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Years ago, Norm Gates (who I have long looked to as a mentor) compared the production results of 5000 ewes, and found no difference between the production of positive ewes verses negative ewes. He was questioned so he repeated the trial with no difference. That didn’t deter anyone and OPP became continued to be researched at the Clay Center.

What stimulated me to discuss this issue today is I got a call from a producer that had about 25 ewes. She had purchased a couple ewes, went thru a quarantine process and these ewes didn’t assimilate well into her flock and become chronically ill. She contacted her veterinarian and she tested her whole flock for OPP. Twelve ewes were positive (the older ewes of course.) Veterinarian recommended she euthanize the 12 ewes. I suspect if we tested all the ewes in the United States we could euthanize half of them too.

I have read The Minnesota Project, OPP Eradication Trial. Testimonials are not scientific evidence and I would suggest when a producer attempts to go into an OPP eradication program because of health problems many of them other than OPP get addressed along the way. OPP research has proved that the major mode of transmission is horizontal (to pen mates) not vertical (mother to offspring).  It does indicate by weaning early (60 days) and keeping ewe lambs segregated from ewe flock successfully reduced transmission of OPP. This is also a method of raising OPP negative replacements from positive ewes.  I would also suggest this is just good management and is already a recommended management tool to increase production and reduce disease.  Test and removal of OPP positive animals is rarely an economic option for a commercial flock.  Early weaning and segregation of replacements from the flock is not expensive and a good management practice.

In a time when sheep and goat producers struggle to get veterinary service, approved drugs and vaccines to help them be successful we concentrate our efforts on OPP, a disease in production medicine to be of little significance.

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