Captive CWD occurred across Minnesota. Endemic CWD did not.

AbstractSummary of the Minnesota Record

Minnesota provides an unusually strong statewide record for evaluating the relationship between chronic wasting disease (CWD) detections in captive cervid herds and subsequent establishment of disease in free-ranging deer. Since 2002, CWD-positive captive herds have been identified in multiple geographically separated regions of the state. Minnesota repeatedly responded with quarantines, trace investigations, depopulation, movement restrictions, and intensive surveillance of surrounding wild deer.

The statewide outcome was not repeated development of endemic wild CWD around infected captive facilities.

Minnesota’s first captive detections occurred in Aitkin, Stearns, Lac qui Parle, Olmsted, Ramsey, Crow Wing, Meeker and other counties. In several of these areas, hundreds or thousands of surrounding wild deer were subsequently tested. Most produced no wild detections. Olmsted County produced one nearby wild positive, but more than 4,000 additional wild deer were tested without another positive. Crow Wing County similarly produced a wild positive near a heavily infected captive facility, but thousands of subsequent samples failed to establish a comparable expanding focus. Minnesota DNR’s own history documents these repeated intensive surveillance responses. (MN DNR)

Southeastern Minnesota followed a fundamentally different chronology. CWD was detected in free-ranging deer near Preston in Fillmore County in 2016, before the principal Winona captive-herd events. That wild focus persisted and expanded. Separate wild concentrations subsequently emerged in Winona and northern Houston counties. Minnesota DNR later stated that it was uncertain whether the Winona and northern Houston disease areas were related or represented independent origins. (Minnesota DNR files)

The statewide comparison therefore presents a direct epidemiologic challenge. Captive CWD detections occurred repeatedly across Minnesota, but endemic disease developed only in southeastern Minnesota, where CWD was already established in the free-ranging population and regional environment.

Minnesota currently identifies deer permit areas 646, 647 and 648 in southeastern Minnesota as endemic, defined by the agency as areas where CWD prevalence has exceeded 5%. DNR identifies these as the core infection areas where CWD was first detected in 2016. (MN DNR)

This review reconstructs that history chronologically and examines whether the statewide pattern supports captive cervid movement as a sufficient explanation for regional CWD establishment, or whether southeastern Minnesota represents a broader environmental exposure system affecting both wild and captive cervids.

Section 01Study Objective

The objective of this review is to reconstruct Minnesota’s CWD history in the order detections occurred and evaluate four questions.

First, what happened after each captive CWD detection in Minnesota?

Second, did infected captive facilities consistently lead to establishment and increasing prevalence of CWD in surrounding wild deer?

Third, how did the chronology in southeastern Minnesota differ from captive-associated events elsewhere in the state?

Fourth, does the southeastern pattern require investigation of regional environmental exposure — including feed, forage, agricultural commodities, manure and litter, soil, water, equipment and other pathways capable of moving prion contamination through a shared landscape?

The analysis separates documented animal movement, geographic association, surveillance intensity and disease establishment. A captive facility near a later wild detection is not treated as equivalent to a documented transmission event. Likewise, absence of detected disease is interpreted in relation to the amount of surveillance actually conducted.

Section 02Biological Basis for Environmental Analysis

Minnesota DNR states that CWD can spread through both direct animal-to-animal contact and indirect environmental contact. Infected deer shed prions through saliva, urine, blood, feces and antler velvet, while infected carcass material can remain a source of exposure. DNR also notes that infected deer can appear healthy for much of an incubation period that commonly lasts approximately 1½ to three years while continuing to shed infectious material. (MN DNR)

The Minnesota Board of Animal Health likewise states that prions can persist in the environment for years and that CWD can be transmitted indirectly through environmental exposure. (Minnesota Board of Animal Health)

Environmental exposure is therefore not external to established CWD biology. It is an acknowledged transmission pathway and must be evaluated alongside direct cervid movement.

Section 032002–2004: Aitkin and Stearns Counties

Minnesota’s first CWD-positive animal was detected in a captive elk farm in Aitkin County in 2002.

