|Bovine venereal diseases, such as Tritrichomonas foetus (T. foetus) infection, can be economically devastating to the cattle industry. Decreases in calf crops due to abortion and infertility, premature culling, and loss of animals with valuable genetics are among the costliest effects of venereal diseases. Unidentified T. foetus carrier bulls spread disease throughout a herd very efficiently. There is evidence supporting clearance of this disease state in young bulls, but infected mature bulls are often chronic, lifelong carriers of T. foetus and serve as the major reservoir for the disease (Clark et al., 1974).
The reasons mature bulls fail to eliminate the T. foetus and become chronic carriers as opposed to the apparent resolution of venereal infections in young bulls have not been illuminated. It has been hypothesized that there may be variation in the inflammatory response of the reproductive tract as a bull ages. At the present time, little is known about the normal inflammatory cell populations in bovine penile and preputial epithelium. Hence, the first objective of this study was to evaluate the cell population of the normal bovine penile and preputial epithelium. The second objective was to examine any differences in cell populations between young (n=6) and mature (n=6) age groups. Our hypothesis was that there is a significant difference in immune cell types between young bulls and mature bulls.
Two penile and one preputial biopsies were obtained from each bull. Slides were prepared with hematoxylin and eosin stain and immunohistochemistry markers for MUM1, IBA1, CD79a and CD3 were applied for identification of plasma cells, macrophages, T lymphocytes, and B lymphocytes, respectively. Histologic evaluation was performed by a board-certified anatomic pathologist.
Inflammation scores, marginated neutrophil infiltration scores, CD3 positive T cell numbers, CD 3 positive T cells numbers around vessels, CD79a positive B cell infiltration scores within lymphoid nodules, IBA1 positive cell numbers in the epidermis, IBA1 positive cells numbers in the superficial dermis, epidermal dermal junction basement membrane disruption scores, and epidermal junction cellular hyperplasia scores were all found to be statistically different (p<0.05) when comparing Group A versus Group B (bull type). Location was found to be significant (p<0.05) for CD3 positive T cells numbers in the epidermal-dermal interface and CD79a positive B cell infiltration score within the lymphoid nodules between the three sampling sites (distal, proximal, and preputial). Additionally, the interaction between group (bull type) and location was found to be significantly different (p<0.05) when comparing the numbers of IBA1 positive macrophages within the superficial dermis between groups and locations.
The results support the hypothesis that there are changes in the cellular populations in the penile and preputial epithelium as bulls age. Hence, the null hypothesis was rejected and the alternative hypothesis was accepted. There seems to be an increase in the amount of inflammation seen in the young bulls which may be integral for clearance of T. foetus from the penis and prepuce. The increase in the other cell types, such as macrophages in the mature group is understandable due to exposure of these bulls to numerous cows and/or heifers. This study provides a starting point for further investigations to more fully elucidate the variation in cell types present in the preputial and penile skin between young and mature bulls.