Chapter V of this report describes other diseases of freshwater fish encountered in the examination of specimens of fish in British rivers for furunculosis during the early 1930s. The authors report "a disease of salmon, in which areas of necrosis occur in the spleen, and Gram-positive bacilli can be demonstrated in that organ", which is now believed to be the first record of BKD. The description is as follows.
"Fifteen cases of this condition have been examined, 14 being from the Dee (Aberdeenshire) and one from the Spey. These cases occurred in the spring and early summer (1930, 1931 and 1932). Small necrotic areas, whitish in colour, were seen in the spleens of all the affected fish. A small Gram-positive bacillus (1-2 u x 0.3-0.5 u approx.) was demonstrated in the lesions, but was difficult to grow on culture medium. Subcutaneous and intramuscular infection of tissue emulsion from the spleens of the salmon into brown trout proved lethal (in 3-5 weeks). On autopsy, the tissues around the site of inoculation were found to be softened and haemorrhagic, but the spleens of the trout did not show the same appearance as those of the salmon, although that organ was in all cases distincly enlarged and greyish. Gram-positive bacilli could readily be found in the necrotic lesions formed at the site of inoculation, in the spleen, heart-blood, etc, of the trout. A strain of the bacillus has been passed through a series of trout (by injection of emulsion of spleen) over a period of 9 months. Organisms resembling those seen in the tissues of the diseased salmon have been cultivated on media containing fresh trout blood or tissues, but so far have not proved pathogenic for trout."