Rapid testing leads to the underestimation of the scrapie prevalence in an affected sheep and goat flock

Reckzeh, Claudia; Hoffmann, Christine; Buschmann, A.; Buda, Silke; Budras, Klaus-Dieter; Reckling, Karl-Friedrich; Bellmann, Steffi; Knobloch, H.; Erhardt, G.; Fries, R.; Groschup, Martin H.

doi:10.1016/j.vetmic.2007.04.009

Cited by 16 publications

(15 citation statements)

References 30 publications

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“…Previous work had suggested that examination of LRS tissues in addition to brain provides better estimates of scrapie infection in sheep [13,25,28]. Our results are a noticeable example that this is also the case in goats and that, in agreement with those earlier sheep studies, the medial retropharyngeal lymph node would be the sample of choice, together with the obex, for post-mortem surveillance.…”

Section: Implications For Surveillance Of Goat Tsesupporting

confidence: 88%

High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect ofPRNPgenotype and age

González¹,

Martin²,

Sisó³

et al. 2009

Vet. Res.

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-Following a severe outbreak of clinical scrapie in 2006-2007, a large dairy goat herd was culled and 200 animals were selected for post-mortem examinations in order to ascertain the prevalence of infection, the effect of age, breed and PRNP genotype on the susceptibility to scrapie, the tissue distribution of diseaseassociated PrP (PrP d ), and the comparative efficiency of different diagnostic methods. As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the prevalence of preclinical infection was very high (72/200; 36.0%), with most infected animals being positive for PrP d in lymphoreticular system (LRS) tissues (68/72; 94.4%) compared to those that were positive in brain samples (38/72; 52.8%). The retropharyngeal lymph node and the palatine tonsil showed the highest frequency of PrP d accumulation (87.3% and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid tissue (RAMALT) was positive in only 30 (41.7%) of the infected goats. However, the efficiency of rectal and palatine tonsil biopsies taken shortly before necropsy was similar. The probability of brain and RAMALT being positive directly correlated with the spread of PrP d within the LRS. The prevalence of infection was influenced by PRNP genetics at codon 142 and by the age of the goats: methionine carriers older than 60 months showed a much lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last showed prevalence values similar to isoleucine homozygotes of any age (40/80; 50.0%). Two of seven goats with definite signs of scrapie were negative for PrP d in brain but positive in LRS tissues, and one goat showed biochemical and IHC features of PrP d different from all other infected goats. The results of this study have implications for surveillance and control policies for scrapie in goats.scrapie / goat / prion disease / transmissible spongiform encephalopathy

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Section: Implications For Surveillance Of Goat Tsesupporting

confidence: 88%

High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect ofPRNPgenotype and age

González¹,

Martin²,

Sisó³

et al. 2009

Vet. Res.

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“…The early and consistent involvement of the medial retropharyngeal lymph node and the palatine tonsil has been widely reported [1, 7, 16, 19, 26, 27], and it is believed to result from the early exposure of those tissues to infectivity following ingestion of the scrapie agent [1, 27, 29]. If that were the case, it would be difficult to explain the late and inconsistent involvement of the distal ileum Peyer’s patches observed in our study.…”

Section: Discussionmentioning

confidence: 89%

Pathogenesis of natural goat scrapie: modulation by hostPRNPgenotype and effect of co-existent conditions

González¹,

Martin²,

Hawkins

et al. 2010

Vet. Res.

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After detection of a high prevalence of scrapie in a large dairy goat herd, 72 infected animals were examined by immunohistochemistry with prion protein (PrP) antibody Bar224 to study the pathogenesis of the infection. Tissues examined included the brain and thoracic spinal cord (TSC), a wide selection of lymphoreticular system (LRS) tissues, the distal ileum and its enteric nervous system (ENS), and other organs, including the mammary gland. The whole open reading frame of the PRNP gene was sequenced and antibodies to caprine arthritis-encephalitis virus (CAEV) infection were determined. Unexpectedly, accumulation of disease-associated PrP (PrPd) in the brain was more frequent in methionine carriers at codon 142 (24/32, 75.0%) than amongst isoleucine homozygotes (14/40, 35.0%). The latter, however, showed significantly greater amounts of brain PrPd than the former (average scores of 9.3 and 3.0, respectively). A significant proportion of the 38 goats that were positive in brain were negative in the ENS (44.7%) or in the TSC (39.5%). These results, together with the early and consistent involvement of the circumventricular organs and the hypothalamus, point towards a significant contribution of the haematogenous route in the process of neuroinvasion. Chronic enteritis was observed in 98 of the 200 goats examined, with no association with either scrapie infection or presence of PrPd in the gut. Lymphoproliferative interstitial mastitis was observed in 13/31 CAEV-positive and scrapie-infected goats; PrPd in the mammary gland was detected in five of those 13 goats, suggesting a possible contribution of CAEV infection in scrapie transmission via milk.

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“…Of all animals present in the flocks at the time of the flock cull, close to 36% was culled, and of these culled animals approximately 66% was tested, producing 191 secondary cases of classical scrapie. We note that the number of animals actually infected at the time of culling is expected to be higher than that, as infected animals will be tested positive only when they are at a sufficiently advanced stage of incubation [17,18]. Mathematical modelling would be needed to derive infection prevalence estimates from detectable prevalence; for examples of such modelling applied to clinical case surveillance data in Great Britain, see [19,20].…”

Section: Resultsmentioning

confidence: 99%

Scrapie prevalence in sheep of susceptible genotype is declining in a population subject to breeding for resistance

et al. 2010

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BackgroundSusceptibility of sheep to scrapie infection is known to be modulated by the PrP genotype of the animal. In the Netherlands an ambitious scrapie control programme was started in 1998, based on genetic selection of animals for breeding. From 2002 onwards EU regulations required intensive active scrapie surveillance as well as certain control measures in affected flocks.Here we analyze the data on genotype frequencies and scrapie prevalence in the Dutch sheep population obtained from both surveillance and affected flocks, to identify temporal trends. We also estimate the genotype-specific relative risks to become a detected scrapie case.ResultsWe find that the breeding programme has produced a steady increase in the level of genetic scrapie resistance in the Dutch sheep population. We also find that a significant decline in the prevalence of scrapie in tested animals has occurred a number of years after the start of the breeding programme. Most importantly, the estimated scrapie prevalence level per head of susceptible genotype is also declining significantly, indicating that selective breeding causes a population effect.ConclusionsThe Dutch scrapie control programme has produced a steady rise in genetic resistance levels in recent years. A recent decline in the scrapie prevalence per tested sheep of susceptible prion protein genotype indicates that selective breeding causes the desired population effect.

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Rapid testing leads to the underestimation of the scrapie prevalence in an affected sheep and goat flock

Cited by 16 publications

References 30 publications

High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect ofPRNPgenotype and age

High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect ofPRNPgenotype and age

Pathogenesis of natural goat scrapie: modulation by hostPRNPgenotype and effect of co-existent conditions

Scrapie prevalence in sheep of susceptible genotype is declining in a population subject to breeding for resistance

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