not choose to join a group, an individual approach could be taken, but only if that farmer was seeking a higher level of control. Social pressures to comply with the majority may be excessive and in effect force an individual farmer into adopting an approach that they otherwise may not have adopted. Where a group of farmers can not agree, this approach would not be effective.
9.72 Because this approach involves a wide choice of control options, most control techniques are relevant. Those of most general importance have to do with containing infection and identifying localities free from infection.
Flexible property approaches rely on co-operation between groups of farmers and physical circumstances and in some regions may have limited applications. They do, however, offer the potential to eliminate OJD in a manner that gives farmers choice.
9.73 Under the Standard Definitions and Rules, there are currently restrictions on introducing sheep into Victoria from infected or residual zones elsewhere as enforced by regulations under State legislation. Penalties exist under the relevant legislation of each State for those who trade or move sheep contrary to such regulations.
9.74 Excluding new sources of infection from Victoria would be particularly relevant if OJD were eradicated from the State, but is also important if the disease is to be contained. Either the introduction of all sheep to the State would have to be prevented, or adequate techniques to identify sources of `clean' sheep employed. This would involve the same techniques as were described in the preceding section for excluding infection from districts from which OJD had been eradicated.
9.75 This approach would need enforceable border controls and identification of individual sheep. The Committee is aware that the introduction of such controls would not be an entirely new initiative, as it understands that in the 1940s sheep permits were required to transfer sheep out of Victoria. - as a tool to discourage the theft of sheep.
1 For example, Hussey and Morris (1998); and also Hirst, R. (2000), James Cook University, Townsville, Written Submissions, OJD 068, Visard, A. (2000), Mackinnon Project, University of Melbourne, Minutes of Evidence, 24 July 2000 and Tobin, F. (2000), OJD Action Group, Minutes of Evidence, 24 July 2000.
2 For example Esson, C. (2000) Written Submissions, OJD 025.
3 For example Esson, C. (2000) Written Submissions, OJD 025.
4 For example Poynton, J. (2000), Written Submissions, OJD 46 and also Belcher, J. (2000), Written Submissions, OJD 048.
5 Kefford, B. (2000), Executive Director Agriculture, Written Submissions, OJD 087.
6 Prowse (2000), pp17-20.
7 Button, K. (2000), Acting Senior Veterinary Officer, Maffra, Department of Natural Resources and Environment. Personal communication, 16 May 2000.
8 Prowse (2000), p. 17.
9 Allworth, B. (2000), National OJD Operations Co-ordinator, personal communication, 7 June 2000.
10 Sykes, W. (2000), Animal Health and Research Consultant, Minutes of Evidence, 24 July 2000.
11 Simpson, G. (2000) District Veterinarian with the NSW Central Tablelands Rural lands Protection Board, personal communication, 3 July 2000.
12 Denholmn, L. (2000), NSW Agriculture, personal communication, 8 June and 3 July 2000.
13 Denholmn, L. (2000), NSW Agriculture, personal communication, 8 June and 3 July 2000.
14 Allworth, B. (2000), National OJD Operations Co-ordinator, personal communication, 7 June 2000.
15 Picken, K. J. (2000), Executive Officer, Australian Veterinary Association, Minutes of Evidence, 24 July 2000.
16 For example Lawson, D. (2000), Written Submissions, OJD 033; and also McDonald (2000).
17 Carter, J. and Lawson, D. (2000), Australian Beef Association, Minutes of Evidence, 7 August 2000.
18 Division of Animal Health (2000).
19 Millar, H. (2000), Acting Chief Veterinary Officer, Department of Natural Resources and Environment, personal communication, 6 September 2000.
20 Prowse (2000), p. 6.
21 Wraight, McNeil, Beggs, Greenall, Humphris, Irwin, Jemmeson, Morgan, Brightling, Anderson and Mansell (1999).
22 Wraight, McNeil, Beggs, Greenall, Humphris, Irwin, Jemmeson, Morgan, Brightling, Anderson and Mansell (1999).
23 Gee (1999a).
24 Prowse, S. (2000), Program Manager, Infectious Diseases and Food Safety, Animal Health Laboratories, CSIRO, Minutes of Evidence, 24 July 2000.
25 Pemberton, D. (2000), Veterinarian, Minutes of Evidence, 24 July 2000; and also Visard, A. (2000), Mackinnon Project, University of Melbourne, Minutes of Evidence, 24 July 2000.
26 Australian Animal Health Council Limited (1998).
27 Webb Ware, D. (2000), personal communication, 13 June 2000.
28 Button, K. (2000), Acting Senior Veterinary Officer, Maffra, Department of Natural Resources and Environment. personal communication, 16 May 2000.and also Messrs. B. and E. Newcomen (2000), personal communication, 17 May 2000.
29 Pemberton, D. H. (2000), Written Submissions, OJD 042.
30 Pemberton, D. H. (2000), Written Submissions, OJD 042.
31 Roberts, S. (2000), Kowree District Council, Written Submissions, OJD 081.
32 Denholm, Ottaway, Cornish and Merton (1997).
33 Prowse (2000), p. 17.
34 CSL Veterinary (1996), p. 21.
35 Kefford, B. (2000), Executive Director, Agriculture, Department of Natural Resources and Environment, Minutes of Evidence, 7 August 2000.
