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Almost gone but not forgotten - the human impact of OJD

Bill Johnson, Gunning, Former District Veterinarian, Goulburn

Posted Flock and Herd July 2023
Introduction

Ovine Johne's Disease (OJD) had a marked effect on sheep owners and others in the livestock industry. The disease impacted owners of infected flocks, their families, neighbouring landholders, livestock agents, livestock husbandry and shearing contractors, livestock carriers, abattoir managers, saleyards operators, veterinarians and biosecurity officers. For a few, it was the distress of high death rates up to 17% per annum of their adult sheep from OJD (Bush et al., 2006); while for the majority, their distress was attributed to the failed attempt to control and eradicate OJD in NSW (Hassall et al., 2000). Fallout from that program is still evident.

Diagnosis of OJD, and its subsequent regulation, brought with it a range of financial, social and emotional impacts. These human impacts are not restricted to OJD control, but have been encountered to some extent by government veterinarians and biosecurity officers involved in other animal disease control and eradication programs, including ovine footrot, bovine tuberculosis, bovine brucellosis, and more recently varroa mite of European honeybees. So why is OJD considered to have had such a great effect on humans?

Principles of disease eradication

Global eradication of human smallpox is regarded as a monumental public health achievement (Dowdle & Cochi, 2011). It highlighted four principles of successful disease eradication: biologic feasibility; adequate public health infrastructure; sufficient funding; and sustained political/societal will.

Earlier, both bovine tuberculosis and bovine brucellosis were declared eradicated from Australia. A review concluded that the successful eradication was based on a sound technical program with strong, joint industry and government funding and decision making (Radunz, 2006).

The adverse human impacts of the OJD control and eradication program can be largely attributed to ignorance or neglect of these principles by policy makers.

The initial program was poorly supported by the available science, and sheep owners were quickly aware of its practical deficiencies. There was a long delay from infection to first clinical signs; clinical signs were similar to those caused by endemic conditions, usually meaning the disease was well established before it was identified; tests used were of poor sensitivity (about 30% for both the AGID and ELISA test), and were useless as a single animal test; the causative organism could only be cultured from 8% of clinically affected sheep (Carrigan & Seaman, 1990); infection moved through boundary fences far more readily than infected straying sheep, casting doubt on feasibility of eradication on individual properties; the pathway to exit quarantine was not clear, and not tried; the pillars of proposed OJD eradication were undermined by continuing research; and the market assurance program designed to identify sources of sheep for restocking frequently failed.

The program provided no financial, emotional or social support.

There was poor understanding of OJD in the sheep community. Sheep producers in areas where OJD was identified became more knowledgeable, but the overwhelming reaction to OJD in other areas was fear, which led to poor decision-making in industry advisory bodies, and adversely impacted policy.

Background

The first diagnosed case of OJD in Australia was recorded from the NSW Central Tablelands near Bathurst in 1980 (Seaman et al., 1981). Further cases of OJD, caused by infection with Mycobacterium avium subspecies paratuberculosis (MAP), were diagnosed only in the general vicinity of the first identified flock until 1991, when OJD was detected in flocks on the NSW Southern Tablelands near Goulburn. By the end of 1996, when OJD was first reported in Victoria, 158 OJD-infected flocks had been recorded in southern NSW, and an OJD control and eradication plan was developed by NSW Agriculture (later NSW DPI).

At that time, movement of sheep from known infected flocks was restricted, by quarantine or undertaking, to sale for slaughter; neighbours were informed; and prior movements of sheep to and from the property were traced. Governed by the official perception that OJD affected only a small number of flocks in a relatively small and defined area of Australia, owners of known infected flocks were given no practical means by which to remove that infected status, other than by completely destocking the sheep flock from the property to slaughter, without compensation.

Diagnosis of OJD, usually based on a field post-mortem examination of a clinically affected sheep with confirmation by histopathology, was followed by the application of the regulatory program. In most cases, this process involved the same veterinarian who had performed the autopsy imposing quarantine of the flock, and requesting the owner to provide details of neighbours and of the previous five years of sheep movements. One former District Veterinarian recalls "the lady of the house turning her back on me, whilst grown tough men have tears welling up when sitting at the kitchen table" as an image that is "hard to erase".

