Health knowledge made personal
Join this community!
› Share page:
Go
Search posts:

Both Sides of the Fence: A Strategic Review of Chronic Wasting Disease

Posted Feb 20 2009 5:33pm
Both Sides of the Fence: A Strategic Review of Chronic Wasting Disease

Management Costs and Benefits

A Report Prepared for the Canadian Wildlife Federation by Dr. Paul C. James Research Fellow, Canadian Plains Research Center, University of Regina

October 2008

This analysis by Dr. Paul James, Research Fellow, Canadian Plains Research Centre, University of Regina, was funded by the Canadian Wildlife Federation. The views are those of the author and do not necessarily reflect the views of the Canadian Wildlife Federation.

2

Table of Contents

1. Executive Summary……………………………………………………………….3

2. Acknowledgements……………………………………………………………….3

3. Introduction: The Need for a Review……………………………………………..4

4. Chronic Wasting Disease: A Brief Overview…………………………………….5

5. An Integrated Approach…………………………………………………………..9

6. CWD in the Saskatchewan Wild Herd: Costs and Benefits………………………9

7. CWD in the Saskatchewan Farmed Herd: Costs and Benefits…………………...16

8. Synthesis and Conclusions………………………………………………………..18

Ecological, social and economic risks of CWD…………………………………..19 Cost benefit analysis of CWD control and management………………………….20 – both sides of the fence

Efficacy of control and management – both sides of the fence……………………21

Lessons for future CWD and wildlife disease management……………………….21

9. References………………………………………………………………………...22

10. Appendix A. Saskatchewan Cervid Game Farming Economic Analysis………..23

3

1. Executive Summary

A review of the current situation with respect to Chronic Wasting Disease (CWD) in wild and farmed deer and elk was conducted. An overview of the disease and its environmental, social and economic risks is presented. Attention is also paid to the economic costs and benefits of current CWD control and management on both sides of the fence of Saskatchewan. At present, CWD has no known significant risk, other than the one it poses for some economic markets of game farming. Despite this, game farming income has grown consistently since its inception, mainly due to the rising demand for deer and elk trophies harvested from game farms operating as ‘shoot’ farms’. Despite the expenditures of countless millions of dollars fighting CWD across North America, it has not been eradicated or contained to any significant extent, and continues to gain ground. As such, the ‘fence’ between the wild and farmed herds no longer exists, and regulations and policies of both government and non-government agencies regarding CWD need to be revisited in this light. Perhaps the biggest lesson learned for future disease management is that if proper risk analysis had been conducted prior to the hasty establishment of the game farm industry, much economic hardship could have been avoided, and less government regulation would have been ultimately required.

2. Acknowledgements

I would like to thank the following persons for information and/or assistance in putting this report together: Nathan Clements (Canadian Wildlife Federation), Yeen Ten Hwang (Fish and Wildlife Branch, Saskatchewan Ministry of Environment), Greg Douglas and Lynn Bates (Canadian Food Inspection Agency), Kenneth Belcher and James Lokken (College of Agriculture and Bioresources, University of Saskatchewan), Trent Bollinger (Canadian Cooperative Wildlife Health Centre, University of Saskatchewan), Terry Kreeger (Wyoming Game and Fish), Bruce Trindle (Nebraska Game and Parks Commission), John Dungavell (Ontario Ministry of Natural Resources), Darrel Crabbe (Saskatchewan Wildlife Federation), Mike Miller (Colorado Division of Wildlife), Bryan Richards (United States Geological Service, National Wildlife Health Center), and Michelle Carstensen (Minnesota Department of Natural Resources).

4

3. Introduction: The Need for a Review Increasing globalization and the attendant emergence and spread of wildlife diseases around the world has created new challenges for wildlife management, livestock management and human health (Wobeser 1994). Approximately 70% of important diseases affecting human health and economies worldwide are believed to have a wild animal source (Saskatchewan Ministry of Environment 2005). In response, governments have directed billions of dollars to the detection, monitoring, reporting, containment, and eradication of such diseases as Avian Influenza, SARS, HIV-AIDS, West Nile Virus, BSE, Tuberculosis, Lyme Disease, and Chronic Wasting Disease (CWD). However, the net benefits of such programs have often been assumed rather than demonstrated, presumably because of perceived or real threats to human health, wildlife health and economies. Such is the case with CWD in Canada, which first appeared on a Saskatchewan deer farm in 1996. There is a growing public concern about the efficacy and image of the mass culling of wild animals that has paralleled the eradication of infected deer herds on farms. Wildlife groups and landowners are beginning to wonder if the cure may be worse than the disease itself - for every diseased animal found in Saskatchewan during CWD control efforts since 1997, 188 healthy mule deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus), have been shot (Saskatchewan Ministry of Environment 2008). Despite this, the rate of infection in the wild deer herd is still increasing, its geographic range expanding in the province, and it was recently discovered in wild elk (Cervus elaphus). These, and other factors, may have led to the recent change in Saskatchewan’s CWD management approach in which the province admits that eradication in the wild is not possible. However, ‘aggressive harvest methods’ will continue in areas of greater CWD prevalence (Saskatchewan Ministry of Environment 2008a) and along the eastern border of Alberta (Pybus 2008). On the agricultural side, the proposed eradication of CWD on Canadian farms has already cost tens of millions of dollars to governments and industry (Saskatchewan Ministry of Environment 2005). Despite this, the disease continues to re-emerge on Canadian deer farms as recently as 2008 and will likely do so in the foreseeable future given that the disease is now firmly established in wild populations. Since the appearance of CWD on Canadian deer farms, the market for domesticated deer products has collapsed. Although game farms proved to be economically lucrative in the 1990s, the main markets of velvet antler and breeding stock have diminished greatly in value and size and newer markets, such as meat, have not developed sufficiently to support the industry alone (Curry 2003). This has left an industry with questionable economic benefits and considerable environmental impacts as summarized above and elsewhere (Bollinger et al. 2004), although the continuing use of captive animals on ‘shoot farms’ 5 has lessoned the impact. Options for game farming in Saskatchewan have been evaluated and include a complete dismantling of the industry (Curry 2003). This review brings together, for the first time, perspectives from both sides of the fence and provides a full socio-economic analysis of the current situation within an ecological context. Such a review has been called for before (Curry 2003, PrioNet Canada and Alberta Prion Research Institute 2006, Kreeger 2008, Slenning 2008), yet has not been forthcoming from the players involved. The future direction of CWD management in a socially acceptable, economically neutral, and ecosystem-based manner remains elusive at the present time. This report is intended to illuminate this path, and to perhaps inform the sustainability of other CWD and wildlife disease management programs elsewhere and in Canada.

