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This article was published in 2000
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Ovine Johne's Disease In New South Wales Update To 31 May 2000
I Links a, I Roth b, E Sergeant b, M Evers c, L Denholm d, and C Taragel d
a NSW Agriculture, Wagga Wagga Agricultural Institute, Wagga Wagga
b NSW Agriculture, Division of Animal Industries, Orange
c NSW Agriculture, Division of Animal Industries, Young
d NSW Agriculture, Orange Agricultural Institute, Orange
Summary
Zoning for ovine Johne's disease (OJD) was introduced in NSW on 1 July 1999. At 31 March 2000 there had been 512 infected flocks identified in NSW since 1980 with 451 (1.5% of the State's flocks) still having an infected status. Of the 451 currently infected flocks, 73% are in the Residual Zone. About 6% of Residual Zone flocks are known to be infected compared to <0.5% of flocks in the Control Zone. A further 563 flocks are Suspect and 1330 Under Surveillance. There are 313 flocks in the sheep Market Assurance Program (306 MN1 and 7 MN2). The Pooled Faecal Culture (PFC) was introduced for surveillance and assurance testing in NSW in December 1999. By detecting excretion of bacteria, it provides a powerful new tool for detecting infection as well as clearing suspect flocks identified by tracing. Abattoir monitoring commenced in November 1999 (in parallel with an Abattoir Sensitivity Trial) and offers a more random, cost effective surveillance strategy to complement targeted surveillance based on tracing from infected flocks. By March 31st 2000, about 3000 lines, comprising 985,000 adult sheep, had been monitored with 250 lines confirmed positive by histopathology. Preliminary estimates of the district of origin confirm that much of NSW remains free of known OJD cases with the disease predominantly localised to the central and southern tablelands, with some extension into the central and south-west slopes area. A wide range of initiatives introduced since commencement in March 1999 of the National Ovine Johne's Disease Control and Evaluation Program (NOJDP) are outlined.
Introduction
Johne's disease (OJD) was first diagnosed in sheep in NSW in 1980. By 30 June 1997, OJD had been confirmed in about 170 flocks in NSW, as well as in flocks in Victoria and on Flinders Island, Tasmania. Since then, there have been ongoing discussions to develop a national approach to the control and eradication of OJD. At its February 1998 meeting, the Agricultural and Resource Management Council of Australia and New Zealand (ARMCANZ) accepted the Hussey—Morris report as a way forward. In addition, an interim surveillance program (ISP) was implemented, to further clarify the distribution and prevalence of 01D. This program ran from 1 April to 30 September 1998. Testing continued at a reduced rate pending implementation of the National Ovine Johne's Disease Control and Evaluation Program (NOJDP) in March 1999. This report provides an update on the current situation regarding OJD in NSW, including the numbers and distribution of infected and suspect flocks, policy and technical developments and some discussion of the likely extent of the disease.
The Current Situation
Zoning
Zoning for OJD was introduced across Australia on 1 July 1999 with an agreement by Chief Veterinary Officers to harmonise zoning implementation in the Eastern states. The Rural Lands Protection Boards (RLPBs) of Central Tablelands, Goulbum and Braidwood plus parts of Yass and Molong were declared residual zones with the remainder of the state declared Control as were Victoria, Queensland and South Australia. Subsequently national Veterinary Committee (VetComm) approved progression to Control Status of Braidwood (February 2000) and the Residual part of Molong (May 2000).
Distribution of OJD in NSW
At 31 March 2000 there had been 512 infected flocks identified in NSW since 1980 with 451 (1.5% Of the State's flocks) still having an infected status. Of the 451 currently infected flocks, 73% are in the Residual Zone. Approximately 6% of Residual Zone flocks are known to be infected compared to <0.5% of flocks in the Control Zone. A further 563 flocks are Suspect and 1330 Under Surveillance. Figure 1 shows the location of Rural Lands Protection Boards in NSW. Table 1 summarises the current situation in NSW with the distribution of currently infected flocks shown in Figure 2. Table 2 summarises the current situation in NSW by RLPB.
