Apart from some laboratory studies conducted in 1926-28 by the NSW Department of Agriculture, however, no further studies were undertaken until Dr. (later Dame) Jean Macnamara of Melbourne gained first-hand experience of the disease while working in the USA. At Dr. Macnamara's instigation, CSIR arranged for further investigations to be carried out in Cambridge by Sir Charles Martin and he subsequently reported that the virus appeared to be suitable for rabbit control.

A CSIR team, led by Dr. L. B. Bull, then examined the virus and investigated means of transmitting it first in the laboratory and later under field conditions. The first field studies in South Australia gave mixed results and the infection generally failed to spread from warren to warren. For various reasons, including the generally unsympathetic attitude of quarantine authorities, the research was discontinued until the increasing seriousness of the rabbit plague and the public insistence of Dr. Macnamara persuaded CSIRO to resume field studies in 1950.

This time several sites in the Murray Valley were selected for the release of the virus and, at first, it appeared that the disease could only survive for short periods in localized situations. In December, 1950, however, myxomatosis suddenly

flared up in one of the trial sites, and was reported almost simultaneously at several points along the river nearby; and in the following weeks it spread with dramatic speed over south eastern Australia. It has never since disappeared, and is now firmly established as an enzootic disease of the Australian wild rabbit, with epizootics developing periodically in association with local and season vector activity.[72]

The economic significance of the infestation was literally incalculable but immediately after its control following the initial spread of myxomatosis in south-eastern Australia (1953) Australia's wool clip reached record levels and it was estimated that the additional return to the sheep industry alone due to the absence of rabbits was worth some£34 million in one year. The benefits that accrued to the wheat, beef, dairy and horticultural industries have never been assessed.

A detailed scientific account of the biology and behaviour of the rabbit, together with a description of the myxoma virus and the mechanisms of its transmission, has been published by F. Fenner and F. N. Ratcliffe.[73]

Although other methods of rabbit control (poisoning, ploughing out the burrows, boundary fencing, fumigation and trapping) have all been used with varying degrees of success, myxomatosis was and is the main means of control. It has been of enormous economic importance to the agricultural industry and has also had a profound effect ecologically, particularly in encouraging the widespread regeneration of native herbs, shrubs and trees, together with the indigenous animals and birds that are associated with them.

Australian Academy of Technological Sciences and Engineering