The environmental distribution of Giardia spp. and Cryptosporidium spp. is dependent upon human, agricultural, and wildlife sources. The significance of each source with regard to the presence of parasites in the environment is unknown. This 2-year study examined parasite prevalence in human sewage influent, wildlife, and agricultural sources associated with the North Saskatchewan River Basin in Alberta, Canada. Fecal samples were collected from cow-calf, dairy, and hog operations in the watershed area. Sewage-treatment facilities were sampled bimonthly during the 2-year study, and wildlife scat was collected at locations along tributaries of the North Saskatchewan River. All samples were analyzed for the presence of Giardia and Cryptosporidium, using sucrose-gradient separation followed by immunofluorescent microscopy. Giardia and Cryptosporidium were detected in all three sources. The lowest prevalence of both Giardia (3.28%) and Cryptosporidium (0.94%) was found in wildlife, with 6 of 19 species testing positive. Sewage influent had the highest prevalence of Giardia (48.80%) and Cryptosporidium parvum-like oocysts (5.42%); however, the concentration of both parasites was minimal compared with the concentration detected in cattle feces. Cow-calf sources contained the highest concentration of Giardia (mean 5800/g feces, P < 0.01), and dairy sources contained the highest concentration of C. parvum-like oocysts (mean 295/g feces, P < 0.01). Although prevalence and concentration are higher in cattle feces than in sewage, the Giardia and Cryptosporidium in animal manure do not have direct access to water draining into the North Saskatchewan River. PCR-based characterization of rDNA from isolates of Cryptosporidium collected from Alberta human, pig, calf, mature steer, dog, cat, and beaver hosts revealed distinct genetic differences that may reflect host specificity.

Confusion exists over the species status and host-specificity of the tapeworm Rodentolepis (= Hymenolepis) nana. It has been described as one species, R. nana, found in both humans and rodents. Others have identified a subspecies; R. nana var. fraterna, describing it as morphologically identical to the human form but only found in rodents. The species present in Australian communities has never been identified with certainty. Fifty one human isolates of Rodentolepis (= Hymenolepis) nana were orally inoculated into Swiss Q, BALB/c, A/J, CBA/ CAH and nude (hypothymic) BALB/c mice, Fischer 344 and Wistar rats and specific pathogen free (SPF) hamsters. Twenty four human isolates of R. nana were cross-tested in flour beetles, Tribolium confusum. No adult worms were obtained from mice, rats or hamsters, even when immunosuppressed with cortisone acetate. Only one of the 24 samples developed to the cysticercoid stage in T. confusum; however, when inoculated into laboratory mice the cysticercoids failed to develop into adult worms. The large sample size used in this study, and the range of techniques employed for extraction and preparation of eggs provide a comprehensive test of the hypothesis that the human strain of R. nana is essentially non-infective to rodents.

This study describes the complete development (from sporozoites to sporulated oocysts) of Cryptosporidium parvum (human and cattle genotypes) in the HCT-8 cell line. Furthermore, for the first time the complete life cycle was perpetuated in vitro for up to 25 days by subculturing. The long-term maintenance of the developmental cycle of the parasite in vitro appeared to be due to the initiation of the auto-reinfection cycle of C. parvum. This auto-reinfection is characterised by the production and excystation of new invasive sporozoites from thin-walled oocysts, with subsequent maintenance of the complete life cycle in vitro. In addition, thin-walled oocysts of the cattle genotype were infective for ARC/Swiss mice but similar oocysts of the human genotype were not. This culture system will provide a model for propagation of the complete life cycle of C. parvum in vitro.

In less than five months, COVID-19 has spread from a small focus in Wuhan, China, to more than 5 million people in almost every country in the world, dominating the concern of most governments and public health systems. The social and political distresses caused by this epidemic will certainly impact our world for a long time to come. Here, we synthesize lessons from a range of scientific perspectives rooted in epidemiology, virology, genetics, ecology and evolutionary biology so as to provide perspective on how this pandemic started, how it is developing, and how best we can stop it.

Polymerase chain reaction (PCR)-coupled single-strand conformation polymorphism (SSCP) approaches utilizing nuclear DNA regions of the small subunit (SSU) of ribosomal RNA and heat shock protein 70 gene (HSP70) were established for genotyping Cryptosporidium parvum. The regions were amplified (individually or in a multiplex reaction) by PCR from DNA extracted from oocysts from ruminant or human hosts, then denatured and subjected to electrophoresis in a mutation detection enhancement (nondenaturing) gel matrix. Single-strand profiles produced in SSCP allowed the unequivocal identification/differentiation of the two common (human, 1 and cattle, 2) genotypes of C. parvum and the direct display of sequence variability within some samples, reflecting population variation. As these are considered among the most closely related genotypes (based on SSU and HSP70 sequence data), these findings and other preliminary results for C. felis (from cat) C. serpentis (from snake) and C. baileyi (from bird) indicate that the SSCP approaches established could be employed to identify any of the currently recognised genotypes and species of Cryptosporidium.