Figure 1— Location of Rural Lands Protection Board districts in NSW
Figure 2 — Distribution of OJD infected flocks in NSW at 31st March 2000
Ovine Johne's Disease - Infected Flocks in RLPBs, April, 2000
Table 1: Summary of current flock OJD status by zone at 31st March 2000
| Current Status | ||||||||
|---|---|---|---|---|---|---|---|---|
| ZONE | Flocks* | IN | SU | US | NA | MN1 | MN2 | Total |
| Control | 26008 | 112 | 229 | 457 | 725 | 248 | 7 | 1768 |
| Residual | 4488 | 339 | 334 | 883 | 327 | 58 | 0 | 1958 |
| Total | 30496 | 451 | 563 | 1330 | 1052 | 306 | 7 | 3726 |
* Total flock numbers in Control and Residual zones are approximate only
Table 2: Summary of OJD flock status, and number of lines monitored by abattoir surveillance at 31 March 2000 by Rural Lands Protection Board
| BOARD | Zone | Flocks | Total IN (1) | Current IN (2) | SU Flocks | US Flocks | NA Flocks | MAP Flocks | IN Goat herds | Abattoir Lines Monitored |
|---|---|---|---|---|---|---|---|---|---|---|
| Armidale | CON | 2000 | 0 | 0 | 1 | 1 | 168 | 62 | 0 | 162 |
| Brewarrina | CON | 175 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 15 |
| Bombala | CON | 293 | 0 | 0 | 2 | 0 | 8 | 1 | 0 | 67 |
| Bourke | CON | - | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 19 |
| Braidwood (3) | CON | 565 | 16 | 15 | 19 | 43 | 12 | 2 | 0 | 33 |
| Broken Hill | CON | 108 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 3 |
| Cobar | CON | - | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 27 |
| Condobolin | CON | 1642 | 2 | 0 | 0 | 0 | 16 | 0 | 0 | 39 |
| Cooma | CON | 668 | 3 | 3 | 9 | 7 | 37 | 23 | 1 | 72 |
| Coonabarabran | CON | 670 | 1 | 1 | 2 | 6 | 7 | 2 | 0 | 28 |
| Coonamble | CON | 390 | 1 | 1 | 3 | 3 | 8 | 4 | 0 | 31 |
| Dubbo | CON | 1314 | 0 | 0 | 0 | 0 | 18 | 13 | 0 | 248 |
| Forbes | CON | 1540 | 17 | 15 | 58 | 45 | 32 | 7 | 0 | 132 |
| Gundagai | CON | 867 | 7 | 5 | 10 | 41 | 50 | 3 | 0 | 146 |
| Hay | CON | 394 | 0 | 0 | 0 | 0 | 1 | 4 | 0 | 19 |
| Hillston | CON | 180 | 0 | 0 | 1 | 0 | 4 | 0 | 0 | 3 |
| Hume | CON | 963 | 28 | 25 | 23 | 104 | 55 | 22 | 2 | 80 |
| Hunter | CON | 215 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 17 |
| Maitland | CON | 13 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 0 |
| Moree | CON | 223 | 1 | 1 | 5 | 0 | 1 | 0 | 0 | 37 |
| Moss Vale | CON | 675 | 2 | 1 | 1 | 2 | 2 | 4 | 0 | 6 |
| Mudgee-Merriwa | CON | 879 | 2 | 2 | 3 | 1 | 40 | 23 | 0 | 29 |
| Murray | CON | 1049 | 7 | 7 | 8 | 24 | 10 | 8 | 1 | 37 |
| Narrabri | CON | 255 | 0 | 0 | 0 | 0 | 0 | 2 | 0 | 22 |
| Narrandera | CON | 978 | 1 | 1 | 2 | 0 | 4 | 3 | 0 | 42 |
| Northern New England | CON | 1248 | 0 | 0 | 5 | 0 | 21 | 5 | 0 | 50 |
| Northern Slopes | CON | 520 | 0 | 0 | 4 | 0 | 2 | 0 | 0 | 30 |
| Nyngan | CON | 600 | 0 | 0 | 3 | 0 | 3 | 6 | 0 | 44 |
| Riverina | CON | 740 | 0 | 0 | 0 | 0 | 0 | 10 | 0 | 4 |
| South Coast | CON | 490 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 1 |
| Tamworth | CON | 1157 | 1 | 1 | 3 | 3 | 5 | 1 | 0 | 109 |
| Wagga Wagga | CON | 1803 | 11 | 6 | 36 | 50 | 92 | 13 | 0 | 216 |
| Walgett | CON | 526 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 97 |
| Wanaaring | CON | - | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Wilcannia | CON | - | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 4 |
| Young | CON | 1945 | 44 | 38 | 39 | 153 | 131 | 19 | 0 | 206 |
| Molong | R/C | 1104 | 32 | 30 | 23 | 56 | 20 | 13 | 0 | 78 |
| Yass | R/C | 1200 | 25 | 24 | 47 | 8 | 173 | 22 | 0 | 95 |
