CHOROBA CREUTZFELDTA - JAKOBA
INFORMACJE PODSTAWOWE



 
 
 
 
 

ARTYKUŁ W KWARTALNIKU DLA LEKARZY 
"ALERGIA" 2002, 4 (15) 

Zbigniew Hałat
Wariant Choroby Creutzfeldta-Jakoba (vCJD) w kapsułce

pełny tekst artykułu


 
 
 
Wiek, w którym chory umiera: przeciętnie 30 r. ż., ale w rzeczywistości zależny jest od wieku, w którym doszło do narażenia na priony wywołujące m. in. gąbczaste zwyrodnienie mózgu bydła, czyli BSE
Okres wylęgania:  prawdopodobnie 6-12 lat i więcej (nawet 30)
Objawy wstępne: zaburzenia czucia, lęk, depresja, zamknięcie w sobie, utrata pamięci, otępienie, narastające zmiany zachowania, brak reakcji słownych, ataxia, ruchy mimowolne
Objawy kliniczne w przebiegu choroby: nieobecność trójfazowych fal w zapisie EEG
Czas trwania choroby: przeciętnie 13 miesięcy.
Podatność:
 
Aminokwasy
w kodonie 129
Ogółem rasa kaukaska
Choroba Creutzfeldta - Jakoba
sporadyczna
jatrogenna
nowy wariant
nvCJD
Metionina/Metionina
37%
25%
31%
100%
Walina/Walina
12%
69%
50%
-
Metionina/Walina
45%
6%
19%
-

POTENCJALNA ZAKAŹNOŚĆ
 NARZĄDÓW BYDŁA, OWIEC I KÓZ ZAKAŻONYCH BSE
Opinions adopted by the Scientific Steering Committee 
at its meeting of 19-20 February 1998

WYSOKA ZAKAŹNOŚĆ

a) Mózg bydła, oczy, rdzeń kręgowy bydła, grzbietowe korzonki nerwowe bydła, opona twarda, przysadka mózgowa, głowa, ozór i kręgosłup bydlęcy, płuca
b) Mózg owiec i kóz, oczy i rdzeń kręgowy, grzbietowe korzonki nerwowe i kręgosłupy , śledziony owiec i kóz, płuca

ŚREDNIA ZAKAŹNOŚĆ

a) Całe jelito od dwunastnicy do odbytnicy, migdałki
b) Bydlęca i kozia śledziona, łożysko, macica, tkanki płodowe, nadnercza, płyn mózgowo-rdzeniowy,
węzły chłonne

NISKA ZAKAŹNOŚĆ

Wątroba, trzustka, grasica, szpik kostny, inne kości, śluzówka nosa, nerwy obwodowe

NIE WYKRYTO ZAKAŹNOŚCI

Mięśnie szkieletowe, serce, nerki, siara, mleko, tłuszcz, ślinianki, ślina, tarczyca, gruczoł mlekowy, jajnik, jądro, tkanka chrzęstna, tkanka łączna, skóra, sierść, skrzepy krwi, surowica, mocz, żółć, kał


 
 
Tkanka
Gęstość materiału zakaźnego
(CoID50/g)*
Ciężar (kg) w ogólnej masie zwierzęcia o wadze 537 kg
Dawek zakaźnych
ID50
na zwierzę
Odsetek całej zakaźności zwierzęcia
Mózg
10
0.5
5000
64,0
Rdzeń kręgowy
10
0,2
2000
25,6
Zwoje nerwu trójdzielnego
10
0,02
200
2,6
Grzbietowe korzonki nerwowe
10
0,03
300
3,8
Jelito kręte
3,2x10-2
0,8
256
3,3
Kręgosłup
3,2x10-3
5,0
16
0,2
Śledziona
3,2x10-3
0,8
3
0,04
Oczy i pozostała część głowy
3,2x10-3
11,6
37
0,5
*Cattle oral Infectious Dose 50%
 

BEZPIECZEŃSTWO ŻELATYNY POZYSKIWANEJ Z KOŚCI PRZEŻUWACZY I ZE SKÓR PRAWDOPODOBNIE ZANIECZYSZCZONYCH SUROWCAMI SPECJALNEGO RYZYKA


