First detection of microsporidia in dairy calves in North America.

Fecal specimens were obtained from a total of 413 dairy calves from farms in Vermont, New York, Pennsylvania, Maryland, Virginia, North Carolina, and Florida. After removal of fecal debris by sieving and density gradient centrifugation, specimens were examined by fluorescence microscopy, polymerase chain reaction (PCR), and DNA sequencing analysis for the presence of microsporidia. Microscopic examination revealed no spores. PCR using generic primers for microsporidia revealed 70 positive calves. PCR was then conducted using specific primers for Enterocytozoon bieneusi, the most frequently found microsporidian in human infections. These primers revealed 13 positive calves from six farms in five states. DNA sequencing analysis of the 13 E. bieneusi-positive specimens confirmed the PCR results and indicated 96.8-99.8% similarity with E. bieneusi sequences in GenBank. This is the first report of E. bieneusi in cattle in North America.