The development of a new rapid test for determining the serogroup and virulence of footrot affecting Merino sheep

Summary

Virulent footrot is an economically significant disease in most sheep rearing countries. The clinical manifestation of footrot in sheep are determined by the virulence of the strain of Dichelobacter nodosus involved, environmental conditions and the innate and acquired resistance of the host. Interactions between these factors determine the severity of the disease which is expressed as a continuous spectrum from benign to highly virulent in which there is severe underrunning of the horn of the hoof. These terms are also used to describe the strains of D. nodosus which are isolated from and have potential of causing the respective clinical forms in exposed, susceptible animals. Clinical differentiation of the different forms of footrot is difficult in the early stages of the disease when there are only interdigital lesions, or under adverse climatic conditions when expression of the disease is suppressed. Field diagnosis of virulent footrot is not always easy, so a number of laboratory tests have been developed to help in the diagnosis. In addition, the serogroup of D. nodosus is determined in order to select an appropriate vaccine for control and prevention of footrot

Supervisor(s)

Professor Richard Whittington

Research Location

Faculty of Veterinary Science

Program Type

PHD

Synopsis

Current phenotypic virulence detection tests are not reliable and the agreement between the available phenotypic tests is poor. There is a need for a test for virulent footrot which offers more consistent results, or at least results that closely match the clinical potential of isolates of D. nodosus to cause disease. Genetic tests for the virulence factors of D. nodosus may overcome some of the limitations of the phenotypic tests. They may be more stable, are not likely to be influenced by the physiological state of the organism, and may be quicker and cheaper, particularly if tests can be devised that do not require prior microbial culture, and that can be applied directly to field samples like lesion swabs.   In this project the whole genome sequence of D. nodosus  will be examined to identify markers for virulence and serogroup, and tests devised. The tests will be applied in laboratory studies of archival samples, and in current pen and field trials. This study will also involve studying and analysing data collected from 12 farms over 5 years, to correlate within-flock prevalence and severity of footrot with microbial characteristics. The study is a high priority for the sheep industries in Australia.

Additional Information

EligibilityThese scholarships are available only to Australian or New Zealand residents who are also eligible for an APA/UPA scholarship. Application for an APA/UPA scholarship must be successful in order to receive this award (http://sydney.edu.au/scholarships/research/postgraduate_awards.shtml). Scholarships will commence in 2013. Scholarship termsThe scholarship provides a tax free “top-up” amount of $15,000 per annum as a stipend for three years and is in addition to the tax free APA/UPA award of $23,729 p.a. (2012 rate) The total value of the combined scholarship is $38,728 per year tax free. Separate applications are required for the APA/UPA and the Ian (Peter) Wrigley Scholarship. Interested candidates may contact the supervisors for further details: Dr. Om Dhungyel (om.dhungyel@sydney.edu.au and Professor Richard Whittington (richard.whittington@sydney.edu.au ). To apply for the Ian (Peter) Wrigley Scholarship, please submit a letter of application and relevant supporting documentation outlining your suitability to Dr Om Dhungyel by the 31st October 2012. 

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Keywords

footrot, ovine footrot, ovine

Opportunity ID

The opportunity ID for this research opportunity is: 1606

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