An outbreak of granulomatous vulvitis in feedlot heifers

An unusual form of vulvitis occurred in outbreak form affecting at least 18 of a group of 35 to 40 heifers soon after their introduction to a feedlot in the western Transvaal area of the Republic of South Africa. Initially, affected animals showed a knob-like swelling of the ventral commissure of the vulva. This grew in size up to approximately 6 cm in diameter and then appeared to burst open and give rise to a granulomatous lesion. Bovine herpesvirus type-1, Moraxella bovis, Mycoplasma bovigenitalium and Mycoplasma bovis were isolated from 2 affected heifers referred for diagnostic investigation. Mycoplasma canadense was isolated from one of the heifers. Attempts to reproduce the disease by transferring an excised portion of the lesion to unaffected animals, resulted only in lesions typical of uncomplicated infectious pustular vulvovaginitis. It is proposed that that multifactorial aetiology, including synergistic pathogenic action between the organisms isolated, was responsible for this outbreak. Administration of oxytetracycline to affected animals was followed by prompt resolution of symptoms. No further outbreaks have been reported.