Volume 9, Issue 4, 2015
Porcine prion protein amyloid
DOI:10.1080/19336896.2015.1065373Per Hammarströma & Sofie Nyströma*
Received: 1 Jun 2015 Accepted: 17 Jun 2015 Accepted author version posted online: 28 Jul 2015
© 2015 The Author(s). Published with license by Taylor & Francis Group, LLC Additional license information
Mammalian prions are composed of misfolded aggregated prion protein (PrP) with amyloid-like features. Prions are zoonotic disease agents that infect a wide variety of mammalian species including humans. Mammals and by-products thereof which are frequently encountered in daily life are most important for human health. It is established that bovine prions (BSE) can infect humans while there is no such evidence for any other prion susceptible species in the human food chain (sheep, goat, elk, deer) and largely prion resistant species (pig) or susceptible and resistant pets (cat and dogs, respectively). PrPs from these species have been characterized using biochemistry, biophysics and neurobiology. Recently we studied PrPs from several mammals in vitro and found evidence for generic amyloidogenicity as well as cross-seeding fibril formation activity of all PrPs on the human PrP sequence regardless if the original species was resistant or susceptible to prion disease. Porcine PrP amyloidogenicity was among the studied. Experimentally inoculated pigs as well as transgenic mouse lines overexpressing porcine PrP have, in the past, been used to investigate the possibility of prion transmission in pigs. The pig is a species with extraordinarily wide use within human daily life with over a billion pigs harvested for human consumption each year. Here we discuss the possibility that the largely prion disease resistant pig can be a clinically silent carrier of replicating prions.
CONCLUDING REMARKS Should the topic of porcine PrP amyloid be more of a worry than of mere academic interest? Well perhaps. Prions are particularly insidious pathogens. A recent outbreak of peripheral neuropathy in human, suggests that exposure to aerosolized porcine brain is deleterious for human health.43,44 Aerosolization is a known vector for prions at least under experimental conditions.45-47 where a mere single exposure was enough for transmission in transgenic mice. HuPrP is seedable with BoPrP seeds and even more so with PoPrP seed (Fig. 1), indicating that humans could be infected by porcine APrP prions while neurotoxicity associated with spongiform encephalopathy if such a disease existed is even less clear. Importantly transgenic mice over-expressing PoPrP are susceptible to BSE and BSE passaged through domestic pigs implicating that efficient downstream neurotoxicity pathways in the mouse, a susceptible host for prion disease neurotoxicity is augmenting the TSE phenotype.25,26 Prions in silent carrier hosts can be infectious to a third species. Data from Collinge and coworkers.21 propose that species considered to be prion free may be carriers of replicating prions. Especially this may be of concern for promiscuous prion strains such as BSE.19,48 It is rather established that prions can exist in both replicating and neurotoxic conformations.49,50 and this can alter the way in which new host organisms can react upon cross-species transmission.51 The na€ıve host can either be totally resistant to prion infection as well as remain non-infectious, become a silent non-symptomatic but infectious carrier of disease or be afflicted by disease with short or long incubation time. The host can harbor and/or propagate the donor strain or convert the strain conformation to adapt it to the na€ıve host species. The latter would facilitate infection and shorten the incubation time in a consecutive event of intra-species transmission. It may be advisable to avoid procedures and exposure without proper biosafety precautions as the knowledge of silence carrier species is poor. One case of iatrogenic CJD in recipient of porcine dura mater graft has been reported in the literature.52 The significance of this finding is still unknown. The low public awareness in this matter is exemplified by the practice of using proteolytic peptide mixtures prepared from porcine brains (Cerebrolysin) as a nootropic drug. While Cerebrolysin may be beneficial for treatment of severe diseases such as vascular dementia,53 a long term follow-up of such a product for recreational use is recommended.
The case for mad pigs in the US
From the Consumer Policy Institute and Consumers Union: March 24, 1997
Stephen F. Sundlof, D.V.M., Ph.D
Center for Veterinary Medicine Food and Drug Administration 7500 Standish Place, Room 482, HFV 1 RockvLIle, MD 20855
Dear Dr. Sundlof:
We are writing to you to submit information that has recently come to our attention which suggests that a TSE like disease (transmissible spongiform encephalopathy) might exist in pigs in the U.S. We believe this new informantion calls for intensive research and makes it urgent to ban the use of all mammalian proteins, including swine, in the feed of all food animals, until better answers are found.
The evidence for the potential PSE (porcine spongiform encephalopathy ) is as follows. In 1979, an FSQS veternarian, Dr. Masuo Doi, noticed some unusual central nervous system (CNS) symptoms in young (about 6 months old) hogs coming into a slaughter plant In Albany, New York. Since the plant received hogs from a wide variety of sources (New York, Canada, Indiana, Illinois, Ohio, and other Midwestern states) and was not a plant used to dealing with diseased animals, Dr. Doi thought that the problem might be affecting hogs slaughtered nationwide. So, he decided to conduct a detailed study on central nervous system (CNS) symptoms/disease in young hogs coming into that slaughter plant. The study ran for 15 months (January, 1979 to March, 1980) and consisted of extended observations of the behavior of animals with suspected CNS symptoms at the plant, followed by pathological, histopatholpgical, and microbiological work on tissues from various organs of particular animals after slaughter.
For his behavioral observational work, Dr. Doi extended the usual two day observation period to three to four days, during which he took careful notes on the animals' behavior and other vital signs. During the 15 month period of the study, some 106 animals exhibiting CNS symptoms were retained during antemortem inspection.
A 1980 paper that summarized Dr. Doi's findings on the clinical symptoms and incidence of the 'disease," contained descriptions of these symptoms that sound remarkably similar to the symptoms noted for bovine spongiform encephalopathy (BSE):
"Excitable or nervous temperament to external stimuli such as touch to the skin, handling and menacing approach to the animals is a common characteristic sign among swine affected with the disease.... In the advanced stage of the disease, manifestation of neurological signs are evidenced in the form of general ataxia . . . Many animals have been found to be "downers' at first observation; if the hindquarters of these downers are raised they may be able to walk one or two steps and then fall to the ground" (Doi et al., 1980: 2, 4). Indeed, a table of symptoms includes, for the early stage: "excitability and nervousness (squealing, smacking of lips, grinding of teath, chewing, gnawing ant foaming at mouth); stiffness of limbs . . . 'tic'; weakness of hindquarters; focal tremors of skeletal muscles"; and for the advanced stage: depression; ataxia; crossing over of limbs . . . kneeling posture . . . crawling". In addition to his clinical observations, Dr. Doi also made an 8 mm film of thirteen of the affected animals; film of two of the pigs was shown at the MPI National Pathology Meeting in Seattle, Washington on flay 20, 1979.
