Current Research Projects - Sheep
Ovine Johne's Disease: enhanced diagnosis and prevention
Evaluation of the effectiveness of Gudair
Eradicating footrot by specific vaccination
Dichelobacter nodosus genes in pathogenesis of footrot in sheep
Ovine Johnes Disease – Applications of basic research on enhanced diagnosis and prevention P.PSH.0311
Farm Animal & Veterinary Public Health Staff
Professor Richard Whittington
Dr Douglas Begg
Dr Kumi de Silva
Dr Karren Plain
Dr Auriol Williams
Ms Nicole Carter
Ms Sophie Hoft
Mr Craig Kristo
Mrs Rebecca Maurer
Mr Jesse McIvor
Mr Nobel Toribio
Mrs Anna Waldron
Mrs Ann-Michele Whittington
PhD Students
Ms Satoko Kawaji
Mrs Kate Bower
Mr RB Gurung
Ms Shyamala Thirunavukkarasu
National Collaborators
Dr Ian Marsh, NSW Department of Primary Industries
Elizabeth Macarthur Agricultural Institute
International Collaborators
Dr Jayne Hope, Compton Institute, UK
Dr Gregers Jungerson, Danish Veterinary Laboratory
Dr Yasuyuki Mori, National Animal Health Institute, Japan
Dr Torsten Eckstein, Colorado State University
Summary
Ovine Johnes disease (OJD) is caused by Mycobacterium avium subsp. paratuberculosis (MAP) remains a significant issue for sheep industries throughout southern Australia. It can be responsible for significant losses if left uncontrolled. Vaccination to reduce the prevalence of clinical disease within infected flocks has been very successful, with widespread adoption by affected producers. In addition, vaccination is used to improve flock status in a risk based trading scheme. However, vaccination does not prevent infection, and rates of shedding of MAP remain high on several properties where the vaccine has been used, there are injection site reactions in sheep and occupational health and safety risks for producers. Furthermore, some producers have ceased to vaccinate due to reductions in flock mortality rates, high cost of vaccine and reduced farm incomes due to the drought. In addition, producers in some regions where OJD is uncommon or absent continue to exclude sheep from endemic regions, which is impacting on trading options of producers. Food safety is also a concern. Although controversial and still unproven, MAP has been proposed as a potential cause of Crohns Disease in humans.
Internationally, JD is considered to be a significant threat to the livestock sector, regardless of the species affected. Public health authorities in many develop countries have adopted a neutral position on the possible link between MAP originating in livestock and the occurrence of the organism and disease in humans. Nevertheless, animal health authorities in many countries have introduced, or plan to introduce control programs for JD. These will depend on research programs on JD in the EU/Europe, Japan and North America and smaller research programs in many other places. These countries are trading partners and/or competitors of the Australian red meat industries. For market access insurance, Australia needs to be engaged with R&D at an international standard. Currently there is very little basic research on JD in Australia other than that in a recently completed MLA project, OJD.031. That research program led to a substantial Australian capacity in this field of research. The research needs for OJD are complementary to those of BJD.
This project is a program of basic and applied research that aims to develop new diagnostic tests for OJD and, through a program of basic research on the pathogenesis of the disease, increase understanding of the immune response to infection, dormancy of the bacterium and how this relates to chronic infection and transmission of the bacterium.
Source of Funding
Meat & Livestock Australia
Project Timeframe
January 2008 - March 2011
Evaluation of the effectiveness of GudairTM vaccination for the control of OJD in flocks vaccinating for at least five years P.PSH.0309
Farm Animal & Veterinary Public Health Staff
Professor Peter Windsor
Professor Richard Whittington
Mrs Anna Waldron
National Collaborators
Dr Jeff Eppleston,
Central Tablelands Rural Lands Protection Board
Dr Evan Sergeant, AusVet Animal Health Services
Summary
Ovine Johnes disease (OJD) caused by Mycobacterium avium subsp. paratuberculosis (MAP) is a major issue for the sheep industries of southern Australia, causing significant on-farm losses, division within the industry, plus potential public health concerns. Control of OJD in Australia now depends heavily on use of Gudair TM vaccine to control on-fa losses and to reduce the risk of disease spread. Research undertaken during the six-year National Ovine Johne’s Disease Program (NOJDP) demonstrated that the current vaccine is highly effective in reducing mortalities due to OJD and shedding of organisms, but some sheep still develop severe clinical disease, shed heavily and die. This research supported the registration of the vaccine for use in sheep in Australia, and it is now widely used as a disease control and risk management tool. However, the original vaccine evaluation was undertaken in a single generation of vaccinated lambs in three heavily infected flocks in the central tablelands area of NSW, under conditions of very high challenge. This has given rise to speculation that:
- Efficacy of the vaccine might have been underestimated because of the high-challenge situation in the trail flocks; and
- The vaccine may be more effective in lower-prevalence flocks than was observed in the high-prevalence trial flocks.
- Although modelling suggests that long-term use of vaccine will provide highly effective control and suppression of shedding, even in heavily infected flocks, this has never been verified experimentally. This has important implications for the value attributed to flock-vaccination in any flock-assurance scheme, as highlighted in recent discussions for continuation of the national program.
