Comparative molecular investigation of Nc5-PCR amplicons from Neospora caninum NC-1 and Hammondia heydorni-Berlin-1996.

The clinical relevance of Neospora caninum as a cyst-forming coccidian parasite is increasingly acknowledged within veterinary medicine, although the pathways of transmission are far from being solved. The parasite is well known for causing diaplacental infections in cows associated with abortion and/or severe damage of the fetus. In addition, it may cause neuromuscular disease in dogs, which thus apparently act as intermediate hosts as well as final hosts. In our previous studies, we have demonstrated that molecular diagnosis of N. caninum infections has a high performance when a highly sensitive polymerase chain reaction (PCR) targeted to the Nc5 region of the parasite is used. The present study indicates that the high sensitivity of the PCR is the consequence of a target dose effect which reflects a high redundancy of Nc5-type sequences within the genome of the parasite. The PCR was shown to amplify a set of DNA molecules exhibiting significant sequence differences. A complex composition of Nc5-type sequences was observed in the parasite isolate N. caninum NC-1 but also in another isolate, designated Hammondia heydorni-Berlin-1996. Investigation of the infection pattern of this parasite in its intermediate and final canine hosts showed it to be indistinguishable from N. caninum NC-1.