In 2003, another CWD-positive elk farm was identified in Stearns County. Minnesota documented the Stearns facility as a trace-out from the Aitkin farm, establishing an actual animal-movement connection between the two captive operations.

The state then completed a three-year statewide surveillance project. Approximately 28,000 wild deer were tested. CWD was not detected in the wild population. (MN DNR)

This is the first important statewide comparison. CWD moved between captive facilities through documented animal movement. Yet that movement did not produce an identifiable endemic wild-deer focus surrounding those operations.

Section 042006: Lac qui Parle County

In 2006, CWD was detected in a captive white-tailed deer in a mixed deer and elk operation in Lac qui Parle County.

The Minnesota timeline does not document development of a sustained wild CWD focus surrounding that captive event. (MN DNR)

Again, captive infection occurred without subsequent development of an endemic regional wild-deer population.

Section 052009–2013: Olmsted County — A Critical Natural Comparison

In 2009, CWD was detected in a captive elk herd in Olmsted County. USDA determined that the herd had an apparent long-standing infection.

Minnesota responded with three years of intensive wild-deer surveillance surrounding the facility. During the second year, in 2010, Minnesota detected its first CWD-positive free-ranging deer. The deer was located within approximately two miles of the infected elk farm. (MN DNR)

This event provides one of the strongest tests of the captive-to-wild establishment hypothesis in Minnesota. There was:

• an infected captive herd;
• evidence that infection had existed in that herd for a substantial period;
• a wild CWD-positive deer within two miles;
• and intensive follow-up surveillance.

Minnesota subsequently tested more than 4,000 wild deer in the immediate area. No additional CWD-positive deer were detected. After three years, intensive surveillance was discontinued. (MN DNR)

An infected captive herd and a nearby infected wild deer were both present. What did not follow was a progressively expanding endemic CWD focus.

Section 062012–2014: Ramsey County

A captive European red deer was diagnosed with CWD in Ramsey County in 2012. Minnesota again implemented its three-year surveillance response.

By 2014, the surveillance period had been completed with no positive wild deer detected around the facility. (MN DNR)

This created another captive CWD event without establishment of a surrounding endemic wild population.

Section 072014: Houston County Is Already Identified as a Regional Risk Area

In 2014, CWD was detected in wild deer in Allamakee County, Iowa, immediately south of Minnesota’s Houston County. Minnesota responded by testing approximately 400 deer along the Minnesota-Iowa border. No CWD was detected in those Minnesota deer. (MN DNR)

Houston County entered Minnesota’s CWD surveillance history because of disease in the regional wild-deer landscape, not because of a Minnesota captive facility.

Section 082016: Preston, Fillmore County — The Southeastern Epidemic Begins in Wild Deer

Ongoing CWD detections in southwestern Wisconsin and northeastern Iowa led Minnesota to conduct surveillance in southeastern Minnesota. During the 2016 deer season, three adult male free-ranging white-tailed deer near Preston in Fillmore County tested positive.

Minnesota created deer permit area 603 as a CWD management zone and began aggressive disease-management activities.

The Preston detections were wild-deer detections. No captive cervid facility was identified as the source of this initial southeastern Minnesota focus. (MN DNR)

During winter 2017, eight additional CWD-positive wild deer were found through special hunts, landowner shooting permits and USDA agency culling. During fall 2017, another six CWD-positive wild deer were detected within DPA 603. (MN DNR)

Thus, before the major Winona captive detection occurred, Minnesota already had a persistent and growing CWD focus in its southeastern free-ranging deer population.

This is the foundational fact of the southeastern chronology. Endemic southeastern Minnesota CWD did not begin with the Winona captive facilities. It began in free-ranging deer near Preston.

Section 092016–2017: Crow Wing and Meeker Counties — Documented Captive Movement Without Endemic Wild Establishment

During 2016, Minnesota detected CWD in a captive deer farm in Crow Wing County. In spring 2017, another positive captive facility was detected in Meeker County. Minnesota identified the Meeker operation as a trace-out from the Crow Wing facility. This is another case in which animal movement between captive facilities was documented.

