This article was written by Dr. Lisa Sharko (Lead Veterinarian Animal Health and Welfare, OMAFA). This article was originally published in the Spring 2026 issue of the Dairy Goat Digest.
Introduction
Caprine arthritis-encephalitis (CAE) virus is a Lentivirus that infects a goat’s white blood cells leading to caprine arthritis-encephalitis disease. The virus travels through the body inside infected white blood cells, where it is unable to replicate and stays inactive. During this time, the goat is infected, but the virus is almost impossible to detect via testing and the goat may look and act completely normal for a long time. The virus can remain inactive for months to years, allowing the virus to spread throughout the body like a “Trojan horse”. This long inactive period is one reason why CAE can be difficult to manage and why proactive testing strategies are important when raising or buying in replacement animals.
CAE virus primarily targets the lungs, udder, joints and nervous system. When the infected white blood cells mature, the virus becomes activated and starts to multiply. At this time:
- The goat becomes infectious
- The immune system mounts a response
- The infection can be identified with diagnostic tests
- Clinical signs of CAE may appear (e.g.: swollen joints, weight loss, or lameness)
There are different strains/genotypes of CAE virus globally. Diagnostic test kits vary in their ability to detect different strains of the virus. This is why international patented test kits are verified in Canada to confirm that they can effectively detect the strain of virus causing disease in Canada.
Understanding CAE Test Performance
Sensitivity and specificity are key measures used to assess the accuracy of a diagnostic test.
Sensitivity describes how well a test correctly identifies animals who are truly diseased (true positives), minimizing false negatives. A test with high sensitivity is good at finding disease, which is an important feature when using the test to eradicate disease.
Specificity describes how well the test correctly identifies animals who do not have the disease (true negatives), minimizing false positives. A test with a high specificity is good at correctly identifying animals that do not have disease but at the risk of not identifying all diseased animals.
Unfortunately, tests rarely perform highly in both sensitivity and specificity. Sensitivity and specificity are often inversely related, meaning improving one may come at the risk of weakening the other. As a result, a test that is very good at finding infected animals (high sensitivity), may produce more false positives. Even a partial percentage point of a difference in sensitivity or specificity between tests can have an impact on how the test performs.
False positives are possible regardless of the test being used, but the number of false results should be low. Possible reasons false positives can occur include:
- Low test specificity
- Recent vaccination
- Recent infection
- Stressful event (e.g., moving or kidding)
If you are concerned about a false positive result, retest the animal in 4-6 weeks. When a kid is tested too young (i.e., before 3 months old), there is a high risk of a false negative resulting from the infection still being inactive. Young animals may test positive later after the virus becomes active and an immune response has occurred.
CAE Diagnostic Test Options
Diagnostic tests are not all created equally, and there is “no gold standard” or perfect test for CAE. All tests perform differently, with varying sensitivities and specificities, and can be a good choice in certain situations. Enzyme-linked immunosorbent assay (ELISA) is a laboratory technique that detects the binding of antibodies and antigens to diagnose an infection. ELISA tests typically have a high sensitivity compared to other test types, which makes them the preferred test for disease eradication and surveillance programs. There are several available ELISA test kits available and being used across Ontario and internationally.
First, the ELITEST ELISA by HPHEN BioMed has been historically used by the Animal Health Lab (AHL) for the diagnosis of a different Lentivirus in sheep. In 2023 the IDEXX ELISA test, which was being used for CAE testing at AHL, was discontinued. The HYPHEN test was then validated by AHL and started to be used to diagnose CAE in goats. This test has the highest sensitivity because it detects multiple antigens and proteins. This also allows it to detect early, low-grade infections. It is the test of choice for herds trying to eradicate CAE that have a low prevalence of CAE positive animals because of its high sensitivity and its ability to detect earlier infections. When using the Hyphen ELISA, false positive low reactors occur in less than 1% of tests. If the AHL suspects a positive result is a false reactor, the lab re-runs the test and it is noted in the comments.
The second test available is the cELISA test by VMRD, Inc. being used by veterinary clinics for in-clinic CAE testing and is used at other international laboratories. When compared to other ELISA tests, including the HYPEN test, the sensitivity and specificity is lower. Research done by the manufacturer reported a 96.4% specificity and 100% sensitivity (Herrmann, 2003) but no other research study has found the VMRD test’s sensitivity and specificity to be this high, especially in low prevalence herds trying to eradicate CAE. The VMRD test cannot detect early low-grade infections that would test positive with AHL’s ELITEST, therefore it is common to see more false negative results. With repeat testing, these “negative” animals may test positive later when they have had a stronger immune response that the VRMD test can detect. This test would be best utilized in herds with a higher prevalence of CAE, trying to control CAE but not eradicate it.
CAE Virus Testing Practices to Prevent Introducing Infection
- Before kids are exposed to mature stock (breeding bucks or does), test kids greater than 3 months of age and remove positive animals from the group. Retest the group at least 60 days later to ensure the positives removed did not transmit CAE before their removal.
- Ensure at least two negative tests, the last being after >60 days since the last positive kid herd mate was removed.
- Follow BMPs (see Reducing the Risk of CAE in Your Herd, Dairy Goat Digest Fall 2025).
- Ensure no direct contact between untested animals with unknown disease status and the rest of your herd until testing and culling of positives have occurred.
With many testing strategies and diagnostic tests available, it is important to work with your herd health veterinarian to choose what works best for you and your herd. Setting CAE goals for your herd (eradication vs. control) and gaining a better understanding of the testing options available will help facilitate conversations with your veterinarian and shape your CAE management plan.
Sources
Herrmann, L. M., Cheevers, W. P., McGuire, T. C., Adams, D. S., Hutton, M. M., Gavin, W. G., & Knowles, D. P. (2003). Competitive-inhibition enzyme linked immunosorbent assay for detection of serum antibodies to caprine arthritis-encephalitis virus: diagnostic tool for successful eradication. Clinical and diagnostic laboratory immunology, 10(2), 267–271. https://doi.org/10.1128/cdli.10.2.267-271.2003
Jerre, A., Nordstoga, A. B., Dean, K. R., & Holmøy, I. H. (2022). Evaluation of three commercial ELISA tests for serological detection of maedi-visna virus using Bayesian latent class analysis. Preventive veterinary medicine, 208, 105765. https://doi.org/10.1016/j.prevetmed.2022.105765
Schaer, J., Cvetnic, Z., Sukalic, T., Dörig, S., Grisiger, M., Iscaro, C., Feliziani, F., Pfeifer, F., Origgi, F., Zanoni, R. G., & Abril, C. E. (2022). Evaluation of Serological Methods and a New Real-Time Nested PCR for Small Ruminant Lentiviruses. Pathogens (Basel, Switzerland), 11(2), 129. https://doi.org/10.3390/pathogens11020129
