Associations between Theileria orientalis Ikeda type infection and the growth rates and haematocrit of suckled beef calves in the North Island of New Zealand

• Published in: New Zealand veterinary journal 2019-03, Vol.67 (2), p.66-73
• Main Authors: Lawrence, KE, Lawrence, BL, Hickson, RE, Hewitt, CA, Gedye, KR, Fermin, LM, Pomroy, WE
• Format: Article
• Language: English
• Subjects: anaemia; Anemia; anorexia; beef calves; Calves; Cattle; Diseases; growth rate; Ikeda type; Theileria orientalis; Theileriosis; Ticks as carriers of disease
• ISSN: 0048-0169; 1176-0710; 1176-0710
• DOI: 10.1080/00480169.2018.1547227

AIMS: The principle aim of this study was to examine the association between infection with Theileria orientalis Ikeda type and growth rates of suckled beef calves on four beef farms. In addition, associations between calf sex, sampling time, and individual farm and T. orientalis Ikeda type infection intensity and haematocrit (HCT) were investigated. METHODS: The study was a prospective longitudinal study in which 240 calves from four purposively selected beef farms in the North Island of New Zealand were blood sampled and weighed in late spring, mid-summer and early autumn. Two farms were from high-risk (A and B) and two from low-risk (C and D) tick areas. Blood samples were analysed to determine HCT, and the number of T. orientalis Ikeda type organisms/µL of blood (infection intensity) using a quantitative PCR assay. A calf was defined as infected if >415 organisms/µL were detected in a blood sample. Linear mixed models were used to examine associations between infection intensity, mean daily liveweight gain (MDG), HCT, calf sex and time of sampling on the four farms. RESULTS: On Farms A and B nearly all calves were infected at each sampling time, on Farm C