Characterization of a U.S. Sheep Scrapie Isolate with Short Incubation Time
Hamir, Amirali Richt, Juergen Kunkle, Robert Greenlee, Justin Bulgin, M - UNIVERSITY OF IDAHO Gregori, L - VA MEDICAL CENTER, MD Rohwer, R - VA MEDICAL CENTER, MD
Submitted to: Veterinary Pathology Publication Type: Peer Reviewed Journal Publication Acceptance Date: April 16, 2009 Publication Date: N/A
Interpretive Summary: Scrapie is a naturally occurring fatal disease of sheep and goats. In a previous study it was shown that sheep inoculated with US scrapie inoculum (No. 13-7) induced terminal disease within an average of 19 months. We have since produced an inoculum, No. X124 from pooled brains of US origin sheep scrapie, that results in incubations nearly 3 fold shorter. The present study documents laboratory findings in tissues of sheep inoculated with No. X124. All inoculated sheep developed clinical disease and were euthanized within an average of 7.7 months post inoculation (MPI). Sheep that were genetically susceptible developed the disease faster (within 6 months). Also, the inoculum was able to induce disease in a short time (7 MPI) in a sheep that was supposed to be highly resistant to scrapie. This indicates that inoculum No. X124 appears to be more virulent than inoculum No. 13-7. Importantly this strain of scrapie represents a significant development in that it provides a natural model that requires less than 25 percent of the time for the disease to develop, thus enabling a faster pace for research investigating prion disease pathogenesis and inactivation. Technical Abstract: Scrapie is a naturally occurring fatal neurodegenerative disease of sheep and goats. Susceptibility to the disease is partly dependent upon the genetic makeup of the host. In a previous study it was shown that sheep intracerebrally inoculated with US scrapie inoculum (No. 13-7) developed terminal disease within an average of 19 months. We have since produced an inoculum, No. x124 from pooled brains of US origin sheep scrapie, that results in incubations nearly 3 fold shorter. The present study documents clinicopathological findings and the distribution of abnormal prion proteins (PrP**Sc) by immunohistochemical (IHC) and Western blot (WB) techniques, in tissues of sheep inoculated with No. x124. All inoculated sheep developed clinical disease and were euthanized within an average of 7.7 months post-inoculation (MPI). Sheep that had VV or AV at codon 136 of prion protein (PRNP) gene developed the disease faster and were euthanized at an average of 4.3 and 5.6 MPI, respectively. Also, the inoculum was able to induce disease in a short time (7 MPI) in a sheep that was relatively resistant (QR at codon 171) to scrapie. This indicates that inoculum No. x124 appears to induce scrapie in shorter time than inoculum No. 13-7, especially in sheep homozygous or heterozygous for valine at codon 136.
Towards that end, ARS Pullman geneticist Stephen White is leading a team of ARS and university scientists to characterize the prion protein gene of goats and identify important gene variants in individuals and breeds. The Pullman team has so far examined the prion protein gene sequences from 446 goats representing 10 breeds, 8 of which have never been genetically characterized for their potential scrapie response. The team’s analysis found four gene variants (R143, S146, H154, and K222) in the genes of Boer, Nubian, Saanen, Toggenburg, and a few other goat breeds. These gene variants were relatively rare or absent in animals that developed scrapie in previous outbreaks, which suggests these gene variants might help the animals in some way. A fifth variant (M142) was found mainly in Alpine and Toggenburg goats, and it is known to delay incubation of scrapie from infection to clinical disease. More work is needed to demonstrate true resistance for any of these genetic variations, notes the team in a paper published in the September-October 2008 issue of Genetic Selection Evolution.
To be published in the Proceedings of the Fourth International Scientific Congress in Fur Animal Production. Toronto, Canada, August 21-28, 1988
Evidence That Transmissible Mink Encephalopathy Results from Feeding Infected Cattle
R.F. Marsh* and G.R. Hartsough
•Department of Veterinary Science, University of Wisconsin-Madison, Madison, Wisconsin 53706; and ^Emba/Creat Lakes Ranch Service, Thiensville, Wisconsin 53092
Epidemiologic investigation of a new incidence of transmissible mink encephalopathy (TME) in Stetsonville, Wisconsin suggests that the disease may have resulted from feeding infected cattle to mink. This observation is supported by the transmission of a TME-like disease to experimentally inoculated cattle, and by the recent report of a new bovine spongiform encephalopathy in England.