Cryptosporidium meleagridis is a common cause of cryptosporidiosis in birds. In addition, recent reports have described the parasite as an etiologic agent of cryptosporidiosis in both immunocompetent and immunocompromised humans. Therefore, it is important to genetically characterize isolates of C. meleagridis from different hosts and geographic areas, and to develop molecular tools to differentiate isolates from various hosts or areas. In this study, a total of 11 isolates of Cryptosporidium meleagridis from both human and avian hosts were examined at three genetic loci: the small-subunit rRNA, 60-kDa glycoprotein precursor, and 70-kDa heat shock protein genes. Two genotypes of C. meleagridis were seen at the small-subunit rRNA locus. These differed from each other by the presence or lack of a heterogeneous copy of the gene and an ATT repeat. The 60-kDa glycoprotein precursor gene divided these eleven isolates of C. meleagridis into six genotypes with high sequence diversity between groups. The highest genetic heterogeneity, however, was seen at the 70-kDa heat shock protein locus, and was primarily present at the 3' end of the gene. This heterogeneity separated eight isolates of C. meleagridis into six genotypes. These data could be useful in the development of molecular tools to promote understanding of the transmission of C. meleagridis in humans.

Oocysts of Cryptosporidium, from the feces of a naturally infected dog and from an HIV-infected human, were identified as the previously reported canine genotype of Cryptosporidium parvum, hereafter referred to as Cryptosporidium canis n. sp. Also among the oocysts from the dog, a trace amount of C. parvum bovine genotype was detected. Cryptosporidium canis oocysts from both the dog and human were infectious for calves. Oocysts excreted by calf 1 (dog source) were approximately 90% C. canis and 10% C. parvum, whereas those excreted by calf 3 (human source) were 100% C. canis. Oocysts from calf 1 infected calf 2 resulting in excretion by calf 2 of oocysts approximately 90% C. parvum and 10% C. canis. Oocysts of C. canis were not infectious for BALB/c neonatal mice or immunosuppressed C57 juvenile mice, although all control mice became infected with the C. parvum Beltsville isolate. Oocysts of C. canis from calf 1 and the human were structurally indistinguishable from oocysts of the C. parvum Beltsville isolate (bovine). However, C. canis oocysts differed markedly at the molecular level from all known species of Cryptosporidium based on sequence data for the 18S rDNA and the HSP 70 gene. The differences in genetics and host specificity clearly differentiate C. canis as a new species.

Avian isolates of Cryptosporidium species from different geographic locations were sequenced at two loci, the 18S rRNA gene and the heat shock gene (HSP-70). Phylogenetic analysis of the sequence data provided support for the existence of a new avian species of Cryptosporidium infecting finches and a second species infecting a black duck. The identity of Cryptosporidium baileyi and Cryptosporidium meleagridis as valid species was confirmed. Also, C. baileyi was identified in a number of isolates from the brown quail extending the host range of this species.

Cryptosporidium parvum, an intestinal coccidian parasite, was isolated from faeces and intestinal biopsies of a 9-week-old puppy with acute parvoviral gastroenteritis. Gene sequence analysis identified a Cryptosporidium genotype not previously recorded in Australia. The puppy-recovered after treatment with crystalloid fluids, synthetic and natural colloids and jejunostomy tube feeding.

The aim of this prospective study was to determine the prevalence of Cryptosporidium parvum in hospitalized children in Kota Bharu, Malaysia. Over a 19 month study period, 258 stool samples were examined from 159 children; 109 with diarrhea and 50 controls without diarrhea. Modified Ziehl-Neelsen staining method and a polymerase chain reaction (PCR) assay were used to detect C. parvum and the samples were also examined for the presence of other intestinal parasites. Only 1 of the 109 (0.9%) children with acute diarrhea was positive for C. parvum by microscopy and PCR. Thirty-one percent of children were infested with other intestinal parasites, the most common being Ascaris lumbricoides and Trichuris trichiura. In conclusion, we found C. parvum to be an uncommon infective agent in hospitalized children with or without diarrhea in Kota Bharu, Malaysia.

