摘要 : The objective of this study was to compare the occurrence and the genotypes and species of <i>Giardia duodenalis</i> and <i>Cryptosporidium</i> spp. in beef and dairy cattle from farms in the Regional Municipality of Waterloo, Ont... 展开 The objective of this study was to compare the occurrence and the genotypes and species of <i>Giardia duodenalis</i> and <i>Cryptosporidium</i> spp. in beef and dairy cattle from farms in the Regional Municipality of Waterloo, Ontario, in an effort to determine the potential for zoonotic transmission from these animals. Pooled manure samples were collected from 45 dairy cattle farms and 30 beef cattle farms. The presence of <i>Giardia</i> cysts and <i>Cryptosporidium</i> oocysts was determined by immunofluorescence microscopy, while nested-PCR and DNA sequencing were used to determine genotypes and species. The overall farm prevalence was very high for both <i>Giardia</i> and <i>Cryptosporidium</i>, and was similar for dairy cattle farms (96 and 64%, respectively) and beef cattle farms (97 and 63%, respectively). However, on dairy cattle farms, <i>G. duodenalis</i> and <i>Cryptosporidium</i> spp. were detected in 44% and 6% of total pooled pen manure samples, respectively, with the occurrence of both parasites being generally higher in calves than in older animals. Most <i>Giardia</i> isolates were identified as either the host-adapted genotype <i>G. duodenalis</i> Assemblage E or the zoonotic Assemblage B. <i>Cryptosporidium parvum</i> and <i>Cryptosporidium andersoni</i> were the most frequently identified species in dairy cattle, while the non-zoonotic species <i>Cryptosporidium ryanae</i> and <i>Cryptosporidium bovis</i> were also found. On beef cattle farms, 72% and 27% of the total pooled pen manure samples were positive for <i>Giardia</i> and <i>Cryptosporidium</i>, respectively, with no obvious correlation with age. All <i>Giardia</i> isolates in beef cattle were identified as <i>G. duodenalis</i> Assemblage E, while all <i>Cryptosporidium</i> isolates were identified by sequence analysis as <i>C. andersoni</i>, although microscopic analyses, and subsequent restriction fragment length polymorphism analyses, indicated that other <i>Cryptosporidium</i> species were also present. The results of this study indicate that although <i>Giardia</i> and <i>Cryptosporidium</i> were identified in a higher overall percentage of the pooled beef cattle manure samples than in dairy cattle, firmly established zoonotic genotypes and species were much more common in dairy cattle than in beef cattle in this region. Dairy cattle, and especially dairy calves, may, therefore, pose a greater risk of infection to humans than beef cattle. However, these results may also provide evidence of potential zooanthroponotic transmission (human to animal). 收起