USAHA Live Animal Testing for Chronic Wasting Disease CWD TSE Prion
RESOLUTION NUMBER: 30 APPROVED
SOURCE: COMMITTEE ON CAPTIVE WILDLIFE AND ALTERNATIVE LIVESTOCK
SUBJECT MATTER: Live Animal Testing for Chronic Wasting Disease
BACKGROUND INFORMATION:
Detection of chronic wasting disease (CWD) in live animals is an important component of CWD prevention and control programs. With the funding decrease for CWD indemnification, the need for a successful live animal test option, with a high rate of sensitivity and specificity, is critical in both a trace-forward/trace-back scenario, as well as in herd management plans.
There have been numerous studies evaluating the sensitivity and specificity of tonsillar biopsies in cervids. Similar to scrapie, PrP (CWD) in deer accumulates in the retropharyngeal lymph nodes and tonsillar follicles before central nervous system involvement or clinical symptoms (Sigurdson et al., 1999; Spraker et al., 2002b; O’Rourke et al., 2003). Ante-mortem testing of these tissues by immunohistochemistry provides a reliable preclinical diagnosis in deer (Wild et al., 2002; Wolfe et al., 2002).
RESOLUTION:
The U.S. Animal Health Association urges the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services to expedite evaluation and approval of tonsillar biopsies into the Chronic Wasting Disease (CWD) Program Standards, providing for rapid implementation and deployment as a viable, accurate, and reliable means of live animal testing for CWD in cervids.
FINAL RESPONSE:
The U.S. Department of Agriculture, Animal and Plant Health Inspection Service (APHIS), Veterinary Services recognizes the concerns of the U.S. Animal Health Association and appreciates the opportunity to respond. APHIS supports research to develop and validate live animal tests for chronic wasting disease. We are obtaining data and collecting samples through pilot projects and routine herd depopulations to evaluate the sensitivity and specificity of tonsil biopsy as an antemortem diagnostic tool. We are working to accumulate an adequate number of tonsil biopsy samples from CWD-positive animals to complete this evaluation.
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RESOLUTION NUMBER: 32 APPROVED
SOURCE: COMMITTEE ON CAPTIVE WILDLIFE & ALTERNATIVE LIVESTOCK
SUBJECT MATTER: Chronic Wasting Disease Testing Protocol for Wild Cervidae
BACKGROUND INFORMATION:
Over the past 15 years, the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (APHIS), Veterinary Services (VS) and State regulatory officials have worked to control and prevent the spread of chronic wasting disease (CWD).
Producers raising CWD-susceptible species can only move their animal’s interstate if they are in compliance with the CWD program set forth in Title 9 Code of Federal Regulations (CFR) Parts 55 & 81, which state animals must originate from herds with at least five years of CWD monitored status.
State wildlife agencies that plan and execute elk restoration projects from one State to another are moving CWD susceptible species interstate without following minimum interstate movement requirements for farmed cervidae. Instead, Title 9 CFR Part 81.3 states the source population be considered “low-risk” by the receiving State and APHIS. To date, over two dozen herds of wild elk have been captured and transported to other States across the Nation that follow no CWD protocol set forth in the CWD Program Standards. The movement of CWD susceptible cervid species with unknown CWD status by State wildlife agencies can undermine the success of CWD control programs that have been in place in many States for more than 15 years. CWD has been found in 23 States. Eight of the 23 States have detected CWD in the free-ranging deer populations, but not in the farmed cervid herds.
The U.S. Animal Health Association Committee on Wildlife Diseases approved a resolution at the 2015 annual conference that requested APHIS Veterinary Services (VS) to develop a guidance document for captive deer, elk, or moose captured from a wild population for interstate movement and release.
APHIS released VS Guidance Document 8000.1 “Surveillance and Testing Requirements for Interstate Transport of Wild Caught Cervids” in October 2016, but the requirement of an antemortem test, such as the rectal biopsy, is only optional.
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USAHA/2016
Resolution 32
Exact language is as follows:
“Optionally, a whole-herd rectal biopsy or other mutually agreed-on method of antemortem CWD test with concurrent genotyping may be performed on the assembled herd. Laboratory results must be “not detected” on all animals. Animals with untestable or incorrect location samples (i.e., samples that are autolyzed or of the wrong tissue type) may be retested.”