Dr. Doi sent tissue samples from suspect cases to the USDA's Eastern Laboratory in Athens, GA for pathological, histopathogical and microbiological work. Known infectious diseases were ruled out. As Dr. Doi points out, "Histopathological studies of tissue collected from the brain and spinal cord of these animals in the early stage of the disease show congestion, hemorrhage and neuronal degeneration. All animals in the advanced stage of the disease have been confined to have Encephalitis or Meningitis by MPI laboratory" (Doi et al., 1980: 5). Eventually some 60 animals were confirmed by the MPI Laboratory to have encephalitis or meningitis, with no ldentifiable cause. As pointed out in a paper presented at the 1979 MPI National Pathology Meetings,
"Since January, a number of hogs in this establishment have been found, in antemortem, to show what appears to be CNS. Sets of tissue samples were sent to the laboratory for examination, various tests were done which include histological study (E H stain), fluorescence antibody technique, virus neutralization and viral and bacteriological isolation. Differential diagnosis was also done to exclude vitamin B deficiency, post vaccination reaction, chlorinated hydrocarbon, arthritis, and transport stress" (Doi et al., 1979). The brains of the 60 animals were examined. The brain of one of these pigs, on histopathological analysis, exhibited signs reminiscent of a TSE. This histopathological work was performed by Dr. Karl Langheinrich, Pathologist-In-Charge at USDA's Eastern Laboratory in Athens, Georgia. According to the USDA FSQS laboratory report, dated early November, 1979, Dr. Langheinrich noted:
"Microscopic examination of the barrow tissues revealed a encephalopathy and diffuse gliosis characterized by vacuolated neurons, loss of neurons and gliosis in a confined region (nucleus) of the brain stem (anterior ventral midbrain). Only an empty sometimes divided vacuole was present instead of the normal morphology of a nerve cell. Occasionally a shriveled neuron was seen. According to . . . Pathology of Domestic Animals, . . . 'The degeneration of neurons, the reactivity of the glia .... are the classical hallmarks of viral infection of the central nervous system' .... Scrapie of sheep, and encephalopathy of mink, according to the literature, all produce focal vacuolation of the neurons similar to the kind as described for this pig. I was unable to locate any lead as to the cause of this interesting phenomenon in other species including swine'' (Langheinrich, 1979). Indeed, Dr. Langheinrich's main diagnosis was, " Encephalopathy and diffuse gliosis of undetermined etiology." Portions of the brain were sent for microbiological testing to a neurologist at the University of Georgia, where they came up negative for pseudo-rabies. The brain was unique enough that USDA scientists, such as Dr. Langheinrich and Or. Dot, mentioned it to student and scientific colleagues over the years.
In 1979-1980, BSE was completely unknown. However, both the behavior of the pigs, as well as the histopathology on at least one pig, both showed sign consistent with a porcine TSE. This raises particular concern became the affected animal was only 6 months old; in an animal this young, one would rust expect to see any physical signs of TSE in the brain. Histopathology of TSEs can be very variable, so that spongiform appearance (i.e. vacuolated neurons) are not always present. Behavioral changes can be seen in TSE-infected animals before any changes in brain morphology are visible. Dr. Clarence Gibbs, in testimony before a Congressional hearing on the TSE issue on January 29, 1997 made just this point:
''In the mid-1960s, we demonstrated with our French and English collaborators that during the early incubation of the TSEs, when the virus titer in the brain was very low, there were already marked functional changes, even though no pathology was yet detectable, even ultrastructurally. A month or hero later, polynucleation of neurons appeared in spider monkeys, incubating kuru, and somewhat later, microvacuolation and membrane changes visible only by electron microscopy. This preceded the pest appearance of astrogliosis and spongiform change. It was only much later that the classical scrapie TSE pathology appeared with virus titers in brain of 10 -5 or higher" (Gibbs, 1997; pg. 4). Given that TSEs can cause behavioral changes in infected animals before any physical changes in the brain can be seen, that the manifestation of TSE in the brain can be quite variable, and that changes in brain morphology are not usually seen in 6 month old animals, we are concerned that the brain of one pig actually showed physical evidence consistent with a TSE.
Following the announcement In March, 1996 of ten cases of new variant CJD (Creutzfeldt-Jakob Disease) in the United Kingdom and their possible connection to BSE, Drs. Doi, Langheinrich and others urged reinvestigation of this case.
In August, 1996, the USDA sent five slides, one of which was a histopathology slide, to Dr. Janice Miller of USDA's Agricultural Research Servicer . Dr. Miller stained four of the slides for prion protein (she didn't stain the H&E slide). Dr. Miller told Consumers Union that Dr. Patrick McCaskey, USDA/FSIS, in charge of the Research Center at Athens, GA, called her, told her that he had five slides that all showed "problems" and asked her to stain four of them. The H&E slide, which clearly show vacuoles in the neurons (one sign of TSE), wasn't stained because to stain for PrP entails removing the slide cover, baking the slide to destain it and then restaining it for PrP; they didn't want to risk destroying the H&E slide.
Dr. Doi had kept frozen samples of the brain and spinal chord of the suspect PSE pig in case the Eastern lab wanted more material for analysis. Unfortunately, these samples were discarded when the packing plant in Albany, NY closed in 1991. It appears that the brain material sent to the Univcrsity of Georgia may have been discarded. [pers com.. Dr. Doi 3/13/97]
Dr. Miller found that the PrP stained in the four pig slides was found only on the inside of neurons, while a positive control slide from a scrapie sheep showed massive amounts of extraneuronal staining. In a letter summarizing her results (copy attached), she concludes that the PrP stained in this pig was normal: "In the pig sections you will see a small particulate type of staining that is confined to neurons and as I indicated on the phone, I would interpret as normal PrP. It is in marked contrast to the massive amount of extraneuronal staining seen in the scrapie section" (Miller, 1996).
