Review of the Food-borne Zoonoses Research ... - ARCHIVE: Defra

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testing laboratories. In addition, as more discriminatory sub-typing methods are developed and applied, evidence for heterogeneity within species is increasing. The studies undertaken in OZ0402 and OZ0407 aimed to investigate the relationship between isolates of Cryptosporidium in human disease and in animal and environmental contacts using molecular analyses to enhance characterisation and discrimination between sub-types. Studies were designed to establish zoonotic potential using infectivity experiments in calves, lambs, pigs, turkeys and chickens to assess whether different genotypes can infect, colonise and be excreted by farm animals. The host range of Cryptosporidium species, genotypes and subtypes was investigated using enhanced surveillance of human cases in defined geographical areas and following up potential sources of zoonotic infection for humans by sampling key pet, farm animal and/or environmental contacts. Although transmission of Cryptosporidium to humans by direct animal contact has been demonstrated and reported, the risk of disease through direct or indirect contact with animals or animal faeces during occupational or recreational activities is unknown. Quantitative risk assessment modeling was used to assess the contribution of farm animals and pets to human infection using data derived from these studies and to suggest intervention strategies for the prevention and control of zoonotic disease. Review Summary This research has substantially improved our understanding of cryptosporidiosis in animals and the linkage with disease in humans. It has allowed the development of centre of expertise at the VLA and has also provided a basis for excellent collaboration between VLA and HPA in this important area. The projects were generally well devised and the methodologies employed in the laboratory and the environment were appropriate. However, there were differing opinions on the importance of the conclusions obtained. The number of novel and pertinent findings were fewer than had been expected from such a large project, which was using new molecular tools to identify genetic differences between C. parvum (which infects calves) and C. hominis (which was thought to infect only humans). One key finding of the studies was that isolates of the putative human-specific species C. hominis could readily reproduce in neonatal animals of three different mammalian livestock species: sheep, cattle and pigs. Furthermore, infections were observed in chickens and poultry. Matches were obtained between C. parvum sub-types isolated from humans and isolates from environmental samples from farms that the patient had visited. Significantly, particular species sub-types may be commonly associated with human infection. This shows that, in principle, molecular typing systems can be employed in epidemiological tracing studies. However, no link was obtained between infection of humans and infection in domestic pets including dogs. The risk assessment part of the project was criticised on the grounds that the sample size was too small, and because a hypothesis had not been properly identified. Overall, the risk assessment work had been difficult to assess because too little detail was provided. Some disappointment was expressed at the rate at which peer-reviewed publications were being produced. In particular, the discovery that C. hominis can grow in other species, including chickens, is a major finding that warranted rapid publication. 66
Project code: OZ0405 Project title: Genotypic and phenotypic comparison of Yersinia enterocolitica from humans and animals Start date (dd/mm/yy): 01/05/2002 End date (dd/mm/yy): 30/04/2005 £245,488 Total cost: Affiliation: Veterinary Laboratories Agency Sub-contractor(s): Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine Abstract of research Many cattle, sheep and pigs in the UK are colonised with Yersinia enterocolitica, which can cause diarrhoea in humans but is also associated with more serious diseases. To investigate the sources of human yersiniosis, a phenotypic and genotypic comparison of human and livestock strains was undertaken in collaboration with the HPA. Results indicated that 58% of the animal isolates and 53% of the human isolates were Biotype (BT)1a, which is considered ―non-pathogenic‖. BTs1b and 2-5 are considered ―pathogenic‖. BT3 (O:5,27) was isolated from sheep (35%), pigs (22%) and cattle (4%) but was not detected in human isolates. Among the human strains, 24% were BT3 (O:9) and 19% BT4 (O:3). Only pigs (11%) carried BT3 (O:9) strains. To further investigate the relationship between human and animal isolates a AFLP-based genotyping technique was developed in collaboration with DFVF and applied to 88 representative strains. The strains separated into two distinct AFLP clusters; cluster A and cluster B (largely BTs2-4 and BT1a respectively). Serotype-associated sub-clusters were observed. AFLP profiles indicated pigs and sheep as sources of human BT3 (O:9) and BT4 (O:3) infections respectively. Some strains causing human disease were undetected in livestock. Further genotyping was undertaken using a pan-Yersinia DNA micro-array in collaboration with LSHTM. Two distinct clades were observed reflecting the AFLP results and providing evidence of evolutionary trends in the Yersinia genus. The representative strains were also assayed for a range of virulence-associated properties. The results indicated that most isolates had the capacity to cause disease in humans on the basis of adherence, invasiveness and survival in macrophages but differences were observed in cytokine secretion induced in vitro between the ―nonpathogenic‖ and ―pathogenic‖ strains. Only 3 non-invasiveness strains, were detected. All were BT1a were non-motile. This was further investigated using site directed mutagenesis, for the first time, in a BT1a strain to construct a flagella-deficient mutant. The results suggest that flagella are important virulence factors for BT1a strains. Overall this project has significantly increased understanding of the role of Y. enterocolitica from livestock in human yersiniosis and indicated that BT1a strains are potentially pathogenic to humans. Review Summary The project was developed following the collection of Yersinia isolates during the sheep, cattle and pig abattoir survey in 1999/2000. Yersinia enterocolitica is not a significant 67
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Contents Section A - Introduction..