| Central Tablelands | RES | 2306 | 259 | 226 | 220 | 749 | 110 | 28 | 2 | 186 |
| Goulburn | RES | 1082 | 51 | 48 | 35 | 33 | 20 | 9 | 0 | 268 |
| Undetermined RLPB | - | - | - | - | - | - | - | - | - | 134 |
| Interstate (4) | - | - | - | - | - | - | - | - | - | 119 |
| Tota1 | - | 30779 | 512 | 451 | 563 | 1330 | 1052 | 313 | 6 | 3030 |
1. Total IN flocks ever identified
2. Flocks currently IN
3. Braidwpod Residual Zone progress to Control Zone in March 2000
4. Interstate: ACT 1, Queensland 55, Victoria 121, South Australia 16
Market Assurance Program (SheepMAP)
At 31st March 2000 there were 313 flocks in the SheepMAP (306 MN1 and 7 MN2). Significant changes have been made to improve the SheepMAP providing a more flexible and practical assurance program for livestock producers.
Some of the changes include:
• Allowing flocks to maintain their current status by less intensive Maintenance Testing.
• Allowing introductions of small numbers of replacement breeding animals from flocks of one status lower.
• Using Pooled Faecal Culture in the SheepMAP.
• Improved standards for shows and sales.
The revised MAP manual was released in March 2000 with copies sent to all Approved veterinarians and producers enrolled in the MAP. NSW Agriculture ran a series of training courses for approved veterinarians to bring them up-to-date with the changes.
Property Disease Eradication Plans (PDEPs)
A total of 153 PDEPs have now been approved by NSW Agriculture with 51 reported as completed following voluntary destocking for two summers.
Abattoir Surveillance
Abattoir monitoring commenced on 22 November 1999 (in parallel with an NOJDP / MLA Abattoir Sensitivity Trial) and offers a more random, cost effective surveillance strategy to complement targeted surveillance based on tracing from infected flocks. By March 31st 2000, more than 3030 lines had been monitored by four specially trained inspectors located primarily in two major export abattoirs with random visits to 4 smaller works. The lines monitored comprised more than 985,000 adult sheep and represented approximately 70% of adult sheep slaughtered in NSW. Preserved samples of intestine were submitted from up to 3 sheep showing gross lesions in a line. There were 250 positive lines (lesions defined as positive or suggestive of OJD on histopathology) out of 592 lines sampled. From the beginning of March all eligible interstate lines are being monitored with positive lines reported to the Chief Veterinary Officer for that state. Preliminary estimates of the zone of origin (based on the abattoir records) of both positive and negative lines are shown in Table 3. More detailed and accurate information will become available as results of tracing are incorporated. The distribution of positive lines is consistent with the known distribution of infected flocks determined by more targeted testing of flocks identified by tracing from known infected flocks. The majority of positive lines in the Control Zone are located in RLPBs adjacent to the Residual Area or in areas where infection has previously been demonstrated.
Table 3: Estimated zone of origin of 3030 lines of adult sheep monitored in NSW abattoirs from 22 November 1999 to 31 March 2000.
| Zone of Origin | No. of Lines Monitored | No. of Lines Positive |
|---|---|---|
| Residual | 493 (16%) | 152 (61%) |
| Residual / Control | 173 (6%) | 21 (8%) |
| Control | 2050 (68%) | 54 (22%) |
| Interstate | 194 (6%) | 2 (1%) |
| Undetermined | 120 (4%) | 21 (8%) |
| Total | 3030 | 250 |
The RLPB of origin of all lines monitored is recorded in Table 2.
