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Cryptosporidium in farmed animals: the detection of a novel isolate in sheep
R M Chalmers1, K Elwin, W J Reilly
1PHLS Cryptosporidium Reference Unit, Swansea PHL, Singleton Hospital, Swansea SA2 8QA, UK. rachel.chalmers@phls.wales.nhs.uk
Abstract:
We describe the discovery of polymorphisms in the Cryptosporidium oocyst wall protein (COWP) gene conferring a novel restriction fragment length polymorphism (RFLP) pattern in 26/60 (43%) isolates from a flock of sheep sampled following a waterborne outbreak of human cryptosporidiosis. The sheep isolates showed identical PCR-RFLP patterns to each other by COWP genotyping but different from those of most currently recognised genotypes, including the major Cryptosporidium parvum genotypes 1 and 2. Sequence analysis of the 550bp amplicon from the COWP gene was compared with a DNA coding region employed in previous studies and showed the novel isolate to differ from other Cryptosporidium species and C. parvum isolates by 7-21%. The sheep-derived isolates were compared at this and further three Cryptosporidium gene loci with isolates from other farmed animals. The loci employed were one in the thrombospondin related adhesive protein (TRAP-C2) gene and two in the 70kDa heat shock protein (HSP70) gene (CPHSP1 and 2). Other animal samples tested in our laboratory were from clinically ill animals and all contained C. parvum genotype 2. The sheep in which the novel isolate was identified were healthy and showed no symptoms of cryptosporidiosis, and the novel sheep isolate could represent a non-pathogenic strain. Our studies suggest that a previously undetected Cryptosporidium sub-type may exist in sheep populations, reflecting the increasingly recognised diversity within the parasite genus.
Insights
A novel Cryptosporidium subtype was discovered in healthy sheep using PCR-RFLP analysis of the COWP gene. This finding suggests a previously undetected Cryptosporidium subtype may exist in sheep populations.
Area of Science:
- Veterinary Parasitology
- Molecular Biology
- Public Health Microbiology
Background:
- Cryptosporidium is a significant cause of diarrheal disease in humans and animals.
- Genetic diversity within Cryptosporidium species is increasingly recognized.
- Waterborne outbreaks highlight the importance of understanding parasite transmission routes.
Purpose of the Study:
- To investigate novel genetic polymorphisms in Cryptosporidium oocyst wall protein (COWP) gene.
- To characterize Cryptosporidium isolates from sheep following a human waterborne outbreak.
- To explore the genetic diversity of Cryptosporidium in sheep populations.
Main Methods:
- Restriction Fragment Length Polymorphism (RFLP) analysis of the COWP gene.
- Polymerase Chain Reaction (PCR) for gene amplification.
- DNA sequencing of COWP gene amplicons.
- Comparative analysis of multiple Cryptosporidium gene loci (COWP, TRAP-C2, HSP70).
Main Results:
- A novel RFLP pattern was identified in 43% of sheep isolates.
- Sheep isolates showed identical PCR-RFLP patterns, distinct from known C. parvum genotypes.
- Sequence analysis revealed 7-21% divergence from other Cryptosporidium species and C. parvum isolates.
- Identified isolates from healthy sheep, suggesting a potentially non-pathogenic strain.
Conclusions:
- A previously undetected Cryptosporidium subtype may be circulating in sheep.
- The genetic diversity of Cryptosporidium is broader than currently recognized.
- Further research is needed to understand the prevalence and pathogenicity of this novel sheep isolate.