Time filter

Source Type

Swansea, United Kingdom

Mason B.W.,Communicable Disease Surveillance Center | Chalmers R.M.,UK Cryptosporidium Reference Unit | Carnicer-Pont D.,Health Protection Team | Casemore D.P.,Aberystwyth University
Journal of Water and Health | Year: 2010

An outbreak in the autumn of 2005 resulted in 218 confirmed cases of Cryptosporidium hominis. The attack rate (relative risk 4.1, 95%CI 2.8-9.1) was significantly higher in the population supplied by Cwellyn Water Treatment Works (WTW). A case-control study demonstrated a statistically significant association (odds ratio 6.1, 95% CI 1.8-23.8) between drinking unboiled tap water and C. hominis infection. The association remained significant in a logistic regression analysis, with an adjusted odds ratio of 1.30 (95 CI 1.05-1.61) per glass of unboiled tap water consumed per day. This evidence together with environmental and associated microbiological investigations, and the absence of effective treatment to remove Cryptosporidium oocysts at the WTW, led to the conclusion that the outbreak was waterborne. Oocyst counts in final treated water at the WTW and at different points in the distribution system were consistently very low, maximum count in continuous monitoring 0.08 oocysts per 10 litres. Data from continuous monitoring and the epidemic curve is consistent with the hypothesis that low numbers of oocysts of C hominis were present in treated water continuously during the outbreak and these were of sufficient infectivity to cause illness. All surface water derived water supplies present a potential risk to human health and appropriate control measures should be in place to minimise these risks. © IWA Publishing 2010.

Ruecker N.J.,University of Calgary | Ruecker N.J.,Alberta Provincial Laboratory for Public Health | Hoffman R.M.,Wisconsin State Laboratory of Hygiene | Chalmers R.M.,UK Cryptosporidium Reference Unit | And 2 more authors.
Applied and Environmental Microbiology | Year: 2011

Molecular methods incorporating nested PCR-restriction fragment length polymorphism (RFLP) analysis of the 18S rRNA gene of Cryptosporidium species were validated to assess performance based on limit of detection (LoD) and for detecting and resolving mixtures of species and genotypes within a single sample. The 95% LoD was determined for seven species (Cryptosporidium hominis, C. parvum, C. felis, C. meleagridis, C. ubiquitum, C. muris, and C. andersoni) and ranged from 7 to 11 plasmid template copies with overlapping 95% confidence limits. The LoD values for genomic DNA from oocysts on microscope slides were 7 and 10 template copies for C. andersoni and C. parvum, respectively. The repetitive nested PCR-RFLP slide protocol had an LoD of 4 oocysts per slide. When templates of two species were mixed in equal ratios in the nested PCR-RFLP reaction mixture, there was no amplification bias toward one species over another. At high ratios of template mixtures (>1:10), there was a reduction or loss of detection of the less abundant species by RFLP analysis, most likely due to heteroduplex formation in the later cycles of the PCR. Replicate nested PCR was successful at resolving many mixtures of Cryptosporidium at template concentrations near or below the LoD. The cloning of nested PCR products resulted in 17% of the cloned sequences being recombinants of the two original templates. Limiting-dilution nested PCR followed by the sequencing of PCR products resulted in no sequence anomalies, suggesting that this method is an effective and accurate way to study the species diversity of Cryptosporidium, particularly for environmental water samples, in which mixtures of parasites are common. © 2011, American Society for Microbiology.

Chalmers R.M.,UK Cryptosporidium Reference Unit | Giles M.,Veterinary Laboratories Agency
Journal of Applied Microbiology | Year: 2010