4. Chronic Wasting Disease: A Brief Overview

The information in this section is largely drawn from the website of The Chronic Wasting Disease Alliance. CWD is an infectious, transmissible spongiform encephalopathy (TSE) of cervids. The TSEs are grouped together because of their similarity in clinical and other features; the infectious agents are believed to be prions (infectious proteins without associated DNA). Scrapie of domestic sheep and goats, and bovine spongiform encephalopathy (BSE) of cattle are also TSEs of domestic animals. Several rare fatal diseases of humans are also TSEs such as Creutzfeldt-Jakob disease (CJD). Since the 1996 announcement of an apparent relationship between BSE and variant CJD, there has been considerable media, public, and animal and human health agency interest in TSEs. Consequently, CWD is a disease of concern for jurisdictions both in CWD ‘endemic’ or ‘enzootic’ areas and across North America (CWD Alliance).

CWD has been known as a clinical syndrome of mule deer for more than 30 years and modeling suggests that the disease may have been present in free-ranging populations of mule deer for more than 40 years. Only four species of the family Cervidae are known to be naturally susceptible to CWD, including the moose (Alces alces). The susceptibility of other cervids and wildlife to CWD is not known although cattle appear to be resistant to natural infection. The origin of CWD is not known and it may never be possible to definitively determine how or when the disease arose. Scrapie, a very similar disease, has been recognized in the United States since 1947, and CWD may be a recent derivative of that. It is possible, for example, that deer came into contact with scrapie either on shared pastures or in captivity somewhere along the eastern slope of the Rocky Mountains, where high levels of sheep grazing occurred in the early 1900s. It may also be possible that CWD is a spontaneous TSE that arose in deer in the wild or in captivity (CWD Alliance).

Among captive cervid herds, CWD distribution has been determined through a combination of surveillance and epidemiologic investigations, and is probably underestimated at present. CWD in free-ranging cervids occurs in contiguous areas of 6 Wyoming, Colorado and Nebraska; this is considered the core ‘enzootic’ or ‘endemic’ area for CWD. Distribution of the disease in free-ranging deer, elk, and moose has been determined primarily through necropsy and examination of tissues from sick and dead animals; this is an efficient approach for detecting new foci of infection. Since 2000, CWD has been detected in both wild and farmed cervids in several additional states and provinces (CWD Alliance, Figure 1). Figure 1.

Current Distribution of Chronic Wasting Disease in North America

No treatment is currently available for animals affected with CWD. Once clinical signs develop, CWD is invariably fatal. Similarly, no vaccine is available to prevent CWD infection in deer or elk. It follows that the control of CWD is problematic. A long incubation period, subtle early clinical signs, absence of a reliable ante mortem diagnostic test, a highly resistant infectious agent, and incomplete understanding of transmission all constrain options for controlling or eradicating CWD. In captive facilities, management options currently are limited to quarantine or depopulation of CWD-affected herds. At least two attempts to eradicate CWD from cervid research facilities have failed, likely due to residual contamination following depopulation and facility clean-up. Whether contaminated environments can ever be completely disinfected remains open to question. Establishment of free-ranging reservoirs of infection in the vicinity of infected game 7 farms, as shown in Saskatchewan and Nebraska could also impair attempts at eradication from captive facilities (CWD Alliance).

Managing CWD in free-ranging animals has presented even greater challenges. Management programs established to date have focused on trying to contain CWD and reducing its prevalence in localized areas (Richards 2008). The management goals vary among affected states and provinces. In areas where CWD is not yet enzootic, eradication is usually considered as an ultimate goal. However, in enzootic states like Colorado (and now Saskatchewan and Wisconsin), wildlife managers are pulling back from eradication because it appears unattainable (interestingly, Wyoming has never committed to the mass culling of cervids). Moving and artificially feeding cervids in enzootic areas have been controlled and/or banned in attempts to limit range expansion and decrease the transmission rate of the disease. Selective culling of clinical suspects has been practiced throughout the core endemic area for a number of years, but this has proven insufficient to reduce CWD prevalence in affected populations. In many jurisdictions, more aggressive reductions of deer numbers in newly-identified enzootic foci have been undertaken in attempts to eliminate CWD from these areas (CWD Alliance). However, surveillance limitations may delay detection of newly infected free-ranging populations for a decade or more after CWD has been introduced.

Infected deer can travel great distances (Figure 2) and it has been shown that CWD prions are released from both the salivary and alimentary tracts of sick deer (Miller et al. 2004, Mathiason et al. 2006, Richards 2008), that CWD prions can bind to soil particles and increase their infectivity several hundred fold (Johnson et al. 2006, 2007, Richards 2008), and that wildlife scavengers, such as crows, can excrete the CWD prion following the ingestion of infected carcasses (VerCauteren et al. 2008). Research on carcass/scavenger interaction in Wisconsin has shown that deer carcasses take over 50 days to fully decompose, during which time 18 mammal and 21 bird species were observed near or consuming the carcasses. The American crow (Corvus brachyrhynchos) and raccoon (Procyon lotor) were the most frequently observed scavenger species (Samuel 2006). In addition, CWD related scrapie prions can remain active in the soil for at least 16 years (Georgsson et al. 2006). Understanding the role of the ecosystem, and not just the deer, in CWD management is therefore likely going to become much more important in the years to come (Miller et al. 2004).

No cases of human prion disease have yet been associated with CWD. In fact, research from Colorado confirms that the incidence of CJD in humans living within 7 CWD enzootic counties has not significantly increased between 1970-2001 and no case of a human prion disease resulting from CWD exposure has ever been documented (MaWhinney et al. 2006). The tendency towards a natural ‘species barrier’ reducing human susceptibility to CWD and other prion diseases has also been demonstrated by laboratory studies. However, lingering uncertainty remains about interpreting these data and accurately assessing any potential risk that CWD may pose to humans. In the absence

8

of complete information, public health officials and wildlife managers are recommending those hunters and others handling cervid carcasses take common sense measures to avoid exposure to the CWD agent, for example, by boning game meat (CWD Alliance). However, it should be remembered that CWD prions have been detected in the muscles of infected deer and elk (Angers et al. 2006, Jewell et al. 2006).

