Update on medical control of reproduction in bitch with a focus on deslorelin implant

Abstract

Medical control of reproduction in the bitch is a huge challenge. Currently, only progestins are officially marketed for this purpose but
they have undesirable effects. Subcutaneous implants containg GnRH agonist deslorelin have been released in the European market.
They may be used ‘off-label’ to prevent cyclicity in adult bitches. A 4.7 mg deslorelin implant (after an initial ‘flare-up’ in increases
in pitutary release of gonadotropins [FSH and LH] and subsequent downregulation) prevents estrus for ~ 10 months on an average,
with large individual variations. The major disadvantage of using deslorelin implants in adult bitches is the initial induction of estrus
soon after implantation. Currently, there are no 100% satisfactory protocols aviable to prevent this effect. Additionally, deslorelin
treatment may sometimes cause side effects (e.g. prolonged estrus, ovarian cysts, prolonged lactation or even and rarely uterine disease).
Ultrasonographic examination of ovaries and uterus is mandatory to ensure that there are no pathologies (e.g. ovarian cysts or cystic
endometrial hyperplasia) present prior to treatment. If the bitch does not develop any side effects in the first weeks after first implantation,
she can be reimplanted regularly several times and even life-long without any subsequent problem. A single treatment with a deslorelin
implant does not compromise fertility of the bitch in subsequent estruses. Treatment of prepubertal bitches before 6 months of age is
useful to prevent induced estrus. However, it delays puberty and therefore prevents external genital development during treatment, but it
does not seem to have any subsequent effect on growth or health. Future approaches of contraception in bitches are in use of aromatase
inhibitors, immunocontraception, especially antiGnRH immunization, drugs counteracting the effects of kisspeptins, and genetically
mediated contraception.