The protozoan parasite Cryptosporidium infects all classes of vertebrates. Of the major human pathogenic species, Cryptosporidium parvum and Cryptosporidium hominis predominate in the UK. Cryptosporidium hominis is a human-adapted species, while C. parvum has many animal hosts and is particularly common in preweaned farmed ruminants. Evaluation of zoonotic risks has been provided mainly by descriptive and analytical epidemiological studies and enhanced recently by genetic typing of isolates. The robust nature of the transmissive oocyst stage, multiple transmission routes, lack of antiparasitic treatment options and vaccines, and resistance to chlorine disinfection present challenges for control. Subtyping C. parvum isolates has been used to link human cases and suspected sources of infection in sporadic cases and outbreaks. Although it is possible that all C. parvum isolates are potentially zoonotic, populations with and without farm animal linkage have been identified. New zoonotic risks have emerged in at least one outbreak, caused by the Cryptosporidium sp. rabbit genotype. This re-enforces the need to characterize infecting and contaminating isolates to ensure appropriate interventions. This study describes the risks of zoonotic cryptosporidiosis by detailing the hosts providing a potential reservoir, the risks of transmission to humans, outbreaks in animal-associated settings and guidance for control with special emphasis on the UK. © 2010 Public Health Wales NHS Trust. Journal compilation © 2010 The Society for Applied Microbiology.

Hadfield S.J.,UK Cryptosporidium Reference Unit | Chalmers R.M.,UK Cryptosporidium Reference Unit
Parasitology Research | Year: 2012

Cryptosporidium cuniculus was originally detected in rabbits and has been identified as an emerging human pathogen, but the occurrence, prevalence, and epidemiology in human and rabbit populations are poorly understood. As identification of C. cuniculus can be time-consuming and costly using existingmolecular assays, a real-time polymerase chain reaction (PCR)-based method targeting specificmarkers for this species was developed. The assay is based on amplification of the C. cuniculus-specific 60-kDa glycoprotein (GP60) gene using two PCRs targeting subtype families Va andVb.PCRproduct formationwasmonitoredbySYBRGreen I fluorescence measurement followed by post-amplificationmelt curve analysis; high resolution melt curve analysis was found to give increased sensitivity over standard melt curve analysis. The real-time PCR correctly identified all 41C. cuniculus isolates (40 from humans, one from a rabbit) tested, with subtype family in agreement with GP60 gene sequencing. Specificity was demonstrated by lack of detection of nine other Cryptosporidium species and genotypes, including 88 isolates of the closely related species, Cryptosporidium hominis. The PCRs were performed in separate tubes to maximize the possibility of detecting mixed Va-Vb infections; however, none were detected. The potential for multiplexing the reactions was also demonstrated, furthering the utility of the assay for large-scale occurrence and prevalence studies. © Springer-Verlag 2012.

Robinson G.,UK Cryptosporidium Reference Unit | Chalmers R.M.,UK Cryptosporidium Reference Unit
Zoonoses and Public Health | Year: 2010

Cryptosporidium spp. have been found in the faeces of over 150 mammalian host species, but the risks to public health from wildlife are poorly understood. In summer 2008, the Cryptosporidium sp. rabbit genotype was identified as the aetiological agent in an outbreak of waterborne human cryptosporidiosis. The source was a wild rabbit that had entered a treated water tank. To establish current knowledge about Cryptosporidium spp. infecting lagomorphs, especially the host range and biological characteristics of the rabbit genotype, and the potential risks to public health that rabbits may pose in the transmission of zoonotic cryptosporidiosis, we undertook a literature and data review. The literature returned demonstrates that although the European rabbit (Oryctolagus cuniculus) has been the most widely studied lagomorph, few large scale studies were found. The prevalence of Cryptosporidium spp. in wild rabbit populations in the two large scale studies was 0.9% (95%CI 0.2-5.0) and 0.0% (95%CI 0.0-1.6). Neither study provided age nor sex profiles nor typing of Cryptosporidium isolates. The infecting Cryptosporidium species was confirmed in just four other studies of rabbits, all of which showed the rabbit genotype. Human-infectious Cryptosporidium species including Cryptosporidium parvum have caused experimental infections in rabbits and it is likely that this may also occur naturally. No published studies of the host range and biological features of the Cryptosporidium rabbit genotype were identified, but information was generated on the identification and differentiation of the rabbit genotype at various genetic loci. Both pet and wild rabbits are a potential source of human cryptosporidiosis and as such, good hygiene practices are recommended during and after handling rabbits or exposure to their faeces, or potentially contaminated surfaces. Water supplies should be protected against access by wildlife, including rabbits. © 2009 Blackwell Verlag GmbH.

Discover hidden collaborations