Ovine Brucellosis
Also Known As – Ram epididymitis – Orchitis – Ovine Contagious Epididymitis – Brucella ovis Epididymitis.
Caused By – Brucella ovis
Introduction
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 Lost B of the Office des International des Epizooties [www.oie.int/ (OIE)]
Signalment
Unique to sheep
Distribution
Present in all countries where sheep are intensively farmed.
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 – swelling and enlargement of testes, scrotum, penis and prepuce.
Decreased reproductive performance due to impaired spermatogenesis.
Testicular atrophy occurs in chronic infections.
Occasionally also abortion in ewes and weak lambs. This only occurs in ewes exposed in the first two trimesters or pregnancy, due to placental necrosis.
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/