Submitted to: Veterinary Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/19/2008
Publication Date: 8/30/2008
Citation: Fayer, R., Santin, M., Trout, J.M. 2008. Cryptosporidium ryanae n.sp. (Apicomplexa:Cryptosporidiidae)in cattle (Bos Taurus). Veterinary Parasitology. 156:191-198. Interpretive Summary: A new species, Cryptosporidium ryanae, is described from cattle. Oocysts of C. ryanae were previously identified as the Cryptosporidium deer-like genotype. Genetic differences from 3 independent genes combined with biological differences relating to natural and cross-transmission host specificity, an age bias for infection of post-weaned cattle under field conditions, a lack of cross species immunity, and the lack of pathogenicity indicate that C. ryanae is a different from all other species of Cryptosporidium. The correct identification of Cryptosporidium species in clinical and epidemiological specimens has important and far reaching veterinary and public health implications. Cattle of all ages have been found infected with Cryptosporidium. Some animals suffer severe illness and others appear healthy. The diagnosis of infection, often made by microscopic identification of the oocyst stage, but infrequently confirmed by molecular methods, has led to the widespread misconception that cattle of all ages are major sources of the zoonotic species C. parvum that is pathogenic for humans, cattle, and other animals. Identification of C. bovis and C. ryanae as the primary species of Cryptosporidium found in post-weaned cattle, species not found to infect humans or to cause illness in livestock, provides clarification to the complicated epidemiologic paradigm associated with the genus Cryptosporidium.
Technical Abstract: A new species, Cryptosporidium ryanae, is described from cattle. Oocysts of C. ryanae, previously identified as the Cryptosporidium deer-like genotype and recorded as such in GenBank (AY587166, EU203216, DQ182597, AY741309, and DQ871345), are morphologically similar to those of C. parvum and C. bovis but smaller. In earlier point prevalence studies of 14 farms in 7 states in the United States, the deer-like genotype was found in 3.8% of 1411 dairy cattle 5 days to 2 yr of age and in a 2 yr longitudinal study on one dairy farm it was found in 60% of 30 cattle examined. Oocysts obtained from a calf on the latter farm for the present study measured 2.94-4.41 x 2.94-3.68 µm (mean = 3.16 x 3.73 µm) with a length/width shape index of 1.18 (n=40). Oocysts were infectious for 2 Cryptosporidium-naïve calves. The prepatent period for the calves was 11 days, the patent period was 15-17 days. Fragments of the SSU-rDNA, HSP-70, and actin genes amplified by PCR were purified and PCR products were sequenced. Multi-locus analysis of the 3 unlinked loci demonstrated the new species to be distinct from all other species and also demonstrated a lack of recombination, providing further evidence of species status. Oocysts cleaned of fecal debris and stored in water at 5 C appeared to deteriorate rapidly. Based on morphological, molecular and biological data, this geographically widespread parasite found only in Bos taurus calves is recognized as a new species and is named Cryptosporidium ryanae.