Includcd in the 250 positive lines were 27 of the 30 lines examined blind (to 31st March 2000) from known infected properties submitted under the Sensitivity Trial. These flocks were included in the trial based on a history indicating a significant level of infection.
After consultation with the NSW OJD Advisory Committee, tracing to the property of origin of all positive lines detected was initiated on 14th April 2000. The source of OJD positive lines will be identified and the property placed Under Surveillance while the relevant RLPB district veterinarian confirms the trace back information and carries out a risk assessment. Where the likelihood of flock infection is high and there is a strong risk posed to other producers, the property will be immediately re-classified as Suspect and placed under quarantine. Irrespective of whether the flock remains Under Surveillance or is reclassified to Suspect, further testing (using pooled faecal culture, post-mortem or blood testing) will, in most cases, be necessary to determine the disease status of the flock. There will be no quarantine restrictions placed on properties until the district veterinarian has confirmed the origin of the sheep and performed a risk assessment. In cases where the origin of the sheep is not clear-cut and depending on the degree of doubt and the perceived risk no action may be taken.
It is recognised that abattoir surveillance has its limitations but is considered to be very successful in detecting well-established infections or where, disease is widespread in a flock. However it may not be as effective in detecting disease in its early stases or where it is of low prevalence in a flock. Strategies are currently being developed to assess the sensitivity of abattoir monitoring in low prevalence flocks.
Abattoir monitoring of adult sheep in NSW for 0JD is a very useful and cost effective tool, which allows a random coverage across a wide area, and increases the monitoring in low prevalence areas.
The availability of a reliable national Stock Identification system would greatly facilitate abattoir surveillance tracing of positive lines as well as allowing cost effective feedback to individual producers on negative lines. This would be an inexpensive method of providing a progressive level of assurance on a regional and individual property basis. The Sheep Meats Council is currently progressing a low cost voluntary national birth tag system.
Proposed Revised National Surveillance Strategies
Revised national OJD surveillanee strategies are currently being finalised by the Program Management Committee of the NOJDP. These proposed strategies include:
1. A national abattoir survey to determine regional prevalence of OJD
2. Additional abattoir monitoring for disease detection and zone maintenance
3. Continued on-farm investigations including use of PFC
4. Continued tracing from known infected properties
5. A subsidy for Check Testing (2 pools using PFC) for non-assessed flocks to promote risk management assurance testing by flocks with no evidence of disease
6. A subsidy for flocks entering the Market Assurance Program or testing to progress to Monitored Negative 2 (MN2) status
7. Continued subsidy (100%) to test to MAP equivalence for non-assessed flocks in the Residual Zone with a history of trading
8. Payment of the cost of testing for flocks detected infected while entering or progressing in the MAP
9. Payment for follow-up testing under the surveillance program where flocks are PFC positive including flocks testing under the MAP.
Pooled Faecal Culture (PFC)
PFC was endorsed by VetComm in October 1999 as an approved test in NSW with a follow-up process for flocks yielding a positive PFC approved in December 1999. The follow-up process provides a risk management strategy to allows flocks which are negative on retest to revert to their previous status while flocks that are positive on retest remain Suspect (if DNA consistent with Mycobacterium paratuberculosis is identified at initial and follow-up testing) or are declared Infected (if M. paratuberculosis is isolated at either initial or follow-up testing). A major advantage of the PFC is that it enables determination of whether animals are infectious i.e. shedding organisms and thus contaminating the land, as opposed to animals which are infected (i.e. antibodies/lesions) but may not be shedding. VetComm also approved a reduced period of 2 years since "last dangerous contact" before a Suspect flock could be cleared of suspicion (7 pools of 50 faeces providing 95% confidence of detecting a 2% level of infection) compared with 3 years using the blood testing (450 - 500 gel tests).
A dedicated PFC diagnostic facility has been established at Elizabeth Macarthur Agricultural Institute at MenangIe with a current laboratory charge for the PFC of $96 per pool. Use of the PFC will also be encouraged for assurance testing where the cost of PFC testing is significantly over than the cost of blood sampling.
