Observations on a strain of bluetongue virus by electron microscopy.

For many years blueto ngue has been known as a n importa nt a nd often fatal virus di sease of sheep in South Africa, (Henning, 1956) . As a result of extensions of the d isease to countries outside Africa considerable interest in this d isease has recently developed. The biological characteristics of the virus and its transmission by the biting midges have been studied extensively, but very little information on its biophysical properties are available (Du Toit, 1944 ; Howell , 1963 ; F oster, Jones & McCrory 1963).