Testing for Caprine Arthritis Encephalitis (CAE) requires a blood draw from your goat and submission to a veterinary diagnostic laboratory, where the most common screening method is an ELISA blood test. The test detects antibodies the goat’s immune system produces in response to the virus, not the virus itself. A single blood sample costs around $6.50 at major veterinary diagnostic labs, with results typically available in 2 to 4 business days.
The ELISA Blood Test
ELISA (enzyme-linked immunosorbent assay) is the standard screening test for CAE and the one most veterinary diagnostic laboratories run. It works by detecting antibodies in the goat’s blood serum. Different commercial ELISA kits use different viral proteins as their target, and their accuracy varies slightly. Indirect ELISA kits generally perform best, with sensitivity ranging from about 89% to 96% and specificity between 95% and 98%. That means they catch the vast majority of infected goats while producing relatively few false positives.
An older test called AGID (agar gel immunodiffusion) is still available but less sensitive. ELISA catches every positive that AGID catches and then some, making it the preferred first-line option for most herds.
How to Collect and Submit a Sample
You’ll need to draw blood into a red top vacutainer tube (sometimes called a “plain” or “serum separator” tube). Let the blood clot at room temperature, then refrigerate it. Goat serum degrades quickly when left sitting on the clot, so labs recommend spinning the sample down and separating the serum before shipping. Most labs need at least 0.5 to 1.0 mL of serum.
Ship the sample refrigerated, with ice packs, to your chosen lab. Many state veterinary diagnostic laboratories and university labs accept mail-in submissions. The University of Minnesota’s Veterinary Diagnostic Laboratory, for example, runs CAE testing on Tuesdays and Fridays and charges $6.50 per sample. Your state’s animal health lab likely offers similar pricing. Samples need to arrive by noon the day before the scheduled test day to allow for processing.
When PCR Testing Makes Sense
PCR (polymerase chain reaction) testing looks for the virus’s genetic material directly rather than relying on antibodies. On its own, PCR is less sensitive than ELISA for routine screening, catching about 70% of infected goats compared to ELISA’s roughly 96%. But PCR has perfect specificity: if it says positive, the goat is infected.
Where PCR becomes valuable is in combination with ELISA. Running both tests in parallel pushes overall sensitivity to nearly 99%, which is especially useful when you’re trying to confirm that a herd is truly clean or when you suspect a goat may be in the early stages of infection before antibodies develop. PCR can also detect the virus in goats that haven’t yet seroconverted, a window period that can stretch for months after exposure.
The Seroconversion Window
This is the detail that trips up many goat owners. After a goat is exposed to CAE, it can take a long time for antibodies to reach detectable levels. In one study of 81 goats that tested seronegative on standard blood tests, 20 were found to be carrying the virus when checked by PCR. Of those 20, only half had seroconverted eight months later. The other half still would have tested negative on a standard antibody test despite being infected.
This delayed seroconversion is why a single negative test doesn’t guarantee a goat is CAE-free, particularly if the animal was recently exposed. It’s also why eradication programs require repeated testing over time rather than relying on one clean result.
Age Restrictions for Testing Kids
Kids under 90 days old should not be tested using antibody-based methods like ELISA. At that age, a positive result almost always reflects maternal antibodies absorbed from colostrum rather than actual infection. These passively acquired antibodies fade over time and don’t indicate the kid is carrying the virus.
Kids that were infected at birth typically develop their own measurable antibody response 4 to 10 weeks after infection. To avoid confusion between maternal antibodies and a true positive, wait until kids are at least 6 months old before testing. Some programs recommend waiting until 12 months for the most reliable results.
What Equivocal Results Mean
Sometimes a lab report comes back as “suspect” or “equivocal” rather than a clear positive or negative. This happens when the antibody level falls near the test’s cutoff threshold. It doesn’t confirm infection, and it doesn’t rule it out.
The standard follow-up is to retest in 30 to 60 days. If the goat is in the early stages of seroconversion, antibody levels will have risen by then and the result will come back clearly positive. If the original result was due to a sample issue or a nonspecific reaction, the retest will likely come back negative. In the meantime, keep the goat separated from the rest of the herd.
Testing Schedules for Herd Programs
If you’re working toward or maintaining a CAE-free herd status, testing needs to follow a consistent schedule. The Minnesota Board of Animal Health’s program, which is representative of most state programs, lays out clear requirements.
To maintain “test-negative” status, you need to test at least 10% of your herd annually (with a minimum of 5 animals), within 10 to 14 months of the previous qualifying test. Any goats you purchase or any animals that have been off-site, such as at shows or breeding visits, must be quarantined and tested on arrival. If they test negative, they get tested again 60 days later before joining the herd. They stay in quarantine for the full 60 days regardless of their initial result.
For herds actively trying to eliminate CAE, whole-herd testing is typically done every 6 to 12 months. Positive animals are permanently removed. Because of the long seroconversion window, most programs require at least two consecutive whole-herd negative tests before declaring a herd free of the virus.
Practical Tips for Accurate Results
- Test annually at minimum. A single negative test is a snapshot, not a guarantee. Annual testing catches goats that were in the seroconversion window during previous rounds.
- Separate serum promptly. Goat serum breaks down faster than cattle or sheep serum when left on the clot. Spin and separate the same day you draw blood.
- Test before buying. Ask for recent CAE test results from any seller, and retest the animal yourself after a 60-day quarantine before it joins your herd.
- Test the whole herd, not just symptomatic animals. Many CAE-positive goats never show obvious signs like swollen knees or hard udders. They still spread the virus through milk, blood, and close contact.
- Use the same lab consistently. Different labs may use different ELISA kits with slightly different cutoff values. Sticking with one lab makes it easier to track trends in your herd’s results over time.