Diagnosis of Theileria annulata infection of cattle in Tunisia: comparison of serology and blood smears.

The immunofluorescent antibody test (IFAT) using schizont and piroplasm antigens was compared with the microscopic examination of Giemsa-stained blood smears for the diagnosis of Theileria annulata infection in experimentally and naturally infected cattle. The results obtained on 100 naive cattle showed that non-specific fluorescence disappeared at serum dilution levels of 1/40 and 1/160 for the piroplasm and schizont antigens, respectively. These levels were therefore retained as the starting dilutions for this study. On day 30 post-infection, 16 experimentally infected calves were shown to be serologically positive for schizont and piroplasm IFAT, while 13 of them were positive for blood smears. A total of 109 cattle from an endemic region of tropical theileriosis were sampled before the onset of the disease season in April and later in September. Globally the IFAT results revealed more cattle exposed to T annulata infection than the blood smear examination. The piroplasm IFAT and the blood smears were less reliable than the schizont IFAT. The latter appeared to be the best test for detecting exposure to T annulata.