Cluster analysis of the clinical histories of cattle affected with bovine anaemia associated with Theileria orientalis Ikeda type infection

AIM: To determine the most commonly used words in the clinical histories of animals naturally infected with Theileria orientalis Ikeda type; whether these words differed between cases categorised by age, farm type or haematocrit (HCT), and if there was any clustering of the common words in relation to these categories. METHODS: Clinical histories were transcribed for 605 cases of bovine anaemia associated with T. orientalis (TABA), that were submitted to laboratories with blood samples which tested positive for T. orientalis Ikeda type infection by PCR analysis, between October 2012 and November 2014. chi(2) tests were used to determine whether the proportion of submissions for each word was similar across the categories of HCT (normal, moderate anaemia or severe anaemia), farm type (dairy or beef) and age (young or old). Correspondence analysis (CA) was carried out on a contingency table of the frequency of the 28 most commonly used history words, cross-tabulated by age categories (young, old or unknown). Agglomerative hierarchical clustering, using Ward's method, was then performed on the coordinates from the correspondence analysis. RESULTS: The six most commonly used history words were jaundice (204/605), lethargic (162/605), pale mucous membranes (161/605), cow (151/605), anaemia (147/605), and off milk (115/605). The proportion of cases with some history words differed between categories of age, farm type and HCT. The cluster analysis indicated that the recorded history words were grouped in two main clusters. The first included the words weight loss, tachycardia, pale mucous membranes, anaemia, lethargic and thin, and was associated with adult (p<0.001), severe anaemia (p<0.001) and dairy (p<0.001). The second cluster included the words deaths, ill-thrift, calves, calf and diarrhoea, and was associated with young (p<0.001), normal HCT (p<0.001), beef (p<0.001) and moderate anaemia (p<0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Cluster analysis of words recorded in clinical histories submitted with blood samples from cases of TABA indicates that two potentially different disease syndromes were associated with T. orientalis Ikeda type infection. One was consistent with the affected cattle suffering from a severe regenerative extravascular haemolytic anaemia, the second displaying as ill thrift and diarrhoea, particularly in young beef cattle.