Clinical disease associated with Trypanosoma theileri infection in a calf in Ireland.
Clinical examination of a 4-month-old calf with a clinical history of pyrexia, anaemia, weight loss and behavioural abnormality showed evidence of regenerative anaemia and a lymphocytosis which was characterized by a relatively large B cell population. The calf deteriorated clinically while under observation and its prescapular and prefemoral lymph nodes became enlarged. Examination of a blood smear detected a large number of circulating T. theileri. Serological examination showed the presence of the invariant, stage-specific, trypanosome surface antigen, ISG70 and antibodies against ISG70. ISG70 was first identified in the bloodstream forms of T. brucei and has not previously been found in T. theileri. Clinical recovery was associated with an increase in packed cell volume, a decrease in circulating anti-ISG70 antibodies and the complete disappearance of circulating ISG70.