ABSTRACT. A new species of Cryptosporidium is described from the feces of domestic cattle, Bos taurus. Oocysts are structurally similar to those of Cryptosporidium muris described from mice but are larger than those of Cryptosporidium parvum. Oocysts of the new species are ellipsoidal, lack sporocysts, and measure 7.4 ± 5.5 μm (range, 6.0–8.1 by 5.0–6.5 μm). The length to width ratio is 1.35 (range, 1.07–1.50). The colorless oocyst wall is < 1 μm thick, lacks a micropyle, and possesses a longitudinal suture at one pole. A polar granule is absent, whereas an oocyst residuum is present. Oocysts were passed fully sporulated and are not infectious to outbred, inbred immunocompetent or immunodeficient mice, chickens or goats. Recent molecular analyses of the rDNA 18S and ITSI regions and heat‐shock protein 70 (HSP‐70) genes demonstrate this species to be distinct from C. muris infecting rodents. Based on transmission studies and molecular data, we consider the large form of Cryptosporidium infecting the abomasum of cattle to be a new species and have proposed the name Cryptosporidium andersoni n. sp. for this parasite.

There is controversy in the taxonomy of Cryptosporidium parasites and the public health significance of Cryptosporidium isolates from various animals. Recent advances in molecular characterization of Cryptosporidium parasites have allowed the re-examination of species structure of the genus Cryptosporidium. Non-parvum Cryptosporidium spp and new C. parvum genotypes in immunocompromised humans can now be clearly detected. In this article, Lihua Xiao and colleagues summarize the current biological and molecular evidence for different Cryptosporidium spp, and the public health importance of these species and new C. parvum genotypes.

The Cryptosporidium "human" genotype was identified in a paraffin-embedded tissue section from a dugong (Dugong dugon) by 2 independent laboratories. DNA sequencing and polymerase chain reaction/restriction fragment length polymorphism analysis of the 18S ribosomal RNA gene and the acetyl CoA synthethase gene clearly identified the genotype as that of the Cryptosporidium variant that infects humans. This is the first report of the human Cryptosporidium genotype in a nonprimate host.

We examined the occurrence of 2 virus-like double-stranded (ds)RNAs in human and calf isolates of Cryptosporidium parvum senso latu and other microorganisms, including 7 other members of the genus. A total of 32 isolates of C. parvum, 16 from humans (5 from acquired immune deficiency syndrome patients) and 16 from calves, were analyzed. Ethidium bromide staining, or Northern blot analysis, or reverse transcription/polymerase chain reaction, or all 3 methods, revealed that both genotype 1 and genotype 2 isolates of C. parvum possessed these dsRNAs. No other Cryptosporidium spp. or other organisms examined possessed these dsRNAs. Comparison analysis of partial cDNA sequences of dsRNAs from human and calf isolates revealed a high degree of similarity (>92% and >93% identical nucleotides for large and small dsRNAs, respectively). Slight, consistent differences in nucleotide sequences could be seen at select sites and were associated with an isolate being either genotype 1 or 2. Because of the widespread distribution of the dsRNAs, the similarity of these molecules between isolates, and high host specificity, these nucleic acids may prove to represent species-specific molecular markers for C. parvum. Evidence also suggests that the dsRNA can be utilized for molecular genotyping of C. parvum.

Objective To perform a morphological and genetic characterisation of a Cryptosporidium infection in an Indian ring-necked parrot ( Psittacula krameri ) and to compare this with C meleagridis from a turkey. Design Tissue and intestinal sections from an Indian ring-necked parrot were examined microscopically for Cryptosporidium. The organism was also purified from the crop and intestine, the DNAextracted and a portion of the 18S rDNA gene amplified, sequenced and compared with sequence and biological information obtained for C meleagridis from a turkey as well as sequence information for other species of Cryptosporidium. Results Morphological examination of tissue sections from an Indian ring-necked parrot revealed large numbers of Cryptosporidium oocysts attached to the apical border of enterocytes lining the intestinal tract. Purified Cryptosporidium oocysts measured about 5.1 × 4.5 μm, which conformed morphologically to C meleagridis. The sequence obtained from this isolate was identical to sequence information obtained from a C meleagridis isolate from a turkey. Conclusion Cryptosporidium meleagridis was detected in an Indian ring-necked parrot using morphological and molecular methods. This is the first time that this species of Cryptosporidium has been reported in a non-galliform host and extends the known host range of C meleagridis.

ABSTRACT Genetic and phylogenetic characterization of Cryptosporidium isolates at two loci (18S rRNA gene and heat shock gene) from both Australian and United States dogs demonstrated that dog-derived Cryptosporidium isolates had a distinct genotype which is conserved across geographic areas. Phylogenetic analysis provided support for the idea that the “dog” genotype is, in fact, a valid species.