Further research on vaccine efficacy is well advanced, in a longitudinal study of shedding from three generations of sheep vaccinated as lambs (MLA project OJD.033). However, as this project is limited to only 12 flocks in central NSW and final results are not expected until early 2009, there is a need for a broader study on the impact of vaccination on shedding rates in flocks of varying initial prevalence. As recent results from OJD.033 have indicated that the profound decrease in shedding over time may not be achieved in all participating flocks, the reasons for this need to be investigated. In addition, investigations in a greater number of flocks to support this project and to provide an earlier indication of longer-term effects of vaccination in flocks of known infection and vaccination history, is needed.
The purpose of the project is to evaluate the effectiveness of GudairTM vaccine in reducing OJD prevalence and bacterial shedding in a range of flocks of known OJD prevalence, at about five years after the commencement of vaccination.
Source of Funding
Meat & Livestock Australia
Project Timeframe
January 2008 - November 2009
Eradicating footrot by specific vaccination EC.511
Farm Animal & Veterinary Public Health Staff
- Professor Richard Whittington
- Dr Om Dhungyel
- Ms Angela Reeves
National Collaborators
- Emeritus Professor John Egerton
- Dr Jeff Eppleston, Central Tablelands Rural Lands Protection Board
- Dr John Seaman, NSW Department of Primary Industries
- Dr Alison Lee, Department of Primary Industries, Victoria
- Dr Neil Buchanan, Department of Primary Industries & Resources, South Australia
- Dr Mick Middleton and Dr Cameron Bell, Tasmanian Department of Primary Industries, Water & Environment
Summary
Footrot is caused by the bacterium Dichelobacter nodosus, a parasite of the feet. This bacterium is unable to survive off the foot for more than one week. Eradication of footrot is therefore possible if all sheep with footrot are removed from a flock. Current techniques to achieve this are labour intensive, expensive and often take several years to achieve eradication. Vaccination is an alternative approach.
Current footrot vaccines contain ten strains of bacteria to provide coverage of the major D. nodosus serogroups. These vaccines offer only temporary (12 weeks) protection against footrot, so they are used in control campaigns, rather than for eradication. It has been demonstrated that eradication of footrot using vaccines is possible if the vaccines only target one or two groups of the bacterium at a time because immunity is long-lasting. This project will evaluate this approach under Australian conditions.
Objectives of the project:
- Produce specific footrot vaccines for local (Australian) strains of the footrot bacterium.
- Evaluate the use of these targeted footrot vaccines using one or two different antigens per vaccination in the eradication of virulent footrot in Australian sheep.
- Demonstrate the use of these vaccines to remove virulent footrot on 12 commercial farms across areas of high footrot prevalence in southeast Australia.
- Evaluate the minimum interval between vaccination with different vaccines to deliver an accelerated eradication program (less than twelve months between different vaccines)
- Enable application for a minor use permit from the Australian Pesticides and Veterinary Medicines Authority (APVMA) to allow the use of these vaccines on-farm and also aid transfer of the vaccine to commercial production facilities.
Source of Funding
Australian Wool Innovation
Project Timeframe
July 2005 - June 2010
The role of Dichelobacter nodosus genes in pathogenesis of footrot in sheep
Farm Animal Health Staff
- Professor Richard Whittington
- Dr Om Dhungyel
- Mr Craig Kristo
National Collaborators
Professor Julian Rood*, Monash University
Dr Leslie Reddacliff,
NSW Department of Primary Industries
Elizabeth Macarthur Agricultural Institute
* Principal Investigator
Summary
Ovine footrot is a highly infectious bacterial disease that is of major ongoing concern to the Australian wool industry, causing significant economic losses as a result of its effect on wool production, farm management, animal welfare and the cost of control and treatment programs. The causative bacterium is Dichelobacter nodosus.
The overall objective of this research is to develop improved methods for the control and treatment of ovine footrot. The specific research aims are:
- To identify D. nodosus genes that are differentially expressed in the virulent footrot lesion.
- To determine the role of differentially expressed genes in the disease process.
- To determine the value of whole genome based microarrays for the epidemiological analysis and diagnosis of field isolates of
D. nodosus. - To identify surface or secreted D. nodosus antigens that induce the production of bactericidal antibodies in sheep.
- To determine the vaccine potential of D. nodosus antigens that are either essential for the disease process or induce the production of bactericidal antibodies.
The successful completion of the project should lead to the subsequent commercial development of a protective footrot vaccine, with significant cost savings to wool producers and the Australian wool industry. It will also lead to a greater understanding of the epidemiology of footrot infections and may result in the development of improved methods for the laboratory diagnosis of ovine footrot.
This research program represents the pre-commercialisation phase of the development of a new generation of footrot vaccines. The successful identification of candidate antigens that can be used to develop a protective footrot vaccine will be subject to the uncertainty of dealing with a variable biological system.
Source of Funding
Australian Research Council,
Centre for Structural and Functional Microbial Genomics
Project Timeframe
February 2005 - December 2010