The enzyme-linked immunosorbent assay (ELISA) was used to examine cross-reactivity of Neospora caninum with Toxoplasma gondii and Hammondia heydorni. Anti-T. gondii mouse and cat sera cross-reacted with N. caninum soluble antigen (NLA), but not with the recombinant surface antigen (NcSRS2). Anti-H. heydorni dog sera showed no cross-reactivity with either the NLA antigen or the NcSRS2. Lack of cross-reactivity between anti-H. heydorni sera and N. caninum antigens, and the cross-reactivity of anti-T. gondii sera with the NLA suggest that N. caninum has common antigens to T. gondii except for NcSRS2 based on serology. In light of several studies suggesting a closer relationship between N. caninum and H. heydorni than with T. gondii, examination of serological cross-reactivity with N. caninum may be necessary to further classify the parasites in addition to molecular and morphological studies and clarification of the life cycle.
2002 by the Japanese Society of Veterinary Science