SHEEP WITH MASTITIS TRANSMIT INFECTIOUS PRIONS THROUGH THE MILK
SHEEP WITH MASTITIS TRANSMIT INFECTIOUS PRIONS THROUGH THE MILK
Ciriaco Ligios*, Maria Giovanna Cancedda, Antonello Carta, Cinzia Santucciu, Caterina Maestrale, Francesca Demontis, Mariangela Saba, Cristiana Patta, James C. DeMartini, Adriano Aguzzi*, and Christina J. Sigurdson* Istituto Zooprofilattico Sperimentale della Sardegna, Sassari, Italy; Research Unit: Genetics and Biotechnology, DIRPA, AGRIS Sardinia, Olmedo, Italy; Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA; Institute of Neuropathology, UniversitätsSpital Zürich, Zürich, Switzerland; Department of Pathology, School of Medicine, University of California, San Diego, CA, USA; Department of Pathology, Microbiology, and Immunology, University of California, Davis, CA USA
* To whom correspondence should be addressed. Email: email@example.com . firstname.lastname@example.org . email@example.com .
Abstract Prions are misfolded proteins that are infectious and naturally transmitted, causing a fatal neurological disease in humans and animals. Prion shedding routes have been shown to be modified by inflammation in excretory organs such as kidney. Here we show that sheep with scrapie and lentiviral mastitis secrete prions into the milk and infect nearly 90% of suckling naive lambs. Thus lentiviruses may enhance prion transmission, conceivably sustaining prion infections in flocks for generations. This study also indicates a risk of prion spread to sheep and potentially to other animals through dietary exposure to pooled sheep milk or milk products.
Previous studies have found that the cellular fraction of milk harbours the most infectivity (4), and the higher leukocyte count in milk that occurs with mastitis could conceivably have increased the infectious prion titres in milk. Although our studies in ARQ/ARQ sheep suggest that mammary gland inflammation is necessary for prion transmission through milk, it remains possible that large milk volumes from sheep without mastitis would transmit prions to nursing lambs. Milk from VRQ/VRQ sheep without clinical mastitis was previously shown to transmit prion infection to the lambs as evidenced by PrPSc deposits in lymphoid tissue biopsies (3).
Taken together, these findings demonstrate that ingestion of as little as 1 – 2 L of milk from sheep with scrapie and lymphofollicular mastitis can cause prion infection in ARQ/ARQ lambs with an attack rate of 86%. These data show that a common lentivirus can induce an inflammatory setting highly conducive for prion propagation and release into the environment, although a role for the virus in transporting prions into the milk or stimulating PrPSc release from infected cells (6) cannot be excluded. Considering that MVV and other lentiviruses are endemic in sheep and goat populations worldwide, the possibility that lentiviruses have enabled prion transmission through milk and ultimately propagation of scrapie through some flocks should be considered. Together with two other recent reports on infectious prions in sheep milk (3, 4), these studies indicate a risk of prion spread to sheep and potentially other animals through dietary exposure to sheep milk or milk products. World milk production contributes to 13% of the protein supply for humans, thus studies to determine the extent of infectious prions entering our global food supply would be worthwhile and important for accurate risk assessment.
Prion infectivity has now been detected in blood, urine and milk and this has potential consequences on risk assessments for the environment and food as well as for contamination of surfaces including medical instruments. Furthermore the procedures recommended for decontamination of MBM (Meat and Bone Meal), which are based on older methodologies not designed for this purpose, have turned out to be of very limited efficacy and compromise current policies concerning the reuse of these high value protein supplements (cross-contamination of feed circuits are difficult to control). It should be noted that the destruction or very limited use of MBM is estimated to still cost 1 billion euros per year to the European economy,
whereas other countries, including the US,
Brazil, and Argentine do not have these constraints.
