Retrospective Review of Surgical Outcomes and Pair-housing Success in Vasectomized Rhesus Macaques (Macaca mulatta)

Providing social housing for adult male macaques can be challenging. One successful strategy for long-term social housing of adult male macaques is to pair them with adult females; however, unwanted breeding must be prevented by sterilization of the male or female. Vasectomy is a simple, highly effective, and minimally invasive method of contraception that is used at our institution to facilitate social housing. We performed a retrospective review to analyze the surgical outcomes and rate of postoperative complications after vasectomy of adult rhesus macaques at our research facility. In addition, we evaluated the success rate of pairing vasectomized macaques with female partners. Over 10 y, 16 macaques were vasectomized, of which 5 developed postoperative complications such as orchitis, epididymitis, or surgical site infection. These complications resolved completely and without incident after antibiotic and analgesic therapy; an additional male had postoperative incisional swelling that resolved quickly after NSAID treatment. This complication rate is consistent with that in humans by surgeons who perform open vasectomies relatively infrequently. In addition, 5 of the vasectomized macaques (31%) developed sperm granulomas, which are a common and generally benign complication in humans and have been reported to develop in 40% of macaques after vasectomy. Successful pair housing with a female partner was achieved for 13 of 16 (81%) of the vasectomized macaques. We conclude that surgical vasectomy is a safe and simple procedure that can be used as a highly effective method to facilitate social housing of adult male rhesus macaques in research facilities.