Studies of the epidemiology and control of bluetongue in China

• Yunnan Tropical and Subtropical Animal Virus Disease Laboratory, China
• Department of Primary Industries and Fisheries, Australia

Bluetongue is a viral infection of ruminants. The disease normally occurs only in sheep. Cattle and possibly buffaloes, are the main vertebrate reservoirs of the arbovirus and act as sources of infection for a few species of Culicoides midges which biologically transmit the virus to fresh susceptible ruminants.

China is at risk from problems with bluetongue because of the populations of ruminant livestock in the country (81 million cattle; 22 million buffaloes; 113 million sheep; and 97 million goats). In 1979, bluetongue was reported in Yunnan Province and has since been confirmed in three additional provinces and suspected in others.

Cross-breeding with Australian stock is dependent on strategies to control and manage bluetongue. It is a high priority for the Chinese Government and considerable study has been undertaken. Research in Australia, which has an international reputation for bluetongue research, will also contribute to greater knowledge of the disease.

The main aim is to research the epidemiology and pathogenicity of bluetongue virus in China and Australia by mutual technology transfer, and to achieve both national and regional recognition of the Yunnan Tropical and Subtropical Animal Virus Disease Laboratory as a reference centre for bluetongue.

Specifically, scientists from China will undertake exchange visits with Australian scientists to learn methods for the diagnosis of bluetongue infection (cell culture, virus isolation and identification, serology and antigen detection). Links will be established with other bluetongue research projects in the region and a regional symposium on the disease will be hosted during the project.

Researchers at Kunming will establish 35 herds of sentinel animals close to the laboratory. A minimum of 10 animals per herd with mainly cattle plus some buffaloes and sheep will be studied with scientists regularly obtaining heparinised blood and serum. As the project develops herd numbers and locations will be expanded.

Virus isolation methods currently used in Australia will be modified as necessary for Chinese conditions. Virus identification and further serotyping will be undertaken at the Kunming laboratory.

Conventional virus neutralisation tests currently take 10 days. Alternative methods consist of competitive enzyme-linked immunosorbent assay (ELISA) using anti-Bluetongue monoclonal antibody or an indirect ELISA using subunit antigens.

Scientists will use sera collected from the sentinel herds for serological procedures. Once procedures for both bluetongue virus identification and serology have been established, tests for the detection of other arboviruses will be introduced.

Antigen detection ELISA, polymerase chain reaction, (PCR), antigen and nucleic acid blotting and DNA and RNA hybridisation will also be used as appropriate. Researchers will also assess the relative pathogenicity of different virus serotypes identified.

A data recording system for lodging, storage and retrieval of data on viruses, sera, specimens, vectors, reagents and field and laboratory records will be introduced.