Long-term non-surgical contraceptive methods for cats, especially community cats, are of global interest for cost-effective and humane reasons. This study aimed to investigate the effectiveness of a gonadotropin-releasing hormone (GnRH)-based vaccine for immunocontraception and to confirm its safety in intact female cats. Recombinant Salmonella typhimurium flagellin fljB (STF2)-GnRH protein was expressed in Escherichia coli. We divided female cats into vehicle control group (n = 4) and two experimental groups (100 μg injection group [n = 7] and 1000 μg injection group [n=7]), and immunized them twice intramuscularly (0.2 mL/cat at zero week and 4 weeks later into the other leg). Breeding trials started on day 120. All control cats (n = 4/4), 71% of the 100 μg injection group (n = 5/7), and 57% of the 1000 μg injection group (n = 4/7) became pregnant within 203 days after the introduction of male cats. The 1000 μg injection group had significantly a longer median time to conception following treatment (166 days) than the control (17 days, p < 0.05). Average litter size was significantly lower in the 1000 μg GnRH-vaccinated cats (2.8 ± 0.7) than in the control cats (4.5 ± 0.5, p < 0.05). Injection site reactions were not observed in any cat. The E. coli-expressed STF2-GnRH vaccine did not provide contraception in a sufficient proportion of the cats. However, it might be effective to suppress fertility through infertility vaccines before inducing permanent infertility through the trap-neuter-return.

Feral cats are widely considered to be leading the potential impacts on public health. This study aimed to provide estimates of vital data for feral cats relating Trap-Neuter-Return (TNR) to establish strategies effectively to manage feral cats in Pyeongtaek. Thus, this study focused on estimating feral cat population in Pyeongtaek and conducted a comparative analysis of the data for feral cats in Seoul (2013). The number of feral cats was estimated from 23,069 to 26,655 in Pyeongtaek, 2019. In relation to human population, when comparing the number of feral cats of Pyeongtaek and Seoul, it ranged from 4.57% to 5.28%, and from 1.97% to 2.55% respectively. This showed that Pyeongtaek was higher than Seoul. Fewer kittens were found in high-density areas, which the TNR project is believed to be generally effective in controlling the number of feral cats. In conclusion, in urban and rural complexes such as Pyeongtaek City, the number of feral cats compared to the population was higher than that of Seoul City, and the TNR program is believed to be somewhat effective in controlling the number of feral cats. When implementing TNR, it is necessary periodically to investigate the population and reflect them in policymaking.