Figure 2.

Movements of a CWD-infected deer between two disease foci in Nebraska (Trindle 2008)

Where it occurs in captive and free-ranging cervids, CWD represents a serious and expensive management issue. Captive populations are quarantined, thus limiting the use and value of infected or exposed animals. Indemnity for depopulating herds has been made available only recently in the United States; in Canada, the magnitude of infection

9

in farmed elk herds so far has cost the Canadian government millions in control and clean-up costs. The movement of CWD into local free-ranging cervid populations has likely occurred in some locations, thereby impairing the long-term viability of both cervid farming and wildlife management in those areas. Agencies do not move wild deer and elk from CWD enzootic areas. Ongoing surveillance programs are expensive and draw resources from other wildlife management needs. Perhaps most important, the impacts of CWD on the population dynamics of deer and elk are presently unknown. Modeling currently suggests that CWD could substantially harm cervid populations by lowering adult survival rates, although at the same time, concerns and perceptions about the human health risks associated with CWD may erode participation in hunting (CWD Alliance).

5. An Integrated Approach

The environmental costs of human economic activities are rarely considered against their presumed economic gains. This is often why such things as pollution, resource over-harvesting, and habitat destruction occur. These undesirable impacts are usually referred to as ‘externalities’ by economists. An externality occurs when an economic activity causes external costs (or benefits) to other stakeholders who cannot directly affect the economic transaction. The producers and consumers in such a market either do not bear all of the costs, or do not reap all of the benefits, of the economic activity. For example, manufacturing that creates air pollution imposes costs on others, including society and the ecosystem. The impacts of CWD outlined above can be considered in a similar way. One approach to avoiding unwanted costs is to adopt ‘full cost accounting’, which refers to the process of collecting and evaluating information (costs and benefits) for each proposed alternative when a decision is required. Since costs and advantages are usually considered in terms of environmental, economic and social impacts, full cost calculations are collectively called the ‘triple bottom line’. The following sections will present such an approach for CWD by comparing the benefits of the wild and farmed cervid herds of Saskatchewan with the costs of post-CWD regulation, including the associated social and environmental impacts. The resulting costbenefit analysis is also considered within the environmental and social risks now present in post-CWD Saskatchewan in an effort to inform the future strategic direction of wildlife disease management in Canada. See Appendix A for a more complete summary of the economic theory surrounding economic costs and benefits.

6. CWD in the Saskatchewan Wild Herd: Costs and Benefits

In Saskatchewan wild deer populations, CWD was first detected in mule deer in 2000 (Bollinger et al. 2004). Since then, the disease has spread both geographically and between species (Figures 3 and 4) with white-tailed deer first diagnosed in 2002 and then elk in 2008 (Saskatchewan Ministry of Environment 2008b). CWD was first detected in

10

the wild in Alberta in 2005 (Alberta Sustainable Resource Development 2008a) and the disease continues to persist there despite a million dollar control program in 2007 (Alberta Sustainable Resource Development 2008b, Garrett et al. 2008). In addition, the rate of infection in Saskatchewan has increased ten-fold since 2000 (Figure 5), with some areas having a prevalence rate of over 3% (Fernando et al. 2008). All of these indications, and those drawn from the longer history of CWD in the United States, suggest that the situation may become much worse in Saskatchewan, and possibly Canada, over the next decade. In Colorado and Wyoming, for example, where CWD is considered to be endemic, the disease continues to spread despite millions of dollars invested in control efforts (Colorado Division of Wildlife 2005, Miller and Conner 2005, Wyoming Fish and Game 2006, Figure 6). Levels of CWD infection in these states are much higher than in Saskatchewan (up to 40% locally in Wyoming, Kreeger 2008) and may be a sign of things to come. Saskatchewan’s management response to the outbreak in wild deer has generally followed those of other government agencies to the south: aggressive monitoring and containment within infected areas (Figure 3). However, as mentioned above, the Ministry of Environment now no longer believes that elimination of the disease in the wild is possible.

Figure 3.

CWD distribution and spread in Saskatchewan: 2000-2008 (Saskatchewan Ministry of Environment)

11

The potential costs of CWD in the wild deer herd of Saskatchewan can be viewed from three perspectives. First, the increased mortality causes deer populations to decline. Second, hunters lose interest in pursuing diseased and/or reduced numbers of deer, and finally, the economic expenditures associated with deer hunting decline as well. In 2000, a very influential paper was published that predicted drastic declines and extinctions in deer populations infected with CWD 20 years following infection (Miller et al. 2000). The predictions of their model are shown in Figure 7. This, and other similar models, were the primary basis to convince various expert panels, governments, the media, hunters, and the general public that immediate and drastic action was necessary to avoid the collapse of infected wild deer herds. Interestingly, no such collapse has yet been recorded, even in the decades long infected states of Colorado and Wyoming (Kreeger 2008, Figure 8). In 2003, a critique of CWD models was published (Schauber and Woolf 2003) that sought to explain this disparity, and suggested that the assumption of frequency dependent disease transmission in the models, independent of deer density, may be unrealistic. They also concluded that inclusion of density dependent disease transmission in modeling predicts the coexistence of CWD host and pathogen, as currently observed throughout North America. They finally concluded that the known base of scientific knowledge is not adequate to justify large scale deer eradication programs. More recent research has supported the theory of a positive relationship between deer density and the prevalence of CWD (Joly et al. 2006) as well as the potentially critical role of an environment contaminated with CWD-shed and dispersed prions (Miller et al. 2004).

