Morphology Is Not a Reliable Tool for Delineating Species Within Cryptosporidium

Abstract

. Midpoint-rooted neighbor-joining tree reconstructed from variation in the rpoB B gene. Kimura 2-parameter distances were calculated for each pair of sequences. The percentage of bootstrap replicates (n = 1,000) in which a given node was recovered is indicated. Five hundred base pairs of the rpoB gene were sequenced from Sarcocystis sp. and from representatives of S. neurona, S. falcatula, and S. lindsayi in the sea otter (see Table I for details on isolates). The Neospora caninum and Toxoplasma gondii homologs were obtained from GenBank (accession nos. AF095904 and AF138960, respectively). a polymerase chain reaction (PCR) by using degenerate primers designed to amplify the rpoB gene, encoded by the plastid genome of apicomplexans-primers Fl (5'-gcg gtc cca aaa ggg tca gtg gat atg atw twt gaa gat gc) and R3 (5'-gcg gtc cca aaa ggg tca gtc ctt tat ktc cat rtc t). The resulting 504-bp PCR products were directly sequenced using BigDye chemistries and an ABI 3100 automated fluorescent sequencer. Homologous sequences were characterized from isolates of S. neurona, S. falcatula, and S. lindsayi, the origins of which are summarized in Table I. These were aligned to each other and to homologs from Neospora caninum and Toxoplasma gondii by using CLUSTAL W 1.8 (Thompson et al., 1994), available on the bioinformatics server of the Baylor College of Medicine. Relationships of these sequences were investigated by constructing a gene genealogy by calculating Kimura 2-parameter distances from 1,000 bootstrap replicates of the alignment and using the Neighbor-Joining algorithm using MEGA 2.1 (Kumar et al., 2001).The rpoB sequence obtained from the otter isolate was placed as a basal member of a clade that also contained the other examined isolates belonging to Sarcocystis but that included neither N. caninum nor T. gondii (Fig. 3). Concordant topologies were obtained when the minimum evolution and maximum parsimony criteria were used (data not shown). Several nucleotide substitutions distinguish this otter specimen from the isolates representing other species of Sarcocystis. In contrast, the rpoB of isolates representing S. falcatula are comparatively homogeneous. Thus, morphological and genetic evidence indicates that sea otters, in addition to being at the risk of exposure to S. neurona parasites, serve as host to at least 1 other species of parasites belonging to the genus Sarcocystis. LITERATURE CITEDDUBEY

Molecular Characterization of Bubaline Isolate of Cryptosporidium Species from Egypt

“…The Cryptosporidium oocysts detected in buffalo calf fecal smears in this study were morphologically similar to those of C. parvum described in calves in many previous studies (Fall et al, 2003;Fayer et al, 2006;Hassanain et al, 2011;Randhawa et al, 2012b). Identification of the Cryptosporidium species depended upon the oocyst morphology and measurements (Fayer et al, 2000).…”

“…Traditionally, the detection of Cryptosporidium oocysts in environmental, water, food, fecal and/or tissue samples had primarily relied on examination by microscopy (O'Donoghue, 1995;Quintero-Betancourt et al, 2003). Oocyst morphology played an important role in Cryptosporidium taxonomy but was inconvenient to clearly differentiate species and genotypes (Fall et al, 2003). Therefore, molecular analyses had been widely used to characterize the genetic structure of Cryptosporidium parasites and assessment of their zoonotic significance (Xiao, 2010).…”

Cryptosporidium huwi n. sp. (Apicomplexa: Eimeriidae) from the guppy (Poecilia reticulata)

“…sp., however piscine genotype 4 was detected in 199 one of these isolates (Morine et al, 2012). Cryptosporidium species and size measurement is not a useful criterion for delimiting 206 species in this genus (Fall et al, 2003). 207…”

Identification of the Cryptosporidium Isolate from Chickens in Japan by Sequence Analyses

“…In several papers, variation was observed in oocyst size even in the same species of Cryptosporidium [2]. Further more, the measurement of oocysts by light microscopy occasionally leads inaccurate results [2,14].…”

“…In several papers, variation was observed in oocyst size even in the same species of Cryptosporidium [2]. Further more, the measurement of oocysts by light microscopy occasionally leads inaccurate results [2,14]. In addition, several differences in biological features, such as prepatent period or parasitic location in organs, observed between C. baileyi and the chicken isolates [4,8,9] indicate that several phenotypic variations exist among various C. baileyi strains.…”