Submitted to: American Association of Veterinary Parasitologists
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2006
Publication Date: 7/15/2006
Citation: Santin, M., Trout, J.M., Fayer, R. 2006. Prevalence of Cryptosporidium species and genotypes in a 12-month longitudinal study in dairy calves. American Association of Veterinary Parasitologists 51st Annual Conference, July 15-18, 2006, Honolulu, Hawaii. Interpretive Summary:
Technical Abstract: Fecal specimens were collected regularly from 30 calves from birth until 12 months of age at a dairy farm in Maryland to determine the prevalence of Cryptosporidium species/genotypes. Samples were collected weekly the first 8 weeks after calves were born, biweekly for calves 3 to 5 months of age, and monthly for calves 6 to 12 months of age. Fecal specimens were sieved and subjected to density gradient centrifugation to remove debris and concentrate oocysts. Specimens then were examined by immunofluorescence microscopy and polymerase chain reaction (PCR). All PCR positive specimens were sequenced using the 18S rRNA gene of Cryptosporidium. All 30 calves shed Cryptosporidium oocysts at some time during the study. Of 630 specimens collected, 163 were infected with Cryptosporidium (25.9%). Prevalence was higher in pre-weaned calves (less than 8 weeks of age) (38.3 %) than post-weaned calves (3-12 months of age) (18.2%). Sequence data for 163 PCR-positive specimens identified Cryptosporidium parvum, C. bovis and Cryptosporidium deer-like genotype. The prevalence of these species and this genotype was age related. Cryptosporidium parvum, the only zoonotic species constituted 96.7% of Cryptosporidium infections in pre-weaned calves but only 4.2% of Cryptosporidium infections in post-weaned calves. The highest prevalence of Cryptosporidium was at 2 weeks of age with 28 out of the 30 calves shedding oocysts of C. parvum. Our findings clearly demonstrate that the risk of zoonotic infection cannot be determined without molecular characterization to identify the Cryptosporidium species/genotype present in fecal specimens. Calves less than 2 months of age are the predominant population infected with C. parvum (zoonotic species) and any effort designed to control this infection must be directed primarily at this age group.