Produkty spożywcze
i kosmetyczne
Leki podlegające rejestracji i produkty do wprowadzania drogą pozajelitową

 

Przemysł

Doustne 
i miejscowe
Pozajelitowe, Oczne;
Implanty
Żelatyna jako składnik
do produkcji
Źródło:

WOLNE OD BSE LUB RYZYKO ZNIKOME

- nadaje się do spożycia przez ludzi

- właściwy proces produkcyjny

- jak do produktów spożywczych i kosmetycznych

- żelatyna specjalnej jakości przy stosowaniu na duże powierzchnie uszkodzonej skóry lub na otwarte rany 

- ustalone prawem procedury rejestracyjne

- jak do produktów spożywczych i kosmetycznych

- żelatyna specjalnej jakości przy stosowaniu na duże powierzchnie uszkodzonej skóry lub na otwarte rany

- jeżeli wykorzystywany jest materiał bydlęcy nie powinien nieść ze sobą ryzyka większego niż znikome 

- właściwy i nadzorowany proces oczyszczania

- wydzielone linie produkcyjne

– wytwarzanie produktów do wykorzystania pozajelitowego lub leków ocznych lub do produkcji szczepionek. 

- jak do implantów 

- właściwy proces produkcyjny
Źródło:

NISKIE RYZYKO

- nadaje się do spożycia przez ludzi

-odrzucić ssr 

- właściwy proces produkcyjny 

- właściwy proces produkcyjny
Źródło:

WYSOKIE RYZYKO

- odrzucić:

wszystkie surowce z przeżuwaczy, z wyjątkiem skór 

- skóry z przeżuwaczy tylko ze zwierząt nadających się do spożycia przez ludzi

-surowce ze świń należy przetwarzać na osobnych liniach produkcyj-nych

- właściwy proces produkcyjny 

- właściwa ochrona parcowników

- przy spożyciu lub innej ekspozycji: jak do wykorzystania przez ludzi

Sytuacja nieznana do dalszej ewaluacji; 
gdy brak możliwości oceny należy traktować jako źródło wysokiego ryzyka

Powyższe informacje przekazano uczestnikom
Seminarium Medycznego Centrum Konsumenta

SEMINARIUM # 2: CHOROBY ODZWIERZĘCE
  "ZAGROŻENIE ZDROWIA KONSUMENTÓW ZE STRONY
PRODUKTÓW SPOŻYWCZYCH, KOSMETYCZNYCH I LECZNICZYCH
POCHODZENIA ZWIERZĘCEGO,
ZE SZCZEGÓLNYM UWZGLĘDNIENIEM
RYZYKA ZARAŹLIWYCH GĄBCZASTYCH ZWYRODNIEŃ MÓZGU"
 WARSZAWA, 7. KWIETNIA 1998r.



28. grudnia 2001r. prof. Stanley Prusiner powiadomił o wykryciu prionów także w tkance mięsnej zwierząt doświadczalnych, co mogłoby podważyć przekonanie o wystarczalności dotychczasowych środków zapobiegania zarażeniom prionami.
 

Proc. Natl. Acad. Sci. USA, Vol. 99, Issue 6, 3812-3817, March 19, 2002
 

Prions in skeletal muscle

Patrick J. Bosque, Chongsuk Ryou, Glenn Telling, David Peretz,
Giuseppe Legname, Stephen J. DeArmond, and Stanley B. Prusiner
 