The PFC has a long incubation period, 12 weeks in liquid BACTEC medium before the test can be declared negative. Those BACTEC cultures with growth are tested using PCR (polymerase chain reaction) for "DNA consistent with M. paratuberculosis". Results during the Interim Surveillance Program (ISP) confirmed that about 95% of BACTEC PCR positive cultures showed growth within 3 to 7 weeks of incubation, consistent with the more heavily infected flocks yielding a more rapid PCR positive BACTEC test. BACTEC cultures showing growth (whether positive or negative PCR) are subcultured onto solid medium and incubated for a further 10 weeks to determine whether typical slow-growing colonies of M. paratuberculosis can be isolated. While the vast majority of BACTEC growth positive/PCR negative tests will yield only contaminant bacteria on solid medium, a small percentage (about 6% of true positive tests) will yield typical colonies of M. paratuberculosis. Approximately 80% of BACTEC growth positive/PCR positive tests will yield typical colonies of M. paratuberculosis. Individual Tissue Culture (IFC) - Culture of Terminal Ileum Following research investigations by NSW Agriculture, culture of terminal ileum for M. paratuberculosis was endorsed by VetComm as an approved test early in 1999. It has been utilised in NSW as an effective tool to resolve situations where an animal has been autopsied and yielded histopathology "suggestive" of OJD and where infection has not otherwise been confirmed in that flock. Animals with "suggestive" histopathology / negative culture of terminal ileum are cleared while those with "suggestive" histopathology / positive culture are declared Infected. Individual faecal culture (IFC) is less sensitive than ITC and hence is not the test of choice in the above situation. It is essential that a small section (5cm length) of fresh terminal ileum be submitted in a sterile container from ALL animals autopsied under both the MAP and Surveillance programs. Where an animal yields "Suggestive" histopathology in NSW, the flock is made Suspect status and quarantined pending clarification of disease status either by or in the absence of ITC then through the normal pathways for progression of Suspect flocks.
Serial Faecal Culture (SFC)
The SFC overcomes the lower sensitivity of IFC by faecal sampling an animal on 3 occasions at 10-14 day intervals. The samples are stored at the laboratory before pooling all 3 samples at the end of the collection period. At least 15 faecal pellets are required per sampling to provide sufficient volume for effective blending of the pool. SFC provides a very high confidence of detecting animals, which are low level or intermittent excretors of organisms. SFC provides an alternative pathway for assessing the status of a high value animal without autopsy with a negative SPC accepted as evidence that the animal had not been excreting at the time of the first of the 3 samplings. Management strategies can then be implemented to manage the risk of continued use of that animal with the option of repeated SFC for the economic life of the animal.
New approaches to risk assessment — "Acceptable Risk" strategies
Information gained from the Research and Surveillance Programs under the NOJDP is being used to implement an "acceptable risk" approach for progressing the status of Suspect and Under Surveillance flocks. This has been incorporated into the amended Appendix 4 of the National Standard Definitions and Rules endorsed by VetCom in December 1999. Pathways for progression of the Under Surveillance status of neighbours of Infected flocks has been specifically addressed. Endorsement of the 2 year clearance test using PFC will enable US and Suspect flocks to be cleared more quickly.
Testing strategies for Suspect flocks will be tailored to individual flock situations following a risk assessment. Pooled Faecal Culture is the test of choice for flock investigations where disease is considered to be present at low prevalence or the flock is unlikely to be infected. Where the prevalence in a flock is likely to be higher, autopsy of low condition score animals or limited blood testing may be a more cost effective and rapid strategy.
Progression of Status of Infected Flocks Where Disease Has Not Become Established
NSW Agriculture has progressed an amendment to the SD&Rs which will enable certain infected flocks (eg where the disease was diagnosed in introduced sheep only) to resolve their status provided a comprehensive long-term testing program demonstrates that the disease has not been transmitted to the balance of the flock. Abattoir surveillance has been used effectively as an initial low cost screening tool.