Figure 4. Summary of Saskatchewan’s CWD control efforts: 1997-2008 (Saskatchewan Ministry of Environment) 12 0 0.2 0.4 0.6 0.8 1 1.2 1999 2001 2003 2005 2007 Percent Figure 5. Proportion of sampled mule and white-tailed deer infected with CWD in Saskatchewan: 2000-2007 Figure 6. Current CWD prevalence rates across Colorado 13 0 5 10 15 20 25 30 35 40 45 50 0 25 50 Prevalence (%) 0 500 1000 Number of deer â = 1.1 (highest observed prevalence – HA 65) â = 1.3 â = 1.2 Prevalence Population change â = Infection rate Year Figure 7. Predicted CWD prevalence and population decline in a theoretical mule deer population (from Miller et al. 2000). Also shown is the highest prevalence observed in WY Hunting Area 65. 0 5 10 15 20 25 30 35 40 45 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Bucks/100 Does CWD Prevalence (%) Population (x 1,000) Figure 8. CWD prevalence, buck-doe ratios, and population size of mule deer in Wyoming Hunting Area 65 1998-2007 14

The next question to consider is whether or not deer hunters are losing interest in pursuing their quarry as a result of CWD infection. For example, license sales for the 2002 Wisconsin gun deer hunting season declined approximately 11% following the discovery of CWD in the state, of which more than half did not participate because of the disease (Vaske et al. 2004). Revenues to the management agency declined and other programs suffered as money was reallocated to control CWD. Hunters were hardest hit, losing approximately $60 million in recreational benefits or a 20% decline in the annual surplus value of deer hunting in the state (Heberlein 2004). In a survey of hunters from 8 states, it was estimated that 3-5% of them would stop hunting at current prevalence levels. This would rise to 42-54% if 50% of the deer and elk were infected, and in the case of a hypothetical hunter death from CWD, this would rise to 68% (Needham et al. 2004). Other states have also reported changes in CWD-related hunter behaviour (Crum 2008, Richards 2008, Trindle 2008). Despite this, and an overall historic decline in hunting in the United States, CWD does not seem to be a significant factor at present. For example, in the CWD core enzootic states of Colorado and Wyoming, hunter participation in deer and elk hunting remains strong (Colorado Division of Wildlife 2006, Wyoming Game and Fish Department 2005). In Saskatchewan, the number of Resident First White-tailed Deer licenses sold from 1993 to 2007 has declined overall (Figure 9). The discovery of CWD in the wild in 2000 does not seem to have greatly exacerbated this trend, although some recovery in these sales is occurring, perhaps suggesting an initial impact. In contrast, over the same time period, the number of non-resident hunters purchasing white-tailed deer licenses has steadily increased (Figure 9).

Given that the presence of CWD in the deer populations has not yet significantly deterred hunters in Saskatchewan, it is perhaps reasonable to conclude that the overall economic impact of the disease on the wild population to date has been minimal. This is good news given the high economic value of the wild herd in Saskatchewan. In a recent independent study, the Saskatchewan Ministry of Environment (2006) estimated that the total hunting expenditures in the province were more than $107 million annually, of which $63 million was marginal benefits or new money to the economy. This, in turn, translated into a GDP impact of more than $36 million per year (Figure 10). For nonoutfitted hunting alone, the figures were $68 million, $24 million, and $9 million. There is also a significant transfer of money within the province, with $6 million annually moving from urban to rural areas. Hunters in Saskatchewan primarily hunt big game, with 85.2% of Saskatchewan residents and 65.7% of visiting Canadian residents doing so. Of more than 86,000 big game licenses issued in 2007, more than 80% of them were for white-tailed deer, mule deer, and elk. The wild deer and elk populations of Saskatchewan therefore generate four-fifths of the economic benefits associated with hunting in the province.

15

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 1993 1996 1999 2002 2005 Non-Resident Resident Figure 9. Number of Saskatchewan Resident and Non-Resident First White-tailed Deer Licenses Sold 1993 – 2007 (from Saskatchewan Ministry of Environment files) Figure 10. Total Economic Impacts of Hunting in Saskatchewan (Saskatchewan Ministry of Environment 2006) 16

7. CWD in the Saskatchewan Farmed Herd: Costs and Benefits

Cervids farmed in Canada include elk, fallow deer (Dama dama), mule deer, red deer, reindeer (Rangifer tarandus), and white-tailed deer. Elk is the species most commonly farmed, and the farms produce antler velvet, venison, trophy animals for shooting, and breeding stock (Kahn et al. 2004). Antler velvet is a commercially important product that was primarily exported to markets in Asia, while venison and trophies are utilized mainly in North America. White-tailed deer is the second most commonly farmed cervid in Alberta and Saskatchewan. In 2001, 36% of elk herds and 22% of white-tailed deer herds were located in Saskatchewan. Most of the other herds were located in Alberta. Animals are typically raised on tame pasture, and they are fed supplemental forage (including beef products) and grain during the winter months. Fencing, constructed according to provincial government requirements, is supposed to prevent contact between farmed and wild cervids, although two-way transmission likely occurs (Clyburn et al. 2008).

In 1987, when the provinces of Alberta and Saskatchewan first allowed game farming, the elk industry grew very rapidly and the domestic demand for breeding elk could not be met. As a result, herds were built upon the importation of 695 elk in Saskatchewan and 1318 in Alberta from the United States. Manitoba did not allow elk farming until 1997. Regulations restricted the importation of white-tailed deer from the United States onto game farms, primarily due to concerns about the translocation of the meningeal worm (Parelaphostrongylus tenuis). White-tailed deer were captured from the wild in Alberta until 1990 when the practice was eliminated. Saskatchewan has never permitted the capture of live white-tailed deer for game farming. The populations of white-tailed deer on farms increased during the 1990s from natural increase with some supplementation from provincial imports, game parks and zoos (Kahn et al. 2004).

In 1990, an outbreak of bovine tuberculosis (TB) was diagnosed in an elk herd in Alberta. From 1990 until 1993, 16 TB-infected herds were depopulated to protect the TBfree status of Alberta’s cattle and to eradicate TB from farmed elk. The destruction of these herds imported from the United States into Alberta may have helped to limit the exposure of elk farms in Alberta to infection with CWD if, as hypothesized, CWD was introduced into Canada via the importation of infected elk from the United States (Kahn et al. 2004). Other control measures introduced in the late 1980s and early 1990s likely had some effect in reducing the movement of farmed cervids within western Canada and may have helped to minimize the dispersion of animals infected with CWD. In 1988, the province of Alberta prohibited the importation of ungulates from other provinces and from the United States. In 1990, the Canadian Food Inspection Agency (CFIA) introduced national requirements for movement permits and individual identification for farmed cervids. These requirements were later to provide the means of tracing farmed cervid movements that enabled CFIA to carry out the CWD control program introduced in 2000. In 1998, the province of Manitoba placed a ban on the importation of farmed

17

elk. The federal government banned the importation of live cervids from the United States from 1990 to 1999 to prevent the entry of TB. However, while provincial government control measures may have limited the spread of CWD between provinces, there were no veterinary controls in place to prevent CWD from spreading within Saskatchewan during the early part of the 1990s (Kahn et al. 2004).

