A longitudinal study of Enterocytozoon bieneusi in dairy cattle.

Feces from each of 30 Holstein cattle on a Maryland dairy farm were examined at weekly, bimonthly, and then monthly intervals from 1 week to 24 months of age for the presence of Enterocytozoon bieneusi. DNA was extracted from spores cleaned of fecal debris, and a two-step nested PCR protocol was used to amplify a fragment of the internal transcriber spacer region of the rRNA gene. All PCR-positive specimens were sequenced to determine the genotype of E. bieneusi. The overall prevalence was 24% (239/990) with a lower prevalence in pre-weaned calves (less than 8 weeks of age; 11.7%) and heifers (13-24 months of age) than post-weaned calves (3-12 months of age; 44.4%). Over the course of 24 months, the cumulative prevalence of E. bieneusi was 100% since all 30 calves shed spores at some time during the study. One or more of three genotypes of E. bieneusi, J, I, and BEB4, were detected in all 30 animals. Genotype I was detected in all 30 cattle between 1 week and 22 months of age with some cattle remaining infected as long as 17 months. At 4 months of age, 28 cattle were infected with genotype I. Genotype BEB4 was detected briefly in seven cattle, most between 15 and 20 months of age. Genotype J was detected in eight cattle, all between 16 and 24 months of age. This longitudinal study strongly supports the findings of point prevalence, multiple farm studies in which genotypes J, I, and BEB 4 were found. These genotypes appear to be cattle specific and have not been found in humans or other animals.