Bovine spongiform encephalopathy: the effect of oral exposure dose on attack rate and incubation period in cattle

Wells, G. A. H.; Konold, Timm; Arnold, Mark; Austin, A. R.; Hawkins, Steve; Stack, M.J.; Simmons, Marion; Lee, Y. H.; Gavier‐Widén, Dolores; Dawson, M.; Wilesmith, J. W.

doi:10.1099/vir.0.82421-0

Cited by 107 publications

(136 citation statements)

References 42 publications

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“…All the data related to BSE pathogenesis in sheep and cattle (distribution in tissues and incubation period) were produced using this experimental approach (Bellworthy et al, 2005a, b;Foster et al, 1996Foster et al, , 2001a. In cattle, the oral challenge experiments performed with low doses (1 g or below) reproduced the main features observed in field cattle BSE (Wells et al, 2007), which supports the fact that oral inoculation is, in that context, a relevant model.…”

Section: Impact Of Oral Challenge On Tse Pathogenesismentioning

confidence: 66%

Relevance of oral experimental challenge with classical scrapie in sheep

Tabouret

Lacroux

Lugan

et al. 2010

Journal of General Virology

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Oral inoculation is currently considered as the best approach to mimic natural TSE contamination in ruminants. In this study, we compared the timing of abnormal prion protein (PrP Sc ) dissemination and accumulation in the organism of susceptible sheep either orally inoculated or naturally infected with classical scrapie. Both animal groups shared a similar PrP Sc dissemination scheme and accumulation dynamics in lymphoid tissues. However, orally challenged animals displayed an earlier neuro-invasion and a dramatically shorter incubation period than naturally exposed sheep. No differences were observed between the groups with regards to the neuroinvasion route. These results unambiguously indicate that oral inoculation can have an impact on both the earliness of neuro-invasion and the incubation period. They also support the statement that oral inoculation is a relevant model for investigating transmissible spongiform encephalopathy pathogenesis. Nevertheless, data obtained under such experimental conditions should be used with some caution.

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Section: Impact Of Oral Challenge On Tse Pathogenesismentioning

confidence: 66%

Relevance of oral experimental challenge with classical scrapie in sheep

Tabouret

Lacroux

Lugan

et al. 2010

Journal of General Virology

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“…All the data related to BSE pathogenesis in sheep and cattle (distribution in tissues and incubation period) were produced using this experimental approach (Bellworthy et al, 2005a;Bellworthy et al, 2005b;Foster et al, 1996;Foster et al, 2001). In cattle the oral challenge experiments performed with low doses (1g or below) reproduced the main phenotypic features observed in field cattle BSE (Wells et al, 2007), which support the relevance of the oral inoculation model in this context. However, it is accepted that oral challenge can reduce the incubation period and accelerates the dissemination of the agent into the organs (Ryder et al, 2009;Tabouret et al, 2010).…”