Despite all of these measures, the first case of CWD in Canada was diagnosed in 1996 from a Saskatchewan farmed elk. The herd was destroyed; all animals were tested for CWD and found to be negative. Second and third cases were diagnosed in an elk herd in 1998 by the CFIA and the herd destroyed. The herd that was the original source of the infected elk found in 1996 and 1998 was investigated and was placed in quarantine in 2000. Following the identification of the source herd, trace-outs identified a total of 39 infected elk herds between 1996 and 2002 in a single epidemic, many in the northwest agricultural region of the province (Argue et al. 2007). Import records from 1989 and 1990 showed that CWD in the source herd traced back to a CWD positive herd in South Dakota (Lind 2005). All CWD infected game farm herds were subsequently depopulated. Since 1999, the CFIA has permitted the importation of cervids from the United States into Canada, subject to measures to prevent the entry of CWD and other diseases of concern.

The Saskatchewan cervid (caribou, deer, elk or moose) Health Surveillance Program for Chronic Wasting Disease (CWD) was implemented in 2001. The agriculture department issues tags to identify velvet antler from animals participating in the program. Later in the year, the program became mandatory in order to help eradicate CWD and to allow game farmers to regain markets for animals and products (Saskatchewan Agriculture & Food 2002). Despite these measures, CWD continues to infect Saskatchewan and Alberta game farms. A total of 54 farms have been contaminated to date, nine since March 2007, over 9,000 animals have been destroyed, and millions paid in compensation (Greg Douglas, CFIA, pers. comm.).

Appendix A reports on the costs and benefits of cervid game farming in Saskatchewan and only a summary is presented here. Game farm numbers and animal numbers have declined since the early 2000s as farmers have downsized or exited from the industry. At present, the number of farms has stabilized but total farmed cervid numbers continue to decline. Despite failing antler velvet and venison markets since the discovery of CWD on game farms, total farm cash receipts from game farming in Saskatchewan have increased almost every year since game farming began in the province. In 2007, the industry had record cash receipts of about $14.3 million, a jump of 45% over 2005. This somewhat unexpected performance is due almost solely to the rapid growth of ‘cervid harvest preserves’ or shoot farms, which contributed more than $10 million to the 2007 cash receipts. This is because Saskatchewan allows the paid hunter harvest of domestic animals to take place on farms in general by accepting this as an allowable slaughter practice of livestock. In future years, several factors may negatively

18

affect the current surge in cash receipts, including continuing low antler velvet prices, the lack of a federally licensed slaughter facility in Saskatchewan, and the recent outbreaks of CWD, some of which occurred on shoot farms. Finally, CWD was discovered in wild elk this year, drawing further scrutiny from the public. On the minus side, game farming in Saskatchewan and across Canada is heavily regulated, especially since the discovery of CWD. The cumulative cost of this regulation, including CWD testing, farm depopulation, and compensation is now $42 million, of which $34 million has accrued to Saskatchewan.

8. Synthesis and Conclusions

Taken together, the information presented above and in Appendix A can be distilled down to several areas of consideration, including the present and future risks of CWD, the cost benefit analysis of CWD control and management, the efficacy of control and management on both sides of the fence and its associated policy considerations, and the lessons learned for future CWD management and wildlife diseases in general.

Ecological, social and economic risks of CWD

Despite the fact that CWD is caused by a prion, a review of the known risks associated with the disease reveal little to be concerned about other than its impact on game farming itself. Despite dire predictions from earlier modeling, deer populations infected with CWD have not undergone population crashes, even those with relatively high rates of prevalence, such as those in Wyoming and Colorado. The disease itself also seems to be confining itself to cervid species, thus the risks to other species of wildlife appear to be minimal at present. One possible exception might be the threatened woodland caribou (Rangifer tarandus), should it ever be exposed to the CWD agent. Given these facts, it seems that the current response of government agencies to CWD management and control in the wild is somewhat out of proportion to the known environmental and socio-economic risks posed. Even in jurisdictions with longer histories of relatively high CWD prevalence rates, such as Wyoming and Colorado, deer populations and hunter participation are healthy. It might be argued that it is prudent to apply the precautionary principle in the case of a prionic agent. Certainly, while one should never say never in such cases, there are far greater known risks to our wildlife in North America, most notably continuing habitat loss and the impacts of certain invasive species. As such, it may be a wiser strategy not to redirect scarce resources from the efforts to address these much more powerful ecologically disruptive forces.

On the human side, CWD at present appears not to be posing a significant health hazard - despite the fact that many people have certainly eaten contaminated meat, especially from the wild - although the situation warrants ongoing common sense measures and vigilance. Again, despite earlier dire predictions, the levels of deer and elk hunting in jurisdictions with CWD appear to be healthy, with minimal threat to the

19

important social and economic benefits that hunting brings. However, this could all change should a hunter ever succumb to CWD. On the inside of the fence, the story is much different. The risk of CWD to game farming is now a known entity, and its impact has been significant on velvet and venison markets. Interestingly, the demand for venison has increased in the last few years suggesting either confidence in the food production system, or indifference to the issue of CWD. Fortunately, other species of livestock appear to be at low known risk at present, although continuous monitoring of the situation is important.

Future changes in the risk levels of CWD remain unclear, mainly due to the extremely persistent, infectious, and mobile nature of the prion involved. If, in the future, the prion moves into other wildlife species, the outcome may not be so relatively benign.