Unfortunately, Dr. Miller's finding toes not conclusively rule out a TSE. We are concerned that while British BSE and serapie create a massive amount of extraneuronal staining, there are TSEs where this isn't the case. Three experiments were done in He U.S. -- in Mission, TX (APHIS work), Pullman, Washington (ARS work), and Ames, Iowa (ARS work) -- to see whether sheep scrapie can possibly infect cows. In all the experiments, cattle were inoculated with tissue from scrapie -infected sheep primarily by intra-cranial injection, but in the case of the Texas and Iowa studies also by oral feeding -- to see if cattle were susceptible to scrapie at all. In all three experiments, the majority of cows injected in the brain with scrapie-infected sheep material (usually brains) also developed a fatal spongiform encephalopathy.
However, in all three examples, the symptoms of the spongifonn encephalopathy differed from "mad cow" disease ~ England, as did the appearances of slides from their brains. The brain lesions seen in ail these animals were more variable than those seen in England. When Dr. Miller did similar staining for PrP from these brains (what she called "bovine scrapie") she only found PrP stains on the inside of the neurons, not the massive extraneuronal staining seen in BSE (Miller, pers. comm., March 7, 1997). Thus, Dr. Miller's finding of PrP stains only inside the neurons in the suspect pigs is not particularly reassuring.
In November 1996, USDA sent the single histopathology slide to Dr. William Hadlow, one of the foremost spongiform encephalopathy pathologists in the world. (For unknown reasons, Dr. Hadlow was only sent the one slide; he was not told of the existence of the other slides, nor of Dr. Miller's findings, nor was he told or given the behavioral report from Dr. Doi or the morphology work by Dr. Langheinrich, or shown film of the affected pigs [Dr. Hadlow, pers. com., 3/13/97] From this single slide, Dr. Hadlow found some evidence consistent with TSEs but not enough for a conclusive diagnosis. He noted that the slide contained vacuoles inside neurons, one of the signs of a TSE (Dr. Langheinrich had noted this as well).
However, since such vacuoles occasionally occur normally in pigs, he thought that was not something special: "About twelve (12) neurons in the parasympathetic nucleus have unilocular optically empty vacuoles in the perikaryon. This is the site where such vacuolated neurons have been seen in the swine (as well as in cats and sheep) as an incidental finding. So I do not think such cells have any significance in this pig" (Hadlow, 1996). However, he did see evidence, Including changes in astrocytes, that suggested a TSE, but without examining other parts of the brain to look for other evidence of TSE, he couldn't be sure:
"I am impressed, though, with what seems to be an increase in the number of astrocytes in the section. Some astrocytes are in clusters, some are enlarged and vesicular. Where they are most numerous, a few rod cells (activated microglia) are seen. These findings suggest some perturbation of the nervous tissue. Although such a global response occurs in the transmissible spongifonn encephalopathies, I do no! know its significance in this case without examining other parts of the brain for changes characteristic of these diseases. Thus, from looking; at this one (1) section of brain, I cannot conclude that the pig was affected with a scrapie-like spongiform encephalopathy" (Hadlow, 1996). In sum, Dr. Hadlow~s letter does not rule out the possibility of a TSE. He says that there is suggestive evidence, but that he would need to look at other slides/sections of the brain, to make a conclusive diagnosis.
In our view, the implications of this data are extremely serious. Experiments in the United Kingdom have shown that pigs are susceptible to BSE. Pigs inoculated with BSE develop a TSE (Dawson et al., 1990). Feeding experiments are underway in the UK to see if BSE can be orally transmitted to pigs; as of March, 1997, some 6 years after the start of the experiment, none of the pigs fed BSE brain have come down with a TSE. Unfortunately the design of this experiment severely limits what we will learn from it, and will most likely not tell us conclusively if pigs can get BSE from feed. It turns out that the pigs were not fed BSE brain continuously. Rather, the pigs were only fed BSE brain material on three days, over a three week period (i.e.. one day each week). Following these three doses, the pigs were never fed contaminated material again. The total amount of infective material given to the pigs was therefore quite small. Thus, a negative finding would be hard to interpret and would not mean that BSE is not orally active in pigs.
We believe that as a top priority USDA should conduct follow-up studies to look for potential CNS/PSE cases in pigs (we plan to communicate about this to USDA separately). In brief, we feel that the following kinds of studies need to be done:
i) TSE pathology experts should examine all the slides from the suspect pig (2709). To our knowledge, at least 12 separate slides exist.
ii) Determine if any brain material from the suspect pig (2709) still exists at the Unlverslty of Georgia. If so, this material should be retrieved and used for transmission studies. In particular, suckling pigs should be inoculated with the material and then permitted to live unto they die of a disease or old age, at which point their brains should be examined for physical signs of a TSE as well as for immunchistochemical evidence (i.e. staining looking for the abnormal PrP).
iii) Increase antemortem inspection for CNS symptoms at hog facilities. Inspectors should be trained to detect the subtle CNS symptoms seen in the Doi et al. study. At a select number of slaughter facilities, animals exhibiting CNS symptoms should be removed and held for observation until they die, at which time their brains should be examined for evidence of a TSE.
iv) Research on CNS symptoms among Me 6,000 or so breeding sows which are permitted to live for 3+ years. Sows exhibiting CNS symptoms should be removed and held for observation until they die, at which time then brains should be exernined for evidence of a TSE.
While such work is underway, given the above inforrnabon, we believe that as a precutionary measure the FDA must expand the proposed ruminant plus mink-to-ruminnant feed ban to prevent protein from any material, including hogs, being fed to any food animal.
Michael Hansen, Ph.D Research Associate
Jean Halloran Director
Dawson, M., Wells, G.A.H., Parker, B.N;J. and A.C Scott. 1990. Primary parental transmission of bovine spongiform encephalopathy to the pig. Veternary Record, pg. 338.
Doi, M., Matzner, N.D. and C. Rothaug. 1979. Observation of CNS disease in market hogs at Est. 893 Tobin Packing Co., Inc. Albany, New York. United States Department of Agriculture, Food Safety and Quality.Service, Meat and Poultry Inspection Service. 7pp.