RESOLUTION:
The U.S. Animal Health Association urges the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services (VS) to amend the language in VS Guidance Document 8000.1 “Surveillance and Testing Requirements for Interstate Transport of Wild Caught Cervids,” the Chronic Wasting Disease Program Standards, and Title 9 Code of Federal Regulations (CFR) Part 81.3, (b) Animals captured for interstate movement and release, to indicate that any wild cervid of a Chronic Wasting Disease (CWD) susceptible species captured and transported interstate for release shall require:
1) A rectal biopsy or other mutually agreed-on method of antemortem CWD test with concurrent genotyping performed on the assembled herd; and
2) Documentation of a sampling scheme sufficient to detect CWD at 1 percent prevalence with 95 percent confidence in wild cervids within the defined source population from which the animals are being moved and conducted within the most recent three-year period. Such sampling scheme shall include both passive (hunter harvest and found dead) and targeted surveillance for CWD.
FINAL RESPONSE:
The U.S. Department of Agriculture, Animal and Plant Health Inspection Service (APHIS), Veterinary Services recognizes the concerns of the U.S. Animal Health Association and appreciates the opportunity to respond. APHIS revised Guidance Document 8000.1 in response to several comments we received, including the proposed language contained in this resolution.
We clarified the requirements about the description of the area’s disease history, surveillance, and epidemiology for chronic wasting disease (CWD). Specifically, we added the requirement that, “Cumulative sampling over the most recent three-year period should be sufficient to detect at least a 1 percent prevalence of CWD in the source population with 95 percent confidence.” Ante-mortem testing for CWD may help to inform decisions about the risk of CWD in the source population for the wild-caught cervids. However, APHIS does not intend to require the rectal biopsy for routine herd surveillance or as a pre-movement test in farmed cervids. In light of this, we retained the option for State animal health officials to require ante-mortem testing for CWD in the guidance document. We also clarified Appendix 1 of the guidance document. APHIS issued the revised Guidance Document 8000.2 in September 2017. APHIS will not pursue changes to the Code of Federal Regulations (CFR) Part 81.3, at this time.
RESOLUTION NUMBER: 6, 13, 29, 34, and 42 Combined APPROVED
SOURCE: COMMITTEE ON INFECTIOUS DISEASES OF CATTLE, BISON AND CAMELIDS
COMMITTEE ON INFECTIOUS DISEASES OF HORSES COMMITTEE ON CAPTIVE WILDLIFE AND ALTERNATIVE LIVESTOCK
COMMITTEE ON TRANSMISSIBLE DISEASES OF POULTRY AND OTHER AVIAN SPECIES
COMMITTEE ON SHEEP AND GOATS
SUBJECT MATTER: Laboratory Approval for Regulatory Diseases
BACKGROUND INFORMATION:
Laboratories performing animal surveillance testing are integral to establishing the health status of the national herds and flocks as well as individual animals destined for export. Currently, the United States Department of Agriculture has no authority to restrict laboratories from conducting foreign animal disease diagnostic testing on livestock and poultry samples. For example, one private laboratory in the United States is advertising Polymerase Chain Reaction (PCR) testing for all of the following Foreign Animal diseases African swine fever, African horse sickness, avian influenza, classical swine fever, foot and mouth disease, nipah virus, newcastle disease virus, pestes des petits ruminants virus, rinderpest, rift valley fever, contagious equine metritis, glanders, piroplasmosis, and surra.
Additionally, there is limited state authority or oversight over laboratories conducting diagnostic testing for diseases of regulatory importance on samples obtained from livestock and poultry. The same laboratory conducting the above listed foreign animal disease tests offers PCR tests for equine infectious anemia, brucellosis, infectious bursal disease, influenza, Johnes disease, pseudorabies, Q fever, rabies, West Nile Virus and vesicular stomatitis.
***Other private laboratories are promoting new diagnostic testing modalities for diseases of regulatory importance such as chronic wasting disease.
***There is no requirement that the tests offered by unregulated laboratories are approved and validated to accurately assess infection status, nor are there requirements that tests offered by unregulated laboratories conform to national regulatory testing requirements.
***Diagnostic tests, especially PCR, are difficult to perform and a small deviation from standards could potentially result in a false positive or false negative test result.
***The practitioner or producers are likely not aware of these difficulties in performing the test or the potential regulatory ramifications of a false test result reported to state animal health USAHA/2016 Resolution 6 officials.