Minnesota implemented mandatory surveillance around both facilities. During fall 2017, no CWD-positive wild deer were detected in the north-central or central surveillance areas surrounding those farms. (MN DNR)

Meeker County surveillance continued for three consecutive years. In 2019, 544 wild-deer samples were collected and none tested positive. Having completed three consecutive years without a wild detection, DNR ended the intensive surveillance program there. (MN DNR)

Crow Wing eventually produced a different result. In February 2019, a wild CWD-positive deer was found near the infected captive facility. DNR responded by creating DPA 604 within approximately a 15-mile radius. During fall 2019, 3,966 wild deer were sampled with no additional positives detected. In 2020, another 951 deer were sampled in DPA 604 with no additional positives detected. (MN DNR)

Crow Wing reproduces the earlier Olmsted pattern: infected captive herd → nearby wild detection → extremely intensive surveillance → failure of the event to develop into a southeastern-style endemic focus.

Section 10November 2017: First Winona County Captive-Herd Detection

In November 2017, CWD was detected in a captive white-tailed deer herd in Winona County. Minnesota subsequently reported that all nine captive deer associated with the farm were infected. (MN DNR)

Seven remaining deer were depopulated in early 2018 and all seven tested positive. Three deer that had previously been moved from the producer’s herd into Winona City Park were also removed and tested. No CWD was detected in any of those three deer. (Minnesota Board of Animal Health)

The timing is essential. By the time this captive herd was identified, the Preston/Fillmore free-ranging focus had already existed for approximately a year and had produced repeated wild positives. The Winona captive event entered an existing southeastern CWD landscape.

Section 112018: Southeastern Surveillance Expands

During 2018, Minnesota expanded mandatory surveillance throughout southeastern Minnesota. DNR identified three reasons for the expansion: the CWD-positive captive herd in Winona County; continued detections in the Preston wild-deer focus; and additional wild CWD detections in Wisconsin.

During that year, CWD was detected in 16 wild deer in Fillmore County and one wild deer in Houston County. (MN DNR)

The Houston detection marked the beginning of an important second question. Was disease throughout southeastern Minnesota simply expanding outward from a single source, or were geographically separate disease foci developing within the same affected regional landscape?

Section 12Winter 2018–2019: Unequal Surveillance of the Emerging Clusters

Minnesota’s own operational data demonstrate that surveillance intensity differed dramatically among southeastern locations. During winter 2018–19:

(Minnesota DNR files)

The disparity is substantial. The Winona targeted-removal effort produced approximately 11 times as many samples as the Houston/Looney Valley effort. The Preston USDA effort alone produced more than 27 times as many samples as Looney Valley.

These sampling differences matter because cumulative CWD maps represent detections, not equal-effort measurements of disease prevalence. A location in which hundreds of deer are deliberately removed and tested has a much greater probability of producing numerous mapped positives than an area receiving fewer than twenty targeted samples.

If surveillance is concentrated around the captive facility because the facility is considered a risk source, and additional positives are then discovered because that area was sampled intensely, those detections cannot independently establish that the facility caused the surrounding disease. The surveillance design itself increases detection probability near the presumed source.

Section 132019–2020: Minnesota Identifies Potentially Independent Wild Disease Foci

By the 2019–20 surveillance period, Minnesota DNR’s own assessment had become more complex. DNR described the Preston-Lanesboro infection as persistent, with 56% of positive cases located within an approximately 8-by-8-mile core. DNR separately reported increased cases in Winona County surrounding the formerly infected captive deer facility.

But DNR also documented a cluster of four positive wild deer on the same parcel in northern Houston County. The agency then made the critical statement that it was uncertain whether the Winona and Houston areas were related or represented independent sources for origination of disease. (Minnesota DNR files)

That statement materially changes interpretation of southeastern Minnesota. By this point, three distinct epidemiologic patterns existed:

• Preston/Fillmore: an established wild CWD focus without an identified captive source.
• Winona: a wild focus receiving heavy surveillance around a previously infected captive herd.
• Northern Houston: a concentrated wild cluster for which DNR itself recognized the possibility of an independent origin.