Doi, M, Langheinrich, K. and F. Rellosa. 1980. Observations of CNS signs in hogs at Est. 893 Tobin Packing C:o., Inc. Presented by Dr. Lngheinrich at the MPI National Pathology Meeting in Seattle, Washington on July 20, 1979.
Gibbs, C. 1997. Statement to the Committee on Governnent Reform and Oversight, Subcommittee on Human Resources and Intergovernmental Relations, U.S. House of Representatives. January 29,1997.
Hadlow, WJ. 1996. Letter to Patrick McCaskey, USDA/FSIS/Eastem Lab, dated November 13, 1996.
Langheinrich, KA. 1979. USDA/FSQS Laboratory report on specimen 2709. Dated November 8, 1979
Miller, J. 1996. Letter to Patrick McCaskey, USDA/ESIS/Eastern Lab, dated September 6, 1996.
Dr. Janice Miller, ARS< USDA responds Mon, 31 Mar 1997 Correspondence My involvement in the "pig incident" (I refuse to say "mad pig disease" since no such disease has been recognized):
I was asked by Dr. Al Jenny at the National Veterinary Services Laboratory if I had ever done immunohistochemistry on slides that had already been stained by hematoxylin and eosin, the standard stain used for histopathology. I had done it on a few scrapie cases so he asked if I would do the procedure on some pig brain slides that he had received from Dr. Pat McCaskey, an FSIS pathologist in Athens, GA.
At the time I didn't know the history of the situation but Dr. Jenny said I should call Dr. McCaskey and discuss it with him before proceeding. Only then did I learn a little about the history of the case. We decided that I wouldn't try to stain all of the slides because I was afraid the procedure required to remove the cover slips might damage the sections and Dr. McCaskey was concerned about preserving the sections for other pathology consultations, if necessary.
We agreed that I would stain 4 of the 5 slides, leaving the slide with the best lesions untouched. I was also concerned that I didn't know whether the antiserum we use would stain pig PrP but decided it was worth a try. When I completed the staining procedure the only positive material I observed was a small amount of particulate staining within the cell body of some neurons. We have occasionally observed that kind of staining in brains from control cattle and sheep in our experiments and interpret it to be normal PrP. (A similar finding was reported by Dr. Haritani, who first described the technique for BSE).
That observation was reported in our 1994 paper and we stated that consequently we could not interpret intraneuronal staining as indicative of scrapie (although it may be present, the bulk of staining is in neuropil, around vessels and neurons, etc). In that study I think our interpretation was somewhat validated by the very close correlation we had between immunohistochemistry and western blot results. At any rate, I told Dr. McCaskey that my interpretation on the slides was that the only staining present was consistent with normal PrP. The good news was that the antiserum did in fact stain something and that it was in the correct location for normal PrP, indicating that the antiserum would have detected abnormal PrP, had it been present. Subsequently, I called Dr. Richard Rubenstein, who provided the antibody we use, and asked if he knew whether it would react with pig PrP and he said he didn't know. However, he said it reacted with almost all mammalian species, except ferret and mink, that he had tried so he would be surprised if it wasn't reactive with pig PrP.
So, having all of this information at hand, people can decide whether the immunohistochemical test means anything or not. The lack of a positive control pig tissue (positive sheep tissue is included in every test) may be viewed by some people as diminishing the value of a negative result, but feel we did the best we could under the circumstances.
The above recitation describes my experience with the case in question. I did not photograph the slides and returned all 5 to Dr. McCaskey. It was later that he had Dr. Hadlow look at the case for histopathologic interpretation. I did not examine the slides for that purpose because I do not have experience in scrapie diagnosis and would not consider my observations meaningful.
I appreciated the additional information about the original study done by Dr. Doi. Although I've heard bits and pieces of the story from different people, this was the first time I had heard that 60 of the pigs were diagnosed as having encephalitis or meningitis. I think that fact, plus the fact that the pigs were only about 6 months old, should certainly indicate that it's highly unlikey that a spongiform encephalopathy epidemic was causing the CNS signs observed. Whether the 1 pig with the questionable encephalopathy lesions was a TSE could be debated, I suppose. The age would seem to argue against it and the immunohistochemistry result would also (at least that's my opinion).
We disagree about the implications of age regarding the liklihood of TSE in a 6-month old pig. Certainly dose has an effect on incubation period in experimental transmissions and probably also in the "natural" acquired transmissions. However, regardless of the manner of transmission, I don't know of any first passage experimental interspecies transmission where the incubation period was as short as 6 months.
Early onset in mice were achieved only after adaptation through at least 1 intraspecies transfer. I believe the same is true for development of the hamster models. With regard to acquired transmissions, Linda Detwiler's review on scrapie cites research that indicated infectivity was found in CNS tissues of lambs as early as 4 months of age: however, they were not showing clinical signs. From what I can find in the literature, a clinical case of scrapie under 2 years of age would be exceptional, but with the amount of material published on that disease I wouldn't want to say it hasn't happened.
With TME the shortest incubation I've seen reported was 9 months. Elizabeth Williams has indicated that the youngest case of CWD observed in their wildlife facilities was 18 months old. You stated that in England calves were getting BSE by one year. In the experimental BSE transmissions cattle didn't develop clinical signs until the second year of observation and the earlest sign we observed in cattle inoculated with sheep scrapie was 14 months.
With respect to swine, the only model we have is the experimental transmission of BSE. The animal first developed signs about 17 months after inoculation. I think that it would be highly unlikely for a 6 month old pig to be showing CLINICAL signs of a TSE (the claim in this particular situation). One can never say never but it seems reasonable to at least examine what is known and make an educated estimate about what is likely.