Contributed by Stanley B. Prusiner, December 28, 2001

Considerable evidence argues that consumption of beef products from cattle infected with bovine spongiform encephalopathy (BSE) prions causes new variant Creutzfeldt-Jakob disease. In an effort to prevent new variant Creutzfeldt-Jakob disease,
certain "specified offals," including neural and lymphatic tissues, thought to contain high titers of prions have been excluded from foods destined for human consumption [Phillips, N. A., Bridgeman, J. & Ferguson-Smith, M. (2000) in The BSE Inquiry (Stationery Office, London), Vol. 6, pp. 413-451]. Here we report that mouse skeletal muscle can propagate prions and accumulate substantial titers of these pathogens. We found both high prion titers and the disease-causing isoform of the prion protein (PrPSc) in the skeletal muscle of wild-type mice inoculated with either the Me7 or Rocky Mountain Laboratory strain of murine prions. Particular muscles accumulated distinct levels of PrPSc, with the highest levels observed in muscle from the hind limb. To determine whether prions are produced or merely accumulate intramuscularly, we established transgenic mice expressing either mouse or Syrian hamster PrP exclusively in muscle. Inoculating these mice intramuscularly with prions resulted in the formation of high titers of nascent prions in muscle. In contrast, inoculating mice in which PrP expression was targeted to hepatocytes resulted in low prion titers. Our data demonstrate that factors in addition to the amount of PrP expressed determine the tropism of prions for certain tissues. That some muscles are intrinsically capable of accumulating substantial titers of prions is of particular concern. Because significant dietary exposure to prions might occur through the consumption of meat, even if it is largely free of neural and lymphatic tissue, a comprehensive effort to map the distribution of prions in the muscle of infected
livestock is needed. Furthermore, muscle may provide a readily biopsied tissue from which to diagnose prion disease in asymptomatic animals and even humans.
 


 
 
 
Journal of General Virology (2002), 83, 2897-2905.
Society for General Microbiology

Transmission of prion diseases by blood transfusion

Nora Hunter1, James Foster1, Angela Chong1, Sandra McCutcheon2, David Parnham1, Samantha Eaton1, Calum MacKenzie1 and Fiona Houston2

Institute for Animal Health, Neuropathogenesis Unit, West Mains Road, Edinburgh EH9 3JF, UK1
Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK2

Author for correspondence: Nora Hunter. Fax +44 131 668 3872. e-mail nora.hunter@bbsrc.ac.uk

Attempts to detect infectivity in the blood of humans and animals affected with transmissible spongiform encephalopathies (TSEs or prion diseases) have often been inconclusive because of the limitations of cross-species bioassays and the small volumes of blood that can be injected by the intracerebral route. A model has been developed for the experimental study of TSE transmission by blood transfusion using sheep experimentally infected with bovine spongiform encephalopathy (BSE) or natural scrapie as donors and susceptible scrapie-free sheep as recipients. Donors and recipients of the same species greatly increase the sensitivity of the bioassay and in sheep large volumes of blood can be injected by the intravenous (i.v.) route. Transmission of BSE to a single animal using this approach was reported recently. This study confirms this result with a second transmission of BSE and four new cases of transmission of natural scrapie. Positive transmissions occurred with blood taken at pre-clinical and clinical stages of infection. Initial studies indicate that following such infection by the i.v. route, deposition of the abnormal prion protein isoform, PrPSc, in peripheral tissues may be much more limited than is seen following oral infection. These results confirm the risks of TSE infection via blood products and suggest that the measures taken to restrict the use of blood in the UK have been fully justified.
 


 
 
The Lancet, 1 December 2002

Volume 1, Number 8 
Reflection and Reaction
Apparently sporadic CJD and covert health-care transmissions

 V Lewis , A Boyd , CL Masters , and SJ Collins

Creutzfeldt-Jakob disease (CJD) is the most common human phenotype of a group of fatal neurodegenerative diseases known as the transmissible spongiform encephalopathies, or prion diseases. 1 A unifying feature of this group of disorders is the presence of abnormal protease-resistant conformations of the prion protein (PrPres) in the brains of affected human beings and animals. PrPres is derived from a ubiquitously expressed cellular protein of uncertain function (PrPc): the former is thought to be a key component of, or perhaps even the entire, infectious unit (prion). 1 PrPres is also integrally linked to disease pathogenesis.1
Classical CJD can occur on a genetic, iatrogenic, or sporadic basis. Systematic genotyping of the prion protein gene (PRNP) by surveillance units has determined a genetic basis of CJD in approximately 14% of  cases. On a global perspective, a small but increasing number of deaths due to CJD are attributed to inadvertent transmission as a result of medical treatments, such as therapy with human cadaveric pituitary hormones, dura-mater implants, corneal grafts, and neurosurgery. At present, the vast majority of CJD cases (around 85%) occur without explanation and are designated sporadic CJD. The aetiology of sporadic CJD remains enigmatic. Potential explanations focus on spontaneous somatic mutations in neuronal PRNP or rare stochastic conformational changes in PrPc that lead to the development and accumulation of disease-associated PrPres. 1 Proof that either of these mechanisms is the explanation for all, or indeed any, of the sporadic cases of CJD is lacking.

