Genetic Diversity of Cryptosporidium spp. within a Remote Population of Soay Sheep on St. Kilda Islands, Scotland

Abstract

ABSTRACT This is the first report to characterize the genotypes and subtypes of Cryptosporidium species infecting a geographically isolated population of feral Soay sheep ( Ovis aries ) on Hirta, St. Kilda, Scotland, during two distinct periods: (i) prior to a population crash and (ii) as host numbers increased. Cryptosporidium DNA was extracted by freeze-thawing of immunomagnetically separated (IMS) bead-oocyst complexes, and species were identified following nested-PCR-restriction fragment length polymorphism (RFLP)/PCR sequencing at two Cryptosporidium 18S rRNA loci. Two hundred fifty-five samples were analyzed, and the prevalent Cryptosporidium species in single infections were identified as C. hominis (11.4% of all samples tested), C. parvum (9%), C. xiaoi (12.5%), and C. ubiquitum (6.7%). Cryptosporidium parvum was also present with other Cryptosporidium species in 27.1% of all samples tested. Cryptosporidium parvum - and C. hominis -positive isolates were genotyped using two nested-PCR assays that amplify the Cryptosporidium glycoprotein 60 gene ( GP60 ). GP60 gene analysis showed the presence of two Cryptosporidium genotypes, namely, C. parvum IIaA19G1R1 and C. hominis IbA10G2. This study reveals a higher diversity of Cryptosporidium species/genotypes than was previously expected. We suggest reasons for the high diversity of Cryptosporidium parasites within this isolated population and discuss the implications for our understanding of cryptosporidiosis.