Lamsiekte (botulism): solving the aetiology riddle.

The reason or reasons why it took Sir Arnold Theiler so many years to unravel the riddle of the aetiology of lamsiekte in cattle and whether P.R. Viljoen's lifelong grudge for receiving insufficient credit from Theiler for his research contribution was justified are analysed in this paper. By 1912, Theiler knew that Duncan Hutcheon had advocated the use of bonemeal as a prophylactic against the disease in the early 1880s. Hutcheon's colleague, J.D. Borthwick, had shown conclusively in a field experiment in 1895 that lamsiekte did not occur in cattle fed a liberal allowance of bonemeal; and bone-craving had been identified by Hutcheon and several farmers as being associated with the occurrence of the disease (a 'premonitory' sign). Hutcheon regarded a phosphate deficiency of the pastures as the direct cause of lamsiekte. However, Theiler did not accept this, was convinced that intoxication was involved and developed a 'grass toxin' theory. Viljoen (1918) also latched onto the grass toxin theory. He did not believe that osteophagia existed, stating categorically that he had not observed it on the experimental farm Armoedsvlakte where > 100 cases of lamsiekte had occurred during the > 3 years that he spent there. Moreover, he did not believe in the prophylactic value of bonemeal. However, careful analysis of a subsequent publication, of which he was a co-author, revealed that in late 1918 and early 1919 he reproduced the disease by drenching cattle with blowfly pupae and larvae as well as with crushed bones from decomposing bovine carcasses. For this breakthrough he did not get proper credit from Theiler. Reappointed to study lamsiekte on Armoedsvlakte in the autumn of 1919, Theiler, probably already aware that the toxin he was seeking was in the decomposing bones or carcass material rather than the grass, deliberately 'walked with the cattle' on the farm to encounter a classic manifestation of bone-craving (osteophagia). The penny then immediately dropped. Theiler, actually rationalising an hypothesis that was about four decades old, did so with a vengeance. Within less than two years he had reproduced lamsiekte by exposing cattle with natural bone-craving to rotten carcass material, had chemical proof that the grazing was phosphorus-deficient, had developed a satisfactory bonemeal prophylactic dosage programme, and the bacterial toxin concerned - perhaps the trickiest contribution - had been produced in culture. Hence the table was set for the later development of an excellent lamsiekte vaccine.