Coprodiagnosis of Hammondia heydorni in dogs by PCR based amplification of ITS 1 rRNA: differentiation from morphologically indistinguishable oocysts of Neospora caninum.

Hammondia heydorni is thought to be a non-pathogenic coccidian parasite of dogs that is closely related to Neospora caninum, an important parasite of cattle and dogs. Oocysts of these two species are morphologically indistinguishable from each other. A population of 2240 dogs in the Czech Republic was screened for the presence of H. heydorni/N. caninum oocysts and five (0.22%), represented by five of 3135 faecal samples (0.16%), were positive. The internal transcribed spacer 1 region of the rRNA gene (ITS1) from two isolates were cloned and the DNA sequences were identical with those of the ITS1 of H. heydorni. Based on the rRNA sequences available for H. heydorni and related coccidia, the primer pair JS4-JS5 was designed to amplify the 3' end of the small subunit (SSU) rRNA gene and ITS1 of H. heydorni. When tested on DNA extracted from a variety of parasites, the primers amplified a specific 267 bp fragment in our isolates only. The presence of DNA equivalent to 10 oocysts was sufficient for the amplification of the ITS1. We present a PCR-based diagnostic method as the only fast and reliable method for the diagnosis of H. heydorni in dogs.