An alternative hypothesis of sporadic CJD aetiology is suggested by the recent case-control risk analysis by Ward and colleagues, 2 which substantially corroborates the findings of our previous study in Australia. 3 Both studies support the possibility that some cases of sporadic CJD are the result of covert, low-level contamination events that occurred during the provision of health care, particularly surgery. An earlier case-control study suggested that sporadic CJD may be linked to prior head, face, or neck surgery or other medical procedures such as tonometry. However, the small case numbers and the inclusion of hospital controls effectively rendered the findings inconclusive. Larger case-control studies did not find any risk associated with medical treatments and surgery, and were also compromised by methodological issues such as the preponderance of hospital-based controls with the possibility of inherent biases. 4

The large Australian risk analysis study 3 exclusively used community-based controls and found a significant relation between surgical procedures and the risk of CJD , independent of the anatomical site or complexity of the operation. Operations associated with significantly increased risk included cardiac surgery, hysterectomy, haemorrhoidectomy, cataract extraction, carpal tunnel release, and "other surgery" (as specified). 3 Furthermore, the risk of CJD progressively increased with the number of surgical procedures: the odds ratio reached a maximum of 2·13 for three or more operations. However, a major limitation of this study was the potential for time trends that could have biased the results (784 controls were interviewed by telephone in 1997 and 241 CJD cases were retrospectively and prospectively ascertained between 1970 and 1997). Additional possible sources of bias included differences in the technique of data acquisition for cases and controls and validation of medical histories for the CJD cases only.

To assess whether the major findings of the Australian study could be independently replicated, a large multinational European case-control analysis of medical risk factors was undertaken with analogous methods. Ward and colleagues 2 report broadly similar results, with a history of any surgery approximately doubling the risk of developing sporadic CJD. In 326 cases, a significant association of CJD with "other operations" (excluding neurological, eye, ear, gallbladder and gastrointestinal operations, tonsillectomy, and appendectomy) and gynaecological surgery was found. Consequently, the risk associated with surgery was higher in females. In contrast to the Australian study, Ward and co-workers found no correlation between risk and the number of operations. The issue of time trends biasing results was largely overcome by recruitment of cases between 1993 and 1995 and controls in 2000. Other design limitations, particularly sources of bias such as differing data acquisition techniques for cases and controls, militate against the validity of the results. However, the fact that neither the Australian nor the European case-control studies, which both used community-based controls, found any risk associated with blood transfusions or other selected medical treatments is of some reassurance.

On the basis of these two studies, the suggestion that an uncertain but potentially significant number of sporadic CJD cases occur as a consequence of unrecognised low-level contamination events arising from the provision of invasive medical care (especially surgery) deserves serious consideration. This postulate is strengthened by studies showing the existence of chronic subclinical prion infection in animal models 5 and hence the possibility of an analogous human situation. The absence of risk associated with neurosurgery is counterintuitive to the inherent infectivity and risk posed by CNS tissue, and tempers the findings of both studies. Nevertheless, the shift towards community-based and prospectively recruited controls appears to be an improvement on previous sporadic CJD case-control risk assessments. Other potential biases need to be addressed, such as the manner of sourcing control and case data and validating control medical histories. The results of future methodologically improved case-control studies is awaited with interest.

Authors' contributions
 VL and AB share primary authorship of this article.

Acknowledgments
The Australian National Creutzfeldt-Jakob Disease Registry is funded by the Commonwealth Department of Health and Ageing.