36 Veterinary Committee (1998).
37 Denholmn, L. (2000), NSW Agriculture, personal communication, 8 June 2000.
38 For example NSW Agriculture (1997).
39 Papers in Henderson (2000) - particularly Kelly, C. (2000), `On Property OJD Management - a Producer's Viewpoint', pp. 22-27.
40 NSW Agriculture (1999b).
41 Morrison, A. (2000), farmer, personal communication, 4 July 2000.
42 McDonald, J. W. (2000), Written Submissions, OJD 057.
43 Evers, M. (2000), OJD Policy Development Officer, NSW Agriculture, personal communication, 3 July 2000.
44 Allworth, B. (2000), National OJD Operations Co-ordinator, personal communication, 7 June 2000.
45 Newcomen, E. and D. (2000), Written Submissions, OJD 058; and also Slatter, K. (2000), Rural financial Councellor, personal communication, 13 June 2000.
46 For example Denholmn, L. (2000), NSW Agriculture, personal communication, 8 June 2000.
47 Denholm, Ottaway, Cornish and Merton (1997).
48 NSW Agriculture (1999c), and also Veterinary Committee (1998)
49 NSW Agriculture (1999c); and also Veterinary Committee (1998).
50 Allworth and Kennedy (1999); and also NSW Agriculture (1999a).
51 Allworth and Kennedy (1999).
52 Oliver, G. (2000), President Pole Dorset Association, personal communication, 20 July 2000.
53 Prowse (2000), p. 41; and also Allworth and Kennedy (1999) and NSW Agriculture (1999a).
54 Prowse (2000), p. 33; and also NSW Agriculture (1999a).
55 Visard, A. (2000), Mackinnon Project, University of Melbourne, Minutes of Evidence, 24 July 2000.
56 For example Ahsam, B., Written Submissions, OJD, OJD 004; and also
57 For example Lade, A. (2000), merino stud breeder, personal communication, 13 June 2000; and also Esson, C. (2000) Written Submissions, OJD 025.
58 NSW Agriculture (1999c) and also Veterinary Committee (1998).
59 Meat and Livestock Australia (1999), p. 6.
60 Wardrop, I. D. (2000), Written Submissions, OJD 055.
61 For example Visard, A. (2000), Mackinnon Project, University of Melbourne, Minutes of Evidence, 24 July 2000; and also Hirst, R. (2000), James Cook University, Townsville, Written Submissions, OJD 068.
62 Meat and Livestock Australia (1999), p. 6; and also Pemberton, D. (2000), Veterinarian, Minutes of Evidence, 24 July 2000 and Prowse (2000).
63 McDonald, J. W. (2000), Written Submissions, OJD 057.
64 Hirst, R. (2000), James Cook University, Townsville, Written Submissions, OJD 068.
65 Kefford, B. (2000), Executive Director, Agriculture, Department of Natural Resources and Environment, Minutes of Evidence, 7 August 2000; and also Denholmn, L. (2000), NSW Agriculture, personal communication, 3 July 2000 and Shea, R. A. and M. M. (2000), Written Submissions, OJD 082.
66 Allworth, B. (2000), National OJD Operations Co-ordinator, personal communication, 7 June 2000; and also Simpson, G. (2000), District Veterinarian with the NSW Central Tablelands Rural lands Protection Board, personal communication, 3 July 2000.
67 Gee (1999a).
68 Bailey, P. J. (2000), Director, Quality Assurance, Department of Natural Resources and Environment, Minutes of Evidence, 7 August 2000.
69 For example Benedictus, Verhoeff, Schukken and Hesselink (1999); and also Denholmn, L. (2000), NSW Agriculture, personal communication, 8 June 2000and Allworth, B. (2000), National OJD Operations Co-ordinator, personal communication, 7 June 200 Allworth, B. (2000), National OJD Operations Co-ordinator, personal communication, 7 June 2000.
70 Vickers, B. (2000), farmer, Carcoar, NSW, personal communication, 3 July 2000.
71 Webb Ware, D. (2000), personal communication, 13 June 2000.
72 For example Richardson, J. and J. (2000), Written Submissions, OJD 102.
73 Prowse, S. (2000), Program Manager, Infectious Diseases and Food Safety, Animal Health Laboratories, CSIRO, personal communication, 24 July 2000; and also Pemberton, D. (2000), Veterinarian, Minutes of Evidence, 24 July 2000.
74 For example Ahsam, B., Written Submissions, OJD, OJD 004; and also Clark, A. and I. (2000), Written Submissions, OJD 040.
75 Kefford, K. (2000), Executive Director, Agriculture, Department of Natural Resources and Environment, correspondence to the Committee, 22 September 2000.
76 Allworth and Kennedy (1999).
77 For example Ritchie, M. (2000), Written Submissions, OJD 054.
78 Prowse (2000), p. 38.
79 Meat and Livestock Australia (1999), p. 4.
80 Allworth, B. (2000), National OJD Operations Co-ordinator, personal communication, 7 June 2000 and Denholmn, L. (2000), NSW Agriculture, personal communication, 8 June 2000.
81 Neumann, G. (2000), Director, Animal Health Australia, personal communication, 7 June 2000.