Section: Natural Tse and Experimental Challengesmentioning

confidence: 80%

Scientific Opinion on BSE/TSE infectivity in small ruminant tissues

Andréoletti¹,

Budka²,

Bunčić³

et al. 2010

EFS2

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The objectives addressed were i) to provide an update on TSE (Transmissible Spongiform Encephalopathy) infectivity distribution in small ruminant tissues; and ii) to indicate based on the current epidemiological situation as regards to BSE (Bovine Spongiform Encephalopathy) in the small ruminant population in the EU (European Union), whether a review of the existing SRM (Specified Risk Materials) list for small ruminants should be envisaged with regard to the potential exposure to the BSE agent. The appraisal was addressed by reviewing for Classical scrapie, BSE and Atypical scrapie in small ruminants aspects related to: i) tissue infectivity distribution according to the age and the genotype of sheep and goats; and ii) the infectious load in the different tissues. In order to perform the assessment all the currently available scientific results were reviewed, and data on TSE monitoring in small ruminants in the EU and on small ruminants slaughtered by species and age category in each EU Member State were considered. The reduction of the infectivity associated to the carcass of an infected individual achieved by the current SRM policy in small ruminants for Classical scrapie and BSE was estimated. The total number of Classical scrapie infected sheep and goats that could enter yearly into the food chain was provided. Moreover, considerations about Atypical scrapie were given. A set of simulations allowing estimating the impact of different policy options on the BSE infectious load potentially present in an infected sheep was provided. Therefore, the EC asked EFSA: i) to update, as regards small ruminants and on the basis of the most recent scientific data, the SSC scientific opinion from 2002 on TSE infectivity distribution in ruminant tissues; ii) to indicate based on the current epidemiological situation as regards BSE in the small ruminant population in EU, whether a review of the existing SRM list for small ruminants should be envisaged with regard to the potential exposure to the BSE agent. © EuropeanThe BIOHAZ Panel addressed the mandate by reviewing individually for Classical scrapie, BSE and Atypical scrapie in small ruminants aspects related to: i) tissue infectivity distribution according to the age and the genotype of sheep and goats; and ii) the infectious load in the different tissues.In order to perform the assessment all the currently available scientific results were reviewed. Data about the TSE monitoring in small ruminants in the EU were provided by the European Commission and information on small ruminants slaughtered by species and age category in each EU Member State were provided by the EFSA Focal Points Network.It was emphasized that this assessment required several assumptions. Moreover, the estimates of the infectious load are based on a simple approach using computations based on a low and a high estimate of each of the parameters. This provides order of magnitude estimates of the infectious load of TSE agents entering into the food chain at EU 27 level. This approach could be r...

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“…Crosscontamination between feed intended for pigs or poultry and cattle feed could have occurred at the feedstuff factory, if feed lines for cattle and feed for monogastric species were not distinct, during the transport of feed or on the farm, especially in mixed farms with both cattle and pigs or poultry. The potential for cross-contamination is heightened by the potential for low-dose exposure causing infection; in an oral exposure study it was shown that cattle could become infected by as little as 1 mg of brain homogenate [63]. A statistically significant relationship between the pig density in a region and BAB cases has also been found in subsequent studies on both the GB data [58] and for other countries including Northern Ireland, France, Switzerland, and Spain [1,3,26,30,55], supporting this initial hypothesis of cross-contamination of cattle feed with feed intended for pigs, and possibly poultry; a spatial study on feed factories confirmed recently the use of MBM in monogastric feed as a risk factor for BSE [51].…”

Section: Routes Of Infectionmentioning

confidence: 99%

Review on the epidemiology and dynamics of BSE epidemics

Ducrot¹,

et al. 2008

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-The paper describes how the comprehensive surveillance of bovine spongiform encephalopathy (BSE) and studies carried out on these data has enhanced our knowledge of the epidemiology of BSE. Around 7 000 BSE cases were detected through the screening of about 50 million cattle with rapid tests in Europe. It confirmed that the clinical surveillance had a poor capacity to detect cases, and also showed the discrepancy of this passive surveillance efficiency between regions and production types (dairy/beef). Other risk factors for BSE were being in a dairy herd (three times more than beef), having a young age at first calving (for dairy cattle), being autumn-born (dairy and beef), and being in a herd with a very high milk yield. These findings focus the risk on the feeding regimen of calves/heifers. Several epidemiological studies across countries suggest that the feedborne source related to meat and bone meal (MBM) is the only substantiated route of infection -even after the feed ban -, while it is not possible to exclude maternal transmission or milk replacers as a source of some infections. In most European countries, the average age of the cases is increasing over time and the prevalence decreasing, which reflects the effectiveness of control measures. Consistent results on the trend of the epidemic were obtained using back-calculation modelling, the R 0 approach and Age-Period-Cohort models. Furthermore, active surveillance also resulted in the finding of atypical cases. These are distinct from previously found BSE and classified in two different forms based on biochemical characteristics; their prevalence is very low (36 cases up to 1st September 2007), affected animals were old and some of them displayed clinical signs. The origin and possibility of natural transmission is unknown.

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Bovine spongiform encephalopathy: the effect of oral exposure dose on attack rate and incubation period in cattle

Cited by 107 publications

References 42 publications

Relevance of oral experimental challenge with classical scrapie in sheep

Relevance of oral experimental challenge with classical scrapie in sheep

Scientific Opinion on BSE/TSE infectivity in small ruminant tissues

Review on the epidemiology and dynamics of BSE epidemics

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