 References

1 Prusiner SB. Neurodegenerative diseases and prions. N Engl J Med 2001; 344: 1516-26. [PubMed]
2 Ward HJT, Everington D, Croes EA, et al. Sporadic Creutzfeldt-Jakob disease and surgery. Neurology 2002; 59: 543-48. [PubMed]
3 Collins S, Law MG, Fletcher A, et al. Surgical treatment and risk of sporadic Creutzfeldt-Jakob disease: a case-control study. Lancet 1999; 353: 693-97. [PubMed]
4 Zerr I, Brandel JP, Masullo C, et al. European surveillance on Creutzfeldt-Jakob disease: a case-control study for medical risk factors. J Clin Epidemiol 2000; 53: 747-54. [PubMed]
5 Hill AF, Joiner S, Linehan J, Desbruslais M, Lantos PL, Collinge J. Species-barrier-independent prion replication in apparently resistent species. Proc Natl Acad Sci USA 2000; 97: 10248-53. [PubMed]

Affiliations:
Australian National Creutzfeldt-Jakob Disease Registry, Department of Pathology, The University of Melbourne, Victoria, Australia 3010.

http://neurology.thelancet.com/journal/vol1/iss8/full/neu.1.8.reflection_and_reaction.23079.1
 


 
 
J Gen Virol 84 (2003), 1021-1031; DOI  10.1099/vir.0.18788-0

Studies of the transmissibility of the agent of bovine spongiform encephalopathy to pigs

Gerald A. H. Wells1, Stephen A. C. Hawkins1, Anthony R. Austin2, Stephen J. Ryder1, Stanley H. Done1, Robert B. Green1, Ian Dexter1, Michael Dawson3 and Richard H. Kimberlin4

1 Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
2 FARA, Oak Farm, Harpsden Bottom, Henley-on-Thames, Oxon RG9 4HY, UK
3 NSPAC, DEFRA, Whittington Road, Worcester WR5 2SU, UK
4 SARDAS, 27 Laverockdale Park, Edinburgh EH13 0QE, UK

Correspondence
Gerald Wells

Studies to test the transmissibility of the bovine spongiformencephalopathy (BSE) agent to pigs began in 1989. Parenteralinoculation of the agent by three routes simultaneously (intracranially,intravenously and intraperitoneally) produced disease with anincubation period range of 69–150 weeks. Pre-clinicalpathological changes were detected in two pigs killed electivelyat 105 and 106 weeks post-inoculation. Infectivity was detectedby bioassay in inbred mice in the CNS of those pigs that developedspongiform encephalopathy. Infectivity was also found in thestomach, jejunum, distal ileum and pancreas of terminally affectedpigs. These findings show that pigs are susceptible to BSE.In contrast, disease failed to occur in pigs retained for 7years after exposure by feeding BSE-affected brain on threeseparate days, at 1–2 week intervals. The amounts fed each day were equivalent to the maximum daily intake of meat and bone meal in rations for pigs aged 8 weeks. No infectivitywas found in tissues assayed from the pigs exposed orally. Thisincluded tissues of the alimentary tract. It is suggested thatthese pigs did not become infected. The relatively high oralexposure used in these experiments compared with feed-borneexposure in the field may explain the absence of an epidemicof spongiform encephalopathy in domestic pigs concurrent withthe BSE epidemic in the UK.

 


 
 
 
San Francisco Chronicle, December 30, 2003

Scientists divided on disease's risk to humans

Some see too many unknowns; others say meat is safe

Despite continued reassurances by federal health authorities that meat from cattle infected with mad cow disease is safe, leading scientists who first found the cause of such illnesses insist that the actual risk is not known.

U.S. Department of Agriculture investigators are still trying to track down a batch of meat from 20 slaughtered cows that includes the lone Holstein in Washington state that tested positive last week for the brain-wasting illness also known as bovine spongiform encephalopathy, or BSE.

The infectious proteins called prions that cause mad cow disease have been found in abundance only in the brain stem, spinal cord and small intestine of infected cattle, tissues not included in the cuts of meat made from the doomed animal.

"Clinical studies tell us there's virtually zero risk for BSE in the meat, and that is what gives us confidence that the U.S. supply of beef remains safe,'' said Dr. Ken Petersen, of the USDA Food Safety Inspection Service, during a news conference Monday.

The 10 tons of meat were being recalled, Petersen added, only out of "an abundance of caution.''