These cannot simply be collapsed into a single captive-to-wild transmission narrative.

Section 142019–2020: Douglas and Pine County Captive Detections

In December 2019, CWD was detected in a captive deer farm in Douglas County. In January 2020, another CWD-positive captive herd was confirmed in Pine County. (MN DNR)

Minnesota again established wild-deer surveillance areas around the facilities. During fall 2020: west-central Minnesota around the Douglas event, 446 wild deer were sampled with zero positives; east-central Minnesota around the Pine event, 361 wild deer were sampled with zero positives. (MN DNR)

These events add two more examples to the statewide comparison. Captive infection was detected. Surveillance followed. An endemic surrounding wild focus did not.

Section 152020: Houston County Captive Detection and the Second Winona Herd

In October 2020, CWD was detected in a captive Houston County white-tailed deer. The infected animal had originated from another captive herd in Winona County. The Winona herd was quarantined as part of the investigation. This created an actual captive-animal movement connection between the Winona and Houston operations.

The important distinction is that this was not the same question as the origin of CWD in the surrounding wild population.

By the time this captive movement investigation began, free-ranging CWD had already been established in southeastern Minnesota for years, the northern Houston wild cluster had already emerged, and DNR had already written that the Winona and Houston wild disease areas could have independent origins.

Section 162021: Beltrami County and the Winona Investigation

The Winona investigation subsequently expanded to a captive herd in Beltrami County, where CWD was confirmed in spring 2021. This established another important distinction in the Minnesota record. CWD could clearly move through captive-animal networks. But the existence of captive-to-captive movement did not mean that every surrounding wild CWD focus originated from those farms.

Minnesota’s April 2021 Board of Animal Health investigation produced one of the most significant statements in the entire statewide record. At that time, 32 animals from the quarantined Winona herd had been tested without a positive detection. The Board reported that:

• imported live cervids from the previous five years were no longer alive and had tested CWD not detected;
• the producer did not hunt in CWD-endemic areas;
• the producer did not practice taxidermy;
• there had been no documented escapes;
• no wild cervids had been documented entering the pens;
• and the breeding herd had been protected by double fencing since 2015.

The Board described the fencing as one of its strongest approved exclusionary configurations: eight-foot double fences separated by at least four feet. (Minnesota Board of Animal Health)

Most importantly, the Board stated: “The investigation identified CWD in the surrounding wild herd as the primary exposure or risk factor for CWD to the Winona herd.”

The Board further concluded that even exclusionary fencing preventing commingling and nose-to-nose contact was insufficient to prevent exposure where CWD occurred in surrounding wild cervids. (Minnesota Board of Animal Health)

This is not an interpretation imposed on Minnesota’s record. It is the state’s own investigative finding.

Section 172022: CWD Appears Inside the Double-Fenced Winona Herd

The Winona herd remained under quarantine. In August 2022, CWD was finally confirmed in a four-year-old doe inside the herd. The Board again documented that the property had been double fenced since 2015 and acknowledged direct and indirect environmental transmission, including environmental persistence of CWD prions. (Minnesota Board of Animal Health)

Following the initial detection, two additional deer associated with the farm subsequently tested positive. In October 2022, the remaining herd was depopulated. All 120 remaining white-tailed deer tested CWD not detected. The Board reported that the farm had participated in the national CWD Herd Certification Program since 2012 and had tested more than 100 deer before CWD was detected in August 2022. It also explicitly described the farm as being located in a CWD-endemic region containing a high prevalence of infection in wild deer. (Minnesota Board of Animal Health)

This was not a facility in a previously unaffected landscape followed by growing infection outside its fence. It was a heavily protected captive herd embedded inside an established CWD landscape. The surrounding wild population was already infected. The state itself identified that surrounding population as the herd’s principal exposure risk. CWD was eventually detected inside the double fence.