Cost benefit analysis of CWD control and management – both sides of the fence

The case study for Saskatchewan reveals some interesting economic figures that although tentative, may be taken as illustrative of the value of cervids and the trade-offs involved with the control and management of CWD (Figure 11). Figure 11. Estimated annual economic benefits and costs ($ millions) of farmed and wild cervids in Saskatchewan Farmed Herd Wild Herd Benefits 28.51 29.23 Costs 3.62 .74 Costs/Benefits 12.6 2.4 1 2007 game farm cash receipts using a multiplier of 2.0 (Appendix A) 2 Average of 1996-2008 federal and provincial labour, disease testing, and compensation costs (Appendix A) 3 Total GDP impact of hunting (Saskatchewan Ministry of Environment 2006) using a multiplier of 0.80 for deer and elk (Section 6) 4 2007 labour, administration, and testing costs (Saskatchewan Ministry of Environment)

Firstly, it is of interest to note that the economic value of the farmed and wild cervid herds in Saskatchewan is approximately the same, although it might be argued that the social benefits of hunting wild deer and elk are higher than for shoot farms. The cost of regulation post-CWD is higher for the farmed herd, which is not surprising given the large amounts of compensation paid to farmers. Even so, the cost is not excessive if one considers other forms of government subsidy that usually accompany farming programs. Given the rapid growth of shoot farms, it is possible that the relative proportion of this cost will fall in future years, especially if CWD can be permanently eliminated from farmed cervid herds. At this point in time, the farmed herd faces the same contamination

20

issues as the wild herd does, and game farmers may have to take additional measures to protect their herds.

Efficacy of control and management – both sides of the fence

In an attempt to protect the industry and its markets, government agencies in North America have invested many millions of dollars to eradicate the disease from game farms. However, this goal remains elusive, as new cases continue to appear both in already contaminated jurisdictions (e.g. Saskatchewan) and in previously unaffected ones (e.g. Michigan in 2008). Again, this seems to be related to the characteristics of the prion involved; in addition, cross-contamination from natural ecosystems can now never be completely discounted. Despite the relatively low known risk of CWD in wild cervid populations, most government agencies continue to invest millions of dollars in attempts to eradicate, control, and manage the disease. As with the farmed herd, these attempts have largely proved to be ineffective with the disease spreading and increasing within all contaminated jurisdictions, and spreading to previously unaffected ones such as Alberta. As such, eradication of CWD in the wild appears to be impossible, and the verdict is still very much open on its ultimate control and management. Given the relative failure of control efforts on both sides of the fence, and the nature of the prion agent involved, it is perhaps time to reconsider current control and management policies, particularly as in reality, ‘the fence’ no longer exists.

Lessons for future CWD and wildlife disease management

With the absence of a functional ‘fence’ between the wild and farmed deer herds, it may be the time to review not only government and policies, but also our scientific approach to the control and management of CWD. The study and treatment of wildlife diseases is traditionally undertaken by veterinarians, and CWD has been no exception. Most of the practitioners involved in its control and management are vets that bring a much needed ‘organism-centered’ perspective to the issue. However, while this is entirely appropriate to wildlife diseases that are living entities themselves, it may not entirely serve the needs of CWD in cervids. Other disease organisms lend themselves to treatment, control, and epidemiological modeling; the known and emerging unique characteristics of CWD do not. For example, it is not a living organism; it is a protein molecule, albeit a highly infectious one. It is therefore not a wildlife disease in the traditional sense. In addition, it not only moves freely between the ‘host’ animals, but also throughout the ecosystem as sick, dying, and dead deer shed CWD prions into their environment. The CWD prion adheres to soil where it becomes even more contagious and potentially even more mobile through soil erosion. Wildlife predators and scavengers also likely provide additional vehicles for its dispersal. Like its cousin, scrapie, in the environment, it is extremely stable and perhaps persists for decades. These characteristics are more those of an environmental contaminant rather than a disease organism, and as such, require more of an emphasis on an ecosystem rather than a species specific

21

approach. Perhaps tools such as contaminant pathway models may be more appropriate than epidemiological models, and may reveal as yet unidentified clues to CWD control and management.

Taking an ecosystem approach also means recognizing the North American deer herds as one, and not as two entities. While some cooperation exists between the regulators of wildlife and livestock, it is clearly insufficient and almost non-existent in some jurisdictions. That cooperation also needs to include both game farmers and hunters, who have the most to lose in the long term. The time for finger pointing is over; the time for an integrated approach has begun. Much of the pain suffered by game farmers and taxpayers in Canada could have been reduced or avoided if sufficient risk analyses had been conducted before the hasty introduction of game farming in some provinces. Science has been trying to catch up ever since. Regulations and policies written in reaction to a crisis are never as effective as those created proactively in an atmosphere of cooperation. It is noteworthy that the Canadian game farm industry is currently heavily, or perhaps over-regulated (Appendix A), a situation directly stemming from lack of foresight and planning in the light of known environmental risks. Perhaps it is time to review these rules under the umbrella of an ecosystem approach?

As a final note, it is perhaps also worth considering the question of future actions. CWD is an extremely pervasive disease, albeit a relatively benign one to date. Some may argue that CWD monies would be better spent elsewhere and that minimal efforts should be directed at the control of the disease. Compared to other higher risk human pressures on the environment, this is certainly true. However, while it may be time to acknowledge that eradication and containment are unachievable, it may also be prudent to recognize that our knowledge of prion diseases remains in its infancy. In this light, ongoing monitoring and surveillance of CWD in both the wild and farmed herds is the most sensible option, while research continues to fill knowledge gaps such as lack of rapid field tests for both cervids and the ecosystem, and the ultimate fate of CWD prions from both wild and farmed carcasses.

