Comparative studies on the detection of Theileria annulata infection by clinical, parasitological and molecular techniques in buffaloes (Bubalus bubalis)

During the period of 2019-2021, a total of 715 buffaloes were screened for Theileria infections. A set of clinical parameters were used to identify the theileriosis suspected animals which were later confirmed through microscopic tests (peripheral thin blood smear examination and lymph node biopsy smear examination) and molecular assay (cytochrome b based T. annulata specific polymerase chain reaction test). On the basis of clinical evaluation, 33.43% (239/715) buffaloes were suspected for the presence of theileriosis. Through laboratory examination, 63.60% (152/239), 7.48% (16/214) and 100% (239/239) were found positive for Theileria infection by blood smear examination, lymph node biopsy and PCR, respectively, among the clinically suspected theileriosis animals. The efficiency of PCR was recorded to be highest, followed by microscopic examination of peripheral blood smears, and the lowest value was obtained for lymph node biopsy smear examination. The results indicated that PCR is a highly sensitive diagnostic technique for confirmatory diagnosis of T. annulata parasitic infection in buffaloes, even at very low level of parasitemia. Analysis of the data based on thin blood smear examination revealed that the field incidence of theileriosis was 11.55% in the south-western region of Gujarat, India. The high incidences of T. annulata infection in buffaloes may be due to the sub-tropical climate of the region which is favorable for the growth and development of vector ticks and parasites.