Development of a PCR assay for detection and identification of Eimeria spp. in cattle

Eimeria spp. are important coccidian parasites causing diarrhea and significant mortality in cattle worldwide. To date, at least 13 Eimeria species with varying pathogenicity have been identified in cattle. Efficient detection and identification of Eimeria spp. is therefore essential for the prevention and control of bovine coccidiosis. However, the commonly used microscopic examination for Eimeria spp. is time-consuming and requires considerable expertise. In this study, we aligned the nucleotide sequences of the small subunit (SSU) rRNA gene of common Eimeria species and developed a nested PCR assay targeting the polymorphic SSU rRNA region of Eimeria spp. from cattle. Initially, the SSU rRNA gene PCR assay was compared with microscopic examination for sensitivity and detection range of Eimeria species using fecal samples from dairy cattle. Of the 193 fecal samples, 131 (67.9 %) and 78 (40.4 %) were positive for Eimeria by PCR and microscopy, respectively. Sequence analysis of the PCR products identified six Eimeria species, including E. cylindrica (n = 76), E. bovis (n = 54), E. auburnensis (n = 30), E. zuernii (n = 25), E. wyomingensis (n = 10), E. canadensis (n = 1), and co-infections of 2-4 species (n = 55). In contrast, only the first four species and co-infections of 2-3 species were identified by microscopy. The PCR assay was able to detect as few as 50 Eimeria oocysts per gram of feces. Thus, the developed SSU rRNA gene PCR assay has a high sensitivity and allowed easy identification of at least six common Eimeria species and their co-infections in cattle. It should be useful in molecular epidemiological studies of bovine coccidiosis.