Page 4 and 5:
Review of the Food-borne Zoonoses (
Page 6 and 7:
Plans for taking forward these prio
Page 8 and 9:
Policy Objectives The key policy ob
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Figure 2. Laboratory reports of Sal
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Figure 4. Laboratory reports of Cam
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6. Aims of the FBZ research review
Page 16 and 17: Section B - Review Summaries 16
Page 18 and 19: epidemiology of Salmonella and anti
Page 20 and 21: There is a need to objectively asse
Page 22 and 23: 2. Campylobacter review summary 2.1
Page 24 and 25: for this organism. Research within
Page 26 and 27: 3. E. coli review summary 3.1 Succe
Page 28 and 29: 4. Other zoonotic pathogens of inte
Page 30 and 31: Annex 1 - Projects Reviewed 30
Page 32 and 33: OZ0311 Conventional versus capillar
Page 34 and 35: OZ0402 OZ0404 OZ0405 OZ0407 OZ0604
Page 36 and 37: OZ0704 OZ0705 OZ0706 OZ0707 Quantif
Page 38 and 39: Annex 2 - Project Abstracts and Pro
Page 40 and 41: To test the suitability of the AFLP
Page 42 and 43: Project code: OZ0324 Project title:
Page 46 and 47: Review Summary The knowledge that t
Page 48 and 49: Review Summary The project was felt
Page 52 and 53: It is clear that the EC legislative
Page 54 and 55: if the vaccines currently available
Page 56 and 57: Four published papers have come out
Page 58 and 59: Review Summary This epidemiological
Page 60 and 61: Project code: OZO316 Project title:
Page 64 and 65: agricultural industry/public health
Page 68 and 69: animal pathogen but is a human path
Page 70 and 71: esearch has also substantially impr
Page 72 and 73: to elucidate the antigenic repertoi
Page 74 and 75: and have contributed to our underst
Page 76 and 77: Fundamental issues concerning the f
Page 78 and 79: Review summary Project OZ0606 focus
Page 80 and 81: Abstract of research OZ0608 The ado
Page 82 and 83: thinning process for molecular trac
Page 84 and 85: Project code: LK0665 Project title:
Page 86 and 87: Review summary While poultry meat i
Page 88 and 89: Review summary A key aim of this pr
Page 90 and 91: Review summary This project aimed t
Page 96 and 97: Project code: OZ0138C Project title
Page 102 and 103: Abstract of research Projects OZ070
Page 104 and 105: produced were both relevant and imp
Page 106 and 107: List of External Reviewers. Mr. Pau
Page 108 and 109: Review of Defra’s FBZ Research Pr
Page 110 and 111: Review of Defra’s FBZ Research Pr
Page 112 and 113: Annex 5 - Review Timetable 112
Page 114 and 115: 11.45 - 12.00 Bovine and Porcine Fo
Page 116:
Campylobacter Other 11.50 - 12.05 P
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