Identification of Babesia bigemina in the tick Boophilus decoloratus by the indirect fluorescent antibody technique.

Developing stages of Babesia bigemina were detected in the Giemsa-stained haemolymph smears of replete Boophilus decoloratus females engorged on infected animals. Replicate smears of these were prepared for staining by the indirect fluorescent antibody (IFA) technique. With specific antisera to B bigemina in dilutions up to 1/160 and rabbit antibovine globulin conjugated with fluorescein isothiocyanate (conjugate) the B bigemina stages were seen to fluoresce under the fluorescent microscope. When antisera against cattle Theileria spp or negative control sera were used, fluorescence was not detected in dilution above 1/5 and there was a complete absence of fluorescence when the conjugate alone was used. Thus the developing stages of B bigemina from the haemolymph could be identified using the IFA technique. Both spherical and elongated developing stages were seen to fluoresce specifically. The apical and the perinuclear regions and the posterior end of the vermicules appeared to fluoresce more intensely than the rest of the cytoplasm.