Ovine Brucellosis

Also Known As: Ram Epididymitis — Orchitis — Ovine Contagious Epididymitis — Brucella ovis Epididymitis.

Caused By: Brucella ovis and Brucella melitensis

Introduction

Bisected testicle form B. ovis ram showing grossly enlarged epididymis with fibrous tissue bands. Copyright AFSPH Iowa State

Ovine brucellosis causes reproductive disease in sheep, mainly in rams.

B. ovis is the least virulent of all the Brucella species.

The disease is on List B of the Office des International des Epizooties [www.oie.int/ (OIE)] It is therefore notifiable to the OIE.

Signalment

The disease is unique to sheep.

Distribution

Present in all countries where sheep are intensively farmed. It is transmitted mainly through semen but shedding is unreliable.

Ewes can also act as indirect vectors for brucellosis if they mate with both an infected and uninfected ram during the same oestrus cycle.

Abortion materials and vaginal discharge also contain Brucella organisms

Brucellosis is not considered zoonotic.

Clinical Signs

Epididymitis in rams with swelling and enlargement of testes, scrotum, penis and prepuce. Decreased reproductive performance will be noticed due to impaired spermatogenesis.

Testicular atrophy occurs in chronic infections.

Occasionally also abortion in ewes and weak lambs. This only occurs due to placental necrosis in ewes exposed in the first two trimesters of pregnancy.

Diagnosis

Palpation of the testes is suggestive but not definitive.

Specific immunofluorescent staining of semen smears is confirmatory.

Brucella organisms can also be isolated from the epididymis and accessory sex glands at necropsy, although excretion is intermittent so false negatives are not uncommon.

ELISA and Complement Fixation are also commonly used for serological diagnosis.

Treatment

Antibiotic therapy is very expensive, prolonged and ineffective.

Control

Testing and culling of breeding stock is essential to ensure carriers are not present within a flock.

No vaccine is available for B. ovis and vaccination against B. melitensis can interfere with serological diagnosis.

References

Animal Health & Production Compendium, Brucellosis (B ovis) datasheet, accessed 06/06/2011 @ http://www.cabi.org/ahpc/