Thursday, August 12, 2010
Seven main threats for the future linked to prions
PPo3-40: Mother to Offspring Transmission of Chronic Wasting Disease
Candace K. Mathiason, Amy V. Nalls, Kelly Anderson, Jeanette Hayes-Klug, Nicholas Haley and Edward A. Hoover
Colorado State University, Department of Microbiology, Immunology and Pathology, Fort Collins, CO USA
Key words: Chronic wasting disease, vertical transmission, muntjac deer
We have developed a new cervid model in small Asian muntjac deer (Muntiacus reevesi) to study potential modes of vertical transmission of chronic wasting disease (CWD) from mother to offspring. Eight of eight (8/8) muntjac doe orally infected with CWD tested PrPCWD lymphoid positive by 4 months post infection. Six fawns were born to these CWD-infected doe. Six fawns were born to 6 CWD-infected doe; 4 of the fawns were non-viable. The viable fawns have been monitored for CWD infection by immunohistochemistry and sPMCA performed on serial tonsil and rectal lymphoid tissue biopsies. PrPCWD has been detected in one fawn as early as 40 days of age. Moreover, sPMCA performed on rectal lymphoid tissue has yield positive results on another fawn at 10 days of age. In addition, sPMCA assays have also demonstrated amplifiable prions in maternal placental (caruncule) and mammary tissue of the dam.
Additional pregnancy related fluids and tissues from the doe as well as tissue from the nonviable fawns are currently being probed for the presence of CWD. In summary, we have employed the muntjac deer model, to demonstrate for the first time the transmission of CWD from mother to offspring. These studies provide the foundation to investigate the mechanisms and pathways of maternal prion transfer.
PRION 2010 Meeting Report International Prion Congress: From agent to disease; September 8–11, 2010; Salzburg, Austria Volume 4, Issue 3 July/August/September 2010
Prion infectivity in milk from ARQ/ARQ sheep experimentally infected with Scrapie and MAEDI-VISNA virus
Ciriaco Ligios1, Maria Giovanna Cancedda1, Antonello Carta2, Cinzia Santucciu1 Caterina Maestrale1, Francesca Demontis1, Sonia Attene1, Maria Giovanna Tilocca1, Cristiana Patta1, Massimo Basagni5, Paola Melis1, James C. De- Martini3, Christina Sigurdson4 1Istituto Zooprofilattico Sperimentale della Sardegna, Italy; 2Research Unit: Genetics and Biotechnology, DIRPA, AGRIS Sardinia, Italy; 3Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA; 4Department of Pathology, School of Medicine, University of California San Diego, USA; 5Prion Diagnostica Rho, Italy
Scrapie in sheep is characterized by the deposition of misfolded and aggregated prion protein (PrPSc) in the central nervous system (CNS) and within the lymphoreticular system (LRS). PrPSc was shown to accumulate in organs beyond the CNS and the LRS when lymphofollicular or granulomatous inflammation was also present.
Our aim was to determine whether ectopic PrPSc accumulation in the inflamed mammary gland of sheep with scrapie results in infectious prion secretion into the milk.
We fed approximately 1.1 - 2.1 L of milk from sheep with lymphofollicular mastitis and clinical scrapie to each of 8 ARQ/ARQ lambs derived from scrapie-free flocks. The milk donor sheep had been previously inoculated with Maedi-Visna virus (MVV) intratracheally and intravenously and scrapie brain homogenate orally. In addition, 3 ARQ/ARQ lambs were fed approximately 1.4 – 1.7 L of milk from ARQ/ARQ sheep that had been experimentally infected with only scrapie. Additional control ARQ/ARQ lambs were inoculated with scrapie brain homogenate only, or with milk from uninfected sheep.
Two lambs which had received milk from sheep with mastitis and scrapie developed clinical signs of scrapie at 677 and 745 days post-inoculation. One additional clinically healthy lamb from this group, which was sacrificed for a cause unrelated to scrapie, was found to have PrPSc in brain and tonsil. The control lambs and those which received milk from sheep affected only with scrapie are, to date, clinically healthy.
This is the first evidence of clinical scrapie in sheep fed milk from scrapie sick sheep. The experiment is ongoing, however these preliminary results indicate that milk and/or colostrum from ARQ/ARQ sheep with clinical scrapie and lymphofollicular mastitis could contribute to scrapie transmission.
