Surgical sterilization of free-ranging capybaras (Hydrochoerus hydrochaeris): “Passos Nunes” uterine horn ligature

Abstract

Capybaras are the primary hosts of Amblyomma sculptum tick, vectors of Rickettsia rickettsia bacteria, and the zoonotic agent of Brazilian Spotted Fever (BSF). In this context, contraceptive methods have been suggested for population control in order to reduce the number of free-ranging capybaras cohabiting with humans in urban and rural areas and acting as disease amplifiers. To maintain the group's expected behavior and social hierarchy, sterilization techniques that preserve the gonads are recommended. On 126 female capybaras in the Brazilian state of São Paulo, a new surgical technique named “Passos Nunes” uterine horn ligature was performed after adequate general anesthesia. It achieved effective surgical sterilization, with an incision length of about 3 cm in the periumbilical linea alba, cranial to the pubis. After entering the abdominal cavity, the urinary bladder is pulled laterally to access the uterine horns and the cervix. The uterine horn is folded up, forming a strap; the distal portion of the strap is ligated and its distal end sectioned. The exact process is performed on the opposite horn. After the surgical procedure, the musculature is sutured in a sultan pattern and the subcutaneous tissue with a horizontal mattress pattern. The skin is sutured in a separate simple format, using nylon 2.0 for all steps. The wide exposure of the uterine horns facilitates the confirmation of pregnancy, allowing the surgeon to choose between salpingo hysterectomy or ligature of the uterine horns. The present study presents a new technique of surgical sterilization that can be used in female free-ranging mammals in which maintenance of the gonads is recommended, and births of offspring should not occur.

Surgical Anatomy for Sterilization Procedures in Female Capybaras

“…Their high adaptability to modified environments, with high phenotypic plasticity and genetic variability, may result in the remarkable success of the species in anthropogenic areas [4]. This plasticity allied to their high prolificity, with litter size ranging from 1-7 [2], has turned their coexistence with man into a problem in areas where capybaras are overpopulated and/or involved in zoonotic disease transmission, such as Brazilian spotted fever [5][6][7][8]. In this context, surgical sterilization has been recommended by public environmental organizations with the aim of population control [5].…”

“…Contraceptive methods that preserve the gonads are used in free-ranging wildlife population control [6,9,10]. Tube sterilization procedures in capybaras have been reported by Passos Nunes, Yanay, Ferraz, Rodrigues, Passos Nunes, and Yanai, [8,[10][11][12], using a lateral (flank) or ventral midline approach (LA).…”

“…Tube sterilization procedures in capybaras have been reported by Passos Nunes, Yanay, Ferraz, Rodrigues, Passos Nunes, and Yanai, [8,[10][11][12], using a lateral (flank) or ventral midline approach (LA). More effective access to uterine tubes (salpinx) via a bilateral flank approach was described by Yanai, whereas Passos Nunes [6,8] reported a uterine horn ligature technique using a ventral midline approach (on the linea alba-LA), obtaining good uterine horn exposure and hysterotomy performance in pregnant females. Tubal ligation, tubal transection (flank approach), and ovariohysterectomy (ventral midline approach) were also described by Boulanger [13] for surgical control of white-tailed deer (Odocoileus virginianus) populations in the United States, reinforcing both lateral and ventral approaches for contraceptive surgery in wild, free-ranging mammals.…”