Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2004
Publication Date: June 1, 2005
Citation: Fayer, R., Santin, M., Xiao, L. 2005. Cryptosporidium bovis n. sp. (apicomplexa: cryptosporididae) from cattle, bos taurus. Journal of Parasitology. 91(3):624-629.
Interpretive Summary: Based on molecular and biological data, a new species of Cryptosporidium was named. This species, Cryptosporidium bovis, appears structurally identical to the pathogenic species infecting humans and livestock but is a nonpathogen. It is the primary species of Cryptosporidium found in postweaned dairy calves in 7 states in a recent survey. It is important to recognize C. bovis as a separate species, distinguishing it from similar appearing known pathogens, so that risk for humans and livestock can be more clearly evaluated.
A new species of Cryptosporidium is described. Oocysts of the new species, previously identified as Cryptosporidium genotype Bovine B (AY120911), are morphologically indistinguishable from those of Cryptosporidium parvum. They are excreted fully sporulated, contain 4 sporozoites, but lack sporocysts. Oocysts measure 4.76-5.35 (mean = 4.89 'm) X 4.17-4.76 'm (mean = 4.63 'm) with a length to width ratio 1.06 (n=50). Oocysts were not infectious for BALB/c mice, but were infectious for two calves that were previously infected with C. parvum. Oocysts were not infectious for 2 experimentally exposed lambs less than one week of age and were not detected in 42 lambs 2-3 months of age, but were detected in a 2 week old lamb. In an earlier study, 79 of 840 calves on 14 dairy farms in 7 states were found infected with the new species. Most were 2-7 months of age and none exhibited signs of diarrhea. This new species has been found in 10 of 162 calves 9-11 months of age on a beef farm in Maryland. Fragments of the 18S rDNA, HSP-70, and actin genes were amplified by PCR and purified PCR products were sequenced. Multi-locus analysis of the three unlinked loci demonstrated the new species to be distinct from C. parvum and also demonstrated a lack of recombination, providing further evidence of species status. Based on these biological and molecular data, we consider this highly prevalent Cryptosporidium infecting primarily post-weaned calves to be a new species and propose the name Cryptosporidium bovis n. sp. for this parasite.