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In contrast to dogs, red foxes (Vulpes vulpes) did not shed Neospora caninum upon feeding of intermediate host tissuesAbstract To clarify whether red foxes (Vulpes vulpes) can be ®nal hosts of Neospora caninum, foxes and dogs were fed in parallel on tissues of a sheep and a goat experimentally infected with N. caninum. The faeces of at least two of ®ve dogs contained N. caninum oocysts, as determined by bioassay. In the faeces of all six foxes fed in parallel, oocysts were detected that were larger in size (length 12.60.5 lm, width 11.80.4 lm) than the oocysts shed by the dogs. Ribosomal RNA sequences and the results of an immunoblot-based bioassay provided further evidence that these oocysts were dierent from N. caninum. A titration experiment performed to determine the sensitivity of a bioassay utilising gerbils showed that as few as ®ve sporulated N. caninum oocysts could be detected by this test. This indicates that, in two feeding experiments, less than 3,700 and 200 sporulated N. caninum oocysts, respectively, could have been among the Hammondia sp.-like oocysts collected from fox faeces. These results suggest that the red fox is either an inappropriate ®nal host for N. caninum or not at all a ®nal host for this parasite.

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Neospora caninum negatively impacts bovine reproductive performance around the world. Addressing this problem requires a greater understanding of the parasite's molecular biology. In this study, monoclonal antibodies against recombinant proteins were successfully developed and employed to characterise two different proteins of N. caninum: the acute phase-associated NcGRA7 and the chronic phase-associated NcSAG4. Immunofluorescence with the anti-rNcGRA7 monoclonal antibody suggested that NcGRA7 trafficks from tachyzoite dense granules to the matrix of the parasitophorous vacuole and parasite's surroundings. Furthermore, NcGRA7 is also expressed in the bradyzoite stage and localised on the matrix of bradyzoite-positive vacuoles. NcGRA7 appears to be partially involved in the tachyzoite-invasion mechanisms, as an anti-rNcGRA7 monoclonal antibody partially inhibited in vitro tachyzoite-invasion. A monoclonal antibody specific for NcSAG4 confirmed this protein's bradyzoitespecific expression both by western blot and immunofluorescence. However, some bradyzoite-positive vacuoles only weakly expressed NcSAG4, if it was expressed at all. The specificity of the anti-rNcSAG4 monoclonal antibody was confirmed by the recognition of the NcSAG4 in the membrane surface of Nc-1SAG4 c transgenic tachyzoites, which constitutively expresses NcSAG4. Blocking NcSAG4 of Nc-1SAG4 c tachyzoites with the monoclonal antibody did not affect host cell invasion. However, its implication on the host cell adhesion or host immune evasion should not be discarded.

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