A case-control study of CJD. Dietary risk factors. Am J Epidemiol 122 (3): 443-451 (1985) Davanipour Z, Alter M, Sobel E, Asher DM, Gajdusek DC The mode of natural transmission of Creutzfeldt-Jakob disease remains unknown. In a case-control study conducted in 1981-1983 to evaluate possible dietary and other sources of the disease, 26 cases were ascertained in the mid-Atlantic region of the United States, 23 of which were obtained from accumulated records of the Laboratory of Central Nervous System Studies of the National Institutes of Health. Controls included 18 family members and 22 hospital-matched individuals (total sample size, 66). An increased consumption among patients was found for roast pork, ham, hot dogs (p less than 0.05), roast lamb, pork chops, smoked pork, and scrapple (p less than 0.1). An excess consumption of rare meat (p less than 0.01) and raw oysters/clams (p less than 0.1) was also reported among the patients. Liver consumption, among organ foods, was greater (p less than 0.1) among the cases. If Creutzfeldt-Jakob disease is acquired through ingestion of foods containing the agent, then the food items identified may be among those which need to be evaluated more intensively. Larger case-control studies with more focused dietary questions are warranted.
Sundlof can't comment From: Dr. Stephen Sundlof D.V.M., Ph.D. Director, Center for Veterinary Medicine Food and Drug Administration :
At the present time FDA is in the process of developing a final rule which will regulate the feeding of certain animal-derived protein to other animals. In addition to studying the scientific literature pertaining to TSE's, we have received 700 comments relating the proposed rule that was published in the Federal Register on January 3, 1977. The information provided by Dr. Hansen and others will be considered in developing the final rule along with all of the other information and comments that have been officially submitted to FDA. Until the final rule is published, FDA is prohibited from commenting on information that might impact the final rule. Therefore, I am unable to respond to the documents in Dr. Hansen's letter.
I do not have access to the photomicrographs of the histopathology slides, and I was unaware of their existance until Dr. Hansen brought the issue to my attention. Furthermore, I do not have addresses or telephone numbers for Drs. Doi. Langheinrich, or Hadlow. Someone from the USDA would have this information but I am not sure who that would be.
Webmaster had written: " Do photomicrographs of any of the 12 slides exist? If you have any of them, I would like to scan a few of these and post them at high resolution on the internet so that pathologists world-wide could view and comment on them.
Primary parenteral transmission of bovine spongiform encephalopathy to the pig. Veterinary Record 1990 127 13 338 Dawson, M.; Wells, G. A. H.; Parker, B. N. J.; Scott, A. C. Ten, weaned one- to two-week old piglets from a specific pathogen free breeding herd were inoculated under halothane anaesthesia by simultaneous injections intracerebrally (0.5 ml) intravenously (1 to 2 ml) and intraperitoneally (8 to 9 ml) with an inoculum consisting of 10% saline suspension of pooled homogenised brainstem from 4 natural bovine spongiform encephalopathy cases. Control piglets were similarly inoculated with saline. After 69 weeks one challenged pig showed mild aggressive behaviour towards the animal attendants. Intermittent inappetence and depression were also noted. Within one week the behavioural changes included aimless biting activity and there was mild symmetrical ataxia. The ataxia progressed and 5 weeks after onset of signs the gait ataxia was generalised with hypermetria and wide-based stance. At this time the pig was killed. Histopathological examination of the brain revealed spongiosis of grey matter neuropil with greatest intensity in the medial geniculate body, superior colliculus and corpus striatum. There was sparse vacuolation of neuronal perikarya in the dorsal nucleus of the vagina nerve and widespread astrocytic reaction. Characteristic fibrils associated with transmissible spongiform encephalopathies were detected by electron microscopy.
One good question is what _pooled_ medical products do they make from pigs. The key issues for spread of this disease are the amplification cycle and distribution pooling. That is, one rotten apple by itself is less of a problem than if it is in a barrel. – webmaster
EXPERIMENTAL PORCINE SPONGIFORM ENCEPHALOPATHY 1. CMO should be aware that a pig inoculated experimentally (ic, iv, and ip) with BSE brain suspension has after 15 months developed an illness, now confirmed as a spongiform encephalopathy. This is the first ever description of such a disease in a pig, although it seems there ar no previous attempts at experimental inoculation with animal material. The Southwood group had thought igs would not be susceptible. Most pigs are slaughtered when a few weeks old but there have been no reports of relevant neurological illness in breeding sows or other elderly pigs.
...see full text ;
So it is plausible pigs could be preclinically affected with BSE but since so few are allowed to reach adulthood this has not been recognised through clinical disease. ...
CONFIDENTIAL EXPERIMENTAL PORCINE SPONGIFORM ENCEPHALOPATHY
PLEASE NOTE, these old BSE Inquiry links take a while to open with the wayback machine, so be patient. ...tss Title: Experimental Intracerebral and Oral Inoculation of Scrapie to Swine: Preliminary Report In the United States, feeding of ruminant by-products to ruminants is prohibited, but feeding of ruminant materials to swine and poultry still occurs. The potential for swine to have access to scrapie-contaminated feedstuffs exists, but the potential for swine to serve as a host for replication/accumulation of the agent of scrapie is unknown. The purpose of this study was to perform oral and intracerebral inoculation of the U.S. scrapie agent to determine the potential of swine as a host for the scrapie agent and their clinical susceptibility. snip... IN CONFIDENCE EXPERIMENTAL PORCINE SPONGIFORM ENCEPHALOPATHY 1. CMO should be aware that a pig inoculated experimentally (ic, iv, and ip) with BSE brain suspension has after 15 months developed an illness, now confirmed as a spongiform encephalopathy. This is the first ever description of such a disease in a pig, although it seems there ar no previous attempts at experimental inoculation with animal material. The Southwood group had thought igs would not be susceptible. Most pigs are slaughtered when a few weeks old but there have been no reports of relevant neurological illness in breeding sows or other elderly pigs. ...see full text ;
we cannot rule out the possibility that unrecognised subclinical spongiform encephalopathy could be present in British pigs though there is no evidence for this: only with parenteral/implantable pharmaceuticals/devices is the theoretical risk to humans of sufficient concern to consider any action.
May I, at the outset, reiterate that we should avoid dissemination of papers relating to this experimental finding to prevent premature release of the information. ...
3. It is particularly important that this information is not passed outside the Department, until Ministers have decided how they wish it to be handled. ...
But it would be easier for us if pharmaceuticals/devices are not directly mentioned at all. ...