While studies have yet to find prions in the muscle tissue of infected beef cattle, scientists have found them in the muscles of mice, hamsters and humans.

UCSF researcher Dr. Stanley Prusiner, who won the Nobel Prize in 1997 for the discovery of prions, last year found them in the leg muscles of laboratory infected mice; German scientists have found them in muscles of infected hamsters.

Using super-sensitive tests, a Swiss study published in the New England Journal of Medicine last month found prions in 8 of 32 samples of muscle tissue taken from patients who died of variant Creutzfeldt-Jakob disease, a similar brain-wasting illness affecting humans.

Armed with such findings, Prusiner has advocated that all U.S. cattle slaughtered for human consumption be tested for mad cow disease.

"There are still too many unanswered questions for the government to be reassuring the public so strongly,'' Prusiner said in a telephone interview.

Currently, only about 20,000 of the 35 million cattle slaughtered in the United States each year -- or 1 out of 1,750 -- are tested for BSE. Most are "downer cows,'' animals that are unable to walk because of injury or illness and by their behavior show a higher potential of having contracted the disease. The dairy cow in Mabton, Wash., was such a case. She had become partially paralyzed following the birth of her calf.

Yet USDA officials acknowledged yesterday that they did not know how many downer cows are slaughtered annually. The system of testing suspect cows is designed as a surveillance tool that, by sampling the most suspicious animals, could reliably pick up mad cow disease in the U.S. if as few as one in 1 million cows have it.

That system is now up for review, and the pressure is on to adopt a European-style system of massive cattle testing at slaughter.

"I think it's time for people in government to introduce a seamless testing program that could test every one of America's 35 million cows,'' Prusiner said.

Prusiner acknowledges that he could gain financially from such a program. He is a co-founder of InPro Biotechnology of South San Francisco, a company that has developed a rapid test for mad cow disease and a device that can process 8,000 test results per day.

Dean Cliver, a UC Davis expert on food safety, believes that a large scale mad cow disease testing program may now be inevitable, but he does not believe it is necessary or wise.

"The United Kingdom has invested a fortune in testing red meat, milk and milk products (from infected cows), and they have yet to detect a single prion, '' he said. "These are highly competent people, and they've yet to find anything."

Worldwide, there have been 153 cases of variant Creutzfeldt-Jakob disease, the illness caused by eating prion-infected beef. Researchers believe the infections were caused when the victims ate processed meat that contained prion-infected brain or nerve tissue. Only one American -- who had lived in Britain at the height of transmission from beef there -- has come down with the illness in the United States.

The lone cow in Washington state is the first to test positive in the United States; a single beef cow tested positive in Alberta, Canada, last May.

Nevertheless, Cliver believes that public pressure and international trade concerns are likely to bring on a massive and costly mad cow disease testing program. "It will be taking money from the testing for food-borne diseases that are killing people in the United States, such as E. coli O157/H7, " he said.

According to the federal Centers for Disease Control and Prevention, food- borne illnesses afflict 76 million Americans a year, killing an estimated 5, 000.

In light of testing that has not turned up prions in the meat of infected cattle, Cliver said the laboratory findings of prion researchers were not significant. "I promise not to eat hamsters, or humans,'' he said.

But Jiri Safar, a researcher at Prusiner's UCSF Institute for Neurodegenerative Diseases, cautions that the discovery of prions in muscle tissue should not be taken lightly.

Although prions are primarily associated with nerve cells in the brain and spinal cord, he notes that muscle tissue itself is laced with nerves. "Large nerves branch, and finish in muscle tissue," he said. "Muscles move because they intimately relate to nerves, which supply the signals for movement.'' To assume some sort of separation of nerve tissue from muscle tissue "is not anatomically correct,'' he added.

Safar, who says he no longer eats red meat himself, said that the minimum dose of prion-infected brain tissue known to cause disease is the equivalent of one-fifth of a drop of water.

The UCSF researcher, who also holds stock in InPro, contends that tests to determine conclusively whether BSE prions exist in the muscles of beef cattle have yet to be completed.

