Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 21, 2008
Publication Date: June 1, 2008
Citation: Santin, M., Trout, J.M., Fayer, R. 2008. A longitudinal study of Cryptosporidiosis in dairy cattle from birth to two years of age. Veterinary Parasitology. 155(2008):15-23.
Interpretive Summary: The present study documents for the first time a sequential association of species of Cryptosporidium in calves observed over 24 months. It is crucial to know which species and/or genotypes are actually present in Cryptosporidium -positive samples to determine the public health implications. Consequently, studies in which C. parvum-like oocysts have been detected in cattle should be interpreted with caution if molecular characterization has not been performed. Based on our results, C. parvum infects virtually all pre-weaned calves in their first 3 weeks of life. Previous studies have indicated that humans working closely with calves are at risk of becoming infected with C. parvum. Individuals in the presence of young calves should exercise care to protect themselves from acquiring C. parvum infection and thus becoming a source of infection for others.
Fecal specimens were collected from 30 calves from birth to 24 mo of age at a dairy farm in Maryland to determine the prevalence and age distribution of Cryptosporidium species/genotypes. After centrifugation to remove debris and concentrate oocysts, specimens were examined by immunofluorescence microscopy and polymerase chain reaction (PCR). Fragments of the SSU-rDNA gene amplified by PCR were purified and PCR products were sequenced. All 30 calves shed Cryptosporidium oocysts at some time during the 24 mo of the study. Of 990 specimens, 190 were Cryptosporidium-positive (19.2%). The highest prevalence of infection was at 2 wk of age when 29 of the 30 calves were excreting oocysts. Prevalence was higher in pre-weaned calves (less than 8 wk of age) (45.8%) than in post-weaned calves (3-12 mo of age) (18.5%) and heifers (12-24 mo of age) (2.2%). Sequence data for 190 PCR-positive specimens identified: Cryptosporidium parvum, C. bovis, the Cryptosporidium deer-like genotype and C. andersoni, with cumulative prevalences of 100, 80, 60, and 3.3%, respectively. Cryptosporidium parvum constituted 97% of infections in pre-weaned calves but only 4% and 0% of infections in post-weaned calves and heifers, respectively. All C. parvum GP60 nucleotide sequences generated were subtype IIaA15G2R1.