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.
Human-wildlife conflicts are increasing worldwide. For instance, growing numbers of free-roaming feral cattle in Hong Kong are causing traffic accidents and damaging crops. Public antipathy towards lethal methods to manage wildlife has promoted research into alternative options, such as fertility control. The aims of this study were to assess the potential side effects and effectiveness of the injectable immunocontraceptive vaccine GonaCon on free-roaming feral cattle in Hong Kong. Sixty female cattle were captured and randomly assigned to treatment or control groups. Treatment animals were administered one dose of GonaCon, followed by a booster dose 3-6 months later. Control animals were administered an equivalent dose of a saline solution. The side effects of GonaCon were assessed by monitoring injection site, body condition and body weight at vaccination, at the booster stage and one year after initial vaccination. At the same times, blood samples were collected to quantify antibodies to the vaccine and to assess pregnancy status. GonaCon did not affect the body weight or body condition of cattle and had no adverse side effects such as injection site reactions, limping or abnormal behaviour. GonaCon did not appear to interrupt ongoing pregnancies but reduced fertility significantly: the proportion of pregnant animals in the GonaCon-treated group decreased from 76% at initial vaccination to 6% one year after vaccination, compared to 67% and 57% respectively in the control group. There was no difference between antibody titres at the booster stage or one year post vaccination, suggesting the booster dose maintained antibody levels. This study confirmed that GonaCon is safe and effective in inducing infertility in feral cattle, with a booster dose critical for maintaining infertility.
Currently there is no contraceptive vaccine that can cause permanent sterility in mares. This study investigates the effect of vaccination against oocyte-specific growth factors, Bone Morphogenetic Protein 15 (BMP-15) and Growth Differentiation Factor 9 (GDF-9), on ovarian function of mares. It was hypothesized that immunization against these growth factors would prevent ovulation and/or accelerate depletion of the oocyte reserve. For this study, 30 mares were randomly assigned to three groups (n = 10/group) and vaccinated with BMP-15 or GDF-9 peptides conjugated to KLH and adjuvant, or a control of phosphate buffered saline and adjuvant. Horses received vaccinations at weeks 0, 6, 12, and 18. Ovarian activity and estrous behavior were evaluated 3 days a week via ultrasonography and interaction with a stallion. The study was initiated on March1, 2016. Upon evaluation of ovulation rate, the GDF-9 group did not have a difference (P = 0.66) in ovulation rate when compared to controls (10.8 and 10.0 ovulations, respectively), but the number of ovulations in the BMP-15 group was less (P = 0.02; 4.9 ovulations). Average follicle size prior to ovulation was less (P < 0.0001) in both treatment groups compared to controls. Estrous behavior was altered in both the BMP-15 and GDF-9 groups compared to controls after the second vaccination (P = 0.05 and 0.03, respectively). Although further research is required to determine the continued effects of vaccination against GDF-9 on ovulation rates, these results indicate that vaccination against BMP-15 and GDF-9 could serve as a contraceptive in wild horse populations.
An experimental contraceptive vaccine was evaluated in Atlantic salmon (Salmo salar). A peptide derived from the beta subunit of luteinizing hormone (LH) was conjugated to two different carrier proteins, bovine serum albumin (BSA) and keyhole limpet hemocyanin (KLH), and formulated with one of four immunostimulants in a water-in-oil emulsion. Specific antibody responses to the peptide and each carrier protein were evaluated. While the antibody response to KLH was stronger than the response to BSA, both carrier proteins stimulated comparable antibody responses to the LH peptide. The immunostimulant proved to be more important for enhancing the LH peptide antibody response than the carrier protein selection; vaccines containing a combination of Aeromonas salmonicida and Vibrio anguillarum stimulated significantly greater LH peptide antibody production than any of the other three immunostimulants evaluated at 12 weeks post-vaccination. This study provides proof-of-concept for specific antibody production against a hapten-carrier protein antigen in Atlantic salmon and reinforces the importance of vaccine immunostimulant selection.
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