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Ovine Progressive Pneumonia (a.k.a. OPP, lunger disease. Maedi-Visna).

About the disease

OPP is a slow-developing disease; once symptoms appear, it is often too late to fix the problem. There is no cure, so prevention is the only option. Much like Caprine Arthritic Encephalitis (CAE) in goats, OPP has a devastating health and financial impact on sheep herds.

Prevalence of the virus is largely dependent on:

* Flock management

* The strain of the virus

* Genetics/breed of sheep

* Usually occurs in sheep two to four years of age

Physical symptoms include:

* Progressive weight loss

* Difficulty breathing

* Lameness, joint swelling

* Paralysis

* Mastitis

It is important to note that the vast majority of infected sheep will never show respiratory disease or a wasting syndrome.

OPP is transmitted to other sheep via respiratory fluids like coughing or to lambs through infected milk/ colostrum.

Economic and herd impact

It is estimated that more than 50 percent of the flocks in the U.S. are infected with OPP. The number of infected sheep within a positive flock may be anywhere between I percent and 70 percent depending on management practices.

Reduced milk production, especially in younger sheep

Direct costs include:

* Death

* Premature culling

* Increases in the number of orphan lambs

* Slow-growing lambs related to decreased milk production

The difference between severe and minor losses may depend upon management practices, breed, strain of virus and climatic conditions.



* There is no treatment, just prevention

* Ewes in advanced stages of the disease infect their lambs more readily than ewes in early stages of the disease

* OPP can be eliminated from the herd using:

* Annual blood testing and removal of positive-tested animals

* Removal of the lambs from the ewes prior to suckling

* Feeding a colostrum replacement product for lambs

* Raising lambs on Ultra Fresh[R] Lamb Milk Replacer


Two different tests that can be used to detect the virus include:

* Agar Gel Immunodiffusion (AGID) Test (after six months of age): Detects circulating antibodies in the blood.

* Enzyme Linked Immunosorbent Assay (ELISA) Test: Can detect OPP as early as two weeks after infection.


Dr. Thomas Earleywine, Milk and Colostrum Replacer Specialist, Land O'Lakes Animal Milk Products Co.; 608-206-7264. Email:;

USDA APHIS Producer Survey on Sheep Health and OPP Management Practices--2003

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Title Annotation:The sheep shed
Publication:Countryside & Small Stock Journal
Geographic Code:1USA
Date:Nov 1, 2011
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