Friary, J. (2006). Evaluation of a Gonadotropin releasing hormone vaccine for the humane control of female feral cats. (Doctoral dissertation, University of Florida).
The unwanted cat population in the United States numbers in the tens of millions and current control measures have only had limited success in reducing it. Immunocontraception has the potential to humanely reduce this population. The purpose of this study was to investigate the effectiveness of a GnRH-based vaccine for immunocontraception of female cats. It was expected that the treated cats would produce antibodies against GnRH and there would be a positive correlation between high titer and contraception. Adult female cats were divided into a sham group (n = 5) and a treatment group (n = 15) that was immunized once with 200 µg of synthetic GnRH coupled to keyhole limpet hemocyanin and combined with a mycobacterial adjuvant. GnRH antibody titer and serum concentrations of progesterone and estradiol-17β were determined monthly. For the duration of the study the daily photoperiod was manipulated in an attempt to induce estrus. A male breeding cat was housed with the females during the long-day periods, and continuous videography was used to monitor for signs of estrus and breeding. GnRH antibodies were detected in all treated cats by 150 days after immunization, but when the titer in four cats fell below 16,000, they became pregnant and were classified as nonresponders. The titers of the remaining 11 cats (responders) never decreased below 16,000. These cats displayed no signs of behavioral estrus and did not become pregnant by the end of the study 24 months after immunization. All five sham cats became pregnant within one month of the introduction of the male cat. From 60 days after immunization until the end of the study, progesterone concentrations in all responders remained at basal levels, and increased two months before parturition in all cats that became pregnant. The responder cats gained more weight than the nonresponders during the 14 months after immunization (P = 0.004), which is the same response observed in surgically sterilized cats. A single dose of GnRH vaccine resulted in contraception in 73% of the cats for at least 24 months.
The unwanted cat population in the United States numbers in the tens of millions and current control measures have only had limited success in reducing it. Immunocontraception has the potential to humanely reduce this population. The purpose of this study was to investigate the effectiveness of a GnRH-based vaccine for immunocontraception of female cats. It was expected that the treated cats would produce antibodies against GnRH and there would be a positive correlation between high titer and contraception. Adult female cats were divided into a sham group (n = 5) and a treatment group (n = 15) that was immunized once with 200 µg of synthetic GnRH coupled to keyhole limpet hemocyanin and combined with a mycobacterial adjuvant. GnRH antibody titer and serum concentrations of progesterone and estradiol-17β were determined monthly. For the duration of the study the daily photoperiod was manipulated in an attempt to induce estrus. A male breeding cat was housed with the females during the long-day periods, and continuous videography was used to monitor for signs of estrus and breeding. GnRH antibodies were detected in all treated cats by 150 days after immunization, but when the titer in four cats fell below 16,000, they became pregnant and were classified as nonresponders. The titers of the remaining 11 cats (responders) never decreased below 16,000. These cats displayed no signs of behavioral estrus and did not become pregnant by the end of the study 24 months after immunization. All five sham cats became pregnant within one month of the introduction of the male cat. From 60 days after immunization until the end of the study, progesterone concentrations in all responders remained at basal levels, and increased two months before parturition in all cats that became pregnant. The responder cats gained more weight than the nonresponders during the 14 months after immunization (P = 0.004), which is the same response observed in surgically sterilized cats. A single dose of GnRH vaccine resulted in contraception in 73% of the cats for at least 24 months.
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