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Epidemiology of ephemeral fever in China

Overview of Project

Ephemeral fever, a disease of cattle and buffaloes, has been known in China for at least 30 years, although the virus was not isolated until 1976, when the first of two major epidemics occurred. In the second and much larger epidemic, in 1983, it had a prevalence of 30% and a mortality between 1% and 2%. However, the disease has greater economic and social consequences than the morbidity and mortality figures suggest, as it affects milk production, draught power in agricultural areas, and survival of calves. The losses make it important to predict any potential epidemics and to develop a national vaccination policy for controlling the disease, but neither can be achieved until the epidemiology is understood.

Key Outcomes of Project

This project had three main objectives: first, to develop a highly specific serological test capable of detecting ephemeral fever virus antibodies, which is necessary in order to carry out an epidemiological survey; second, to apply monoclonal antibody techniques to identifying a specific antigenic component as a probe for the virus; third, to study the pathogensis of experimental ephemeral fever infections in buffalo. Project staff will utilise the results of the first two objectives to evaluate and monitor the disease, in order to determine the need and usage of the vaccine.

To meet these objectives, the Elisa test (Enzyme-linked Immuno Absorbent Assay) is the most suitable. This test can be highly specific, can be standardised and is capable of automation, although it requires considerable research development. Its high specificity is important because of the close antigenic relationship of at least four members of this group of rhabdoviruses: bovine ephemeral fever virus and the Berrimah, Kimberley and Adelaide River viruses. Evidence from earlier research in Australia indicates that these last three cause subclinical infections of cattle. However, they produce heterologous antibodies in cattle, which cross-react with ephemeral fever virus. At present, no single test can distinguish between homotypic and heterotypic ephemeral fever antibodies.

Each of the virus strains will be incorporated into Elisa tests, and cross-reactions determined on sera obtained from cattle of known history in China and Australia. The heightened specificity of the test should separate the true from the false-positive result often obtained with other methods, and also allow accurate and rapid test results. Serum containing highly specific antibodies can be used to detect virus in viraemic animals or insect vectors, or establish its absence from semen used for artificial insemination, thus replacing the costly and inefficient virus isolation procedures in current use.

To increase the level of selected antigens, the project will include improved growth studies of ephemeral fever virus in tissue cultures. Parallel studies will involve a strain of ephemeral fever virus of Chinese origin and one of Australian origin for use in the respective countries.

A serum bank will be developed in China, at Harbin, in two phases. The first should be a planned initial survey that obtains sera from cattle and buffaloes in provinces where the disease occurs. In the second phase, sentinel groups of cattle and buffaloes on State farms in selected locations will be bled periodically for testing.

No world standard test exists at present for the diagnosis of ephemeral fever. The virus neutralisation test has an inherent variability that prevents standardisation. If successful, an Elisa test may provide the necessary standard. It should be applicable wherever ephemeral fever occurs, in countries throughout Asia and Africa as well as Australia.

Project Dates

01 Jul 1985 - 30 Jun 1988

Partners

CSIRO Division of Animal Health - Australia
Chinese Academy of Agricultural Sciences - China

Website
Launch Website