The prevalence ofCryptosporidiumspecies and subtypes in human faecal samples in Ireland

Abstract

SUMMARYCryptosporidiumis an important cause of diarrhoeal disease worldwide and, as several recent waterborne outbreaks have shown, poses a significant threat to public health in Ireland. We identified theCryptosporidiumspp. in 199 positive human stool samples by PCR–RFLP of the 18S rRNA and COWP gene loci. Subspecies were identified in 104 samples by sequence analysis of the 60 kDa glycoprotein (gp60) gene fragment. OverallC. parvumwas identified in 80%, andC. hominisin 20% of cases. No otherCryptosporidiumspp. were detected.C. parvumwas by far the most common species in the rural, more sparsely populated west of Ireland and exhibited a pronounced spring peak coincident with a peak in the national cryptosporidiosis incidence rate. Our data indicated a trend towards higher proportions ofC. hominisin older age groups. Ninety-nine per cent of all subtypedC. parvumisolates belonged to allele family IIa, of which allele IIaA18G3R1 was by far the most common (63%). According to a recent study by Thompson and colleagues [Parasitology Research(2007),100, 619–624] this allele is also the most common in Irish cattle. Subtyping of theC. hominisisolates indicated that they belonged to a geographically widely distributed allele (IbA10G2) known to have caused several water- and foodborne outbreaks around the world. The predominance ofC. parvum, its geographic and seasonal distribution and the IIaA18G3R1 subtype underlines the importance of zoonoticCryptosporidiumtransmission in Ireland.