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Rural Industries
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Development of a recombinant vaccine against equine herpesvirus 1 (equine abortion virus) and equine herpesvirus 4 (equine rhinopneumonitis virus) diseases.
Objectives
EHV-1 abortion is the virus disease of greatest concern to the equine industry in Australia. EHV-1 is responsible also for neonatal deaths, and neurological and respiratory symptoms, which together with abortion result in major losses to all sectors of the horse industry in Australia and overseas. The closely related virus EHV-4 is associated with severe respiratory disease which is also of consequence to young performance horses and there is evidence that EHV-4 may predispose weaklings to strangles. Available whole virus vaccines against EHV-1 and EHV-4 have a history of limited efficacy and safety and were not permitted for use in Australia until 1997. This project addressed the need for effective new vaccines against EHV-1 and EHV-4.
Research
Genes coding for individual EHV-1 components (subunits) were cloned and the subunits (envelope spike proteins) produced in cell culture. These subunits were tested for vaccine potential, initially in a mouse model of EHV-1 infection, which mimics the disease in the horse. The spike proteins were found to elicit antibody and cellular immune responses in mice and also to confer protection against challenge with EHV-1. Experiments in horses indicated the safety of the subunit material for use in horses. To obtain relevant information on the spread and prevalence of EHV-1 and EHV-4, foals, weaklings and mares on large stud farms in NSW were tested for evidence of virus infection.
Outcomes
A new potential vaccine consisting of protein subunits of EHV-1 is ready for further testing in horses. Antibodies produced against the trial vaccine act also to block infection by EHV-4, indicating that it will be effective against both viruses. New evidence was obtained that EHV-1 is infecting foals as early as 30 days of age, not previously recognised. These foals are a major source of spread of EHV-1 to other susceptible foals.
Implications
The recombinant subunit vaccine has the potential to better protect horses against EHV diseases than other available vaccines. It also has the advantage of enabling EHV-1 infection to be traced in horse populations due to a difference in immune responses from vaccine and infection, which is not possible with whole virus vaccines. The important finding of EHV-1 infection in very young foals has forced a re-evaluation of when and how to vaccinate animals in order to break the annual cycle of EHV-1 infection.
Publications
Csellner H. Whalley JM, Love DN (1995) Equine herpesvirus-1 HVS25A isolated from an aborted foetus produces disease in BALB/c mice. Aust Vet J 72: 68-69
Whalley ~M, Love DN, Tewari D, Field HI (1995) Characteristics of equine herpesvirus 1 glycoproteins expressed in insect cells. VetMicrobiol 46: 193-201
Gilkerson JR, Love DN, Whalley JM (1997) A review of equine herpesvirus vaccines: from the traditional to the experimental.AustEquine Vet 15: 27-32
Kukreja A, Love DN, Whalley JM, Field HI (1998) Study of the protective immunity of co-expressed glycoprotein H and L of EHV-1 in a murine intranasal infection model. VetMicrobiol. 60: 1-11.
Packiarajah P. Walker C, Gilkerson 1R, Whalley JM, Love DN Immune responses and protective efficacy of recombinant baculovirus-expressed glycoproteins of equine herpesvirus 1 (EHV-1) gB, gC and gD alone or in combinations in BALB/c mice. VetMicrobiol. (In press)
Gilkerson ~ Love DN, Whalley 1M (1997) Serological evidence of equine herpesvirus (EHV-1) infection in Thoroughbred foals 30-120 days of age. Aust Equine Vet 15: 128-134
RIRDC Project No: UMA-14A
Researcher: Associate Professors J. M. Whalley and D. N. Love
Organisation: Macquarie University and University of Sydney
Contacts: Phone:
612 98508200 E-mail:
mwhalley@rna.bio.mq.edu.au
Objectives
Rotavirus diarrhoea in foals is an infectious disease characterised by profuse diarrhoea, fever, depression and inappetence. It can affect foals of up to 4-5 months but is more common in young foals. Rotavirus diarrhoea has been recognised in Australian studs and, while the extent of it is not known, it is potentially a major cause of wastage to the Australian horse industry.
Research
Following consultation with stud managers, the RIRDC Equine R&D Committee organised a workshop in Melbourne on July 24th to bring together stud managers from Victoria, New South Wales and Queensland, veterinarians, scientists and vaccine manufacturers, to discuss the possibility of developing a vaccine to protect foals from this infectious disease.