Vaccine Trial
This trial is now under way on 3 properties in the Central Tablelands, which have been suffering significant losses due to OJD. The trial involves the use of the Spanish 'Gudair' vaccine, a killed vaccine that is believed to reduce mortalities and environmental contamination due to the OJD organism. Vaccination commenced on the trial properties during December 1999, and monitoring of the vaccinated stock will continue for the next four years.
Extended Use of Vaccine
Permission has been obtained from the VetComm for limited use of the vaccine on properties other than the three intensive research trial properties. Approval by the Chief Veterinary Officer of NSW is required for the use of the vaccine on an individual property. This extended usage is subject to strict conditions that have been developed in consultation with the sheep industry in the high prevalence areas.
Approval for use is contingent upon several conditions:
• property is located within the Residual Zone
• enterprise is suffering unacceptable losses
• vaccination will be performed by a licensed vaccinator
• stock will be identified as prescribed
• stock will be sold directly to an abattoir for slaughter only
• meat inspectors will be notified prior to slaughter.
By the end of May 2000, more than 28,000 doses had been supplied to close to 50 producers suffering a significant level of mortalities (primarily located in the Central Tablelands with a number in Goulbum and Yass RLPBs). CSL expects an order for a further 100,000 doses of the Spanish vaccine to be in Australia by the end of June 2000.
In May 2000, NSW Agriculture requested the NOJDP Program Management Committee endorse the following proposals for vaccine usage prior to consideration by VetComm:
• That vaccination be recognised nationally as a disease control measure.
• That the 50 property limit for the extended use of vaccine be removed and
• That controlled use of vaccine be allowed within the Residual Zone of NSW.
Payments for Surveillance Activities
OJD Situation Reports were distributed July 1999 covering payments and invoicing for surveillance activities (tracing and flock investigations) performed by District Veterinarians with RLPBs, Approved Private Veterinarians, Stock and Station Agents and NSW Agriculture under the national program.
This set in place a new system of payments and invoicing based on services provided and facilitated processing of payments and invoicing of the NOJDP by NSW Agriculture. The revised payments schedules also provides more appropriate recognition of the costs of provision of surveillance activities and greatly assists in ensuring the outcomes required under the NOJDP.
Mortality Rates Due to OJD
Documentation of losses due to OJD remains a high priority with three reports illustrating the situation.
a. Eppleston and Simpson (1999) reported that the impact of OJD on producers in the endemic Central Tablelands RLPB area varies greatly between individual properties. Long term infected properties with self-replacing Merino flocks appeared to be most affected by the disease itself. Reported losses can reach 15% per annum - with losses increasing with duration of infection. In a survey conducted in July 1999 of all properties in the Central Tablelands RLPB with an Infected status producers were asked to estimate the number of sheep deaths attributable to OJD in the last 12 months and the number of adult sheep shorn at the last shearing. From this data an estimate of annual losses due to OJD was calculated (Figure 3).
Figure 3. Annual sheep deaths reported by owners of properties infected with OJD in the Central Tablelands RLPB.
b. In a more comprehensive analysis of losses, Eppleston et al. (2000) reported estimates by 155 producers whose flocks had been previously diagnosed with OJD. Annual sheep mortalities were estimated as 0% per annum/38 flocks, 0-2%.p.a./42 flocks, 3-5% p.a./35 flocks, 6-9%/24 flocks and >9%/ 1.6 flocks. Average annual mortality was 3.7% with a significant trend to an increasing level of mortalities correlated with number of years since diagnosis - 0-2 years/mean 2.4%, 3-5 years/mean 4.3%, 6-9 years/mean 5.4% and >9 years/mean 5.9%.
c. A comprehensive study was undertaken by NSW Agriculture (Ian Lugton) and Central Tablelands RLPB (Jeff Eppleston) in a self-replacing merino flock of 3,400 head reputed to be suffering severe losses (approximately 10-12% per annum) due to OJD. A total of 3 property visits were made between 8 November and 8 December 1999. The aim was to verify that farmer reported losses from OJD are an accurate reflection of the situation and to establish that the losses were substantial (1. Lugton & J. Eppleston, Pers.Comm.). Moribund or thin sheep believed to be in danger of dying within days or weeks were autopsied. A summary of the results are presented in Table 3.
