CHARACTERIZATION OF A SWEDISH BOVINE ISOLATE OF NEOSPORA-CANINUM

The brain of a stillborn calf, seropositive to Neospora caninum and bo rn to a seropositive cow, was homogenized and cultured on Vero cells, where growth of Neospora-like tachyzoites was detected after 8 weeks. The ultrastructural features of the new isolate (Nc-SweB1) corresponde d to those of previously published Neospora isolates. In indirect immu nofluorescence tests, antigens on Nc-SweB1 tachyzoites were recognized by antibodies raised to a canine N. caninum isolate (Nc-1) but not by antibodies to Toxoplasma gondii, Sarcocystis cruzi, S. tenella, Eimer ia alabamensis, Babesia divergens, or B. motasi. Immunoblot analyses r evealed no major antigenic difference between Nc-SweB1 and Nc-1, where as several differences were seen between Nc-SweB1 and protozoa related to N. caninum. The sequences of 16S-like rRNA and the internal transc ribed spacer 1 of Nc-SweB1 revealed complete homology with correspondi ng sequences of two canine N. caninum isolates. Thus, no dissimilarity between Nc-SweB1 and the canine isolates was found, confirming that N c-SweB1 is N. caninum and suggesting that Neospora-like organisms isol ated from cattle are indeed N. caninum.