Safar credits Britain's policy of destroying all cattle more than 30 months old with reducing the transmission of mad cow disease, but he said that does not eliminate the threat. "The only way to do it completely,'' he said, "is to test every animal."
 


 
Published online: 
3 November 2005; | doi:10.1038/news051031-7

Prions suspected in milk

Sheep mammaries shown to contain agents of fatal brain disease.

Andreas von Bubnoff
The inflamed mammary glands of sheep have been found to contain protein particles that cause scrapie, a sickness similar to mad cow disease. This suggests that the suspect proteins, called prions, may also be present in the milk of infected animals.

If prions exist in the milk of cows infected with both an inflammatory illness and mad cow disease, formally known as bovine spongiform encephalopathy (BSE), this raises concerns for human health. Consumption of prion-contaminated meat from cows with BSE is believed to cause the fatal variant Creutzfeldt-Jakob disease (vCJD) in people; so might contaminated milk.

Adriano Aguzzi, the lead researcher on the study, has not detected prions in milk itself, because it is difficult to analyse for the abnormal proteins. But he says he expects to find them.

"It is unlikely that the prions are not in the milk," says Aguzzi, a pathologist at the University of Zurich Hospital, Switzerland. "And the prospect is not a pleasant one."

Neil Cashman, a prion researcher at the University of British Columbia in Vancouver, is worried too. People have looked for prions in the milk of cows with BSE and haven't found any, he says. "But they haven't looked in cows with mammary-gland infection and BSE."

"This raises very serious questions," concludes Cashman.

Inflamed in the brain

Prions are mainly found in the brain, spinal cord and immune system. Until recently, other body parts were thought to be relatively safe. But in a series of studies, Aguzzi's group has shown that prions can be present in other organs as well, provided that these organs are inflamed.

Earlier this year, his group found prions in inflamed pancreases, livers and kidneys. A study last month showed that the urine produced by inflamed kidneys in mice also contains prions.

All this has helped to solve the mystery of how wild herds of elk and deer, which are vegetarian, might manage to contract prion diseases from each other. And it prompted Aguzzi to look at mammary glands to see if they could carry prions too.

Viral culprit?
The researchers went to Sardinia, a Mediterranean island with more than a million sheep, and analysed 261 sheep that were genetically susceptible to scrapie. Of those, seven had scrapie, and four also had an infection of their mammary glands. All these four had prions in their mammary glands; the others did not. The study appears this week in Nature Medicine1.

The mammary-gland infections were caused by a virus called Maedi Visna. Aguzzi says that if this prion-virus combination is common, it may be a clue to how to fight the transmission of scrapie. "Maybe to eradicate scrapie you have to eradicate the virus first," Aguzzi says.

The prion concentration in the sheep's mammary glands is thousands of times lower than in the brain, says Aguzzi. This is probably good news, although it is not known how many prions it takes to cause vCJD in humans.

References

Ligios C., et al. Nature Medicine, 11. 1137 - 1138 (2005).

 Article |
Nature Medicine 11, 1137 - 1138 (2005)
doi:10.1038/nm1105-1137

PrPSc in mammary glands of sheep affected by scrapie and mastitis

Ciriaco Ligios1, 6, Christina J Sigurdson2, 6, Cinzia Santucciu1, 6, Gabriella Carcassola3, Giuseppe Manco2, Massimo Basagni4, Caterina Maestrale1, Maria Giovanna Cancedda5, Laura Madau1 & Adriano Aguzzi2
1  Istituto Zooprofilattico Sperimentale della Sardegna, I-07100 Sassari, Italy. 
2  UniversitätsSpital Zürich, Institute of Neuropathology, Department of Pathology, CH-8091 Zürich, Switzerland. adriano@pathol.unizh.ch
3  Dipartimento di Patologia Animale, Igiene e Sanitŕ Pubblica Veterinaria, Sez. di Microbiologia e Immunologia, Universitŕ degli Studi di Milano, I-20133 Milano, Italy. 

4  Prion DGN Srl, I-20017 Rho, Italy. 

5  Istituto Zootecnico Caseario della Sardegna, I-07040 Olmedo, Italy. 

6  These authors contributed equally to this work.
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