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 para site is increasingly acknowledged within veterinary medicine, although the pathways of transmission are far from being solved. The parasite is well kn own for causing diaplacental infections in cows associated with abortion an d/or severe damage of the fetus. In addition, it may cause neuromuscular di sease in dogs, which thus apparently act as intermediate hosts as well as f inal hosts. In our previous studies, we have demonstrated that molecular di agnosis of N. caninum infections has a high performance when a highly sensi tive polymerase chain reaction (PCR) targeted to the Nc5 region of the para site 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 redund ancy of Nc5-type sequences within the genome of the parasite. The PCR was s hown to amplify a set of DNA molecules exhibiting significant sequence diff erences. A complex composition of Nc5-type sequences was observed in the pa rasite isolate N. caninum NC-1 but also in another isolate, designated Hamm ondia heydorni-Berlin-1996. Investigation of the infection pattern of this parasite in its intermediate and final canine hosts showed it to be indisti nguishable from N. caninum NC-1.