Outcomes
The participants concluded that rotavirus diarrhoea appears to be becoming increasingly common on studs and in some years can affect up to 50 per cent of foals on some studs. Rotavirus diarrhoea is a major cause of economic loss to the horse breeding industry in Australia with a cost estimate of more than $3 million per annum. The workshop agreed that there was sufficient scientific and technical expertise to develop and produce an effective vaccine and that there was interest in doing so, provided that a detailed cost benefit analysis was satisfactory.
Implications
An increasing number of problems will come to light through interaction between researchers, the horse industry and RIRDC. This workshop was able to highlight an important problem and result in a clear way forward by the interaction between horse stud farm managers, researchers, veterinarians in equine practice and those responsible for R&D management. The model of this workshop will be helpful to deal with other important industry problems.
RIRDC Project No: MS967-44
Researcher: Professor Reuben Rose
Organisation: University of Sydney, Rural Veterinary Centre, PMB 4, Narellan Mail Centre, Narellan NSW 2567
Contacts: Phone No. (02) 4655 0777 Fax No. (02) 4655 6491 Email No. rjrose@camden.usyd.edu.au
Review of devices currently available for assessing racetrack conditions
Objectives
Background
A controversial aspect of grass racetracks is the definition and measurement of the quality or rating of the surface for racing horses, and the real and perceived influence that the surface has on level of performance and horse safety and injury. Track rating methods used in Australia are mostly subjective and open to criticism. A number of mechanical devices for measuring track rating, including the penetrometer, clegg hammer, cone penetration test and shear vane, are currently available and are either being advocated or adopted. A critical review of the available literature and field results of these devices was considered necessary
Research
A comprehensive review was made of world literature relevant to the development and utilisation of various mechanical and other devices for measurement of parameters of grass racetrack quality or "going". Quantitative information on mechanical devices used at four Australian racetracks was also analysed to determine consistency of relationships between measurements and racing performance of horses.
Outcomes
The measurement of track rating to define horse performance and risk of injury is complex and involves several interacting factors including type of surface, surface conditions, soil characteristics, track configuration, season, racecourse location, racing speed, the jockey, and pre-existing injuries. The penetrometer and the clegg hammer are the only devices in regular use for defining track surfaces, however their usefulness is still in debate. Penetrometer readings have shown good relationships with race times in France and New Zealand, and a moderate to good correlation was found on Australian racetracks.
Implications
It would appear that it may not be possible to develop a simple device, meeting all the criteria for rating tracks, when dealing with such a large number of variables. There is scope to undertake further work with the penetrometer and the clegg hammer, however the inclusion of soil physical characteristics may also be necessary. Any future work must incorporate what the horse is experiencing when racing under a range of track conditions.
RIRDC Project No: PTP-5A
Researcher: John Neylan*
Organisation: Turfgrass Technology Pty Ltd, 9 George Street, SANDRINGHAM VIC 3191
Contacts: Phone:
03 9521 6982 Fax:
03 9521 6946 E-mail:
michaelr@cosmos.net.au
* Co-Researcher was Arthur
Stubbs of Primary Tasks Pty Ltd
Identification and characterisation of causes of wastage in the Australian Thoroughbred Racing Industry
Objectives
The term "wastage" has been used to refer to losses that occur at all stages of development of a racehorse and research in other countries has indicated that significant losses occur within their racing industries. Increasingly, concerns are being raised about the animal welfare and economic implications of injuries sustained by Thoroughbreds. Despite the size of the Thoroughbred industry in Australia and the unique features of stabling, training and racing in this country, there has been limited epidemiological research on the extent of wastage occurring here.
Research
An initial indication of the major causes of wastage was obtained through a survey of 40 Sydney trainers in the form of a questionnaire. Based on a frequency score, the most commonly observed conditions were dorsal metacarpal disease (shin soreness), coughing, other joint injuries and nasal discharge. With regard to the impact of conditions on training, the trainers perceived infectious respiratory disease as the most important cause of wastage, followed by general lameness then shin soreness.
Two case-control studies were conducted to identify and quantify risk factors for serious limb injuries sustained at metropolitan racetracks in Sydney and Melbourne. For the two Sydney racetracks, the incidence of limb injuries that resulted in death in flat races was 0.03% per start. The equivalent incidence rates for flat, hurdle and steeplechase races at the four Melbourne racetracks were 0.06%, 0.63% and 1.43%, respectively.