Monday, August 03, 2009
Prions Are Secreted in Milk from Clinically Normal Scrapie-Exposed Sheep
Journal of Virology, August 2009, p. 8293-8296, Vol. 83, No. 16 0022-538X/09/$08.00+0 doi:10.1128/JVI.00051-09 Copyright © 2009, American Society for Microbiology. All Rights Reserved.
TAFS INTERNATIONAL FORUM FOR TRANSMISSIBLE ANIMAL DISEASES AND FOOD SAFETY a non-profit Swiss Foundation (January, 2009) TAFS1 STATEMENT ON TRANSMISSION OF SCRAPIE VIA MILK
Prions in Milk from Ewes Incubating Natural Scrapie
Archive Number 20050211.0467 Published
Date 11-FEB-2005 Subject PRO/AH/EDR> CJD (new var.) update 2005 (02)
 Date: Thu 20 Jan 2005 From: Terry S. Singeltary Sr.
Chronic Lymphocytic Inflammation Specifies the Organ Tropism of Prions
Chronic Lymphocytic Inflammation Specifies the Organ Tropism of Prions
[The following is the summary of a paper by Mathias Heikenwalder and 8 others, published in Science online, 10.1126/science.1106460, Thu 20 Jan 2005
This paper describes work that illustrates that chronic inflammatory conditions may affect and expand the natural and iatrogenic transmission of prions - Mod.CP]
Prions typically accumulate in nervous and lymphoid tissues. Because proinflammatory cytokines and immune cells are required for lymphoid prion replication, we tested whether inflammatory conditions affect prion pathogenesis. We administered prions to mice with 5 inflammatory diseases of kidney, pancreas or liver. In all cases, chronic lymphocytic inflammation enabled prion accumulation in otherwise prion-free organs. Inflammatory foci consistently correlated with lymphotoxin upregulation and ectopic induction of PrPC-expressing FDC-M1+ cells, whereas inflamed organs of mice lacking lymphotoxin-alpha or its receptor accumulate neither PrPSc nor infectivity upon prion inoculation. By expanding the tissue distribution of prions, chronic inflammatory conditions may act as modifiers of natural and iatrogenic prion transmission.
******  Date: Thu 20 Jan 2005 From: Terry S. Singeltary Sr.
Study Finds that Illness May Promote Spread of Mad Cow Prion
The agent that transmits mad cow disease and related diseases may spread further in the body of an animal suffering from certain illnesses, scientists said on Thu 20 Jan 2005. Their finding raises the question of whether measures aimed at curbing the spread of mad cow disease, or bovine spongiform encephalopathy (BSE), are adequate, the researchers said.
Tests on mice showed that prions, the protein-like fragments that transmit BSE and related diseases [e.g. variant Creutzfeldt-Jakob disease in humans], can show up in organs they are not supposed to if the mouse has an inflammatory condition. Scientists have believed that BSE-causing prions are limited to the brain, spleen, spinal cord and lymph tissue, although some tests have suggested blood and muscle tissue may also harbor the prions. The latest study, published in the journal Science, suggests prions may also sometimes be found in the kidney, pancreas and liver. "We administered prions to mice with 5 inflammatory diseases of kidney, pancreas or liver," wrote the researchers, led by top prion expert Dr. Adriano Aguzzi of the University Hospital of Zurich in Switzerland.
Aguzzi and colleagues in Britain and the United States inoculated specially bred mice with prions and checked to see if the prions spread in their bodies when the mice had an inflammatory condition. This is because other studies had suggested that prions might be attracted to immune system inflammatory cells. "In all cases, chronic lymphocytic inflammation enabled prion accumulation in otherwise prion-free organs," the researchers wrote.