Financial Impact of OJD diagnosis

The dramatic impact of OJD diagnosis on livestock businesses was ignored, or at best underestimated, by policy makers. With previous disease control programs with which they were familiar, including bovine brucellosis, bovine tuberculosis and ovine footrot, in all but a few cases it was possible for producers to retain a substantial proportion of the animals in their infected or suspect herds or flocks. They maintained their familiar enterprise, leaving them able to recommence open trading within a few years. The only way out of OJD quarantine was through complete depopulation of the flock. For studs and dedicated merino breeders, this requirement was financially ruinous. The per head slaughter returns were often about 10% of the value of the live animal pre-OJD diagnosis. In addition, the prospect of sacrificing years of genetic selection and strategic breeding was mentally devastating.

OJD was the subject of two Australian Parliament Senate Inquiries, in 1998 and 2001 (Australian Parliament, 1998; 2001). The Committees' reports chronicle changes in knowledge of OJD, and the difficulties of reaching consensus on OJD control, within the sheep industry, between state and national governments, and between government and industry. Both reports identify affected producers as bearing most of the social and financial burden of OJD control. Disturbingly, the need for financial assistance for affected producers, highlighted in 1998, had still not been met by 2001, despite some being involved for two decades.

Living with confirmed or suspected OJD was also a huge financial burden for some enterprises. For most affected producers, the cost of OJD regulation far exceeded the direct impact of OJD (Hassall et al.). The financial success of any business relies on balancing debt and expenditure against expected income. The requirement to sell only to slaughter post-OJD diagnosis reportedly reduced farm income by 60% for some producers. They experienced marked financial pressure to service existing debts, and discretionary expenditure, such as being able to send their kids to boarding school, was curtailed. One smaller tablelands finewool merino stud diagnosed with OJD reported that the requirement to only sell stock to slaughter cost them $120,000 in the first year (1993).

Reduced farm income led to retrenchment of farm employees, and some succession plans were derailed.

OJD-affected producers opting to undertake eradication were prescribed several ways by which to earn an income during the period when their land was supposedly being freed of OJD (sixteen months, including two summers). Many of these were financially fraught, especially in a high rainfall environment with cold winters. And producers were aware of the flaws in these official recommendations.

Running wethers sourced from western NSW was widely promoted, in the belief they would be unlikely to have been previously exposed to OJD, and hence would not contribute to pasture contamination in the short term. Unfortunately, they were unlikely to have been exposed to high internal parasite burdens either, and with little innate or acquired immunity they became severely affected, particularly by scour worms. Their wool type was unsuited to 600mm-plus rainfall areas. The wool was of higher micron and hence lower value, which was further eroded by susceptibility to both fleece rot and flystrike.

Replacing an OJD-infected sheep flock with cattle was also a recommended approach to land use during OJD eradication. Many tablelands OJD-infected flocks ran on land not suited to cattle, without appropriate cattle infrastructure (cattle-proof fences, cattle handling facilities, supplementary fodder handling equipment), and without cattle management skills. Most affected producers were understandably nervous of this approach.

Zoning was introduced in an attempt to limit the spread of OJD, well in advance of widespread surveillance for the disease. This approach to disease control caused immediate hardship for sheep studs, commercial breeders, and several enterprises with properties in adjoining zones. Regular correspondence in the rural press from industry leaders in areas where OJD had not yet been diagnosed shunned trade with all sheep breeders from the southern and central tablelands, and supported calls for OJD eradication. At the same time, these correspondents were not offering to contribute to compensation.

OJD infection and OJD zoning adversely affected land prices and decreased buyer enquiry. The Senate was told that land value discounts up to 40% occurred, and some properties were withdrawn from sale due to lack of buyer interest (Australian Parliament, 2001).

A voluntary levy was introduced for sheep producers in NSW to help fund the OJD program. Those who failed to pay voluntarily faced Government compulsory debt recovery action.

Social and emotional impact of OJD

The first-diagnosed OJD-infected flock in an area was often falsely perceived by neighbours and others in the community to be the index case. These producers were under enormous social pressure to minimise the possible spread of infection, despite no testing of neighbours' sheep. Numerous unpleasant neighbour disputes arose over the state of boundary fences, or the long-standing routine movement of livestock along roads and rights of way.