Our records show that while some use is made of porcine materials in medicinal products, the only products which would appear to be in a hypothetically ''higher risk'' area are the adrenocorticotrophic hormone for which the source material comes from outside the United Kingdom, namely America China Sweden France and Germany. The products are manufactured by Ferring and Armour. A further product, ''Zenoderm Corium implant'' manufactured by Ethicon, makes use of porcine skin - which is not considered to be a ''high risk'' tissue, but one of its uses is described in the data sheet as ''in dural replacement''. This product is sourced from the United Kingdom.....
It was not until . . . August 1990, that the result from the pig persuaded both SEAC and us to change our view and to take out of pig rations any residual infectivity that might have arisen from the SBOs.
4.303 The minutes of the meeting record that: It was very difficult to draw conclusions from one experimental result for what may happen in the field. However it would be prudent to exclude specified bovine offals from the pig diet. Although any relationship between BSE and the finding of a spongiform encephalopathy in cats had yet to be demonstrated, the fact that this had occurred suggested that a cautious view should be taken of those species which might be susceptible. The 'specified offals' of bovines should therefore be excluded from the feed of all species. 17
7 OF 10 LITTLE PIGGIES WENT ON TO DEVELOP BSE;
1: J Comp Pathol. 2000 Feb-Apr; 122(2-3): 131-43. Related Articles, Links Click here to read
The neuropathology of experimental bovine spongiform encephalopathy in the pig.
Ryder SJ, Hawkins SA, Dawson M, Wells GA. Veterinary Laboratories Agency Weybridge, Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK.
In an experimental study of the transmissibility of BSE to the pig, seven of 10 pigs, infected at 1-2 weeks of age by multiple-route parenteral inoculation with a homogenate of bovine brain from natural BSE cases developed lesions typical of spongiform encephalopathy. The lesions consisted principally of severe neuropil vacuolation affecting most areas of the brain, but mainly the forebrain. In addition, some vacuolar change was identified in the rostral colliculi and hypothalamic areas of normal control pigs. PrP accumulations were detected immunocytochemically in the brains of BSE-infected animals. PrP accumulation was sparse in many areas and its density was not obviously related to the degree of vacuolation. The patterns of PrP immunolabelling in control pigs differed strikingly from those in the infected animals. PMID: 10684682 [PubMed - indexed for MEDLINE]
Transgenic mice expressing porcine prion protein resistant to classical scrapie but susceptible to sheep bovine spongiform encephalopathy and atypical scrapie.
Emerg Infect Dis. 2009 Aug; [Epub ahead of print]
Wednesday, July 06, 2011
Swine Are Susceptible to Chronic Wasting Disease by Intracerebral Inoculation snip... In the US, feeding of ruminant by-products to ruminants is prohibited, but feeding of ruminant materials to swine, mink and poultry still occurs. Although unlikely, the potential for swine to have access to TSE-contaminated feedstuffs exists.
Wednesday, July 06, 2011
Swine Are Susceptible to Chronic Wasting Disease by Intracerebral Inoculation (see tonnage of mad cow feed in commerce USA...tss)
In an experimental study of the transmissibility of BSE to the pig, seven of 10 pigs, infected at 1-2 weeks of age by multiple-route parenteral inoculation with a homogenate of bovine brain from natural BSE cases developed lesions typical of spongiform encephalopathy.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=PubMed&list_uids=10684682&dopt=Abstract Title: Experimental Intracerebral and Oral Inoculation of Scrapie to Swine: Preliminary Report
In the United States, feeding of ruminant by-products to ruminants is prohibited, but feeding of ruminant materials to swine and poultry still occurs. The potential for swine to have access to scrapie-contaminated feedstuffs exists, but the potential for swine to serve as a host for replication/accumulation of the agent of scrapie is unknown. The purpose of this study was to perform oral and intracerebral inoculation of the U.S. scrapie agent to determine the potential of swine as a host for the scrapie agent and their clinical susceptibility. snip... snip... In the United States, feeding of ruminant by-products to ruminants is prohibited, but feeding of ruminant materials to swine and poultry still occurs. The potential for swine to have access to scrapie-contaminated feedstuffs exists, but the potential for swine to serve as a host for replication/accumulation of the agent of scrapie is unknown. The purpose of this study was to perform oral and intracerebral inoculation of the U.S. scrapie agent to determine the potential of swine as a host for the scrapie agent and their clinical susceptibility.
see full text and more transmission studies here ;
snip... see full text ;
Thursday, November 10, 2011
National Meat Association v. Harris Docket No., 10-224 DEADSTOCK DOWNER PIGS AND PORCINE SPONGIFORM ENCEPHALOPATHY PSE Court Likely to Overturn Calif. Law on Livestock
Friday, April 20, 2012
Ultrastructural findings in pigs experimentally infected with bovine spongiform encephalopathy agent
Wednesday, July 29, 2015
Porcine Prion Protein Amyloid or mad pig disease PSE
Monday, August 10, 2015
Detection and Quantification of beta-Amyloid, Pyroglutamyl A beta, and Tau in Aged Canines
Friday, August 7, 2015
Transgenic Mouse Bioassay: Evidence That Rabbits Are Susceptible to a Variety of Prion Isolates
PRION 2015 CONFERENCE FT. COLLINS CWD RISK FACTORS TO HUMANS
*** LATE-BREAKING ABSTRACTS PRION 2015 CONFERENCE ***
Zoonotic Potential of CWD Prions
Liuting Qing1, Ignazio Cali1,2, Jue Yuan1, Shenghai Huang3, Diane Kofskey1, Pierluigi Gambetti1, Wenquan Zou1, Qingzhong Kong1 1Case Western Reserve University, Cleveland, Ohio, USA, 2Second University of Naples, Naples, Italy, 3Encore Health Resources, Houston, Texas, USA
***These results indicate that the CWD prion has the potential to infect human CNS and peripheral lymphoid tissues and that there might be asymptomatic human carriers of CWD infection.***
P.105: RT-QuIC models trans-species prion transmission
Kristen Davenport, Davin Henderson, Candace Mathiason, and Edward Hoover Prion Research Center; Colorado State University; Fort Collins, CO USA
Additionally, human rPrP was competent for conversion by CWD and fCWD.