***Ultimately, the inability to prescribe laboratory testing standards necessary for ensuring the health of livestock and poultry, places animal agriculture in the United States at significant risk.
RESOLUTION: The United States Animal Health Association (USAHA) urges the United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service, Veterinary Services to restrict foreign animal disease diagnostic testing to laboratories approved by the USDA and to take regulatory enforcement action against non-approved laboratories conducting testing for foreign animal diseases. If USDA doesn’t currently have authority for these actions, USAHA urges USDA to take measures to establish those authorities.
Additionally, the USAHA recommends state animal health officials assess state authority or oversight over laboratories conducting diagnostic testing for diseases of regulatory importance on samples obtained from livestock and poultry.
WARNING
SAWCorp CWD Test
PLEASE BE AWARE, SOME ARE PUSHING TO USE SAWCorp CWD Test TO ASSURE YOUR CERVID IS CWD FREE, SAWCorp CWD Test HAS _NOT_ BEEN APPROVED BY APHIS !!! IMPORTANT:
SAWCorp CWD Test is Not APHIS Approved
USDA Animal and Plant Health Inspection Service sent this bulletin at 11/18/2016 11:43 AM EST
SAWCorp, a private company, recently issued a press release launching a new, patented live-animal blood test for the detection of chronic wasting disease (CWD) in cervids. A subsequent press release from the same company stated that the USDA is reviewing the test for use in the CWD program. USDA’s Animal and Plant Health Inspection Service (APHIS) does not recognize protein misfolding cyclic amplification (PMCA) prion blood tests as an official test for CWD, bovine spongiform encephalopathy,or scrapie. By definition, an official CWD test is, “Any test for the diagnosis of CWD approved by the Administrator and conducted in a laboratory approved by the Administrator in accordance with §55.8 of this part” (9 CFR Part 55).
***The criteria necessary for approval as an official CWD test includes a standardized test protocol, data to support reproducibility, data to support suitability, and data to support the sensitivity and specificity of the test.
***While APHIS supports emerging technologies, no company has submitted the data needed for APHIS to evaluate the PMCA prion blood test.
***In addition, APHIS is aware of no peer-reviewed scientific publications that establish the efficacy of PMCA as a detection method for CWD in cervid blood.
***If producers elect to use a PMCA test, APHIS will consider positive results to be “suspect” cases that must be confirmed using an official CWD test.
***APHIS will not recognize negative or “not detected” PMCA test results for herd certification or interstate movement purposes.
Testing
Currently, definitive diagnosis is based on IHC testing of the obex area of the brain stem or the medial retropharyngeal lymph nodes. Gross lesions seen at necropsy reflect the clinical signs of CWD, primarily emaciation and sometimes aspiration pneumonia, which may be the primary (acute?) cause of death. On microscopic examination, lesions of CWD in the central nervous system resemble those of other spongiform encephalopathies. At this time, abnormal prion proteins can be detected using immunohistochemistry (IHC), Western blotting, enzyme-linked immunosorbent assay (ELISA), prion misfolding cyclic amplification (PMCA), and real-time quaking induced conversion (RT-QuIC), however, approved diagnostic assays are limited to IHC and ELISA. Research is being conducted to develop live-animal diagnostic tests for CWD. The rectal biopsy test, while not yet approved for routine regulatory testing, appears promising but may have limited applicability due the number of positive animals in the early stages of the disease that may not be detected.
Official CWD tests are performed only at APHIS-approved university, State, or Federal veterinary diagnostic laboratories. If the animal to be tested is a farmed deer or elk, accredited veterinarians should check with Federal or State regulatory veterinarians for information on sample collection and appropriate sample submission. If the animal to be sampled is a wild deer or elk that is suspected of having CWD, accredited veterinarians should inform State and Federal authorities and work with their State wildlife management agency to find out how officials would like the sample collected and submitted.
If the animal to be sampled is a clinically normal wild animal that an individual hunter would like tested, accredited veterinarians should also work with their State wildlife management agency or department of agriculture to find out how best to proceed. Several approved laboratories exist with sufficient capacity to provide fee-for-service testing for samples collected by individual hunters. Accredited veterinarians should always check with the diagnostic laboratory to make sure samples are properly collected, packaged, and shipped.
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Terry S. Singeltary Sr.
posted by Terry S. Singeltary Sr. at
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