Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2005
Publication Date: 9/12/2005
Citation: Fayer, R., Santin, M., Trout, J.M., Greiner, E. 2005. Prevalence of species and genotypes of Cryptosporidium found in one to two-year old dairy cattle in Eastern United States. Veterinary Parasitology. 135:105-112 Interpretive Summary: Cryptosporidiosis is a disease of both cattle and humans. There are 15 species of the protozoan parasite Cryptosporidium that cause illness in different animals; some can be transmitted to humans. The most prevalent of these transmissible species in humans is Cryptosporidium parvum, a species found in our earlier studies in 50.3% of pre-weaned calves and 19.7% of post-weaned calves. The present study was undertaken to determine the prevalence in 1- to 2-year-old heifers on the same 14 dairy farms in 7 states as in the earlier studies. In the present study, although 11.9% of 571 heifers were infected with Cryptosporidium species, only 0.7% were infected with C. parvum. Consequently, the risk of humans acquiring infection with C. parvum from exposure to feces from yearling and older cattle appears much lower than from exposure to younger calves.
Technical Abstract: The prevalence of Cryptosporidium species in 1- to 2-year-old heifers was determined for 571 animals on 14 dairy farms in 7 states on the East Coast of the United States. A fecal specimen collected directly from each calf was processed to remove debris and concentrate oocysts then examined by immunofluorescence microscopy and polymerase chain reaction (PCR). For every PCR-positive specimen the 18S rRNA gene of Cryptosporidium was sequenced. Cryptosporidium was identified by either IFA or PCR from cattle on all 14 farms. On all except 2 farms groups of heifers were housed in a barn or in large covered pens. Others were pastured. From many of the same farms an earlier study reported that 50.3% of 503 pre-weaned calves and 19.7% of 468 post-weaned calves were infected. In the present study 11.9% of 571 heifers were infected with Cryptosporidium, 0.7% with Cryptosporidium parvum, the zoonotic species. Of 68 PCR-positive specimens characterized by gene sequencing 1, 4, 10, 24, and 29 calves were infected with Cryptosporidium suis, Cryptosporidium parvum, Cryptosporidium deer-like genotype, Cryptosporidium bovis, and Cryptosporidium andersoni, respectively. These findings demonstrate a lower prevalence of infection with Cryptosporidium species in 1- to 2-year-old dairy cattle than in younger cattle as well as a change in the diversity of species present. Consequently, the risk of humans acquiring infection with C. parvum from exposure to feces from yearling and older cattle appears much lower than from exposure to pre-weaned calves.