One-year reproductive effects of anti-GnRH and rabies vaccination in female pet cats.

Domestic cats are highly prolific, contributing to overpopulation that negatively affects animal welfare, wildlife biodiversity, and public health. Although surgical sterilization is widely used to prevent cat reproduction, it has important practical, economic, and ethical limitations. We studied the safety, immune response, and reproductive effects of a contraceptive anti-GnRH vaccine (Gonacon), administered concurrently with a rabies vaccine, in female pet cats living under normal home conditions. The combined vaccination was generally safe, and most queens maintained protective immunity against rabies. However, the contraceptive effects varied considerably among animals. Indoor queens developed stronger, longer-lasting immune responses and experienced fewer signs of heat and fewer pregnancies than outdoor queens. In contrast, many outdoor queens showed weaker and shorter-lasting immune responses. These findings suggest that the combined vaccination may provide a practical non-surgical approach to controlling reproduction in some pet cats, but that living conditions can strongly influence its effectiveness.