BSE peaked in British cattle herds in the mid-1990s, and a few cases have been reported in other countries. Canada reported its 3rd case this month. People who eat BSE-infected beef products can develop a related human brain disease called variant Creutzfeldt-Jakob disease or vCJD. There is no treatment or cure. [As of 4 Feb 2005, so far in the UK for the year 2005 there have 8 referrals of suspected CJD; and there have been 8 deaths from sporadic CJC, one from GSS and none from familial, iatrogenic or variant CJD. - Mod.CP]. It has killed 148 Britons, and 5 [now 6] Britons are alive with the disease, according to the British Department of Health's monthly report on the disease. The World Health Organization says it has reports of 6 cases in France, one in Ireland, one in Italy, one in Canada and one in the United States [and one in Japan: see; ProMED-mail post "CJD (new var.) - Japan: death 20050204.0381" - Mod.CP]
Experts believed BSE first appeared when cattle were fed improperly rendered remains of sheep infected with scrapie, a related disease. In 1997, the United States and Canada imposed animal feed bans, and have mandated the removal of materials believed to carry infectious prions. These include the skull, brain, nerves attached to the brain, eyes, tonsils, spinal cord and attached nerves, plus a portion of the small intestine. The study suggests that even symptom-free animals may also have prions in their liver, kidney, and pancreas.
-- Terry S. Singeltary Sr.
******  Date: Fri 21 Jan 2005 From: ProMED-mail
Study Finds Broader Reach for Mad Cow Proteins
Mad cow disease has long been thought to occur in just the brains and nervous systems of infected animals. But scientists are reporting today that the proteins thought to cause the disease can travel to other organs as well. The research is based on experiments with mice, but if it is borne out in other species, it may suggest that no part of an infected animal is safe to eat. The disease leads to a fatal brain disease in humans [variant Creutzfeldt-Jakob disease].
In the mouse experiments, reported in the journal Science [see  above], researchers in Switzerland found that prions, proteins that are the infectious agent in mad cow disease, follow immune cells, called lymphocytes, in the body. When mice were given chronic infectious diseases of the liver, kidney and pancreas and then inoculated with prions, the prions made their way to the infected organs. Dr. Adriano Aguzzi, a neuropathologist at the University Hospital in Zurich, who led the experiments, said this meant that cows and sheep infected with prions could harbor the disease in any inflamed organ.
But Dr. David R. Smith, a veterinarian at the University of Nebraska, said the research did not raise alarms about American beef. For one thing, he said, livestock with obvious signs of systemic infection, like a fever, are not allowed into the food supply. And most American cattle are slaughtered while they are young and at reduced risk of infection.
Many countries, including the United States, require the removal of skulls, brains, eyes, spinal cords and other nervous tissues from slaughtered animals because prions are known to accumulate in those tissues. Even in countries with mad cow disease, mainly in Europe, meat is considered safe if those tissues are removed, Dr. Aguzzi said. But the disease could spread more readily if infections are not obvious or if inspections are sloppily done, he said.
[Byline: Sandra Blakeslee]
******  Date: Fri 4 Feb 2005 From: Terry S. Singeltary Sr.
Source: Spongiform Encephalopathy Advisory Committee (SEAC), Position Paper, January 2005 [edited]
Position Statement: Maternal Transmission of variant Creutzfeldt-Jakob disease
1. The Chief Medical Officer for England asked SEAC to consider current evidence and comment on the potential transmission of variant Creutzfeldt-Jakob disease (vCJD) from mother to child via human breast milk. In utero transmission was also considered. The committee also commented on the scientific basis of a risk reduction measure for possible transmission of vCJD via banked breast milk.
2. No diagnostic test is currently available for the detection of abnormal PrP in milk. Research is under way to develop tests to screen for the possible presence of abnormal prion protein (PrP) in milk samples from cattle experimentally infected with BSE [A joint FSA/SEAC milk working group is monitoring and providing advice on this research carried out at the Veterinary Laboratories Agency.] These modified tests may also be applicable to human milk. However, it is not yet clear when/if a reliable test will be available.
3. A small number of breast milk banks in the UK supply highly vulnerable premature babies for whom no milk may be available from the mother. A model developed by the Department of Health to assess the effect of pooling breast milk from multiple donors on the possible risks of transmission of vCJD via breast milk banks was considered.
