Subtype analysis of Cryptosporidium specimens from sporadic cases in Colorado, Idaho, New Mexico, and Iowa in 2007: widespread occurrence of one Cryptosporidium hominis subtype and case history of an infection with the Cryptosporidium horse genotype

Abstract

Subtyping was conducted in late 2007 on 57 Cryptosporidium specimens from sporadic cases in Colorado, Idaho, New Mexico, and Iowa. One previously rare Cryptosporidium hominis subtype was identified in 40 cases (70%) from all four states, and the Cryptosporidium horse genotype was identified in a pet shop employee with severe clinical symptoms.

FIG. 1.

Phylogenetic relationship among major Cryptosporidium gp60 subtype families inferred by a neighbor-joining analysis of nucleotide sequences, using a sequence alignment generated by the ClustalX 1.81 package and the Kimura two-parameter genetic distances calculated by the Treecon W program. I, C. hominis subtype families; II, C. parvum subtype families; III, C. meleagridis subtype families; V, rabbit genotype subtype families; VI, horse genotype subtype families. The equine and bovine specimens of the Cryptosporidium horse genotype belong to subtype family VIa, while the human specimen of that genotype belongs to subtype family VIb.

FIG. 2.

Oocysts of C. parvum (A), C. hominis (B), and the Cryptosporidium horse genotype (C) under differential interference contrast (magnification of ×1,000) on a Zeiss Axiophot microscope (Carl Zeiss MicroImaging Inc., Thornwood, NY).