Table 3: Autopsy and histopathological findings on 56 sick sheep from an OJD infected property in Central Tablelands RLPB (Lugton & Eppleston, Pers.Comm)
| Gross Pathology | Histopathology Positive | Histopathology Negative | Histopathology Unavailable | Total |
|---|---|---|---|---|
| Not indicative of OJD | 1 | 2 | 0 | 3 |
| Suspicious for OJD | 2 | 0 | 0 | 2 |
| Typical of OJD | 28 | 0 | 23 | 51 |
| Total | 31 | 2 | 23 | 56 |
The findings confirmed that with 56 autopsies over a short time period, the flock was clearly suffering substantial losses and the owner was clearly able to identify OJD affected sheep.
Comparisons of average faecal egg counts for each visit confirmed that clinically affected sheep had substantial parasite burden (range 1187 — 2068 epg V's 180 — 416 epg), markedly lower average body weight (27.4 — 30.5 Kg V's 45.0 - 51.0 Kg) and average condition score on a scale of 0 to 5 (0.3 — 1.0 V's 2.5 — 3.5) compared with healthy sheep selected from a mob representative of the sheep autopsied.
d. A large (10,000 head) self replacing Merino flock in the Yass RLPB detected infected in 1996 has recently reported estimated annual losses of greater than 20% attributed by the producer to OJD. Investigations are currently underway involving cooperation between Sydney University and NSW Agriculture to determine the role of OJD in these losses.
Show and Sale Health Declarations
A meeting was held in Orange in January between representatives of show societies and the RAS, the National OJD Coordinator and NSW Agriculture to draft a show and sale health declaration which was acceptable to all parties and could be used in a variety of situations.
Authorised Feedlots and Slaughter-only Saleyards
Recent amendments to state legislation have facilitated the sale and movement of stock from Infected and Suspect properties to authorised feedlots. Further amendments have improved access to slaughter-only yards, and a number of these slaughter-only outlets have been established at sale centres throughout the central west and southern slopes and tablelands. The provision of competitive outlets for finished and store stock from OJD affected properties is seen as an integral pan of the management of the disease in terms of both disease control and support for affected producers.
NSW Agriculture Internet WebSite - www.agric.nsw.gov.au
A wide range of material concerning OJD is located on the NSW Agriculture Web Site providing universal access to Agfacts and Agnotes about the disease and management on-farm, zoning information, media releases and surveillance reports. The NSW Agriculture OJD Policy Manual is also available at this location where it can be downloaded as a PDF file. This provides immediate access to producers, approved veterinarians and district veterinarians to a regularly updated policy document.
State Industry Funds - NSW OJD Industry Advisoty Committee
The NSW Sheep Industry has a responsibility to raise funds for their contribution to the NOJDP and other state based activities. The NSW OJD Industry Advisory Committee is the statutory body which advises the Minister for Agriculture of the mechanism for collection of funds and their disbursal. To comply with a recent High Court decision which defined an excise and stipulated that under the Australian Constitution an excise may only be collected by the Commonwealth, a mechanism was implemented involving a voluntary contribution of $100 per holding with 50 or more sheep and/or goats (as per the 1998 RLPB Land and Stock Return) payable by the 30 June 2000. Failure to raise sufficient funds from the voluntary contribution triggered the implementation of a compulsory levy set at 7 cents per Dry Sheep Equivalents (DSE), with a minimum payment of $120, on all holdings with a stocking capacity (based on RLPB assessments) of >50 DSE unless the producer had been granted a waiver for that holding. By the end of April more than 30% of eligible producers (estimated between 25,000 and 30,000) had contributed more than $850,000.
It is essential that consultation occurs between the States and the Commonwealth as an urgent priority to develop a less complex mechanism for raising State Industry funds.