22

9. References Alberta Sustainable Resource Development. 2008a. Chronic Wasting Disease. http://www.srd.gov.ab.ca/fishwildlife/livingwith/diseases/chronicwastingdisease. Alberta Sustainable Resource Development. 2008b. Alberta’s Chronic Wasting Disease Response Program: March, 2007. http://www.srd.gov.ab.ca/fishwildlife/livingwith/diseases/pdf/CWD_Executive_Summ y_Winter_Final_07.pdf Angers, R.C., S.R. Browning, T.S. Seward, C.J. Sigurdson, M.W. Miller, E.A. Hoover and G.C. Telling. 2006. Prions in skeletal muscles of deer with chronic wasting disease. Science 311: 1117. Argue, C.K., C. Ribble, V.W. Lees, J. McLean and A. Balachandran. 2007. Epidemeology of an outbreak of chronic wasting disease on elk farms in Saskatchewan. Can. Vet. J. 48: 1241-1248. Bishop, R.C. 2002. The economic effects in 2002 of chronic wasting disease (CWD) in Wisconsin. University of Wisconsin, Madison. Bollinger, T., P. Caley, E. Merrill, F. Messier, M.W. Miller, M.D. Samuel and E. Vanopdenbosch. 2004. Chronic Wasting Disease in Canadian Wildlife: An Expert Opinion on the Epidemiology and Risks to Wild Deer. Canadian Cooperative Wildlife Health Centre, Western College of Veterinary Medicine, University of Saskatchewan. Chronic Wasting Disease Alliance. http://www.cwd-info.org/ Clyburn, P.E., S. Checkley, R. Hudson and J. Berezowski. 2008. Qualitative analysis of farmed and wild cervid CWD data in Alberta. 57th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Colorado Division of Wildlife. 2006. 2005 Annual Report. http://wildlife.state.co.us/NR/rdonlyres/865A5D6E-528E-4067-A461 - 9878E59F3E5C/0/2005AnnualReport.pdf Colorado Division of Wildlife. 2008. CWD Info and testing. http://wildlife.state.co.us/Hunting/BigGame/CWD/ Crum, J. 2008. Response programs in CWD newly detected areas: West Virginia. In: Proceedings of Chronic Wasting Disease Workshop, 57th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Curry, D. 2003. Policy Issues and Options Affecting the Feasibility of the Game Farm Industry in Saskatchewan. Centre for Studies in Agriculture, Law and the Environment. University of Saskatchewan 23 Fernando, C., J. Hill and T. Bollinger. 2008. Survey for infectious agents in mule deer in southern Saskatchewan. 57th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Garrett, C., E. Merrill, M. Pybus, D. Coltman and F. He. 2008. Deer, corridors, and disease: Using corridor theory to project routes of CWD spread. In: Proceedings of Chronic Wasting Disease Workshop, 57th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Georgsson, G., S. Sigurdarson and P. Brown. 2006. Infectious agent of sheep scrapie may persist in the environment for at least 16 years. J. Gen. Virol. 87: 3737-3740. Heberlein, T.A. 2004. ‘Fire in the Sistine Chapel’: How Wisconsin responded to chronic wasting disease. Human Dimensions of Wildlife 9: 165-179. Jewell, J.E., J. Brown, T. Kreeger and E.S. Williams. 2006. Prion protein in cardiac muscle of elk (Cervus elaphus nelsoni) and white-tailed deer (Odocoileus virginianus) infected with chronic wasting disease. J. Gen. Virol. 87: 3443-3450. Joly, D.O., M.D. Samuel, J. A. Langenberg, J. A. Blanchong, C. A. Batha, R. E. Rolley, D. P. Keane and C. A. Ribic. 2006. Spatial Epidemiology of Chronic Wasting Disease in Wisconsin White-Tailed Deer. J. Wildl. Dis. 42: 578-588 Johnson C.J., Phillips K.E., Schramm P.T., McKenzie D., Aiken J.M., et al. 2006. Prions adhere to soil minerals and remain infectious. PLoS Pathog 2: e32. Johnson, C.J., J.A. Pedersen, R.J. Chappell, D. McKenzie and J.M. Aiken. 2007. Oral transmissibility of prion disease is enhanced by binding to soil particles. PLoS Pathog. 3: e93. Kahn, S., C. Dube, L. Bates and A. Balachandran. 2004. Chronic wasting disease in Canada: Part 1. Can. Vet. J. 45: 397-404. Kreeger, T. 2008. Response programs in CWD enzootic areas: Wyoming. In: Proceedings of Chronic Wasting Disease Workshop, 57th Annual International Conference o the Wildlife Disease Association, Edmonton, Alberta. Krumm, C.E., M.M. Conner and M.W. Miller. 2005. Relative vulnerability of chronic wasting disease infected mule deer to vehicle collisions. J. Wildl. Dis. 41:503-511. Lind, R.E. 2005. Chronic Wasting Disease in Saskatchewan. Proc. Second International Chronic Wasting Disease Symposium, Madison, Wisconsin. http://www.cwdinfo. org/pdf/2005-CWD-Symposium-Program.pdf Mathiason, C.K., J.G. Powers, S.J. Dahmes, D.A. Osborn, K.V. Miller, R.J. Warren, G.L. Mason, S.A. Hays, J. Hayes-Klug, D.M. Seelig, M.A. Wild, L.L. Wolfe, T.R. 24 Spraker, M.W. Miller, C.J. Sigurdson, G.C. Telling and E.A. Hoover. 2006. Infectious prions in the saliva and blood of deer with chronic wasting disease. Science 314: 133- 136. MaWhinney S., W. J. Pape, J. E. Forster, C. A. Anderson, P. Bosque, and M. W. Miller. 2006 Human prion disease and relative risk associated with chronic wasting disease. http://www.cdc.gov/ncidod/EID/vol12no10/06-0019.htm. Miller, M.W., E.S. Williams, C.W. McCarty, T.R. Spraker, T.J. Kreeger, C.T. Larsen and E.T. Thorne. 2000. Epizootiology of chronic wasting disease in free-ranging cervids in Colorado and Wyoming. J. Wildl. Dis. 36: 676-690. Miller, M.W., E.S. Williams, N.T. Hobbs and L.L. Wolfe. 2004. Environmental sources of prion transmission in mule deer. Emerg. Infect. Dis. 10: 1003-1006. Miller, M.E. and M.M. Conner. 2005. Epidemiology of chronic wasting disease in freeranging mule deer: spatial, temporal, and demographic influences on observed prevalence patterns. J. Wildl. Dis. 41: 275-290. Needham, M.D., J.J. Vaske and M.J. Manfredo. 2004. Hunters’ behavior and acceptance of management actions related to chronic wasting disease in eight states. Human Dimensions of Wildlife 9: 211-231. PrioNet Canada and Alberta Prion Research Institute. 2006. Workshop in CWD priorities. Saskatoon, Saskatchewan. Pybus, M. 2008. Response programs in CWD newly detected areas: Alberta. In: Proceedings of Chronic Wasting Disease Workshop, 57th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Richards, B. 2008. Overview of Chronic Wasting Disease. In: Proceedings of Chronic Wasting Disease Workshop, 57th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Samuel, M. 2006. Potential for Interspecies Transmission of Chronic Wasting Disease: Assessment of Carcass Decomposition and Identification and Testing of Potentially Affected Species. http://wildlife.wisc.edu/coop/CWD/WCWRU%20Web%20site/CWDinScavengers.htm Saskatchewan Agriculture and Food. 2002. Annual Report 2001-2002. http://www.agriculture.gov.sk.ca/Default.aspx?DN=1686f339-49d9-4164-941e - 077196f3df24 Saskatchewan Ministry of Environment. 2005. Canada’s National Chronic Wasting Disease Control Strategy. CWD Technical Working Group. 25 Saskatchewan Ministry of Environment. 2006. Economic Evaluation of Hunting in Saskatchewan. http://www.environment.gov.sk.ca/adx/aspx/adxGetMedia.aspx?DocID=350,246,94,88,D ocuments&MediaID=146&Filename=Economic+Evaluation+of+Hunting.pdf Saskatchewan Ministry of Environment. 2008a. Chronic Wasting Disease Management Plan 2008. http://www.environment.gov.sk.ca/Default.aspx?DN=601e1215-0105-44d8 - bb9b-4be6cab7dbb9 Saskatchewan Ministry of Environment. 2008b. CWD positive elk in the wild. http://www.environment.gov.sk.ca/adx/aspx/adxGetMedia.aspx?DocID=1961,300,254,9 4,88,Documents&MediaID=1055&Filename=Elk+Positive+Announcement.pdf Schauber, E.M. and A. Woolf. 2003. Chronic Wasting Disease in Deer and Elk: A Critique of Current Models and Their Application. Wildl. Soc. Bull. 31: 610-616. Seidl, A.F. and S.R. Koontz. 2004. Potential economic impact of chronic wasting disease in Colorado. Human Dimensions of Wildlife 9: 241-245. Slenning, B.D. 2008. Economics and foreign animal diseases. Foreign Animal Disease Training Course, USDA Centers for Epidemiology and Animal Health, Fort Collins, Colorado. Pp. 409-413 Trindle, B. 2008. Response programs in CWD enzootic areas: Nebraska. In: Proceedings of Chronic Wasting Disease Workshop,5 th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Vaske, J.J., N.R. Timmons, J. Beaman and J. Petchinik. 2004. Chronic wasting disease in Wisconsin: Hunter behavior, perceived risk and agency trust. Human Dimensions of Wildlife 9: 193-209. VerCauteren, K.C., J.L. Pilon, P.B. Nash, G.E. Phillips and J.W. Fischer. 2008. Infectivity of prions following ingestion and excretion by American Crows (Corvus brachyrhynchos). In: Proceedings of Chronic Wasting Disease Workshop, 57th Annual International Conference of the Wildlife Disease Association, Edmonton, Alberta. Wobeser, G.A. 1994. Disease in Wild Animals: Investigation and Management. Plenum Press, New York. Wyoming Game and Fish Department. 2005. Game and Fish Annual Report. http://gf.state.wy.us/services/news/pressreleases/05/12/30/051230_2.asp Wyoming Game and Fish Department. 2006. Chronic Wasting Disease Activities for 2006. http://gf.state.wy.us/downloads/pdf/CWD2006WYSummaryReport.pdf