***This insinuates that, at the level of protein:protein interactions, the barrier preventing transmission of CWD to humans is less robust than previously estimated.***
From: Terry S. Singeltary Sr.
Sent: Saturday, November 15, 2014 9:29 PM
To: Terry S. Singeltary Sr.
Subject: THE EPIDEMIOLOGY OF CREUTZFELDT-JAKOB DISEASE R. G. WILL 1984
THE EPIDEMIOLOGY OF CREUTZFELDT-JAKOB DISEASE
R. G. WILL
*** The association between venison eating and risk of CJD shows similar pattern, with regular venison eating associated with a 9 FOLD INCREASE IN RISK OF CJD (p = 0.04). (SEE LINK IN REPORT HERE...TSS) PLUS, THE CDC DID NOT PUT THIS WARNING OUT FOR THE WELL BEING OF THE DEER AND ELK ;
*** These results would seem to suggest that CWD does indeed have zoonotic potential, at least as judged by the compatibility of CWD prions and their human PrPC target. Furthermore, extrapolation from this simple in vitro assay suggests that if zoonotic CWD occurred, it would most likely effect those of the PRNP codon 129-MM genotype and that the PrPres type would be similar to that found in the most common subtype of sCJD (MM1).***
*** The potential impact of prion diseases on human health was greatly magnified by the recognition that interspecies transfer of BSE to humans by beef ingestion resulted in vCJD. While changes in animal feed constituents and slaughter practices appear to have curtailed vCJD, there is concern that CWD of free-ranging deer and elk in the U.S. might also cross the species barrier. Thus, consuming venison could be a source of human prion disease. Whether BSE and CWD represent interspecies scrapie transfer or are newly arisen prion diseases is unknown. Therefore, the possibility of transmission of prion disease through other food animals cannot be ruled out. There is evidence that vCJD can be transmitted through blood transfusion. There is likely a pool of unknown size of asymptomatic individuals infected with vCJD, and there may be asymptomatic individuals infected with the CWD equivalent. These circumstances represent a potential threat to blood, blood products, and plasma supplies.
O.05: Transmission of prions to primates after extended silent incubation periods: Implications for BSE and scrapie risk assessment in human populations
Emmanuel Comoy, Jacqueline Mikol, Val erie Durand, Sophie Luccantoni, Evelyne Correia, Nathalie Lescoutra, Capucine Dehen, and Jean-Philippe Deslys Atomic Energy Commission; Fontenay-aux-Roses, France
Prion diseases (PD) are the unique neurodegenerative proteinopathies reputed to be transmissible under field conditions since decades. The transmission of Bovine Spongiform Encephalopathy (BSE) to humans evidenced that an animal PD might be zoonotic under appropriate conditions. Contrarily, in the absence of obvious (epidemiological or experimental) elements supporting a transmission or genetic predispositions, PD, like the other proteinopathies, are reputed to occur spontaneously (atpical animal prion strains, sporadic CJD summing 80% of human prion cases). Non-human primate models provided the first evidences supporting the transmissibiity of human prion strains and the zoonotic potential of BSE. Among them, cynomolgus macaques brought major information for BSE risk assessment for human health (Chen, 2014), according to their phylogenetic proximity to humans and extended lifetime. We used this model to assess the zoonotic potential of other animal PD from bovine, ovine and cervid origins even after very long silent incubation periods. *** We recently observed the direct transmission of a natural classical scrapie isolate to macaque after a 10-year silent incubation period, ***with features similar to some reported for human cases of sporadic CJD, albeit requiring fourfold longe incubation than BSE. Scrapie, as recently evoked in humanized mice (Cassard, 2014), ***is the third potentially zoonotic PD (with BSE and L-type BSE), ***thus questioning the origin of human sporadic cases. We will present an updated panorama of our different transmission studies and discuss the implications of such extended incubation periods on risk assessment of animal PD for human health.
***thus questioning the origin of human sporadic cases...TSS
J. Mikol1, S. Luccantoni-Freire1, E. Correia1, N. Lescoutra-Etchegaray1, V. Durand1, C. Dehen1, J.P. Deslys1, E. Comoy1
1Institute of Emerging Diseases and Innovative Therapies, Service of Prion Diseases, Atomic Energy Commission, 18 Route du Panorama 92265 Fontenayaux- Roses, France
Uncommon prion disease induced in macaque ten years after scrapie inoculation
Introduction: Bovine Spongiform Encephalopathy (BSE) is the single animal prion disease reputed to be zoonotic, inducing variant of Creutzfeldt-Jakob Disease (vCJD) in man, and therefore strongly conditioned the protective measures. Among different sources of animal prion diseases, we show here that after more than ten years of incubation, intracerebral injection of a sheep scrapie isolate can induce a prion disease in cynomolgus macaque, a relevant model of human situation towards several prion strains. Neuropathological studies showed classical and uncommon data.
Material and method: The cynomolgus macaque was intracerebrally exposed to a classical scrapie isolate issued from a naturally infected sheep flock. Upon onset of clinical signs, euthanasia was performed for ethical reasons. Classical methods of biochemistry and neuropathology were used.
Results: The three elements of the triad were present:
spongiosis was predominant in the cortex, the striatum, the cerebellum. Neuronal loss and gliosis were moderate.
The notable data were the following
(i) the brain was small, the atrophy involved mostly the temporal lobe in which axonal loss was histologically demonstrated
(ii) the spongiosis of the Purkinje cells was so intense that most of them were destroyed
(iii) there was a neuronal loss and a massive gliosis of the dorsomedialis nucleus of the thalamus
(iv) iron deposits were present in the lenticular nucleus. PrPres heavily distributed in the cortex, the basal ganglia and the cerebellum consisted in synaptic deposits and aggregates. Western Blot exhibited a type 1 PrPres in all parts of the brain.
Conclusion: We described here the successful transmission of a scrapie prion disease to a non-human primate after an extended incubation period, leading to a fatal, non-relapsing neurological disease with all the features of a prion disease. The cerebral lesional profile we observed was original in comparison to other animal prion diseases (c-BSE, L-type BSE, TME) we previously experimentally transmitted in this model.