4. There is some, albeit limited, published epidemiological and experimental research on maternal transmission of prion diseases. There are also unpublished surveillance data of children born to vCJD cases from the National CJD Surveillance Unit and UK surveillance of neurological illness in children which might inform on potential risks of maternal transmission.
Breast milk banks:
5. There is no evidence that vCJD infectivity has ever been transmitted through breast milk. However, a theoretical risk exists. Modelling studies clearly show that the practice of pooling breast milk increases the number of donors to which a recipient is exposed and thereby increases the potential risk of an infant receiving milk contaminated with vCJD infectivity. The theoretical risk of infection can be minimised by not pooling the milk, by the use of individual hand operated breast milk pumps for single donors, and by the use of single-use sterilised bottles for collection. In addition, available evidence suggests that infection/inflammation of the breast results in increased lymphocytes in milk and therefore increased risk of infectivity. This risk would be minimised if milk from donors showing signs of infection were not used.
6. The committee suggested that, if practicable, milk could be stored for an appropriate period of time to allow the health status of donors to be monitored, before it is released. However, information was not available to the committee on whether long-term storage of human milk is detrimental to its nutritional quality. Maternal transmission
7. There is evidence from animal studies for low-level maternal transmission of prions in cattle and sheep. This transmission may occur in utero, via milk and/or perinatally. However, the possibility that this putative maternal transmission might have been due to another mode of transmission, for example through a contaminated environment or feed, cannot be ruled out.
8. In contrast, in humans there is no evidence for maternal transmission in cases of familial prion disease, other than the transfer of a mutant form of the PrP gene, and there is no evidence of maternal transmission of Kuru [a chronic, progressive, uniformly fatal nervous system disorder caused by prions, associated with cannibalism among the Fore tribe and neighboring peoples in New Guinea. - CopyEd.PG]. However, compared with other human prion diseases vCJD may pose a greater risk because of the greater involvement of the lymphoreticular system in vCJD pathogenesis. Although, breast tissue (and placenta) from a single vCJD case tested negative for PrPvCJD, transfer of infectivity to breast milk may depend on the physiological status of the mammary gland. Similar tests or infectivity bioassays have not been conducted on breast tissue from lactating patients with vCJD.
9. A published study suggesting transmission of sCJD in colostrum (ref. 1) was considered unreliable because tissues not normally associated with high levels of infectivity (blood and placenta) showed equivalent infectivity to that of the brain in this study.
10. Analysis of prospective surveillance data of UK children born to mothers with, or that had subsequently developed clinical vCJD, provide no evidence for maternal transmission of vCJD. However, the number of cases is very small and the incubation period of vCJD, if transmitted from mother to child, is unknown and so the children may yet be too young to have developed symptoms.
11. The phenotype of BSE infection in humans expressing PrP genotypes other than M/M at codon 129 is not known. Given recently published studies in mice expressing the human PrP gene (ref. 2), which suggest that the human PrP genotype may affect disease phenotype, the committee considered it very important that undiagnosed neurological diseases be carefully monitored. In this respect, amongst others, it is recommended that the careful monitoring of neurological illnesses through the PIND surveillance of children (ref. 3) continue.
12. In summary, there is currently no epidemiological evidence for maternal transmission of vCJD, including transmission via breast milk. However, there is a hypothetical risk. Although available evidence is limited and mostly indirect rather than direct, this risk, if any, appears to be low. As a risk cannot be excluded, a watching brief should be maintained.
(1) Tamai Y et al. Demonstration of the transmissible agent in tissue from a pregnant woman with CJD. New Eng J Med 1992 327, 649.
(2) Wadsworth et al. Human prion protein with valine 129 prevents expression of variant CJD phenotype. Science. 2004 306, 1793-1796.
(3) Devereux G et al. Variations in neurodegenerative disease across the UK: findings from the national study of Progressive Intellectual and Neurological Deterioration (PIND). Arch DisChild. 2004 89, 8-12.
-- Terry S. Singeltary Sr.
Thursday, November 18, 2010
Increased susceptibility of human-PrP transgenic mice to bovine spongiform encephalopathy following passage in sheep