Neutering and reproductive disease in small mammals

• What are the reasons for an ovariohysterectomy?

  Prevent unwanted litters e.g. siblings, pelvic closure in guinea pigs.

  Protect against common diseases of the reproductive tract.

  Allow for rabbit pairing (male and female) and for groups of animals to live together e.g. singular male guinea pig with many females.
• What are the reasons for castration in exotic species?

  Prevents unwanted litters.

  Prevent spraying.

  Can help with aggression?

  Allow for rabbit pairing (male and female) and for groups of animals to live together.

  Protect against common diseases of the reproductive tract.
• Ovariohysterectomy in rabbits and guinea pigs

  Abdominal approach between the umbilicus and pubic symphysis.

  Careful tissue handling, especially with the gut adhesions easily formed.

  Haemostatic clips to ligate.

  Always use Intra dermal sutures to close the skin - they nibble and their friends nibble.

  Monofilament suture for ligatures, muscle, subcut and skin. Avoid skin glue if possible.
• Scrotal castration in exotic mammals

  Similar to a cat, except that the ingiunal canals must be closed if an open technique is used.

  1 to 1.5cm incision made through the skin and vaginal tunic ventrally on both sides of the scrotum, parallel to the penis.

  Testis is removed from the tunic and ligatures are placed.

  The large testicular fat pad is removed as well with the testes.

  Skin glue to close, sutures difficult in scrotal tissue.
• Why is scrotal castration not the preferred method for exotic mammals?

  It increases the chances of post-op complications.

  • Wound breakdown.
  • Infections/ Abscessation.
  • Scrotal haemotoma/ self trauma.
  • Gut stasis/ileus
• How to do a pre-scrotal castration?

  Similar to the dog, except an Open inguinal ring.

  Single midline incision cranial to the scrotum and each testis is pushed up into it.

  Except, some rodents have a penis that is positioned cranial to the testicles. In these cases a pre-scrotal technique can not be performed with a single midline incision lin in rabbits. Instead, two parallel incisions are made slightly lateral to the midline.
• How to do an abdominal castration?

  One midline incision going through the linea alba (at the cranial pole of the bladder).

  Testicle is pushed up into the abdomen from the scrotum. The testicle is then visualised from the abdomen and exteriorised.

  The tail of the epididymis os dissected fro the everted hemiscrotal sac to exteriorise.

  Tunic closure is the same with all three techniques.
• Why are pre-scrotal and abdominal castration the preferred method?

  It reduced the chances of some post-op complications:

  • One incision instead of two.
  • Wound further away from the ground so infection is less likely.
  • Less sensitive skin so self-trauma less likely.
  • Can suture the skin closed so you can avoid using itchy skin glue.
• Common reproductive rabbit conditions

  Testicular neoplasia

  Cryptorchidism

  Scrotal trauma

  Inguinal hernia

  Uterine adenocarcinoma

  Pregnancy toxaemia

  Pseudopregnancy

  Syphilis.
• Uterine adenocarcinoma

  Commonly accepted to have an 80% incdence in does >4 years old.

  Several studies showing this does not include a representative sample of rabbits, often related groups of lab bred rabbits.

  They are not as common in clinical practice as studies suggest.
• Clinical consideration of uterine adenocarcinoma

  Metastasise by direct contact, blood and lymph.

  Endometrial hyperplasia/endometritis/pyometra might be present.

  Endometrial venous aneurisms causes potentially life threatening bleeding.
• Syphilis in rabbits

  Caused by the spirochete, Treponema cuniculi.

  Spread during copulation and close contact.

  Crusting lesions on the mucocutaneous junction of nose, lips, eyelids, genitalia and anus.
• Ovarian cysts in guinea pigs

  Common in entire female guinea pigs.

  Easily palpated on physical exam.

  Confirm with ultrasound or just with clinical signs.

  Can be confused with cystic/ irregular kidneys or other masse on radiography.
• Clinical signs of ovarian cysts in the guinea pigs

  Hair loss over flanks without pruritus and normal skin.

  Pear shaped

  Behaviour - mounting/ aggression

  Lethargy, reduced appetite, discomfort when handled
• Common reproductive conditions in the guinea pig

  Testicular neoplasia

  Spermatic pugs

  Inguinal hernia

  Orchitis

  Uterine and ovarian neoplasia

  uterine proplapse

  Pregnancy toxaemia

  Ovarian cysts

  Dystocia
• Normal birth in guinea pigs.

  Normal birth:

  • Relaxin from pituitary and endometrium causes fibrocartilage of the pubic symphysis to disintegrate = pubic symphysis widens to 3cm
• Dystocia in guinea pigs

  Abnormal birth:

  • If an owner does not breed before 8 months of age the pubic symphysis will be unable to separate = dystocia.
  • Parturition is normally in early hours, so if presented during the day = likely dystocia.

  Other causes:

  • Obesity, large foetuses, and uterine inertia.
• Common reproductive conditions in the chinchilla

  Fur ring (paraphimosis)

  Spermatic plugs.

  Inguinal hernia

  Uterine neoplasia.

