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Chronic Wasting Disease

Ten Years of Chronic Wasting Disease Surveillance in Saskatchewan

Beginning in 1997, Saskatchewan Ministry of Environment (MOE) and the Canadian Cooperative Wildlife Health Centre (CCWHC) started a Chronic Wasting Disease (CWD) surveillance program for wild deer, elk and moose. This surveillance program is based primarily on the testing of hunter-killed animals and to a lesser extent on the testing of cervids submitted through the passive surveillance of sick or dead animals in the province. In areas where CWD was detected, MOE implemented herd reduction programs, primarily through increased hunting quotas and reduced hunting licence fees, in an attempt to increase hunter harvest to reduce deer densities and limit the spread of CWD. Between 1997 and 2007 over 34,000 cervids have been tested for CWD with 197 testing positive.

There are four main geographic areas where CWD appears to be well established, the first is south of Lloydminster in the Manitou Sand Hills, where the first CWD positive wild mule deer was detected in 2000. Since that time a total of 12 mule deer have tested positive for CWD with an overall prevalence of 0.45%. The second area is northeast of Lloydminster along the Bronson forest where the disease was first detected in 2002 in a white-tailed deer. Although the number of positives has remained quite low, a cluster of 6 cases were detected in 2007. In the fall of 2002, the disease was detected along the South Saskatchewan River valley near Saskatchewan Landing Provincial Park. The largest proportion of cervids has been tested from this area (over 12, 000) with 102 mule deer and 7 white-tailed deer testing positive for the disease. The disease has extended westward and in 2006, CWD was detected along the river valley near the Alberta border. Adjacent to this area, in 2005 Alberta had also detected their first case of CWD in wild deer.

In 2005, a white-tailed deer found dead adjacent to some farm buildings near the town of Nipawin in north-central Saskatchewan tested positive for CWD. This was the first case of CWD in this area despite previous surveillance in 2001 and 2002. Additional sampling in the area in 2005, 2006 and 2007 detected an additional 35 positive deer (7, 20 and 9 positives respectively) with an average prevalence of 2.6% (with years combined). During the winter of 2008 two elk were found dead west of Nipawin. Both animals were submitted to the CCWHC and tested positive for CWD, marking the first time CWD has been found in elk in the wild in Saskatchewan. Based on the necropsy findings it does not appear that these elk died of CWD.

Other foci of disease with relatively low prevalence are in zones 25 (1 positive), 29E (1 positive) and 43 (2 positives). Although areas in which CWD is known to occur need to be monitored for changes in prevalence, more samples need to be submitted and tested from other areas (outside of these CWD areas) of the province to establish the distribution of CWD in the province.

Authors:
Trent Bollinger and Marnie Zimmer, CCWHC Western/Northern Region;
Yeen Ten Hwang, Provincial Wildlife Health Specialist, Saskatchewan Ministry of Environment

Notes:
This table does not include those specimens which were deemed unsuitable for testing.

1- From 1997 until the fall of 2000, only the brain section (obex) was used to diagnosis CWD. Starting in 2001, tonsils and/or retropharyngeal lymph nodes were also examined.

2- Starting in the fall of 2005 animals under 1 year of age were no longer tested under the program because detectable infection is rare in a young animal and therefore not cost effective in terms of surveillance.