Enzootic posthitis (ulcerative posthitis or pizzle rot) is a well-known condition of Australian wethers on a high protein diet but has also been reported in rams, angora goat wethers, bulls and steers. In this condition, Corynebacterium spp. in the prepuce hydrolyse urinary urea releasing ammonia, which causes local tissue destruction (Southcott 1965, Constable et al. 2017, Parkinson and McGowan 2019).
In this case at least 10 of 40 Hereford and Hereford cross steers on a high protein drought ration of grain, lentils and canola hay developed posthitis from which Corynebacterium spp. were isolated.
Forty August 2018 drop Hereford and Hereford cross steers, initially grazed on drought affected pastures, were supplemented with lentils (tested at 23.5% protein and 12.8 MJ/kg of metabolisable energy) in a self-feeder for the previous five months. As pasture became depleted the steers were also fed canola hay (test not available, but usually ranges from 15-28% crude protein depending on the time of cutting, Grains Research and Development Corporation, 2020). The owner reported that the steers performed well on this ration. On December 12, 2019, the owner noticed at least 10 steers with enlarged sheaths.
On December 13, 2019, the mob was examined. At least 10 steers were observed to have red, scabby lesions on the external prepuce. Three steers were examined more closely and preputial swabs were collected.
Prepuce swabs from three animals were plated on sheep blood agar and incubated at 37°C in 5% CO2. Bacterial identification was determined using a Bruker MALDI Biotyper and 16S rRNA gene sequencing.
Corynebacterium cystitidis was the predominant bacteria cultured in a moderate growth (>20 colonies) from steer 1. Corynebacterium pilosum and Helcococcus spp. were also cultured in sparse numbers (<20 colonies).
From steer 2, three predominant bacteria were cultured in high numbers (>50 colonies). Two of these bacteria were identified as Corynebacterium renale and Corynebacterium pilosum. The third was a bacterium and identified as belonging to the Actinomycetaceae family, sharing highest 16S rRNA gene sequence similarity (95.97%) with Trueperella bialowiezensis strain NCTC13354 (previously Arcanobacterium bialowiezense), followed by Arcanobacterium phocae (95.43%), of sequences in the NCBI Nucleotide collection (nr/nt). It is possible that this third bacterium could be a novel species. Interestingly, Trueperella bialowiezensis was first isolated from the prepuce of European Bison bulls (Bison bonasus) suffering from balanoposthitis (Lehnen et al. 2006).
The third culture (steer 3) was overgrown by a swarming Proteus-like organism.
Molecular testing for Mycoplasma either did not detect Mycoplasma, or detected very low numbers of Mycoplasma.
TREATMENT / MANAGEMENT
The owner clipped the hair from the preputial orfice then flushed the prepuces of the affected steers with dilute chlorhexidine (Chlorodet farm disinfectant, chlorhexidine gluconate 55g/L). The owner removed necrotic tissue and repeated the preputial flushing treatment two weeks later. He commented that all steers responded to this treatment, enabling them to be sold shortly afterwards.
Southcott (1965) commented that external preputial ulceration, probably similar in aetiology to ovine posthitis has been commonly observed in bulls and steers on Chiswick (CSIRO Pastoral Research Station, Armidale, NSW) and has been seen on other Northern Tablelands properties over many years. Parkinson and McGowan (2019) commented that posthitis occurs in young bulls fed a high protein ration or pasture in preparation for sale. Posthitis is also reported to be of economic importance in bulls in South America (Constable et al. 2017).
Southcott (1965) was able to transmit posthitis from infected wethers to steers but was unable to establish persistent vulval lesions in heifers. He further commented that posthitis in steers is usually benign but may become more important with pasture improvement.
We thank the owner of the steers, Peter Rutherford, and NSW DPI Veterinary Bacteriology and Molecular Biology Diagnostic teams for performing the bacterial cultures, 16S rRNA gene sequencing and Mycoplasma PCRs.