OBSERVATIONS AND RESULTS
A New Incidence of TME. In April of 1985, a mink rancher in Stetsonville, Wisconsin reported that many of his mink were “acting funny”, and some had died. At this time, we visited the farm and found that approximately 10% of all adult mink were showing typical signs of TME: insidious onset characterized by subtle behavioral changes, loss of normal habits of cleanliness, deposition of droppings throughout the pen rather than in a single area, hyperexcitability, difficulty in chewing and swallowing, and tails arched over their _backs like squirrels. These signs were followed by progressive deterioration of neurologic function beginning with locomoior incoordination, long periods of somnolence in which the affected mink would stand motionless with its head in the corner of the cage, complete debilitation, and death.
Over the next 8-10 weeks, approximately 40% of all the adult mink on the farm died from TME. Since previous incidences of TME were associated with common or shared feeding practices, we obtained a careful history of feed ingredients used over the past 12-18 months. ***The rancher was a “dead stock” feeder using mostly (>95%) downer or dead dairy cattle and a few horses. Sheep had never been fed.***
Epidemiology Epidemiologic studies suggest that animals contract the disease by external exposure to the infectious agent, such as by eating contaminated feed. No evidence suggests that the TME agent spreads by contact between unrelated mink or from mother to nursing young. The disease has been identified in both genders and all color phases in animals greater than 1 year old. The first documented TME outbreak in the United States occurred in 1947 on one ranch in Wisconsin and then on a ranch in Minnesota that had received mink from the Wisconsin ranch. In 1961, TME outbreaks occurred on five ranches in Wisconsin. In Factsheet Veterinary Services February 2002 APHIS 1963, outbreaks occurred in Idaho, Minnesota, and Wisconsin. Epidemiologic data from the Minnesota and Wisconsin outbreaks trace the cases in those States to one common purchased food source.
The 1985 Stetsonville Outbreak The most recent TME outbreak occurred on one mink ranch in Stetsonville, WI, in 1985. In the herd of 7,300 adult mink, 60 percent of the animals died. Clinical signs included tail arching, incoordination, and hyperexcitability. At the most advanced stages of the disease, the animals were in trancelike states and eventually died. The outbreak lasted 5 months. Microscopic examination of sections of the brain confirmed the spongelike changes characteristic of TME. Diagnostic tests identified the prion protein. The following year, mink born during the outbreak showed no signs of TME. The late Richard Marsh, a veterinary virologist at the University of Wisconsin who studied the transmission of TME and other TSE’s, investigated this outbreak. Marsh learned that the mink were fed a diet composed of fresh meat products from “downer cattle” and commercial sources of fish, poultry, and cereal. Downer cattle are nonambulatory and cannot rise because they are affected with a condition such as a metabolic disease, broken limbs, or a central nervous system disorder. Marsh theorized that the meat from these downer cattle introduced a TSE agent to the mink in which TME resulted. Although Marsh’s hypothesis is based on speculation and anecdotal evidence, in 1993 APHIS adjusted its national BSE surveillance program to include testing downer cattle for evidence of a TSE. The brains of more than 20,141 cattle have been examined at APHIS’ National Veterinary Services Laboratories and other State diagnostic laboratories. Not a single tissue sample has revealed evidence of BSE or another TSE in cattle.
1: J Infect Dis 1980 Aug;142(2):205-8
Oral transmission of kuru, Creutzfeldt-Jakob disease, and scrapie to nonhuman primates.
Gibbs CJ Jr, Amyx HL, Bacote A, Masters CL, Gajdusek DC.
Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were exposed to the infectious agents only by their nonforced consumption of known infectious tissues. The asymptomatic incubation period in the one monkey exposed to the virus of kuru was 36 months; that in the two monkeys exposed to the virus of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively. Careful physical examination of the buccal cavities of all of the monkeys failed to reveal signs or oral lesions. One additional monkey similarly exposed to kuru has remained asymptomatic during the 39 months that it has been under observation.