Producer-led OJD support groups were crucial in disseminating information and providing business and emotional support to affected producers and their families. Great credit is owed to the empathetic leaders of these groups who spent hours on the phone counselling their colleagues. These groups were also ultimately instrumental in changing OJD policy.

Lack of credible information, or misinformation in some cases, added to the social and emotional stress on owners of infected flocks. The last-minute cancellation of a district pony club gymkhana, which had been held for years on a property where OJD was recently diagnosed, caused great distress for that whole family. No guarantee could be given that a pellet of sheep dung might not find its way off the property in a horse's hoof, or on a horse float.

Seeing on-going wasting and deaths as increasing numbers of adult sheep became affected by OJD in well-managed flocks was distressing for owners and their families. Although producers knew vaccination was being used successfully overseas to reduce the impact of OJD in infected flocks, policy makers refused to support calls for small-scale trials of OJD vaccine, even in high prevalence areas. Gudair® vaccine was not registered until April 2002.

Thankfully irony and humour were not totally stripped from affected communities. The 'SLAUGHTER ONLY' signs designating that area of Goulburn saleyards set aside for sheep from OJD-infected and suspect flocks, were quickly defaced by removing the 'S', to read 'LAUGHTER ONLY'. The altered signs remained in place for several years.

Fear of OJD

Fear associated with OJD diagnosis slowed progress with testing suspect flocks identified by tracing. Sheep owners quickly came to understand the plight of those identified with OJD infection, and went to great lengths to avoid being one of them. Once cordial and cooperative working relationships between government employees and livestock agents soured. Livestock agents were reluctant to provide tracing information from producers they regarded both as valuable client and close friends. One stud owner was heavily fined by the Court for failing to provide tracing information that would identify his hard-won and loyal customers.

A Market Assurance Program was promoted, to supposedly identify sources of low-risk re-stocker and stud sheep. While some studs were shown to be infected by initial testing, infection in several flocks was not detected until subsequent rounds of testing. In some cases, sheep sourced from accredited flocks were found to be positive immediately after purchase. Confidence in the program was impacted, and owners were reluctant to enter or continue with the scheme.

Fear of an OJD diagnosis also led to unnecessary sheep deaths. The number of requests for on-farm sheep disease investigations fell dramatically. The author recalls carrying out sheep autopsies to assist sheep owners in determining the causes of death or disease on more than sixty properties one winter prior to OJD. After OJD had been diagnosed in the district, and in a similar winter, fewer than ten on-farm sheep investigations were carried out. One case involved ill-thrift, scouring and deaths in eight-month-old merino weaners. Only when the deaths exceeded 10% of the mob of about 800 did the producer's wife convince him to contact the District Vet to have the problem investigated - even if it was, as he expected, OJD! These young sheep improved dramatically following confirmation of, and treatment for, internal parasitism.

Abattoir monitoring targeted lines of sheep consigned directly from properties, and not from saleyards. This type of surveillance consequently identified infection in larger commercial breeder flocks. Once producers realised the threshold for OJD abattoir monitoring was 100 head, numbers in direct consignments were tailored, or the sheep went to saleyards, or in some cases to interstate abattoirs, to avoid surveillance.

There was ongoing concern at a possible link between MAP and Crohn's disease in humans, which strengthened calls for OJD to be eradicated, with some industry leaders fearing a fall in sheep meat consumption. While MAP is now found in tissues of more than half of people with Crohn's disease, it is not determined to be causal (McNees et al., 2015), with MAP also recovered from tissues of people without Crohn's disease.

Access to information

The most recent scientific information became readily available to sheep owners through simple internet searches. Such information was previously largely only available by subscription to specific scientific journals, or membership of scientific organisations such as Australian Veterinary Association. Producers sequentially learnt that cattle could be infected by the S-strain; that MAP could survive longer than 16 months in the environment; that rabbits could be infected by MAP; and that kangaroos and wallabies could also be infected. There were frequent embarrassing "gotcha" moments, when producers would present one of these findings as a question in a public forum, directed at a veterinary official who was ignorant of the latest research. Each of these findings, and the weakness of the response from veterinarians, further undermined credibility of the OJD eradication strategy, but that continued to be the policy.

