Advancing Prion Science Guidance for the National Prion Research Program (2004) / Chapter Skim
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6 Surveillance for Transmissible Spongiform Encephalopathies in the United States
6 Surveillance for Transmissible Spongiform Encephalopathies in the United States
Pages 125-159
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From page 125... ...
, the evidence that the infectious agent of BSE crossed the species barrier into humans has generated considerable concern about a uniquely North American TSE of animals chronic wasting disease (CWD)
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From page 126... ...
Nevertheless, mortality data for human TSEs are a reasonable surrogate for incidence data because these diseases are uniformly fatal and have a relatively short clinical phase about 4 to 17 months. The United States conducts nationwide surveillance for human TSEs and studies their epidemiology through two principal organizations: the Centers for Disease Control and Prevention (CDC)
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From page 127... ...
Through an analysis of mortality data, CDC determined that the rate and characteristics of human TSE deaths identified in the United States between 1979 and 2000 were stable over time and were consistent with the internationally accepted mortality associated with the disease (Belay and Schonberger, 2002~. The average annual age-adjusted TSE death rate in the United States from 1979 to 2000 was 1.07 cases per 1 million population (Belay, 2003)
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From page 128... ...
D, including the Florida woman, had been identified globally as of April 2003. The vast majority of these cases occurred in the United Kingdom, but a few were identified in continental Europe, Hong Kong, and Canada.3 3The single cases of vCJD in Hong Kong and Canada are not considered endogenous because the infected individuals had lived in the United Kingdom for an extended period of time during the BSE epidemic before effective controls were in place.
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From page 129... ...
The CDC team reviews passively reported cases of human TSE and analyzes national mortality data to determine the trends in human TSE among the U.S. population (Belay et al., 20011.
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From page 130... ...
Thus, the investigators concluded that this second set of three cases also provided no evidence of a causal link between CWD and human neurodegenerative disease. National Prion Disease Pathology Surveillance Center CDC founded NPDPSC in collaboration with the American Association of Neuropathologists in 1996 to establish a national neuropathology laboratory for the analysis of human prion diseases (Belay, 2003~.
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From page 131... ...
autopsy and referral rate of 51 percent for human TSEs prevents comprehensive surveillance for these diseases in this country. Unfortunately, the U.S.
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From page 132... ...
autopsy and referral rate of 51 percent for human TSEs prevents comprehensive surveillance for these diseases in this country. Unfortunately, the U.S.
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From page 133... ...
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From page 134... ...
In an effort to increase the referral and autopsy rates for suspected cases of human TSEs, NPDPSC began in December 2001 to cover the cost of an autopsy for a suspected CJD case; to identify institutions around the country willing to conduct reimbursed autopsies on suspected CAD cases; and, if necessary, to arrange and pay for the body to be moved to the closest location where an autopsy can be performed. If researchers found a way to inactivate prions on metal surfaces or remove prions from those surfaces, more pathologists probably would be willing to autopsy suspected TSE cases (see Chapter 71.
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From page 135... ...
Recommendation 6.1: Provide funds to promote an increase in the proportion of cases of human neurodegenerative disease, especially suspected cases of transmissible spongiform encephalopathy, that are recognized and autopsied. [Priority 217 The Need for More Epidemiological Research to Improve TSE Surveillance The committee sees a number of opportunities for the United States to improve its ability to detect a new human TSE, including a theoretical case caused by the infectious agent of CWD.
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From page 136... ...
; Canada: Health Canada (2003) ; United Kingdom: National Creutzieldt-Jakob Disease Surveillance Unit (2003)
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From page 137... ...
These are just a few of the many epidemiological studies that would provide a firmer scientific foundation for surveillance of human TSEs in the United States. Recommendation 6.2: Provide funds to increase the number and diversity of epidemiological studies on human transmissible spongiform encephalopathies (TSEs)
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From page 138... ...
USDA's surveillance program for scrapie, which includes goats but focuses on sheep, depends partially on flock owners' participation in a certification program administered by Veterinary Services of USDA's Animal and Plant Health Inspection Agency (APHIS) (Williams, 2002~.
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From page 139... ...
Given the small percentage of sheep monitored through the certification program, Veterinary Services launched a year-long study in April 2002 to determine the prevalence of scrapie through the collection and analysis of tissue samples from mature sheep at slaughterhouses (personal communication, L Detwiler, independent consultant, August 27, 20031.