Racing records of Thoroughbred horses catalogued in a major yearling sale in 1991 were analysed to profile the career of racing Thoroughbreds in Australia. The effect of gender and foaling period on the time to first race start, and the effect of gender, age at first start and average inter-race period on career length, were investigated.
Assessment of the causes of lost training days and the identification of major reasons for horses not racing as two-year-olds was achieved through a longitudinal study of two- and three-year-olds in training.
Outcomes
In the studies of different racetracks, in the Sydney study, horses at greater risk were older, started from a wider starting position, ran at the same distance as their previous race and raced in a higher class of race. The Melbourne study identified harder track surfaces, horses being older than three years of age, one of the racecourses (Flemington) and jumping races as risk factors that increased the risk of serious limb breakdown. The incidence rates of limb injuries that resulted in horses being destroyed for flat races were similar to those reported in the United Kingdom but less than the United States. Death rates for hurdle and steeplechase races in the study population were higher than in the United Kingdom.
In the study of career profiles of Thoroughbred yearlings, of the 553 horses catalogued in the 1991 sale, 50% had raced as two-year-olds and 85% had raced by the end of the cohort’s six-year-old racing season. The average number of starts in Australia or New Zealand up to and including the six-year-old racing season was 15. Gender had no significant effect on the time to the first race start, and Thoroughbreds born early in the foaling season were not significantly more likely to race sooner compared to late-born foals. Thoroughbreds that were male, raced less intensively, or first raced at a younger age were more likely to have longer racing careers.
For young horses in training, lameness was a much more important cause of wastage than respiratory conditions. It was concluded that the main veterinary reason for the relatively low proportion of horses that race as two-year-olds was the high number of minor incidents that occur during the first season of training. In contrast, major injury was relatively uncommon in young horses in training.
Implications
The study has shown that Australia compares favourably with other countries in the incidence of serious racetrack injuries and deaths. While only about 50% of two-year-old racehorses have a race start in their first racing season, horses that do start have a greater expectation of a longer racing career. Many two-year-old horses do sustain a range of injuries and diseases but mostly these are relatively minor and not career ending.
Publications
RIRDC Project No: US-25A
Researcher: David Hodgson
Organisation:
University of Sydney, Department of Veterinary Clinical Sciences,
University Veterinary Centre (Camden), PMB 4, Narellan Delivery Centre,
Narellan NSW 2567
Contacts: Phone: (02) 4655 0777 Fax: (02) 4655 1212 E-mail: davidh@camden.usyd.edu.au
A molecular diagnosis of equine parasitism
Objective
The use of modern anti-parasite drugs has had serious adverse effects on the control of parasitism, including the development of anthelmintic resistance in small strongyle (cyathostome) populations, a substantial increase in the prevalence of cyathostomes and associated clinical disease. Thus, an integrated strategy is required for the effective parasite control. Accurate diagnosis of parasitism in horses is a central component of integrated control. However, current coprological methods are inaccurate and time-consuming to carry out. This project developed novel methods for the diagnosis of parasitism.
Research
The specific research aims were to characterise species of equine parasites (strongyles) by their ribosomal DNA sequences, to evaluate the usefulness of these sequences for species-specific identification and to define genetic markers for the development of DNA-based diagnostic systems.
Outcomes
The study defined genetic markers in the first and second internal transcribed spacer (ITS-1 and ITS-2) of nuclear ribosomal DNA for 29 species of horse strongyles. These markers allow the unequivocal identification of each of the 29 species. Utilising the species markers, polymerase chain reaction (PCR) methods were developed for the species-specific detection of egg and larval DNA from faecal samples.
Hence, highly sensitive and specific DNA methods were developed. These novel methods now allow species-specific detection of minute amounts of parasite DNA from biological samples (faeces and copro-cultures), and can be carried out in days compared with weeks using traditional methods.
Other important outcomes of the project have been the training of postgraduate students, the establishment and strengthening of international research links in the area of equine parasitology, and the dissemination of scientific information in the form of a series of seminars and publications in highly regarded international scientific journals.
Implications
The results have major significance for the specific diagnosis of infection and hence for control. They also provide a solid foundation to study in detail the epidemiology, population biology of horse parasites.
RIRDC Project No: UM-30A
Researcher: Robin Gasser
Organisation:
Department of Veterinary Science, The
University of Melbourne, 250 Princes Highway, WERRIBEE VIC
3130
Contacts: Phone:
(03) 97413500 Fax:
(03) 97410401
