High genetic diversity of Giardia duodenalis assemblage E in pre-weaned dairy calves in Shanghai, China, revealed by multilocus genotyping

Abstract

Giardia duodenalis is a common parasitic protozoan in human and animals. Epidemiological and molecular data are available from dairy cattle in many industrialized countries, but information on genetic diversity at multiple genetic loci is limited, especially in pre-weaned dairy calves. In this study, 818 fecal specimens were collected from five dairy cattle farms located in suburbs of Shanghai, China, with two to five samplings per farm. G. duodenalis assemblages and subtypes were determined using multilocus genotyping (MLG) at the β-giardin (bg), glutamate dehydrogenase (gdh), and triosephosphate isomerase (tpi) loci. The overall prevalence was 60.1% (492/818) combining data from the three genetic loci. Three G. duodenalis assemblages were detected, including E (n = 482), A (n = 5), and B (n = 1), with the concurrence of A and E in a few animals (n = 4). Intra-genotypic sequence diversity was high for assemblage E, showing 12, 13, and 17 subtypes at the bg, gdh, and tpi loci, including four, six, and eight new subtypes, respectively. All dominant subtypes (E3, E2, and E8 at the bg locus; E1 and E3 at the gdh locus; and E11 and E3 at the tpi locus) were detected on all farms at most sampling occasions, and only limited differences in subtype distribution were observed among five farms. Altogether, 58 assemblage E MLGs were identified, all of which had not been reported before, and seven (MLG-E1-MLG-E7) were each seen on multiple farms. These results indicate a high occurrence of G. duodenalis in dairy calves, the existence of high genetic heterogeneity of assemblage E on five farms, and frequent exchange of parasite populations among farms within a small geographic area. The clinical and epidemiologic significance of these observations warrants further investigations.

Occurrence and genotyping of Giardia duodenalis and Cryptosporidium in pre-weaned dairy calves in central Sichuan province, China

“…Based on the combination of bg , tpi and gdh loci, 19 MLGs of assemblage E were detected (Table 2). A high degree of nucleotide variation in assemblage E has been also detected in previous studies [18, 22, 26, 29]. Of the 19 MLGs, 17 were unpublished MLGs.…”

“…In this study, the overall infection rate in southwestern China was close to the prevalence in northwestern (9.7% [18]), northeastern (13.3% [13]) and north China (7.1% [7]), but much lower than the infection rates in central (17.6% [26]) and southeastern (60.1% [29]) China. Prior to the present study, these results were interpreted as related to differences in geographic distribution, environmental management and cultivation scale [7, 13, 18, 26, 29]. Cattle were kept in groups or in free stalls, which might promote the transmission of G. duodenalis infection among animals and lead to the high infection rates [26, 29].…”

“…Its prevalence shows substantial differences, ranging from 7.1% to 60.1% in other studies in China [7, 13, 18, 26, 29]. In this study, the overall infection rate in southwestern China was close to the prevalence in northwestern (9.7% [18]), northeastern (13.3% [13]) and north China (7.1% [7]), but much lower than the infection rates in central (17.6% [26]) and southeastern (60.1% [29]) China. Prior to the present study, these results were interpreted as related to differences in geographic distribution, environmental management and cultivation scale [7, 13, 18, 26, 29].…”

“…Prior to the present study, these results were interpreted as related to differences in geographic distribution, environmental management and cultivation scale [7, 13, 18, 26, 29]. Cattle were kept in groups or in free stalls, which might promote the transmission of G. duodenalis infection among animals and lead to the high infection rates [26, 29]. Furthermore, we analyzed the infection rates between intensive feeding and free-ranging farms; there was no significant difference between the two breeding patterns ( X 2  = 0.629, df  = 1, p  = 0.428).…”

“…A previous nomenclature system was used to name subtypes at each genetic locus [29, 30]. Specimens that were successfully subtyped at all three loci were included in multilocus genotyping of G. duodenalis .…”