Chronic Wasting Disease Information |
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CWD in Wild Herds
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CWD Surveillance |
While APHIS' primary focus is on farmed animals, we are concerned about protecting the health of wild animals as well. Because the health of wild cervids can impact the alternative livestock industry and vice versa, APHIS has assisted and will continue to assist with CWD surveillance in wild animals. State wildlife management agencies and in some cases, Federal Land Management agencies, have regulatory authority over wild cervids and, as such, take the lead in decisions regarding surveillance of the animals under their stewardship.
See the State Information page for links to state wildlife agencies. For more information on APHIS' approach to wildlife issues, click here.
2002-2003 Nationwide Chronic Wasting Disease Testing Summary:
Funding was made available from APHIS to States last hunting season (2002-2003) for CWD testing of free-ranging cervids harvested by hunters. In order to receive testing assistance, States were asked to provide a surveillance plan that included: 1) Objective of surveillance; 2) Population/ subpopulation description(s), 3) Justifications for defining populations/ subpopulations; and 4) Sampling estimates (number of animals to be tested in support of the objective). In addition to assisting individual States in determining whether or not CWD was present in their wild populations, the information collected in this effort also would provide a better idea of the national distribution of CWD in wild cervid populations.
For the 2002-2003 testing season, samples collected by 38 States were tested with APHIS funds. The majority of the states conducted surveillance statewide, while some states concentrated their testing in areas with known or suspected CWD risk factors, which may include some or all of the following: areas with CWD-positive herds, areas adjacent to CWD-positive wildlife, areas adjacent to land on which TSE-positive animals have lived (farmed or wild), areas with high concentrations of farmed or captive cervids and areas permitting transport of hunter-killed cervid carcasses from CWD infected areas.
Upon request, APHIS Staff and the Centers for Epidemiology and Animal Health developed a CWD surveillance and sampling template to provide guidance for developing sampling plans. This template included guidance for determining sample size to detect CWD at specific prevalences and associated confidence intervals. Most states used this template, and most sampling plans sought to detect disease between 0.1% - 5% prevalence with confidence intervals between 95% and 99%.
A total of 91,636 samples were submitted for APHIS-funded testing. Of these, 302 were positive. No new areas of CWD infection were detected. CWD testing was performed at the National Veterinary Services Laboratories in Ames, Iowa or in a number of APHIS certified contract laboratories across the country. APHIS now has a total of 26 laboratories available as part of its National Animal Health Laboratory Network to assist the in testing for CWD. For more information on the laboratory network, see the Diagnostics section of the main page. Samples tested consisted of the obex and/or retropharyngeal lymph nodes. All samples were tested using immunohistochemical staining.
Of the 91,636 samples submitted and tested with APHIS funds, 1799 samples were unsuitable. Of these 1799 unsuitable samples, 1762 were from 'unsuitable locations' meaning the tissue was in good condition but was not the medulla at the obex or was not retropharyngeal lymph node. Location of the samples is important to detect CWD in animals that are in the early stages of the disease. Thirty seven samples were considered 'unacceptable,' meaning they were in such poor condition that they could not be tested. The number of unsuitable samples can be reduced in future surveillance efforts with continued training and practice.
All states participated in statewide targeted surveillance. This type of testing occurs when deer or elk that show suspected clinical signs of CWD are reported with samples collected and submitted for testing. This type of sampling takes place throughout the year. Additional testing of hunter-harvested and other samples was performed in several States using other sources of funding. Refer to links to State wildlife agencies for further information on their surveillance efforts.
Surveillance efforts in wildlife will be continued next year with funding provided directly to the States for management as well as surveillance activities via cooperative agreements. Additional funds will be provided for management in States where CWD has been detected in wildlife. A summary of these efforts will be provided next year.
APHIS has supported State surveillance for CWD in free-ranging cervids since 1997. This support has increased annually.
Surveillance of Free-Ranging Cervids
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