12/10/76 AGRICULTURAL RESEARCH COUNCIL REPORT OF THE ADVISORY COMMITTE ON SCRAPIE Office Note CHAIRMAN: PROFESSOR PETER WILDY
A The Present Position with respect to Scrapie A] The Problem
Scrapie is a natural disease of sheep and goats. It is a slow and inexorably progressive degenerative disorder of the nervous system and it ia fatal. It is enzootic in the United Kingdom but not in all countries.
The field problem has been reviewed by a MAFF working group (ARC 35/77). It is difficult to assess the incidence in Britain for a variety of reasons but the disease causes serious financial loss; it is estimated that it cost Swaledale breeders alone $l.7 M during the five years 1971-1975. A further inestimable loss arises from the closure of certain export markets, in particular those of the United States, to British sheep.
It is clear that scrapie in sheep is important commercially and for that reason alone effective measures to control it should be devised as quickly as possible.
Recently the question has again been brought up as to whether scrapie is transmissible to man. This has followed reports that the disease has been transmitted to primates. One particularly lurid speculation (Gajdusek 1977) conjectures that the agents of scrapie, kuru, Creutzfeldt-Jakob disease and transmissible encephalopathy of mink are varieties of a single "virus". The U.S. Department of Agriculture concluded that it could "no longer justify or permit scrapie-blood line and scrapie-exposed sheep and goats to be processed for human or animal food at slaughter or rendering plants" (ARC 84/77)" The problem is emphasised by the finding that some strains of scrapie produce lesions identical to the once which characterise the human dementias"
Whether true or not. the hypothesis that these agents might be transmissible to man raises two considerations. First, the safety of laboratory personnel requires prompt attention. Second, action such as the "scorched meat" policy of USDA makes the solution of the acrapie problem urgent if the sheep industry is not to suffer grievously.
Epidemiology of Scrapie in the United States 1977
Like lambs to the slaughter
31 March 2001
by Debora MacKenzie Magazine issue 2284
FOUR years ago, Terry Singeltary watched his mother die horribly from a degenerative brain disease. Doctors told him it was Alzheimer's, but Singeltary was suspicious. The diagnosis didn't fit her violent symptoms, and he demanded an autopsy. It showed she had died of sporadic Creutzfeldt-Jakob disease.
Most doctors believe that sCJD is caused by a prion protein deforming by chance into a killer. But Singeltary thinks otherwise. He is one of a number of campaigners who say that some sCJD, like the variant CJD related to BSE, is caused by eating meat from infected animals. Their suspicions have focused on sheep carrying scrapie, a BSE-like disease that is widespread in flocks across Europe and North America.
Now scientists in France have stumbled across new evidence that adds weight to the campaigners' fears. To their complete surprise, the researchers found that one strain of scrapie causes the same brain damage in ...
EVIDENCE OF SCRAPIE IN SHEEP AS A RESULT OF FOOD BORNE EXPOSURE
This is provided by the statistically significant increase in the incidence of sheep scrape from 1985, as determined from analyses of the submissions made to VI Centres, and from individual case and flock incident studies. ........
Aspects of the Cerebellar Neuropathology in Nor98
Gavier-Widén, D1; Benestad, SL2; Ottander, L1; Westergren, E1 1National Veterinary Insitute, Sweden; 2National Veterinary Institute,
Norway Nor98 is a prion disease of old sheep and goats. This atypical form of scrapie was first described in Norway in 1998. Several features of Nor98 were shown to be different from classical scrapie including the distribution of disease associated prion protein (PrPd) accumulation in the brain. The cerebellum is generally the most affected brain area in Nor98. The study here presented aimed at adding information on the neuropathology in the cerebellum of Nor98 naturally affected sheep of various genotypes in Sweden and Norway. A panel of histochemical and immunohistochemical (IHC) stainings such as IHC for PrPd, synaptophysin, glial fibrillary acidic protein, amyloid, and cell markers for phagocytic cells were conducted. The type of histological lesions and tissue reactions were evaluated. The types of PrPd deposition were characterized. The cerebellar cortex was regularly affected, even though there was a variation in the severity of the lesions from case to case. Neuropil vacuolation was more marked in the molecular layer, but affected also the granular cell layer. There was a loss of granule cells. Punctate deposition of PrPd was characteristic. It was morphologically and in distribution identical with that of synaptophysin, suggesting that PrPd accumulates in the synaptic structures. PrPd was also observed in the granule cell layer and in the white matter. The pathology features of Nor98 in the cerebellum of the affected sheep showed similarities with those of sporadic Creutzfeldt-Jakob disease in humans.
