The objective of this study was to compare the occurrence and the genotypes and species
of Giardia duodenalis and Cryptosporidium 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 Giardia cysts and Cryptosporidium
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 Giardia and Cryptosporidium, and was similar for dairy cattle
farms (96 and 64%, respectively) and beef cattle farms (97 and 63%, respectively). However,
on dairy cattle farms, G. duodenalis and Cryptosporidium 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 Giardia isolates were identified
as either the host-adapted genotype G. duodenalis Assemblage E or the zoonotic Assemblage
B. Cryptosporidium parvum and Cryptosporidium andersoni were the most frequently
identified species in dairy cattle, while the non-zoonotic species Cryptosporidium ryanae
and Cryptosporidium bovis were also found. On beef cattle farms, 72% and 27% of the total
pooled pen manure samples were positive for Giardia and Cryptosporidium, respectively,
with no obvious correlation with age. All Giardia isolates in beef cattle were identified as
G. duodenalis Assemblage E, while all Cryptosporidium isolates were identified by sequence
analysis as C. andersoni, although microscopic analyses, and subsequent restriction fragment
length polymorphism analyses, indicated that other Cryptosporidium species were
also present. The results of this study indicate that although Giardia and Cryptosporidium
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).