A statistically derived index for classifying East Coast fever reactions in cattle challenged with Theileria parva under experimental conditions

A statistically derived disease reaction index based on parasitological, cl inical and haematological measurements observed in 309 5 to 8-month-old Bor an cattle following laboratory challenge with Theileria parva is described. Principal component analysis was applied to 13 measures including first ap pearance of schizonts, first appearance of piroplasms and first occurrence of pyrexia, together with the duration and severity of these symptoms, and white blood cell count. The first principal component, which was based on a pproximately equal contributions of the 13 variables, provided the definiti on for the disease reaction index, defined on a scale of 0-10. As well as p roviding a more objective measure of the severity of the reaction, the cont inuous nature of the index score enables more powerful statistical analysis of the data compared with that which has been previously possible through clinically derived categories of non-, mild, moderate and severe reactions.