Section 18Minnesota’s Own Broader Assessment of Farm Infection

The Minnesota Board of Animal Health subsequently summarized its farm experience in language that directly bears on this analysis. In a 2022 Board discussion, an agency communication was quoted as stating that most Minnesota farm CWD infections since 2015 had not resulted from moving CWD-positive deer from another infected farm, and that most infected farms were located in regions containing CWD-positive wild deer that could serve as a source through indirect contact. (Minnesota Board of Animal Health)

Whatever debate existed over the wording, the statement confirms that Minnesota’s own animal-health program was evaluating environmental exposure from infected wild populations as an important source pathway to captive facilities. The Board’s Winona investigation provides the clearest documented example.

Section 19Statewide Natural Experiment

Minnesota’s 24-year history effectively creates a natural comparison. If infected captive cervids were sufficient, by themselves, to establish progressively increasing wild CWD prevalence, the expected pattern would be repeated endemic zones surrounding Minnesota’s many infected captive operations. That is not the pattern in the state record.

• Aitkin/Stearns — documented captive-to-captive movement; ~28,000 wild deer tested statewide by 2004; no wild CWD detected.
• Lac qui Parle — captive positive; no subsequently documented endemic wild focus surrounding the facility.
• Olmsted — apparently long-standing captive infection; one wild positive within approximately two miles; more than 4,000 additional wild deer tested; no additional positives.
• Ramsey — captive positive; three years of surveillance; no positive wild deer detected.
• Crow Wing — captive infection; one later nearby wild positive; 3,966 wild deer tested in 2019 with no additional positives; another 951 tested in 2020 with no additional positives.
• Meeker — documented captive trace-out; three years of surrounding surveillance; final year 544 tested, zero positive.
• Douglas — captive positive; 446 surrounding wild deer tested, zero positive.
• Pine — captive positive; 361 surrounding wild deer tested, zero positive.

These are not locations in which Minnesota simply failed to conduct surveillance. DNR states that it conducts intense, concentrated surveillance around known positive captive facilities for a minimum of three years under its response system. (MN DNR)

Yet those captive events did not repeatedly produce endemic CWD.

Section 20Southeastern Minnesota Is the Statewide Exception

Southeastern Minnesota followed the opposite pattern. The environment was already supporting sustained CWD transmission in free-ranging deer before the principal Winona captive detections entered the chronology. The sequence is clear:

• 2014: Minnesota recognizes Houston County border risk from infected wild deer in neighboring Iowa.
• 2016: three free-ranging adult males near Preston test positive.
• Winter 2017: eight additional wild positives are found around Preston.
• Fall 2017: six more wild positives are found.
• November 2017: the first major Winona captive herd is detected.
• 2018: sixteen additional wild positives are documented in Fillmore County and the first Minnesota wild positive is detected in Houston County.
• 2018–19: surveillance is highly concentrated around Preston and the Winona captive-associated area while Houston’s Looney Valley receives dramatically fewer targeted samples.
• 2019–20: Winona cases increase and four positive wild deer are found on a single northern Houston County parcel. DNR states that Winona and Houston may represent independent origins.
• 2020: CWD is identified in a captive Houston animal originating from a second Winona herd.
• 2021: Minnesota’s Board of Animal Health identifies the surrounding infected wild population as the primary exposure risk to that double-fenced Winona herd.
• 2022: CWD is ultimately detected inside that quarantined, double-fenced herd.

The chronology does not show captive infection entering a clean southeastern landscape and subsequently creating the regional epidemic. It shows wild CWD becoming established first, multiple wild disease concentrations appearing across the region, and captive herds inside that same landscape becoming infected during the same period.

Section 21The Surveillance-Intensity Problem

Surveillance intensity must be treated as an epidemiologic variable. Minnesota’s response system deliberately increases sampling around captive detections. That is appropriate for disease surveillance, but it creates an analytical problem when the resulting detections are later used to demonstrate a geographic association between captive facilities and wild CWD.

The 2018–19 comparison illustrates the problem directly. Approximately 493 USDA removals occurred around Preston; 202 targeted landowner and USDA samples were obtained around Winona/Cedar Valley; only 18 targeted landowner samples were obtained from Houston/Looney Valley. (Minnesota DNR files)

Therefore, more mapped positives around Winona cannot be interpreted independently of the fact that far more deer were deliberately sought and tested there. A cumulative map without sampling-pressure adjustment can make the heavily investigated location appear epidemiologically dominant even when an independent cluster receiving far less surveillance is developing elsewhere.

This is particularly important in Houston and Winona counties because DNR itself subsequently recognized the possibility of independent disease origins. (Minnesota DNR files)

Section 22The Endemic Threshold Provides the Strongest Statewide Test

Minnesota now provides an objective endpoint for comparing these histories. DNR identifies three deer permit areas — 646, 647 and 648 — as endemic, meaning CWD prevalence has exceeded 5%. All three are in southeastern Minnesota. DNR describes them as the core CWD infection areas in southeastern Minnesota where the disease was first detected in 2016. (MN DNR)

No equivalent endemic designation developed around Aitkin, Stearns, Lac qui Parle, Olmsted, Ramsey, Meeker, Douglas or Pine as a consequence of those captive detections.

Minnesota had many captive CWD events. Minnesota did not develop many endemic CWD regions. The endemic region developed where CWD was already established in free-ranging southeastern deer.

Section 23Current Surveillance Shows the Same Geographic Concentration

The most recent complete surveillance year reinforces the historical pattern. From July 1, 2025 through June 30, 2026:

(MN DNR)

Wild CWD now exists in several Minnesota locations, and isolated or small clusters have appeared outside the southeast. But nothing elsewhere in Minnesota approaches the scale of southeastern Minnesota.

The distinction is not between “some CWD” and “no CWD.” It is between sporadic or limited detections and a regional environment where CWD became sufficiently established that prevalence exceeded Minnesota’s own endemic threshold.

Section 24Environmental Exposure Must Become the Central Investigative Question

Once the chronology is reconstructed, the central epidemiologic question changes. The statewide record does not ask merely: can infected captive deer move CWD? Minnesota’s trace investigations establish that infected or exposed captive animals can move between farms.

The larger question is: why did those movement events repeatedly fail to produce endemic surrounding wild populations, while southeastern Minnesota developed sustained, increasing prevalence?

The distinguishing condition was the regional disease environment. Southeastern Minnesota already contained infected free-ranging deer. Those deer shed prions into the environment through saliva, urine, feces, blood, tissues and carcasses. Minnesota recognizes that these prions can produce indirect environmental exposure and can remain in the environment for extended periods. (MN DNR)

Captive cervid facilities within that landscape were not isolated biological systems. They occupied the same agricultural region. They consumed agricultural feed products. They received hay, forage, grain and formulated feed. Their surrounding landscape contained cattle, dairy production, row-crop agriculture and poultry production. Manure and litter were transported and applied to agricultural land. Agricultural machinery moved through fields. Soil and sediment moved through drainage systems and waterways. Feed ingredients and forage moved between farms and regions.

These are physical pathways capable of moving environmental material through a landscape. A complete epidemiologic investigation of southeastern Minnesota therefore requires reconstruction of these movements with the same intensity applied to cervid movements.

Section 25Agricultural Exposure Hypothesis

The southeastern Minnesota pattern supports examination of a common regional exposure system. Under this framework, free-ranging and captive cervids are not treated automatically as source and recipient populations. They are treated as populations occupying the same contaminated environment.

That framework produces a different set of questions:

• Where did hay and alfalfa entering southeastern Minnesota originate?
• What forage was fed to the positive captive herds?
• What ingredients entered commercial pelleted feeds?
• Did dairy, beef and captive-cervid operations obtain feed from common suppliers?
• Where was livestock manure applied? Where was poultry litter applied?
• Were any manure, litter, forage or feed sources associated with regions containing established CWD?
• What watersheds connect the independent wild clusters? Where do sediment and agricultural runoff move?
• What row-crop fields overlap the high-prevalence deer landscape?
• Where were deer carcasses, tissues or excreta deposited in agricultural fields?
• What equipment moved between those fields?
• What materials entered the double-fenced Winona facility despite exclusion of direct deer-to-deer contact?

These are not peripheral questions. They follow directly from Minnesota’s own finding that environmental contact transmits CWD and from the Board of Animal Health’s determination that an infected surrounding wild population represented the primary exposure risk to a double-fenced captive herd.

Section 26The Double-Fenced Winona Herd as a Sentinel

The second Winona herd is especially important because it reverses the conventional direction of the epidemiologic assumption.

• The herd was double fenced beginning in 2015.
• No wild deer were documented entering. No captive deer were documented escaping.
• Imported live cervids from the preceding five years had subsequently tested CWD not detected.
• The producer did not hunt in endemic CWD areas and did not practice taxidermy.
• The Board considered the fencing one of its strongest exclusionary designs. (Minnesota Board of Animal Health)

Despite these conditions, the Board concluded that the surrounding infected wild population represented the primary exposure risk to the herd. CWD was later detected inside the facility. The remaining 120 animals ultimately tested negative after depopulation. (Minnesota Board of Animal Health)

This facility therefore cannot be examined only as a potential source of environmental contamination. It must also be examined as a sentinel of environmental exposure occurring inside an endemic region.

The question becomes simple and unavoidable: if deer could not readily cross the exclusionary fence, what infectious material did?

Section 27Captive Movement Versus Disease Establishment

Minnesota’s record demonstrates two separate processes that should not be conflated.

Captive movement. Animal movement successfully explains several captive-to-captive epidemiologic connections. Aitkin to Stearns is one example. Crow Wing to Meeker is another. The later Winona-Houston-Beltrami investigation provides another network of captive exposure and movement.

Regional establishment. Those animal movements did not consistently produce endemic wild populations around the affected captive facilities. That is a separate epidemiologic phenomenon.

A mechanism capable of transporting an infected deer from one facility to another is not automatically sufficient to explain why CWD becomes permanently established across a landscape. Minnesota’s statewide history demonstrates the difference.

Section 28Central Epidemiologic Challenge

A frequently repeated CWD-management premise is that moving captive cervids represents one of the major threats for introducing and establishing CWD in new geographic areas. Minnesota provides a direct real-world test of that premise.

The state experienced numerous captive CWD detections. It documented captive-to-captive movements. It conducted intensive surveillance around affected facilities. It found isolated wild positives near some of them.

If captive infection and movement were sufficient to explain regional CWD establishment, Minnesota should contain multiple areas where those captive events were followed by increasing prevalence and eventual endemic disease in surrounding wild deer.

That predicted pattern did not materialize. Instead, Minnesota developed one overwhelmingly dominant endemic region: southeastern Minnesota — where CWD was established in the free-ranging population before the principal captive events occurred.

That is the epidemiologic result that must be explained.

Section 29Conclusion

Minnesota’s CWD history spans more than two decades and contains numerous captive-herd infections distributed across the state. Those captive events provide something rare in wildlife epidemiology: repeated natural comparisons conducted under the same state surveillance system.

Again and again, Minnesota detected CWD in captive cervids and then looked aggressively in surrounding wild deer. The outcomes were remarkably consistent.

In Aitkin and Stearns, documented captive movement occurred, yet approximately 28,000 wild deer tested during the early statewide surveillance program produced no CWD detections. In Ramsey County, three years of surveillance around the positive captive facility produced no wild positives. In Meeker County, three consecutive surveillance years ended with another 544 wild deer testing negative. In Douglas County, 446 wild deer were sampled without a detection. In Pine County, 361 were sampled without a detection.

Even the two strongest apparent captive-to-wild geographic associations did not progress as expected under a simple captive-origin model. In Olmsted County, USDA identified an apparently long-standing captive infection and Minnesota subsequently found a CWD-positive wild deer within two miles. More than 4,000 additional wild deer were then tested without another positive. In Crow Wing County, a wild deer was found near the infected captive facility. DNR then tested 3,966 deer in 2019 and another 951 in 2020 without finding an additional positive. (MN DNR)

The presence of CWD in a captive herd did not predict establishment of endemic CWD in the surrounding wild population.

