Why Test for OPP?

Rachael Gately, DVM, Cummings School of Veterinary Medicine, Tufts University

Ovine Progressive Pneumonia (OPP) is a viral disease of sheep that has been reported to affect over 25% of sheep in North America. Ovine Progressive Pneumonia is closely related to Caprine Arthritis and Encephalitis (CAE) that affects goats. Both diseases manifest similarly in each species. Ovine Progressive Pneumonia can cause a variety of clinical diseases ranging from chronic and progressive weight loss, difficulty breathing, swollen joints and lameness, as well as hard, unproductive udders. The most common presentation of the disease; however, has no clinical signs of illness. Unfortunately, sheep exhibiting any of the presentations listed above can spread the disease through nose-to-nose contact or through infected colostrum and/or milk. Once a sheep becomes infected, they are infected for life.

Current testing options for OPP include the AGID and the ELISA test. Both blood tests can be performed by laboratories who may also be performing your flocks Scrapie susceptibility genetic testing or by laboratories that your veterinarian is routinely working with. Due to the simplicity of testing, you have the option of drawing your own blood or can have your veterinarian test your sheep for you (for those interested in learning how to pull blood, check out my short how to below!). The ELISA test is the current preferred test as it is more sensitive, thus red topped tubes are the blood storage device of choice. Note: do not use purple topped tubes as these tubes contain EDTA which prevents the blood from clotting. Red topped tubes allows your sample to clot. Once clotted, pour off the serum and place into a new tube for testing submission.

As a means to minimize issues associated with OPP, regularly monitoring your flock via testing is a must. The affects of this effort are fruitful in decreasing the chance for early deaths, poor-doing members of our flocks, and ewes lambing without milk for their lambs…amongst others. Remember, sheep can contract this virus through coming into contact with the nasal secretions of an infected sheep. Therefore, if you purchase an animal at a sale where specific breeds of sheep do not require OPP testing prior to consigning to the sale, it is recommended to retest your purchased animals 30-60 days after leaving the sale in order to ensure infection did not occur in the sale barn.


How to collect a blood sample?

Supplies required:

  • 3cc or 6cc syringe
  • 18g or 20g 1-inch needle
  • Sample tube


1. Shear one side of the sheep’s neck from approximately 2 inches below the jaw and extend halfway down the neck.

  •  Recommendation:
    • Left-handed: shear sheep’s right side
    • Right-handed: shear sheep’s left side

2. Apply strong pressure to the neck with your thumb of fingers to occlude the jugular vein and allow blood to fill the vein above where you’re applying pressure.

3. Visualize the jugular vein filled with blood running the length of the neck above where you’re holding off.

4. Insert needle at a 30-degree angle aiming up towards the head while applying light back pressure while doing so in order to visualize a blood flash indicative of when the vein is entered.

5. Fill your syringe to the desired amount.

6. Remove needle from vein and hold off with your finger where the skin was entered for approximately 10 seconds.

7. Immediately fill sample tubes. (If using a purple topped tube for other testing purposes, the tube should always be filled first and inverted a few time in order to ensure proper mixing with the anticoagulant agent)

8. Label tubes clearly and refrigerate!

For a more detailed tutorial on how to collect blood samples for OPP testing, be sure to check out the video below!

For more information on OPP, please visit the OPP Society webpage.