  Pyometra

  Dystocia
• Common reproductive conditions in the gerbil

  Cystic ovaries

  Neoplasia
• Common reproductive conditions in the hamster

  Cystic ovaries

  Neoplasia

  Pyometra (normal creamy vulvar discharge occurs following oestrus)
• Common reproductive conditions in the rat

  Pyometra

  Neoplasia e.g. mammary adenomas
• Common reproductive conditions in the hedgehog

  Pyometra

  Neoplasia
• Mammary tumours - guinea pigs

  Benign hyperplasia most likely diagnosis in females.

  Males higher chance of malignancy.
• Mammary tumours - rats

  Carcinomas = less than 10% of mammary tumours.

  Fibroadenoma = 85-90% of all mammary tumours. They can become very large, ulcerate, and infiltrate locally, but they rarely metastasise.
• Mammary tumours - mice and gerbils

  Adenocarcinoma most common, highly malignant and common metastasises, poor prognosis.

  Fibrosarcoma only account for up to 6% of mouse tumours.
• Mammary tumours - hamster


  Most are benign
• Common reproductive conditions in the Ferret

  Testicular neoplasia

  Prostate hyperplasia

  Ovarian neoplasia

  Pyometra

  Pregnancy toxaemia

  Persistent oestrus

  Hyperadrenocorticism.
• Ferret persistent oestrus

  Ferret breeding season is March - September

  Jills are induced ovulators

  About 50% of Jill’s will remain in oestrus unless mated.

  Prolonged oestrus results in oestrogen-induced bone marrow toxicosis/hyperoestrogenism.

  Results in pancytopaenia and eventually death.
• Clinical signs of persistent oestrus in ferrets

  Swollen vulva.

  Pale mucous membranes

  Symmetrical bilateral alopecia of flanks and tail.

  Petechiae and/or ecchymoses.

  Lethargy and anorexia.
• Ferret hyperadrenocorticism

  Not cushings (no excess of glucocorticoids).

  In ferrets HAC is related to sex hormones.

  Symptoms start in Spring, mat regress and return next year.

  Suspected causes:

  • >12 hours day lights (indoor ferrets).
  • Early neutering (never seen in entire ferrets)
  • Genetic component
• What are the hormones behind ferret hyperadrenocorticism

  GnRH (hypothalamus) -> FSH/LH (pituitary) -> Oestradiol or Testosterone (Gonads) -> Negative feedback reduced GnRH secretion.
• Clinical signs of ferret hyperadrenocorticism

  Symmetrical/bilateral alopecia and rat tail.

  Vulvar swelling in neutered Jill’s.

  Sexual behaviour in neutered hobs.

  Pruritus

  Dysuria/urinary obstruction in males (Prostate)

  Mammary hyperplasia.
• Common reproductive conditions Diagnostic tests

  Diagnosis can often be made based on clinical exam and history e.g. syphilis, persistent oestrus.

  Blood tests - e.g. biochemsitry, can be useful to rule in or out other differentials. Other body systems specific tests can also help with this, e.g. skin scraps and hair plucks when hair loss is involved.

  Some specific hormone assays are available at exotics labs.

  Culture and sensitivity is useful for diagnosing/treating infections.

  Cytology/histology of masses e.g. mammary, uterine, others.
• Common reproductive conditions diagnosis with imaging

  Radiographs:

  • Useful for screening, can identify large space occupying lesions but it can be hard to identify the organ and structure involved.

  Ultrasound:

  • More detail compared to radiographs, generally more useful for making a diagnosis. Can be challenging in hindgut fermenters due to gas build up.

  CT

  • Superior for diagnosing but expensive and will often require referral.
• Treatment for reproductive issues in exotic mammals

  Ovariohysterectomy e.g. uterine adenocarcinoma, cystic ovaries, pyometra.

  Caesarean section e.g. dystocia.

  Antibiotics e.g. penicillin for syphilis.

  Hormonal therapy e.g. GnRH injections for cystic ovaries, often given after ultrasound guided cyst aspiration.

  Mammary mass removal +/- cabergoline in rats.
• Ferret Hyperadrenocorticism - GnRH Agonists

  Pulse release GnRH over a long period of time.

  This desensitises GnRH receptors on the pituitary so less FSH/LH is produced.

  So temporarily the clinical signs may worsen before desensitisation occurs.
• Ferret Hyperadrenocorticism - Surgical treatment

  Left adrenolectomy relatively straightforward.

  Right adrenalectomy more difficult.

  Some advocate partial right adrenalectomy.

  Post-operative medical treatment for HAC required if partial adrenoalectomy performed.
• Treatment for ferret persistent oestrus - early oestrus

  Stimulate ovulation = hCG

  GnRH agonist implant e.g. Deslorelin.

  These take time to work (10-14 days) and bone marrow suspension occurs 4 weeks into season, death occurs at around 8 weeks
• Treatment for ferret persistent oestrus - Severe oestrus

  Blood transfusion may be required.

  Ovariohysterectomy but must stabilise first and causes HAC risk.
• Reproductive control in female ferrets

  Keep females with a vasectomised hob to induce ovulation.

  Leave entire and give a yearly ‘Jill jab’ to bring females out of season (proligesterone injections as soon as they come into heat).

  Use the hormone implant to chemically neuter on its own (deslorin)