Ulcerative balanoposthitis and vulvovaginitis of sheep

M VAN VUUREN AND C J V TRICHARD*

Introduction

Ulcerative balanoposthitis and vulvovaginitis of sheep is a disease characterized by erosions and ulcers of the external genitalia of rams and ewes. A similar syndrome has been recorded in goats. The condition is transmitted venereally. In South Africa, it occurs most frequently in Dorper sheep; 2 to 4 per cent of the national flock in South Africa is estimated to be affected at any one time. Other breeds are seldomly affected.

This disease was first encountered in South Africa in the Calvinia district in 197613 and during early 1979 in a semiintensive, mutton production unit in the north-eastern areas of the Free State Province. Although the ulcerative balanoposthitis and vulvovaginitis syndrome has not yet been recorded in other countries in southern Africa, vulvovaginitis seems to be a fairly common condition in goats in Nigeria.9 Similar disease syndromes, apparently with various causes, have been encountered in several countries. In some outbreaks in theUKrams and ewes were affected, ¹⁷ while in others in Australia, England, Canada, the USA and India, ewes have shown manifestations of vulvovaginitis, granular vaginitis, vulvitis or vaginitis.^{1, 10, 14, 19, 22, 33, 34}

Aetiology

In South Africa the aetiology of ulcerative balanoposthitis and vulvovaginitis has recently been shown to be a combined infection with Mycoplasma mycoides mycoides large colony (LC) and Trueperella pyogenes.^{20, 38}

Although the bacterium isolated most consistently from field cases is T. pyogenes, several other bacterial species isolated to a lesser extent include Corynebacterium spp., Erysipelothrix rhusiopathiae, Rhodococcus equi and Streptococcus spp.²⁰ The latter organisms, however, have consistently failed to induce disease following intrapreputial instillation. This was true even when preputial massage or the penile mucosa being rubbed with sterile gauze caused mild trauma.

Apart from M. mycoides mycoides LC that is found in the majority of affected sheep, a number of other mollicutes, namely Mycoplasma bovigenitalium, M. arginini, M. mycoides capri, Mycoplasma sp. Group 7, M. agalactiae, M. capricolum, M. mycoides capri, unidentified Mycoplasma spp. and Ureaplasma spp., have been isolated from specimens taken from the penis and vulva, particularly from vesicular lesions.^{20, 30, 35, 38} Although not as pronounced as in natural cases, granular-vesicular vaginitis or balanitis was caused by the application of combinations of some of the mollicute cultures to the mucous membrane. Circumstantial evidence therefore suggests that either a single mollicute, or a combination of species, is responsible for the condition. Prominent lesions have also been induced following experimental infection with several Ureaplasma spp.^{1, 18, 35}

Ulcerative lesions of the vulva, penis and prepuce, associated with Mycoplasma and Ureaplasma spp., have been described in several countries worldwide.¹⁷ Mycoplasma and Ureaplasma organisms have been isolated together, or separately, from rams and ewes and the diseases associated with this group of organisms include vulvovaginitis,¹⁰ vulvovaginitis and granular vulvitis,¹⁴ vulvitis,1 and ulcerative balanoposthitis and vulvovaginitis.³⁸

Although Acholeplasma spp. have been isolated from animals suffering from vulvovaginitis,¹⁹ their potential role as disease causing agents is still uncertain.

Since the first report of ovine urogenital disease associated with ureaplasma,¹⁴ there have been several similar reports from other parts of the world.^{17, 25, 28} Ureaplasma spp. were also implicated in an outbreak of vulvitis in Northern Ireland, and vulvitis and vaginitis with ulceration of the vestibule were evident in some cases following experimental transmission.¹

Several workers who believed ulcerative balanophosthitis and vulvovaginitis is infectious, but failed to associate the disease with mycoplasmas or other bacteria, have suggested that a virus could be the cause. No viruses or Chlamydophila spp. have been isolated from affected animals in South Africa, but in Australia a caprine herpesvirus has been isolated from lesions in goats with ulcerative vulvitis and ulcerative balanoposthitis.³³

Although viruses have consistently not been isolated concurrently with the disease,numerouspathogenic bacteria have been isolated from the lesions.^{12, 20} The role of secondary bacteria in the progression of the mycoplasmal and ureaplasmal infections is supported by reports that clinical lesions improve after broad-spectrum antibacterial treatment.¹

Epidemiology

Ulcerative balanoposthitis and vulvovaginitis in sheep has been recorded on a large number of farms in the North West, Limpopo and Eastern Cape provinces, and southern parts of the Free State Province in South Africa. ^{18, 35, 39} In all outbreaks rams and ewes were severely affected but the disease was particularly prevalent in rams. Young sheep less than 30 months of age are 2,5 times more likely to be affected than adult sheep.²⁰

In South Africa the condition has mostly been observed in the Dorper and Karakul breeds and to a much lesser extent in Merino, South African Mutton Merino, Ile de’France rams, and Angora goats.¹³

There is little doubt that natural transmission of ulcerative balanoposthitis and vulvovaginitis in South Africa is venereal.^{13, 35, 36, 39} Some ewes may remain infected for up to a year after the...