Posthitis (pizzle rot) is a well-known condition of wethers in Australia. Corynebacterium spp. in the prepuce of wethers on a high protein diet hydrolyse urinary urea releasing ammonia, which causes local tissue destruction. The condition less commonly and less severely affects rams and steers (Southcott 1965).
This report details two cases of low prevalence posthitis in rams from which Corynebacterium spp. were isolated. This condition differs from ulcerative balanitis in rams, which is of unknown aetiology (Knight 1958, Mumford 1959, Watt et al. 2016).
Case 1. Two of 14 Dorset rams were noticed at shearing in late October 2018 to have crusty dark red scabs on the end of the prepuce that resembled pizzle rot in wethers. The two rams were examined on 5 November 2018. Both had crusty dark red scabs and surface erosion on the external orifice of the prepuce.In both cases the penis and testes were normal on palpation.
On 17 December 2018 four Dorset rams examined. One affected ram had a 2 cm ulcer on the cranial aspect of the external os of the prepuce. The penis was exteriorised and found to be normal. The external genitalia of 70 of 170 first-cross ewes were also examined with the ewes in a race. There was no visible evidence of vulvovaginitis.
Case 2. In February 2019, one month prior to joining, the owner of 70 white Suffolk rams noticed two rams that had sheath infections. These two rams were examined on 25 February 2019. Both had red, crusty ulcerous lesions at the mucocutaneous junction of the prepuce, most noticeably on the dorsal aspect of the prepuce. In both cases the penis was exteriorised and observed to be normal. Subsequently the owner re-examined the mob of rams and discovered an additional four cases.
In Case 1, Corynebacterium pilosum was cultured from both rams. A Ureaplasma diversum-like strain (with a 98% identity) was also cultured.
In Case 2, a Corynebacterium from the C. renale group was cultured from both rams. Both were culture negative for Mycoplasma.
In both cases the owners treated the affected rams by flushing the prepuce with dilute antiseptic. In Case 2 affected rams were also treated with procaine penicillin. The owners reported that most rams but not all responded to treatment.
While posthitis has been recorded in rams on several occasions, they, like testosterone-treated wethers, are less affected than untreated wethers. Wethers (and rams) most commonly develop external prepucial lesions that have little effect on health and production but in wethers this can progress to an internal ulceration of the prepuce, a 'severe disease of considerable economic importance' (Southcott 1965).
In transmission experiments, rams were again more resistant to posthitis compared to ewes to vulvovaginitis and wethers to posthitis. Of interest, naturally occurring posthitis was also seen in Hereford steers from a property with a high prevalence of posthitis in wethers. Ewes can suffer an analogous vulvo vaginitis and this can be transmitted venereally (Beveridge and Johnstone 1953, Southcott 1965).
In the experience of the author, posthitis in rams is sporadic and of low prevalence and importance but it has been reported as affecting 76 of 80 rams in Spain. In the Spanish case, miaisis complicated the presentation but the rams responded remarkably well to topical treatment with antibiotics and prednisolone. The penis was not involved and C. renale was isolated.
Corynebacterium renale, C. cystitidis, and C. pilosum are referred to as the 'C. renale group.' Originally considered one species, C. renale, the differences were described by Yanagawa (1975) as Immunological Type I, II and III, and later defined genetically as three distinct species in 1978 (Yanagawa and Honda 1978). C. pilosum is reported to cause posthitis (pizzle rot or sheath rot) in wethers and likely rams (Underwood 2015). The bacteria are ubiquitous in the environment and C. pilosum can survive in soil for over 210 days (Hayashi et al. 1985). They are considered part of the normal flora of mucous membranes, but under certain conditions may be pathogenic. High-protein diets, resulting in more basic urine, higher urea concentration, and irritation of the preputial and vaginal mucous membranes are host factors that contribute to clinical disease (Underwood 2015).
Ureaplasma spp. have been implicated in sheep and goats, however the research on these infections doesn't seem to be as extensive or clearly defined.