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From page 140... ...
Williams, University of Wyoming, May 20031. Scrapie Flock Certification Program The Scrapie Flock Certification Program, begun in 1992, helps flock owners identify scrapie-free flocks from which to purchase new animals (Veterinary Services, 19981.
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From page 141... ...
Williams, University of Wyoming, July 11, 20031. As mentioned earlier, 60 percent of the tissue samples examined for scrapie came from slaughterhouses in fiscal year 2002, but this represents a small amount of slaughterhouse surveillance relative to what Veterinary Services plans to do (personal communication, E
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From page 142... ...
Until 1993, the USDA surveillance program for BSE used exclusively histopathological examinations of brain tissue to search for physical evidence of spongiform encephalopathy. In 1993, the program adopted immunohistochemistry and the Western blot to determine whether prions were present in tissue samples (Detwiler, 20031.
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From page 143... ...
Testing at least 12,500 brain-tissue samples would theoretically permit the detection of one or more clinical cases per million adult cattle, given the estimated number of adult cattle in the U.S. subpopulations most vulnerable to BSE.
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From page 144... ...
Between 1991 and 2001, three studies assessing the risk of BSE in the United States led to the conclusion that the country is highly resistant to the introduction and spread of the disease (Health and Consumer Protection Directorate-General, 2000; HCRA and TUCCE, 2001; Veterinary Services, 1991a,b)
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From page 145... ...
The CWD Task Force used that money to begin to implement its plan, which includes comprehensive nationwide surveillance for the disease (USDA and DOI, 2002~. The funds are sorely needed, as many states have to date lacked the resources and infrastructure necessary to conduct CWD surveillance.
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From page 146... ...
The grey areas represent states and provinces where CWD has been diagnosed in captive cervids. Some of these CWD-positive captive herds have been depopulated.
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From page 147... ...
Well-planned and -implemented CWD surveillance programs can enable states and other organizations to detect new outbreaks of the disease early and to take actions to prevent its spread. A nationally integrated program of this sort would enable a central organization to efficiently monitor the prevalence, incidence, and distribution of CWD in the United States, to identify national trends in the disease, to support epidemiological studies of CWD, and to evaluate intervention strategies.
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From page 148... ...
Recommendation 6.3: Provide funds to support the development of a nationwide surveillance system for chronic wasting disease in the United States. [Priority 21 Present CWD Surveillance in the United States Some elements of a national CWD surveillance system are already evolving.
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From page 149... ...
The committee supports the aims of the CWD Task Force's surveillance working group. We encourage the National Prion Research Program (NPRP)
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From page 150... ...
ESSENTIAL RESEARCH TO IMPROVE U.S. CAPABILITIES TO CONDUCT SURVEILLANCE FOR TSEs Many unanswered questions regarding the epidemiology, natural history, and prevalence of animal and human TSEs in the United States hamper the nation's ability to conduct the best possible surveillance for these diseases.
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From page 151... ...
. This finding suggests that cynomologous macaques would be excellent models for evaluating the risk
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From page 152... ...
Genetic variability along the PrP gene sequence in animals suggests that evolutionary pres
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From page 153... ...
Much also needs to be learned about the genetic factors that determine susceptibility to human TSEs. We know that the PRNP gene in humans is polymorphic at certain locations; for instance, PrP may have either methionine or valine at codon 129.
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From page 154... ...
Recommendation 6.4: Provide funds to expand research on the natural history, prevalence, distribution, exposure and transmission characteristics, host susceptibility, and host range of transmissible Spongiform encephalopathies, especially chronic wasting disease. [Priority 11 REFERENCES Andrews N
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From page 155... ...
2003. National chronic wasting disease surveillance in free-ranging cervids: Accomplishments and needs.
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From page 156... ...
Poster presentation at the conference Molecular Aspects of Transmissible Spongiform Encephalopathies (Prion Diseases) in Breckenridge, CO.
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From page 157... ...
223 at the Conference Molecular Aspects of Transmissible Spongiform Encephalopathies (Prion Diseases)
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From page 158... ...
2002. USDA and DOI Announce Formation of Joint Chronic Wasting Disease Working Group.
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From page 159... ...
1980. Chronic wasting disease of captive mule deer: a spongiform encephalopathy.
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