Subtyping Cryptosporidium xiaoi, a Common Pathogen in Sheep and Goats

Abstract

Cryptosporidiosis is a significant cause of diarrhea in sheep and goats. Among the over 40 established species of Cryptosporidium, Cryptosporidium xiaoi is one of the dominant species infecting ovine and caprine animals. The lack of subtyping tools makes it impossible to examine the transmission of this pathogen. In the present study, we identified and characterized the 60-kDa glycoprotein (gp60) gene by sequencing the genome of C. xiaoi. The GP60 protein of C. xiaoi had a signal peptide, a furin cleavage site of RSRR, a glycosylphosphatidylinositol anchor, and over 100 O-glycosylation sites. Based on the gp60 sequence, a subtyping tool was developed and used in characterizing C. xiaoi in 355 positive samples from sheep and goats in China. A high sequence heterogeneity was observed in the gp60 gene, with 94 sequence types in 12 subtype families, namely XXIIIa to XXIIIl. Co-infections with multiple subtypes were common in these animals, suggesting that genetic recombination might be responsible for the high diversity within C. xiaoi. This was supported by the mosaic sequence patterns among the subtype families. In addition, a potential host adaptation was identified within this species, reflected by the exclusive occurrence of XXIIIa, XXIIIc, XXIIIg, and XXIIIj in goats. This subtyping tool should be useful in studies of the genetic diversity and transmission dynamics of C. xiaoi.

Development and Application of a gp60-Based Subtyping Tool for Cryptosporidium bovis

“…Thus, no obvious differences were observed in the distribution of C. bovis gp60 subtype by host. This was different from the observations in other Cryptosporidium species, including the genetically related C. xiaoi and C. ryanae [18,22,36].…”

“…The high prevalence and long duration of C. bovis infection and frequent occurrence of multiple subtype families on a single farm could greatly facilitate the occurrence of genetic recombination among isolates, leading to the emergence of new subtypes. This was in agreement with the observations in C. xiaoi and C. ryanae [18,22]. Several studies on other Cryptosporidium species also indicated the frequent genetic recombination at the gp60 locus [34,35].…”

“…Results of comparative analysis indicate that C. bovis is significantly different from other Cryptosporidium species at the gp60 gene. The length of gp60 gene in C. bovis was ~1353 bp, which is much longer than those in C. parvum, C. hominis, C. meleagridis, and other species (873-1089 bp) [21,[29][30][31][32][33], but similar to those in the genetically related C. xiaoi (~1437 bp) and C. ryanae (~1548 bp) [18,22]. Although the GP60 of C. bovis is structurally similar to those of other species, its sequences for the N-terminal signal peptide and Cterminal GPI anchor are unique.…”

“…[16]. This tool has been used in the identification of infection sources and transmission dynamics of Cryptosporidium species in humans and animals [17][18][19][20]. Among the three common intestinal Cryptosporidium species in cattle, subtyping tools targeting the gp60 gene are available for C. parvum [21] and C. ryanae [22].…”

An Update on Zoonotic Cryptosporidium Species and Genotypes in Humans

“…For example, C. hominis subtype IfA19G1R5 has 19 TCA (A) repeats, 1 TCG repeat (G) repeat and 5 AAGAAGGCAAAGAAG repeats (R). For some divergent species and genotypes, including C. ubiquitum, C. felis, C. canis, C. ryanae, C. xiaoi, C. bovis and Cryptosporidium chipmunk genotype I and skunk genotype, whole-genome sequencing (WGS) has been required to identify the gp60 loci in order to develop typing systems [ 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The trinucleotide repeats (TCA, TCG, TCT) are absent from gp60 genes in C. ubiquitum, C. felis, C. canis, C. ryanae, C. bovis and C. xiaoi [ 44 , 46 , 47 , 48 , 49 , 50 ].…”