This study describes transmission experiments using Hammondia heydorni-like oocysts isolated in 1996 from a naturally infected dog. The isolate was designated as H. heydorni-Berlin-1996. Examination of sera from infected intermediate hosts showed immunoblot reactions that resembled patterns observed after Neospora caninum NC-1 infection. Furthermore, N. caninum DNA could be demonstrated in tissue samples (e.g. heart, brain) of experimentally infected intermediate hosts and in oocyst preparations from H. heydorni-Berlin-1996. The isolated oocysts did not induce any detectable disease in any of the inoculated adult intermediate hosts (goats, sheep, gerbils, guinea pigs, multimammate rats, BALB/c mice, SCID mice), even upon immunosuppression. Furthermore, neither histological lesions nor parasite stages could be identified in the tissues of all fetuses recovered from two multimammate rats that had been infected prior to pregnancy. An experiment with one dog fed a second time on infected intermediate host tissue indicated that immunity may prevent repeated oocyst shedding in N. caninum-infected dogs. In addition, the study clearly demonstrates that N. caninum can be readily transmitted by dogs that have ingested exclusively skeletal muscles of infected intermediate hosts. Therefore, the study has consequences for the recommendations for farmers to prevent postnatal transmission of N. caninum to cattle. It indicates that feeding of any tissues of potential intermediate hosts (including sheep, goats, rodents) to final hosts may induce the shedding of oocysts in these hosts and thus pose a risk for post-natal infection of cattle. With respect to oocyst morphology and the infectivity of muscle tissues for final hosts, no differences were seen in comparison with observations made in the past on Isospora bigemina/I. heydorni/H. heydorni. Therefore, earlier studies made on I. bigemina/I. heydorni/H. heydorni have to be re-evaluated critically to determine whether they may have included N. caninum or other protozoan parasites that use dogs as final hosts and have an oocyst morphology resembling that of I. bigemina/I. heydorni/H. heydorni.

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.

In contrast to dogs, red foxes (Vulpes vulpes) did not shed Neospora caninum upon feeding of intermediate host tissues The alteration of one word during editing the above mentioned article led to a wrong statement at the end of the discussion (last paragraph, first sentence). The mistake remained un-observed during proof-reading. The sentence ''By bioassay, we can conclude that there were more than 3,700 and 200 oocysts of our N. caninum-isolate among the Hammondia sp.-like oocysts collected during the first and the second foxfeeding experiments, respectively.'' has to be corrected into ''By bioassay, we can exclude that there were more than 3,700 and 200 oocysts of our N. caninum-isolate among the Hammondia sp.-like oocysts collected during the first and the second fox-feeding experiments, respectively. '' Parasitol Res (2002) 88: 592

In a previous paper we demonstrated that Hammondia heydorni-like oocysts isolated in 1996 from a naturally infected dog could not be distinguished from the isolate Neospora caninum NC-1. The isolate, designated as H. heydorni-Berlin-1996, was cyclically transmitted using dogs as the ®nal hosts. The present study provides information on the antibody responses of the dogs used for the cyclical transmission of this isolate. The majority of dogs that had shed oocysts showed no sero-conversion with respect to N. caninum tachyzoite surface or immunodominant antigens, either in the indirect¯uorescent antibody test or in two Western-blotbased tests. In addition to the examination of responses to immunodominant antigens, we also analysed the antibody reactions of dogs to a high-molecular-weight antigen (152 kDa) in the tachyzoite antigen preparation. The antibodies against this antigen appeared after the dogs had been fed infected intermediate host tissues and shed oocysts. The reaction was observed in dogs between day 35 and day 447 after feeding of intermediate host tissues. Therefore, our study provides initial information on a 152 kDa tachyzoite antigen, which might be a suitable candidate to identify dogs with a history of shedding N. caninum oocysts.