Implications for future animal disease control and eradication programs

Nine of the first eleven flocks detected with OJD infection in the Goulburn district were the direct result of enquiries from astute sheep owners. The subsequent turmoil and perceived betrayal caused to these more cooperative and observant livestock owners has significant ongoing implications for early detection of a potential exotic disease. Most of the farms caught up in the aborted OJD eradication program still remain in the same family ownership. They are now, in many cases, managed by the next generation. Suspicion of veterinary authority remains, seen as reluctance by these producers to report abnormal or unusual animal health observations - once bitten, twice shy!

The value and use of abattoir sheep disease surveillance was demonstrated during presentations to the 2014 and 2017 DV conferences. Funding was available for NSW abattoirs to participate. The author enthusiastically met with management of Southern Meats, which at the time had the second largest adult sheep throughput in NSW, to encourage them to participate in the 'other diseases monitoring' project. This project would provide feedback to producers on wide-ranging but targeted disease information collected from their sheep at slaughter. Better on-farm management of these diseases would improve returns to producers and abattoirs. The benefits seemed obvious. Abattoir management refused to be involved with the project, citing the effects of the OJD program more than 20 years earlier on both the abattoir and their clients. They had evidence that sheep that would have normally been consigned to them had bypassed the plant in favour of abattoirs in Victoria, which at the time did not require checking for and reporting of OJD in consigned lines. They also remained wary as a result of previous OJD tracing requirements, which involved the abattoir in excessive administration and damaged their commercial relationships with livestock suppliers.

The OJD eradication program predated widespread use of social media. Contact with and between producers was by telephone or letter, and OJD became the main topic of conversation at social gatherings, displacing the weather. The OJD program failed to persuade mainstream media, particularly the widely read rural weekly newspaper The Land. In a review of its first 110 years of publication, The Land described the failed OJD control program in NSW as one of the low points in agriculture. Through social media, future animal health programs will be scrutinised by a far wider audience, information will be more readily and widely disseminated regardless of its accuracy or relevance, and affected producers and communities will be more easily mobilised to support or counteract. There is now also a greater tendency for those affected to apply political pressure by taking their grievances straight to the Minister. Legal firms eagerly look for opportunities to begin class actions.

If the adverse impacts of OJD on humans have taught us anything, then future animal disease control programs must be firmly based on established principles.

Acknowledgements

Terry Hayes, former Chairman, Goulburn branch Tablelands Stockcare Group Inc.
Jim McDonald, former District Veterinarian, Yass Rural Lands Protection Board
John Evers, former District Veterinarian, Young Rural Lands Protection Board

References
  1. Australian Parliament (1998) The Incidence of Ovine Johne's Disease in the Australian Sheep Flock - First Report, Senate Rural and Regional Affairs and Transport References Committee, July 1998. The Incidence of Ovine Johne's Disease in the Australian Sheep Flock - First Report - Parliament of Australia aph.gov.au
  2. Australian Parliament (2001) The Incidence of Ovine Johne's Disease in the Australian Sheep Flock - Second Report, Senate Rural and Regional Affairs and Transport References Committee, July 2001. p 137 of 2001 nla.gov.au
  3. Bush RD, Windsor PA and Toribio J-A LML (2006) Losses of adult sheep due to ovine Johne's disease in 12 infected flocks over a 3-year period Australian Veterinary Journal 84(7):246-53
  4. Carrigan MJ and Seaman JT (1990) The pathology of Johne's Disease in sheep Australian Veterinary Journal 67(2):47-50
  5. Dowdle WR and Cochi SL (2011) The principles and feasibility of disease eradication J. Vaccine 29S:D70-D71
  6. Hassall and Associates (2000) Financial impacts and forms of assistance for OJD affected producers. Report prepared for NSW OJD Industry Advisory Committee. Hassall and Associates Pty Ltd, July 2000;1:30
  7. McNees Al, D Markesich, NR Zayyani and DY Graham (2015) Mycobacterium paratuberculosis as a cause of Crohn's disease Expert Review of Gastroenterology & Hepatology 9(12):1523-1534
  8. Radunz B (2006) Surveillance and risk management during the latter stages of eradication: Experiences from Australia Veterinary Microbiology March 2006; 112(2-4):283-90
  9. Seaman JT, Gardner IA and Dent CHR (1981) Johne's disease in sheep Australian Veterinary Journal 57(2): 102-103

 


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