State industry (SI) funds are being utilised for :
• NOJDP Surveillance in NSW (15% from State Industry)
• Research into destocking / eradication (destocking payments to producers enrolled in NOJDDP research trial 1.1 - 100% SI)
• 100% Subsidy for non-assessed sheep and goat flocks/herds in the Residual Zone with a history of trading to test to MAP Equivalence (50% SI, 50% NOJDP surveillance)
• Appointment of an OJD Support Worker located at Goulburn
• Consultancy on assistance for affected producers
In addition, the Minister for Agriculture has agreed to the provision of $750,000 per annum for 3 years on condition it is matched by State Industry Funds for utilisation as an "OJD Initiatives Fund " to assist producers affected by OJD.
Financial Assistance for Affected Producers
The issue of assistance to affected producers is being progressed through the appointment in early March 2000 by the NSW OJF Industry Advisory Committee (paid for by the "OJD Initiatives Fund") of a consultant Hassall and Associates) to review "Financial Impacts and Forms of Assistance for OJD) Affected Producers". They are due to produce a draft report for consideration by the NSW OM Industry Advisory Committee towards the end of June 2000 with public release proposed for the week of 10th July.
Stud Breeders Package
A group of NSW producers with infected OJD studs are currently developing a proposal in consultation with NSW Agriculture for funding to assist salvage / reestablishment of their enterprises. This has been referred to Hassall and Associates for consideration as an assistance measure.
NSW OJD Advisory Committee
The Advisory Committee has met approximately 3 monthly over the past year to consider a wide range of issues related to OJD and provide advice to NSW Agriculture on policy decisions, particularly acceptable risk strategies, the PFC and abattoir surveillance. The development of an OJD Advisory Committee Strategic and Business Plan has been a high priority with a Draft plan endorsed in March 2000 and circulated to stakeholders for comment. A Technical Sub-Committee has been reconstituted to provide technical input to the Advisory Committee.
Conclusion
Surveillance activities based on flock testing has been at lower than anticipated levels over the past 12 months while sectors of the sheep induslry and individual producers come to grips with the implications of OJD and the aims of the national program. Concurrently, a wide range of strategies and policy initiatives have been implemented in NSW to provide a way forward.
The implementation of abattoir surveillance has proven a very cost effective tool for randomly monitoring lines of adult sheep from across NSW as well as interstate sheep killed in NSW. Abattoir surveillance appears to have high sensitivity in detection of established infection in flocks, however more research is needed into the sensitivity in low prevalence flocks or where infection has been recently introduced. Results to date are consistent with the previously known distribution of infection in NSW.
There is also an increasing urgency for the Sheep Industry to recognise the importance of OJD and the National Program and encourage individual producers, under the principle of "Mutual Obligation", to implement appropriate risk management strategies. Those without the disease should embrace assurance testing (Check tests or MAP) and utilise the Voluntary Vendor Declarations. Those with the disease or under suspicion should be committed to minimising the risk of spread to other producers. Regulatory controls, including zoning, are an essential component of controlling the disease spread — based on experience with previous and current disease control programs, deregulation would he expected to lead to a "Market Failure" situation with individual producers unable to protect themselves against introduction of disease into their flocks.
The important issue of assistance for affected producers is being progressed by the Hassall and Associates review under the auspices of the NSW OJD Industry Advisory Committee. Their report is eagerly awaited.
The implementation of revised national surveillance strategies will provide renewed impetus to the National Program while new diagnostic tools and research developments will assist in reducing uncertainty in producers minds regarding the distribution of the disease and our understanding of the epidemiology.
Improved financial prospects for the sheep industry, with a 47% increase in the 19 micron indicator over the past 12 months and improving lamb exports, will provide further impetus for the sheep industry to address the compexities of OJD.
In the meantime, every effort is being made within NSW to reduce the impact of OJD and ease the plight of affected producers while still adhering to national requirements to control the spread of the disease during the evaluation phase of the 6 year NOJDP.
References
- Eppleston J. and Simpson G. (1999) "Observations of OJD in an endemic area" NSW Agriculture Wool and Sheepmeat Services Annual Conference, November 15-16, University of New England, Armidale p91-93
- Eppleston J., Simpson G., O'Neill S., Thornberry K., Lugton I., Taylor F. and Hall D. (2000) "Reported levels of sheep mortalities in flocks infected with Ovine Johne's Disease in New South Wales", Ann. Conf. Aust. Soc. Animal Prod., July 2000, In Press