Cryptosporidium hominis n. sp. (Apicomplexa: Cryptosporidiidae) from Homo sapiens

Abstract

The structure and infectivity of the oocysts of a new species of Cryptosporidium from the feces of humans are described. Oocysts are structurally indistinguishable from those of Cryptosporidium parvum. Oocysts of the new species are passed fully sporulated, lack sporocysts. and measure 4.4-5.4 microm (mean = 4.86) x 4.4-5.9 microm (mean = 5.2 microm) with a length to width ratio 1.0-1.09 (mean 1.07) (n = 100). Oocysts were not infectious for ARC Swiss mice, nude mice. Wistar rat pups, puppies, kittens or calves, but were infectious to neonatal gnotobiotic pigs. Pathogenicity studies in the gnotobiotic pig model revealed significant differences in parasite-associated lesion distribution (P = 0.005 to P = 0.02) and intensity of infection (P = 0.04) between C. parvum and this newly described species from humans. In vitro cultivation studies have also revealed growth differences between the two species. Multi-locus analysis of numerous unlinked loci, including a preliminary sequence scan of the entire genome demonstrated this species to be distinct from C. parvum and also demonstrated a lack of recombination, providing further support for its species status. Based on biological and molecular data, this Cryptosporidium infecting the intestine of humans is proposed to be a new species Cryptosporidium hominis n. sp.

Cryptosporidiosis: a neglected infection and its association with nutritional status in schoolchildren in northwestern Mexico

“…More than 20 species of Cryptosporidium are recognized, but 90% of human cryptosporidiosis is attributed to Cryptosporidium parvum and Cryptosporidiun hominis [1]. Its transmission has been associated with contaminated drinking water and food, low socioeconomic status and overcrowding conditions [2].…”

Long-term Cryptosporidium typing reveals the aetiology and species-specific epidemiology of human cryptosporidiosis in England and Wales, 2000 to 2003

“…However, C. parvum variants, recognised initially phenotypically (designated human or H and cattle or C types) and latterly through genomic studies, segregate into two genotypes (1 and 2), of which genotype 1 is host-adapted for humans [2]. This is now assigned species status and called Cryptosporidium hominis and genotype 2 remains C. parvum [3]. Although these are the most commonly found species in human cryptosporidiosis worldwide, the distribution varies temporally and geographically [1].…”

Cryptic diversity in intestinal protists

“…However, it should be noted that these opinions are based on current knowledge and should our views of these organisms change so may the need for a new nomen-clature. Such was the case in Cryptosporidium where the two variants of C. parvum were shown to have distinct epidemiological and infection characteristics, as well as molecular divergence, and are now known as C. parvum and C. hominis (Morgan-Ryan et al, 2002). The last few years have seen a dramatic increase in our understanding of genetic variation in Blastocystis.…”