10. Appendix A: Saskatchewan Cervid Game Farming Economic Analysis



end...TSS




Greetings,



>>>Despite the expenditures of countless millions of dollars fighting CWD across North America, it has not been eradicated or contained to any significant extent, and continues to gain ground. As such, the ‘fence’ between the wild and farmed herds no longer exists, and regulations and policies of both government and non-government agencies regarding CWD need to be revisited in this light. < < <


CONSIDERING these factors then, in my opinion, the game farms should all be shut down for good, asap, on both sides of the border. ...


QUESTION and opinions welcome ;


IS a 'do nothing' ... 'don't look, don't tell policy', a good thing, or a bad thing for the management of CWD, just because of 'economic cost' ???


WE know how high some game farm infection rates are, so do we gamble with the wild $$$




kind regards,

Terry




Chronic wasting disease in a Wisconsin white-tailed deer farm 79% INFECTION RATE


http://chronic-wasting-disease.blogspot.com/2008/09/chronic-wasting-disease-in-w



Monday, February 09, 2009

Exotic Meats USA Announces Urgent Statewide Recall of Elk Tenderloin Because It May Contain Meat Derived From An Elk Confirmed To Have CWD

http://chronic-wasting-disease.blogspot.com/2009/02/exotic-meats-usa-announces-u


Saturday, January 24, 2009

Research Project: Detection of TSE Agents in Livestock, Wildlife, Agricultural Products, and the Environment Location: 2008 Annual Report

http://bse-atypical.blogspot.com/2009/01/research-project-detection-of-tse.html


Wednesday, January 07, 2009

CWD to tighten taxidermy rules Hunters need to understand regulations

http://chronic-wasting-disease.blogspot.com/2009/01/cwd-to-tighten-taxidermy-rul


Monday, January 05, 2009CWD, GAME FARMS, BAITING, AND POLITICS

http://chronic-wasting-disease.blogspot.com/2009/01/cwd-game-farms-baiting-and-p


Thursday, December 25, 2008 Lions and Prions and Deer Demise

http://chronic-wasting-disease.blogspot.com/2008/12/lions-and-prions-and-deer-de


Tuesday, January 06, 2009

CWD Update 93 December 29, 2008

http://chronic-wasting-disease.blogspot.com/2009/01/cwd-update-93-december-29-20

Sunday, September 07, 2008

CWD LIVE TEST, and the political aspects or fallout of live testing for BSE in cattle in the USA

http://chronic-wasting-disease.blogspot.com/2008/09/cwd-live-test-and-political-


2008 CWD Laboratory Testing for Wild White-tailed Deer

http://www.michigan.gov/emergingdiseases/0,1607,7-186-25806-202922--,00.html


TSS
Post a comment
Write a comment: