How to Test Deer for CWD: Samples, Labs & Costs

Testing a deer for chronic wasting disease requires collecting specific tissue from the animal, submitting it to a state-approved veterinary diagnostic laboratory, and waiting for results from one of a few standard diagnostic tests. Most hunters encounter CWD testing through their state wildlife agency, which may offer free or subsidized testing at check stations or by mail-in submission. The process sounds simple, but the details matter: the tissue you collect, how you store it, which test the lab runs, and even the genetics of the individual deer all influence whether the test catches an infection.

Which Tissue Samples Are Needed

For a harvested deer, the two tissues that matter most are the retropharyngeal lymph nodes and the obex, a small region at the base of the brainstem. State labs typically ask for one or both. The retropharyngeal lymph nodes sit behind the throat, roughly where the head meets the neck, and they are the single most sensitive tissue for post-mortem CWD detection. In a large study of white-tailed deer, about 80% of CWD-positive animals had abnormal prion protein in both the lymph nodes and the obex, but roughly 20% had it in the lymph nodes alone, and none had it only in the obex.¹ In practical terms, if a lab only tests the brainstem and skips the lymph nodes, it can miss early infections.

There is one notable wrinkle. Deer exposed to low doses of CWD prions through environmental contamination, such as contact with urine or feces from infected animals, sometimes develop infections that show up in the obex before they appear in the lymph nodes, essentially reversing the usual pattern.² This is uncommon in naturally infected wild deer, where exposure tends to be repeated and at higher doses, but it underscores why many labs prefer to test both tissues when possible. If your state asks only for lymph nodes, that covers the majority of cases. If it asks for both, provide both.

How to Collect and Store Samples

Most state agencies publish illustrated guides or short videos showing where to cut. The lymph nodes are roughly almond-sized and located deep in the tissue just below the base of the skull. Extracting them requires cutting the head from the carcass and making incisions along the back of the throat. It is messy work, and many hunters choose to bring the whole head to a check station or drop-off freezer rather than attempting the extraction themselves. If you do extract the nodes, place them in a sealed bag and keep them cold.

Sample preservation is more forgiving than you might expect. The monoclonal antibody staining used in standard lab tests performs well on fresh, frozen, or even mildly decomposed brain and tonsil tissue.³ So if the deer sits overnight before you can get to a freezer, the sample is not necessarily ruined. That said, fresher is always better. Freeze the sample as soon as you can, avoid letting it sit in the sun or in a warm truck bed for hours, and do not place it in formalin or any preservative unless the lab specifically tells you to. Most labs want unfixed tissue for their initial screening tests.

Double-bag the sample and label it clearly with the date of harvest, the county or unit where the deer was taken, the sex of the animal, and your contact information. Many states provide pre-printed submission forms that you can download or pick up at license vendors.

The Tests Labs Run

Veterinary diagnostic labs in the United States use two primary methods, often in sequence. The first is an enzyme-linked immunosorbent assay, usually called ELISA, which serves as the initial screening test. The second is immunohistochemistry, or IHC, which is the gold-standard confirmatory test. Both detect the misfolded prion protein that causes CWD, but they do it differently.

ELISA works by grinding up a small piece of tissue, applying it to a plate coated with antibodies, and looking for a chemical signal that indicates the presence of the abnormal prion protein. It is fast, relatively cheap, and well suited to screening large numbers of samples. Two commercially available ELISA kits correctly identified all positive and negative samples in head-to-head comparisons, though one showed more variation between repeat runs than the other without affecting the final positive-or-negative call.⁴ If ELISA flags a sample as suspect or positive, the lab then runs IHC on the same tissue. IHC involves thinly slicing the tissue, mounting it on a slide, and using antibodies to stain any misfolded prion protein so a pathologist can see it under a microscope. A deer is not officially declared CWD-positive until IHC (or a comparable confirmatory test) confirms it.

Labs have also evaluated whether pooling multiple samples together could speed up surveillance. Using the standard ELISA, positive tissue could still be detected when pooled at ratios up to one positive sample mixed with nine negative ones.⁵ Pooled testing is primarily a tool for agencies conducting large-scale surveillance rather than something an individual hunter would encounter, but it helps explain how states process thousands of samples each season without overwhelming their lab capacity.

A Third Method on the Horizon

A newer technique called real-time quaking-induced conversion, or RT-QuIC, is generating a lot of interest. Rather than simply detecting prion protein that is already present, RT-QuIC amplifies tiny amounts of it, making the test far more sensitive than ELISA or IHC. It can pick up prion seeds in a wide variety of tissues, body fluids, and even environmental samples.⁶ Researchers have used it on lymph nodes, tonsil tissue, blood platelets, ear punches, and rectal biopsies. It is not yet approved by the USDA for official regulatory testing, but some research labs and a few state programs are already using it alongside approved methods to boost detection rates.

The appeal of RT-QuIC goes beyond sensitivity. Because it can work on smaller or less-traditional tissue types, it opens the door to testing samples that would be useless for ELISA or IHC. Work on blood-based RT-QuIC, for example, has explored whether platelet samples from white-tailed deer could serve as a practical diagnostic specimen.⁷ For now, though, most hunters will only encounter ELISA and IHC on their results paperwork.

Testing a Living Deer

Captive deer breeders, wildlife managers conducting herd assessments, and researchers studying CWD sometimes need to test animals without killing them. Two biopsy methods are used: rectal mucosa biopsy and tonsil biopsy. Both involve sedating the deer and removing a small piece of tissue that contains lymphoid follicles, where prion protein accumulates.

Rectal biopsy has an overall pooled sensitivity of about 68%, meaning it catches roughly two out of three infected animals. But that number is deceiving because accuracy depends heavily on how far the disease has progressed. In deer at the very earliest stage of infection, sensitivity drops to around 36%, while it reaches 100% in deer that are further along but still showing no outward symptoms. Specificity is excellent at nearly 100%, so a positive result is trustworthy.⁸ A negative result, on the other hand, does not guarantee the animal is clean, especially if the infection is recent.

Tonsil biopsy performs slightly better overall. Using IHC on tonsil biopsies, one study found a diagnostic sensitivity of about 72%, and in late preclinical infections, the sensitivity of whole tonsil IHC reached about 92%.⁹ But in early infections, tonsil biopsy sensitivity fell to around 55%. Both methods share the same limitation: they are most reliable in animals whose infections have had time to spread through lymphoid tissue, and least reliable in recently infected deer where prions have not yet accumulated enough to see on a slide.

RT-QuIC on rectal mucosa biopsies may eventually improve antemortem testing. In naturally infected, preclinical white-tailed deer, the technique reached sensitivities of 80% to 96% in late preclinical infections, depending on the deer’s genetic background.¹⁰ In early infections, though, sensitivity remained lower, particularly in deer carrying certain genetic variants.

Why a Deer’s Genetics Matter for Test Accuracy

Not all white-tailed deer respond to CWD infection the same way, and the reason is a single gene called PRNP. A variant at position 96 in this gene can dramatically change how the disease progresses and where prion protein accumulates. Deer that carry two copies of the common version (referred to as 96GG) tend to follow the textbook progression: prion protein shows up in lymph nodes first, then spreads to the brain, and both tissues light up on diagnostic tests. Deer that carry one or two copies of the 96S variant often develop the disease more slowly and accumulate less prion protein in lymphoid tissue and in blood.

This matters for testing in a direct, practical way. Rectal biopsy sensitivity drops from about 76% in 96GG deer to roughly 42% in deer carrying the 96S variant.⁸ Blood-based detection using prion amplification techniques showed that only one out of five CWD-infected deer carrying two copies of the 96S allele was correctly identified, suggesting the S variant suppresses prion levels in peripheral tissues like blood in a dose-dependent way.¹¹ The same pattern shows up in RT-QuIC on rectal biopsies, where early-infection sensitivity was 64–71% in GG deer but only 25% in those carrying the S variant.¹⁰

For a hunter sending in a head from a harvested animal, this is less of a concern because post-mortem testing on lymph nodes and brainstem is highly accurate regardless of genotype. But for captive herd testing programs that rely on live-animal biopsies, the genetic background of the herd can introduce a meaningful blind spot. Some state programs now factor PRNP genotyping into their surveillance strategies for this reason.

Experimental Approaches Using Feces, Urine, and Saliva

Researchers are working on ways to detect CWD without handling any tissue at all. CWD prions are shed in feces, urine, and saliva, and prion amplification techniques can pick them up. In experimentally infected deer, prions have been detected in all three fluids as early as six months after infection, long before any clinical symptoms appear.¹²

Fecal testing is probably the furthest along. A screening of fecal samples from naturally infected, preclinical white-tailed deer using a prion amplification method detected CWD prions with a sensitivity of about 55% and a specificity just over 98%.¹¹ That sensitivity is not high enough for individual diagnosis, but it could be useful for herd-level surveillance, where the goal is to determine whether CWD is present in a population rather than to diagnose a single animal.

Saliva testing is trickier. Researchers have combined optimized prion amplification with statistical modeling that accounts for false positives and false negatives, and they were able to distinguish between actual prion shedding in saliva and successful detection in a lab setting.¹³ The concentrations of prions in saliva are extremely low, and sample quality matters a great deal. None of these fluid-based methods are anywhere close to regulatory approval for diagnostic use, but they represent a potential future where testing could be done on samples collected from scrapes, licking branches, or even watering holes without ever handling an animal.

Where to Submit Samples and What Testing Costs

Every state with a CWD management program designates specific laboratories that accept samples from hunters. In most cases, you submit samples through your state wildlife agency, which coordinates with a USDA-approved veterinary diagnostic lab. Some states run the testing at their own state veterinary lab; others contract with university labs. Your hunting regulations booklet or the agency’s CWD webpage will list drop-off locations, mailing instructions, and any submission forms you need.

Costs vary widely. In many CWD-endemic states and in areas where the disease has recently been detected, testing is free for hunter-harvested deer because the state absorbs the cost as part of surveillance. This is especially common when an agency is trying to establish prevalence in a new zone and wants maximum participation. In other situations, particularly when you are voluntarily submitting from outside a mandatory testing area or through a private lab, expect to pay somewhere in the range of $25 to $75 per sample for ELISA screening. IHC confirmation, if needed, may be included in that fee or may add to it. Some university diagnostic labs charge separately for accessioning, tissue preparation, and the test itself, which can push the total higher.

Turnaround time depends on the lab’s workload and the time of year. During the peak of hunting season, some labs process thousands of samples per week, and results can take two to four weeks. Off-season submissions from captive herds or targeted surveillance efforts tend to come back faster, sometimes within a week. Most agencies now post results online through a portal where you can look up your submission number, so you do not have to wait for a letter in the mail.

If you are testing captive deer for a breeding program or interstate movement, the requirements are different and usually more stringent. The USDA’s CWD Herd Certification Program requires participating herds to undergo years of testing under specific protocols. Live-animal biopsies, post-mortem testing of all animals that die in the herd, and regular inspections are all part of the process. Costs for captive herd testing are generally borne by the herd owner and can add up over the five-year enrollment period.

Handling Carcasses and Preventing Contamination

CWD prions are extraordinarily durable. They resist heat, ultraviolet light, standard disinfectants, and enzymatic breakdown. This has practical implications for anyone processing a deer that might be infected, and for anyone handling tools used in CWD testing.

Recent research detected prions in waters used to dissolve deer carcass tissue, in soil that contacted those waters, in dermestid beetles used to clean skulls at a taxidermy site, in other insects found in the beetle shed, and even in dumpsters where carcasses were discarded. Surgical instruments used in surveillance work also retained prions after being washed with aqueous solutions.¹⁴ The takeaway is that normal cleaning is not enough to eliminate CWD prions from surfaces and tools.

For hunters, the practical advice is straightforward. If you harvest a deer in a CWD zone, do not saw through the spine or skull if you can avoid it (to minimize contact with brain and spinal tissue). Wear rubber gloves when handling the head and lymph nodes. Dispose of the head, spine, and any trimmed lymph tissue according to your state’s guidelines, which usually means using a designated dumpster or landfill rather than leaving remains on the landscape. Do not dump gut piles or heads on public land where other deer could contact them, because prions persist in soil and can remain infectious for years.

If you process your own deer and are waiting for test results, many agencies recommend deboning the meat and keeping it refrigerated or frozen until you receive a negative result. If the test comes back positive, the meat should be disposed of according to state guidelines. The CWD prion concentrates in nervous and lymphoid tissue rather than in muscle, but agencies still recommend against consuming any part of a CWD-positive animal.

CWD Prions in Non-Cervid Wildlife

One reason CWD surveillance matters beyond the deer-hunting community is the question of whether the disease can jump to other species. Laboratory experiments have shown that several North American rodent species living in the same habitats as CWD-infected deer are susceptible to the disease when directly inoculated. Transmission was efficient in all species tested, and survival times shortened substantially upon second passage, indicating the prion was adapting to its new host.¹⁵ These were artificial conditions involving direct brain inoculation, not natural oral exposure, so the real-world risk remains uncertain. But the findings challenged earlier assumptions that certain rodent prion protein sequences would be naturally resistant to CWD. This is part of why wildlife agencies increasingly treat CWD as a landscape-level problem rather than just a deer management issue, and why proper carcass disposal and environmental contamination matter to more than just hunters.