Effectiveness of GonaCon as an immunocontraceptive in colony-housed cats

• Published in: Journal of feline medicine and surgery Vol. 20; no. 8; pp. 786 - 792
• Main Authors: Fischer, Amy, Benka, Valerie AW, Briggs, Joyce R, Driancourt, Marc-Antoine, Maki, Joanne, Mora, Darcy SO, Morris, Kevin N, Myers, Kayla A, Rhodes, Linda, Vansandt, Lindsey M, Weedon, George Robert, Wolf, Julie, Levy, Julie K
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01-08-2018
• Subjects: Animals; Cats; Contraception, Immunologic - methods; Contraception, Immunologic - veterinary; Female; Injections, Intramuscular; Male; Original; Pregnancy; Random Allocation; Vaccines, Contraceptive - administration & dosage
• ISSN: 1098-612X; 1532-2750
• DOI: 10.1177/1098612X18758549

Objectives
Non-surgical contraceptive management of free-roaming cat populations is a global goal for public health and humane reasons. The objectives of this study were to measure the duration of contraception following a single intramuscular injection of a gonadotropin-releasing hormone-based vaccine (GonaCon) and to confirm its safe use in female cats living in colony conditions.
Methods
GonaCon (0.5 ml/cat) was administered intramuscularly to 20 intact female cats (queens), and saline was administered to 10 queens serving as sham-treated controls. Beginning in late February, 4 months after injection, all cats were housed with fertile male cats in a simulated colony environment. Time to pregnancy, fetal counts and vaccine-elicited injection-site reactions were evaluated.
Results
All control cats (n = 10/10) and 60% (n = 12/20) of vaccinated cats became pregnant within 4 months of the introduction of males. Two additional vaccinates became pregnant (70%; n = 14/20) within 1 year of treatment. Average fetal counts were significantly lower in vaccinated cats than in control cats. Vaccinates had a significantly longer (P = 0.0120) median time to conception (212 days) compared with controls (127.5 days). Injection-site reactions ranging from swelling to transient granulomatous masses were observed in 45% (n = 9/20) of vaccinated cats.
Conclusions and relevance
A single dose of GonaCon provided contraception lasting for a minimum of 1 year in 30% (n = 6/20) of treated cats. The level of contraception induced by this GonaCon dose and vaccine lot was not sufficiently effective to be recommended for use in free-roaming cats.