Sheep May Not Be an Important Zoonotic Reservoir forCryptosporidiumandGiardiaParasites

Abstract

Little is known of the prevalence of Cryptosporidium and Giardia parasites in sheep and the genotypes that they harbor, although potentially sheep may contribute significantly to contamination of watersheds. In the present study, conducted in Western Australia, a total of 1,647 sheep fecal samples were screened for the presence of Cryptosporidium and Giardia spp. using microscopy, and a subset (n ‫؍‬ 500) were screened by PCR and genotyped. Analysis revealed that although both parasites were detected in a high proportion of samples by PCR (44% and 26% for Giardia and Cryptosporidium spp., respectively), with the exception of one Cryptosporidium hominis isolate, the majority of isolates genotyped are not commonly found in humans. These results suggest that the public health risk of sheep-derived Cryptosporidium and Giardia spp. in catchment areas and effluent may be overestimated and warrant further investigation.

Cryptosporidiumspecies in Australian wildlife and domestic animals

“…Ryan et al 2005;Yang et al 2009, Wang et al 2010bSweeny et al 2011b). In Australia, reported prevalences for ewes in Western Australia ranged from 6·3-8·3% (Sweeny et al 2011b) and for lambs from 9·3-56·3% on different properties (Ryan et al 2005;Yang et al 2009;Sweeny et al 2011a, b).…”

“…In Australia, reported prevalences for ewes in Western Australia ranged from 6·3-8·3% (Sweeny et al 2011b) and for lambs from 9·3-56·3% on different properties (Ryan et al 2005;Yang et al 2009;Sweeny et al 2011a, b). A total of 9 species/genotypes of Cryptosporidium have been reported in sheep and lambs in Australia; C. parvum, C. hominis, C. xiaoi, C. bovis, C. ubiquitum, sheep genotype I, C. andersoni, pig genotype II, C. fayeri and C. suis and sheep genotype I (Ryan et al 2005;Giles et al 2009;Yang et al 2009;Robertson, 2009;Sweeny et al 2011a, b), with C. xiaoi and C. ubiquitum most common although Yang et al (2009) found high proportions of C. parvum isolates in pre-weaned sheep in Western Australia when a C. parvum-specific PCR was used. In that study, using both 18S and a C. parvumspecific PCR for Cryptosporidium produced very different results.…”

Transmission cycles of Giardia duodenalis in dogs and humans in Temple communities in Bangkok—A critical evaluation of its prevalence using three diagnostic tests in the field in the absence of a gold standard

“…In humans, both immunofluorescence antibody tests (IFAT) and ELISA have also been shown to be more sensitive and specific than conventional microscopic techniques ( Addiss et al, 1991;Hopkins et al, 1993;Rashid et al, 2002) . Polymerase chain reaction (PCR) based tests are increasingly being utilised to diagnose and estimate prevalence for Giardia infections in animals and humans in the field ( McGlade et al, 2003;Traub et al, 2004;Trout et al, 2005;Ryan et al, 2005;Fayer et al, 2006) with improved sensitivity to microscopic detection and immunodiagnostic methods (McGlade et al, 2003). Previous studies have typically estimated the sensitivity and specificity of newly developed molecular or immunodiagnostic tests for Giardia by comparing them with known microscopy positive and negative samples (Cirak and Bauer, 2004;Guy et al, 2004) .…”

Prevalence and molecular characterisation of Cryptosporidium and Giardia species in pre-weaned sheep in Australia

“…Conversely, in Belgium, the cervid genotype was the predominant (n = 10) genotype identified in 18 positive lambs (aged 1 day -10 weeks), from 10 farms (Geurden et al, 2008). In Maryland, USA, the cervid genotype and C. bovis were the predominant species identified in both ewes and lambs (Santin et al, 2007), and were also the predominant species infecting post-weaned sheep in Western Australia (Ryan et al 2005).…”

“…Ryan et al, 2005). There appears to be geographic differences in the prevalence of zoonotic and non-zoonotic genotypes in sheep based on recent molecular characterisation studies.…”