Southeastern Minnesota was different from the beginning. CWD was detected in free-ranging deer near Preston in 2016. Additional positives followed immediately. The wild focus persisted. It expanded. Additional disease concentrations developed in Winona and Houston counties. Minnesota DNR explicitly acknowledged that the Winona and northern Houston disease areas might have independent origins. (Minnesota DNR files)

Only after this southeastern wild-deer disease system was established did the principal Winona and Houston captive events become embedded within it.

The surveillance response then created another problem. Captive-associated areas received highly concentrated sampling while independent wild clusters could receive dramatically less. In winter 2018–19, the targeted Preston effort collected 493 USDA samples and the Winona/Cedar Valley effort collected 202 targeted samples, while Houston’s Looney Valley effort produced only 18. (Minnesota DNR files)

That unequal surveillance effort can materially influence the apparent geographic relationship seen on cumulative maps. More testing around a captive facility produces more opportunities to find positives around that facility. It does not establish the direction of transmission.

The strongest evidence comes later. The quarantined Winona herd had been double fenced since 2015. Minnesota documented no escapes, no wild deer entering the pens and no detected infection among imported live cervids from the preceding five years. The Board of Animal Health nevertheless determined that the surrounding CWD-positive wild herd was the primary exposure or risk factor for that captive herd. (Minnesota Board of Animal Health) CWD was subsequently detected inside that double-fenced facility.

That event demonstrates that in southeastern Minnesota the epidemiologic direction cannot simply be assumed to run from inside the fence outward. The infected regional environment was capable of presenting an exposure risk from outside the fence inward.

Minnesota’s current disease distribution reinforces the same conclusion. DNR now classifies only southeastern DPAs 646, 647 and 648 as endemic, with prevalence exceeding 5%. During the 2025–26 surveillance year, the southeast management zone produced 116 positives among 2,981 hunter-harvested deer. The north-central Crow Wing management zone produced zero among 881. Grand Rapids produced zero among 557. The western surveillance zone produced zero among 1,193. Other areas produced isolated or very small numbers of positives. (MN DNR)

After more than two decades of captive CWD detections across Minnesota, endemic disease did not emerge around those captive facilities as a general statewide pattern. It emerged in the one region where CWD was already established in free-ranging deer and environmental contamination was continuously being generated across the landscape.

That is the central finding of the Minnesota record.

Captive CWD occurred across Minnesota. Endemic CWD did not. Captive-to-captive movement occurred. Repeated captive-to-wild establishment did not.

Intensive surveillance around captive facilities repeatedly failed to identify an expanding endemic wild focus. The only Minnesota region to reach endemic prevalence was southeastern Minnesota, where infection was already established in free-ranging deer before the principal captive-associated events and where captive herds subsequently became infected within that same regional environment.

This directly challenges any explanation that treats movement of captive deer as sufficient to account for Minnesota’s regional CWD pattern. The unresolved variable is not simply deer movement. It is the environment.

The next epidemiologic question is therefore not whether southeastern Minnesota contained captive deer. Captive deer existed throughout Minnesota. The question is: what was present and moving through southeastern Minnesota’s environment that was not producing the same disease outcome around captive facilities elsewhere in the state?

That investigation must follow the physical landscape: feed, hay, alfalfa, grain and pellet ingredients; dairy and cattle supply chains; poultry litter and livestock manure; row-crop fields; agricultural machinery; waterways; sediment; soil movement; carcass material; and the movement of agricultural commodities into and through the region.

Because Minnesota’s statewide record establishes the comparison:

Where captive infection occurred without an established contaminated environment, endemic wild CWD did not follow. Where an infected regional environment was already established, CWD persisted, expanded, became endemic in wild deer, and appeared inside captive herds occupying that same landscape.

That is the Minnesota pattern. And that is the pattern any explanation of CWD spread in Minnesota must account for.