Rabbit Reproductive Problems and Surgery
Karen L. Rosenthal, DVM, MS, Diplomate ABVP-Avian
Many disorders seen in pet rabbits are related to the reproductive tract. The veterinarian that treats pet rabbits needs to be aware of the special considerations in neutering procedures and the common diseases of the rabbit reproductive tract.
Castration in rabbits is a frequent procedure. Castration helps to decrease such behaviors as aggression and urine spraying. Like other animals, if these are repetitive behaviors then castration may not stop these offensive activities. But if neutered early enough, both aggressiveness and urine spraying can be curtailed if not totally stopped. Castration also prevents matings in multi-rabbit households. Most rabbits can be castrated at three to four months of age although others have recommended even earlier castration because rabbits may become sexually mature before four months of age.
The disadvantages of castration are few. There is the risk of anesthesia and surgical complications that are always present in rabbit surgery. Also, as in all castrations, the ability to reproduce is lost.
There are two primary methods used to castrate a rabbit- the open method and the closed method. The open technique is used with caution. This is because of an increased risk of herniation using the open method due to the open inguinal rings and the opening of the tunic. In the open method, an incision is made over the ventral aspect of each scrotal sac. The testes is retracted and the tunic is cut and stripped down exposing the vessels and cord. The cord and vessels are double ligated and replaced into the incision site and assessed for bleeding. The inguinal ring and/or tunic is then sutured closed and the procedure is repeated on the opposite side. The open method does allow the advantage of being able to visualize the vessels and greater security in knowing that the vessels are ligated. If an open castration is done by mistake, one can first try to close the tunic if only a small hole or tear is in the tunic. If the hole in the tunic is large, then one can close the inguinal ring. Also, with the open method there is the possibility of infection seeding into the abdomen.
Many prefer the closed method of castration. There is less of a chance of herniation with this method as the tunic remains closed. Again, an incision is made on the ventral aspect of each scrotum. The pedicle is then transfixed once and a circumferential ligature is placed so there are two ligatures on the pedicle. The scrotal skin is closed with tissue glue. The disadvantage of this method is the chance of a slipped ligature on the vessels due to decreased visualization.
Ovariohysterectomy (OHE) in rabbits is a frequently performed. The most common reasons to perform an OHE in a rabbit is to prevent uterine adenocarcinoma and to prevent breeding. All female rabbits are at risk of developing uterine adenocarcinoma. Rabbit spays also prevent the occurrence of pseudopregnancies. Pseudopregnancies can follow sterile matings, LH injections, or mountings by does. Also, female rabbits can become territorially aggressive and OHE may prevent this. The disadvantage of OHE is the risk of anesthesia and surgical complications. Also, the female will not be able to breed.
To perform an OHE in a rabbit, an incision is made on the abdomen. Ovariohysterectomy is performed much like a dog or cat. There are a few differences. The uterus is normally visible and a spay hook is rarely necessary. A double cervix (bicornate) is present. Ligate the reproductive tract just distal to the cervix in the thinner vaginal tissue rather than in the thicker cervical tissue. Unlike in the dog and cat, the uterine arteries do not lie adnexal to the uterus or cervix. They actually lie to the side in the broad ligament. They are ligated separately. About one third of the time there are accessory vessels emanating from the uterine vessels in the broad ligament. They are not always symmetrical and they must be ligated. It therefore is best not to just strip out the broad ligament and tug on it as one might in a dog and cat. Major vessels can be torn. Unlike dogs and cats, it is not recommend to pull on ligaments. In rabbits, they are more delicate structures and can break unexpectedly. Fat storage in the broad and ovarian ligaments impedes visualization of vessels. The ovarian ligament is very slack and cannot be broken by strumming. It is delicate and can be easily broken if tugged upon such as used to lift the ovary into the field of view. The ovaries are usually buried in fat and one is tempted to pull on the ligament. Once the abdominal surgery is completed, the rabbit is closed in the same manner as are dogs and cats except that subcuticular suture patterns are used frequently.
Mastitis occurs mostly in lactating does but can occur in pseudopregnancy. Predisposing causes are heavy milk producers, injury to the glands by young or other does, biting of the teats, and poor sanitation. Signs of mastitis include fever, inappetance, thirst, depression, septicemia, and even death. The mammary glands are usually swollen, hot, and firm. Infection can spread from gland to gland even though originally only one gland was affected. Foster nursing of pups to a healthy doe is not recommended as infection easily spreads with this practice. Staphylococcus sp. is the most commonly isolated organism but Streptococcus sp. is also found. Death is due to septicemia. Treatment is with antibiotics such as quinolones at 10-30 mg/kg q24hrs SC, IM, PO, or trimethoprim-sulfa medications at 30 mg/kg SC, IM, PO q12hrs, or penicillin at 50,000-100,000 units IM q12hrs. Antibiotic decisions should be based on culture and MIC results.
Pregnancy toxemia is seldom recognized in rabbits. It is seen in pregnant, pseudopregnant, and post partum rabbits. Obese rabbits are especially at risk. During pregnancy, it is most common during the last week of gestation. An important contributing factor is an inadequate nutritional supply to the uteroplacental unit. This is normally due to nutritional imbalances such as fasting. Signs of this disease include depression, abortion, acetone odor to breath, coma, ketonuria, and death. Since treatment is usually unrewarding, prevention is most important. This is accomplished by proper nutrition.
Treponema cuniculi causes rabbit syphilis. This is a venereal disease due to spirochetes. Transmission is by genital or extragenital contact. This disease localizes and proliferates on the skin and mucosa near mucocutaneous junctions such as the external genitalia, chin, lips, face, and nostrils. It spreads on the body by autoinfection. Minute vesicles turn into focal ulcerations which then turn into crusts and dry scaly, red areas. Diagnosis is by signs, response to treatment, dark field microscopy, or silver stain smears of tissue sections. Serologic tests are also available. Penicillin is the treatment of choice.
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