Chapter 13 – Chronic Wasting Disease Voluntary Herd Certification Program
13.2 Policy and Principles of Control – July 2017
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The national Chronic Wasting Disease Voluntary Herd Certification Program (CWD VHCP) is a program that cervid owners/cervid farm operators can choose to join. However, once they are participating in the program, their compliance with the national standards is mandatory (see Module 13.6, Appendix 3).
The objectives of the CWD VHCP are to provide owners/cervid farm operators with a means of detecting and preventing introduction of Chronic Wasting Disease in their herds, and the opportunity to have their herds identified as "low" risk with respect to CWD. There is recognition that the risk of CWD diminishes to low risk with progressive participation and successful annual advancement in the VHCP. Enrolment in the VHCP provides reasonable assurance that purchasing cervids from producers enrolled at the same level of the CWD VHCP maintains the farm's current level of risk specific to exposure to CWD. Import requirements of other countries for cervids may be based on enrolment or activities under the CWD VHCP. An owner/cervid farm operator of a licenced (where applicable) farmed cervid premises may enroll in the CWD VHCP.
The CWD VHCP program requirements apply to all animals of the family Cervidae (including, but not limited to, animals of the genera Cervus, Odocoileus, Dama, Alces, Rangifer, and any hybrids).
CWD is a reportable disease under the Reportable Diseases Regulations, prescribed pursuant to section 2 of the Health of Animals Act. Any person suspecting an animal of demonstrating signs consistent with CWD must report that animal to a federal veterinarian at a Canadian Food Inspection Agency (CFIA) district office.
The role of the CFIA is the development, through the use of a consultative process, of national standards for the CWD VHCP (see Module 13.6, Appendix 3), its audit and oversight.
Principles for Disease Control
There are currently no validated tests to definitively rule out CWD in live animals, either individually or as a herd. At this time, CWD VHCP status is determined on a herd basis by post-mortem testing of all eligible animals, the absence of clinical signs, and the prevention of exposure to CWD over a designated period of time.
CWD is the most contagious of the three transmissible spongiform encephalopathies (TSEs) in animals. It can be easily transmitted from animal to animal via direct or indirect contact with secretions or excretions, such as saliva, urine, and feces. Transmission between wild and captive cervids has been recognized. Nose-to-nose contact through fences and the introduction of feed contaminated by wild cervid secreta/excreta outside the fence are believed to be sources of infection in some well-managed herds. Given these risks, using good management practices (GMPs) and focusing on good biosecurity are of paramount importance.
The CWD prion can also persist in the environment for several years. Soil likely serves as a reservoir for infectivity, as prions have been shown to extensively bind to certain soil minerals, remain infectious for a number of years, and even increase infectivity over time with binding of soil minerals. As such, CWD can be transmitted to live animals by a prion-contaminated premises in the absence of infected cervids. There is currently no validated test to detect or quantify infectious prion contamination in the environment.
To achieve certification status, the enrolled herd must meet all of the program requirements to successfully advance from level E to Certified. The core program has four pillars:
- maintenance of accurate, complete inventory records in which all cervids are accounted for;
- ongoing testing of deaths and slaughter cervids;
- limiting herd introductions to enrolled cervids of a similar or higher CWD VHCP level; and
- the implementation of the Program biosecurity measures. A minimum of five years is necessary for an enrolled herd to reach the certified level.
A CWD suspect is any animal that has CWD as a differential diagnosis.
A CWD-positive animal is any animal in which the CFIA confirms the diagnosis of CWD by applying a confirmatory test to lymphoid or brain tissues. The current confirmatory tests are immunohistochemistry (IHC) and Western Blot.
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