Tuesday, December 16, 2014
Evidence for zoonotic potential of ovine scrapie prions
Hervé Cassard,1, n1 Juan-Maria Torres,2, n1 Caroline Lacroux,1, Jean-Yves Douet,1, Sylvie L. Benestad,3, Frédéric Lantier,4, Séverine Lugan,1, Isabelle Lantier,4, Pierrette Costes,1, Naima Aron,1, Fabienne Reine,5, Laetitia Herzog,5, Juan-Carlos Espinosa,2, Vincent Beringue5, & Olivier Andréoletti1, Affiliations Contributions Corresponding author Journal name: Nature Communications Volume: 5, Article number: 5821 DOI: doi:10.1038/ncomms6821 Received 07 August 2014 Accepted 10 November 2014 Published 16 December 2014 Article tools Citation Reprints Rights & permissions Article metrics
Although Bovine Spongiform Encephalopathy (BSE) is the cause of variant Creutzfeldt Jakob disease (vCJD) in humans, the zoonotic potential of scrapie prions remains unknown. Mice genetically engineered to overexpress the human prion protein (tgHu) have emerged as highly relevant models for gauging the capacity of prions to transmit to humans. These models can propagate human prions without any apparent transmission barrier and have been used used to confirm the zoonotic ability of BSE. Here we show that a panel of sheep scrapie prions transmit to several tgHu mice models with an efficiency comparable to that of cattle BSE. The serial transmission of different scrapie isolates in these mice led to the propagation of prions that are phenotypically identical to those causing sporadic CJD (sCJD) in humans. These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.
Subject terms: Biological sciences• Medical research At a glance
why do we not want to do TSE transmission studies on chimpanzees $
5. A positive result from a chimpanzee challenged severly would likely create alarm in some circles even if the result could not be interpreted for man. I have a view that all these agents could be transmitted provided a large enough dose by appropriate routes was given and the animals kept long enough. Until the mechanisms of the species barrier are more clearly understood it might be best to retain that hypothesis.
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.
The successful transmission of kuru, Creutzfeldt-Jakob disease, and scrapie by natural feeding to squirrel monkeys that we have reported provides further grounds for concern that scrapie-infected meat may occasionally give rise in humans to Creutzfeldt-Jakob disease.
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 emphasized by the finding that some strains of scrapie produce lesions identical to the once which characterize 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 scrapie problem urgent if the sheep industry is not to suffer grievously.
Nature. 1972 Mar 10;236(5341):73-4.
Transmission of scrapie to the cynomolgus monkey (Macaca fascicularis).
Gibbs CJ Jr, Gajdusek DC.
Nature 236, 73 - 74 (10 March 1972); doi:10.1038/236073a0
Transmission of Scrapie to the Cynomolgus Monkey (Macaca fascicularis)
C. J. GIBBS jun. & D. C. GAJDUSEK
National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland
SCRAPIE has been transmitted to the cynomolgus, or crab-eating, monkey (Macaca fascicularis) with an incubation period of more than 5 yr from the time of intracerebral inoculation of scrapie-infected mouse brain. The animal developed a chronic central nervous system degeneration, with ataxia, tremor and myoclonus with associated severe scrapie-like pathology of intensive astroglial hypertrophy and proliferation, neuronal vacuolation and status spongiosus of grey matter. The strain of scrapie virus used was the eighth passage in Swiss mice (NIH) of a Compton strain of scrapie obtained as ninth intracerebral passage of the agent in goat brain, from Dr R. L. Chandler (ARC, Compton, Berkshire).
Friday, January 30, 2015
*** Scrapie: a particularly persistent pathogen ***
Thursday, March 26, 2015
Increased Infectivity of Anchorless Mouse Scrapie Prions in Transgenic Mice Overexpressing Human Prion Protein
Increased susceptibility of human-PrP transgenic mice to bovine spongiform encephalopathy following passage in sheep
J. Virol. doi:10.1128/JVI.01578-10 Copyright (c) 2010, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Increased susceptibility of human-PrP transgenic mice to bovine spongiform encephalopathy following passage in sheep.
Chris Plinston, Patricia Hart, Angela Chong, Nora Hunter, James Foster, Pedro Piccardo, Jean C. Manson, and Rona M Barron* Neuropathogenesis Division, The Roslin Institute and R(D)SVS, University of Edinburgh, Roslin, Midlothian, UK; Laboratory of Bacterial and TSE Agents, Food and Drug Administration, Rockville, MD, USA
* To whom correspondence should be addressed. Email: firstname.lastname@example.org .
The risk of transmission of ruminant transmissible spongiform encephalopathy (TSE) to humans was thought to be low due to the lack of association between sheep scrapie and incidence of human TSE. However a single TSE agent strain has been shown to cause both bovine spongiform encephalopathy (BSE) and human vCJD, indicating that some ruminant TSEs may be transmissible to humans. While the transmission of cattle BSE to humans in transgenic mouse models has been inefficient, indicating the presence of a significant transmission barrier between cattle and humans, BSE has been transmitted to a number of other species. Here we aimed to further investigate the human transmission barrier following passage of BSE in a sheep. Following inoculation with cattle BSE, gene targeted transgenic mice expressing human PrP showed no clinical or pathological signs of TSE disease. However following inoculation with an isolate of BSE that had been passaged through a sheep, TSE associated vacuolation and proteinase-K resistant PrP deposition were observed in mice homozygous for the codon 129-methionine PRNP gene. This observation may be due to higher titres of the BSE agent in sheep, or an increased susceptibility of humans to BSE prions following passage through a sheep. ***However these data confirm that, contrary to previous predictions, it is possible that a sheep prion may be transmissible to humans and that BSE from other species may be a public health risk.
BSE: TIME TO TAKE H.B. PARRY SERIOUSLY
If the scrapie agent is generated from ovine DNA and thence causes disease in other species, then perhaps, bearing in mind the possible role of scrapie in CJD of humans (Davinpour et al, 1985), scrapie and not BSE should be the notifiable disease. ...
Tuesday, August 4, 2015
FDA U.S. Measures to Protect Against BSE
Thursday, August 20, 2015 Doctor William J. Hadlow RIP
William J. Hadlow Dr. Hadlow (Ohio State ’48), 94, Hamilton, Montana, died June 20, 2015.
Terry S. Singeltary Sr.