***The pathology features of Nor98 in the cerebellum of the affected sheep showed similarities with those of sporadic Creutzfeldt-Jakob disease in humans.
NOR98 SHOWS MOLECULAR FEATURES REMINISCENT OF GSS
R. Nonno1, E. Esposito1, G. Vaccari1, E. Bandino2, M. Conte1, B. Chiappini1, S. Marcon1, M. Di Bari1, S.L. Benestad3, U. Agrimi1 1 Istituto Superiore di Sanità, Department of Food Safety and Veterinary Public Health, Rome, Italy (mhtml:%7B33B38F65-8D2E-434D-8F9B-8BDCD77D3066%7Dmid://00000064/!x-usc:mailto:email@example.com); 2 Istituto Zooprofilattico della Sardegna, Sassari, Italy; 3 National Veterinary Institute, Department of Pathology, Oslo, Norway
Molecular variants of PrPSc are being increasingly investigated in sheep scrapie and are generally referred to as "atypical" scrapie, as opposed to "classical scrapie". Among the atypical group, Nor98 seems to be the best identified. We studied the molecular properties of Italian and Norwegian Nor98 samples by WB analysis of brain homogenates, either untreated, digested with different concentrations of proteinase K, or subjected to enzymatic deglycosylation. The identity of PrP fragments was inferred by means of antibodies spanning the full PrP sequence. We found that undigested brain homogenates contain a Nor98-specific PrP fragment migrating at 11 kDa (PrP11), truncated at both the C-terminus and the N-terminus, and not N-glycosylated. After mild PK digestion, Nor98 displayed full-length PrP (FL-PrP) and N-glycosylated C-terminal fragments (CTF), along with increased levels of PrP11. Proteinase K digestion curves (0,006-6,4 mg/ml) showed that FL-PrP and CTF are mainly digested above 0,01 mg/ml, while PrP11 is not entirely digested even at the highest concentrations, similarly to PrP27-30 associated with classical scrapie. Above 0,2 mg/ml PK, most Nor98 samples showed only PrP11 and a fragment of 17 kDa with the same properties of PrP11, that was tentatively identified as a dimer of PrP11. Detergent solubility studies showed that PrP11 is insoluble in 2% sodium laurylsorcosine and is mainly produced from detergentsoluble, full-length PrPSc. Furthermore, among Italian scrapie isolates, we found that a sample with molecular and pathological properties consistent with Nor98 showed plaque-like deposits of PrPSc in the thalamus when the brain was analysed by PrPSc immunohistochemistry. Taken together, our results show that the distinctive pathological feature of Nor98 is a PrP fragment spanning amino acids ~ 90-155. This fragment is produced by successive N-terminal and C-terminal cleavages from a full-length and largely detergent-soluble PrPSc, is produced in vivo and is extremely resistant to PK digestion.
*** Intriguingly, these conclusions suggest that some pathological features of Nor98 are reminiscent of Gerstmann-Sträussler-Scheinker disease.
Here we report that both Nor98 and discordant cases, including three sheep homozygous for the resistant PrPARR allele (A136R154R171), efficiently transmitted the disease to transgenic mice expressing ovine PrP, and that they shared unique biological and biochemical features upon propagation in mice. These observations support the view that a truly infectious TSE agent, unrecognized until recently, infects sheep and goat flocks and may have important implications in terms of scrapie control and public health.
Edited by Stanley B. Prusiner, University of California, San Francisco, CA, and approved September 12, 2005 (received for review March 21, 2005)
NOR-98 ATYPICAL SCRAPIE 5 cases documented in USA in 5 different states USA 2007
Tuesday, June 3, 2008 SCRAPIE USA UPDATE JUNE 2008 NOR-98 REPORTED PA
SCRAPIE DETECTED IN ANOTHER GOAT USA UPDATE MARCH 2009
Saturday, May 2, 2009
APHIS AND WHO PLAN TO EXEMPT THE ATYPICAL SCRAPIE NOR-98 FROM REGULATIONS AT MEETING THIS MONTH
Tuesday, April 28, 2009
Nor98-like Scrapie in the United States of America