EFFECTS OF PORCINE ZONA PELLUCIDA IMMUNOCONTRACEPTIVES IN ZOO FELIDS

Lynx canadensis (Carnivora: Felidae)

 Lynx canadensis Kerr, 1792, commonly called the Canada lynx, is a medium size felid and is the second largest of the four species in the genus Lynx. It is distributed throughout the boreal forest of most of Canada and Alaska and across portions of the northern United States. It prefers dense, regenerating coniferous forests with moderate canopy and understory cover. L. canadensis is a snowshoe hare specialist, and its ecology, morphology, and behavior closely reflect that of its main prey. It is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources, is on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and its population size trend is considered stable. However, the status of United States subpopulations, being largely peripheral to the Canadian population, is more tenuous and the species is protected.

Laparoscopic ovariectomy with a single-port multiple-access device in seven African lionesses (Panthera leo)

CASE DESCRIPTION 7 privately owned female African lions (Panthera leo) that had been bred for public exhibition and were housed in outdoor pens were evaluated prior to undergoing elective ovariectomy. CLINICAL FINDINGS All animals were healthy. Median age was 15 months (range, 9 to 34 months), and median body weight was 71 kg (156 lb; range, 48 to 145 kg [106 to 319 lb]). TREATMENT AND OUTCOME Surgical sterilization by means of single-incision laparoscopic ovariectomy was elected. A 2- to 3-cm-long skin incision was made just caudal to the umbilicus, and a single-port multiple-access device was bluntly inserted through the incision. Traction was maintained with stay sutures to provide counterpressure, and three 5-mm-diameter cannulae were introduced through the device's access channels with a blunt trocar. The abdomen was insufflated to a pressure of 12 mm Hg with CO₂. Each ovary was grasped and suspended with a standard 36-cm-long laparoscopic grasper, and ovariectomy was performed with a 5-mm vessel sealer and divider device. Because of the depth of subcutaneous fat, extensive subcutaneous dissection was necessary to insert the single-port device. In contrast, fat content of the mesovarium was minimal and did not vary markedly among animals. Subjectively, single-incision laparoscopic ovariectomy was easily performed, but all surgeons had experience in laparoscopic surgery. Median duration of the surgical procedure was 29 minutes (range, 21 to 49 minutes). No perioperative complications were encountered. CLINICAL RELEVANCE Findings suggested that the single-incision laparoscopic technique may be an acceptable, minimally invasive option for ovariectomy of large felids.

Immunocontraception for Animals: Current Status and Future Perspective

An alternative to surgical sterilization for fertility control of animals (wild, zoo, farm, and domestic) is needed to prevent problems related to overpopulation, including culling and relocation. A PubMed and Google Scholar database search was conducted using the keywords 'contraceptive vaccine animals,' 'immunocontraception animals,' 'non-surgical sterilization animals,' 'PZP vaccine,' and 'GnRH vaccine.' The searches from 1972 to 2015 yielded over 1500 publications. These articles were read, and 375 were selected for detailed analysis. Articles referenced in these publications were also thoroughly examined. PZP and GnRH contraceptive vaccines (CVs) have been extensively investigated for fertility control of wild, zoo, farm, and domestic animal populations. Both vaccines have shown tremendous success with PZP vaccines taking the lead. Novel technologies and targets are being developed to improve existing vaccines and generate second-generation CVs. Single-shot vaccines, which can be delivered remotely, will greatly advance the field of immunocontraception for animal use with potential human application.

Ecological feedbacks can reduce population-level efficacy of wildlife fertility control

Anthropogenic stress on natural systems, particularly the fragmentation of landscapes and the extirpation of predators from food webs, has intensified the need to regulate abundance of wildlife populations with management. Controlling population growth using fertility control has been considered for almost four decades, but nearly all research has focused on understanding effects of fertility control agents on individual animals. Questions about the efficacy of fertility control as a way to control populations remain largely unanswered.Collateral consequences of contraception can produce unexpected changes in birth rates, survival, immigration and emigration that may reduce the effectiveness of regulating animal abundance. The magnitude and frequency of such effects vary with species-specific social and reproductive systems, as well as connectivity of populations. Developing models that incorporate static demographic parameters from populations not controlled by contraception may bias predictions of fertility control efficacy.Many population-level studies demonstrate that changes in survival and immigration induced by fertility control can compensate for the reduction in births caused by contraception. The most successful cases of regulating populations using fertility control come from applications of contraceptives to small, closed populations of gregarious and easily accessed species.Fertility control can result in artificial selection pressures on the population and may lead to long-term unintentional genetic consequences. The magnitude of such selection is dependent on individual heritability and behavioural traits, as well as environmental variation.Synthesis and applications. Understanding species' life-history strategies, biology, behavioural ecology and ecological context is critical to developing realistic expectations of regulating populations using fertility control. Before time, effort and funding are invested in wildlife contraception, managers may need to consider the possibility that many species and populations can compensate for reduction in fecundity, and this could minimize any reduction in population growth rate.

Immunoglobulin to zona pellucida 3 mediates ovarian damage and infertility after contraceptive vaccination in mice

Antibodies reactive with the ovarian glycoprotein zona pellucida (ZP) have been linked with human female infertility. Anti-fertility vaccines that target ZP antigens have been utilized to restrict pest animal populations and their efficacy is associated with ovary-specific antibody induction. However, the necessity for zona pellucida-specific antibody in mediating infertility has not been examined in vivo. A recombinant mouse cytomegalovirus vaccine encoding murine zona pellucida 3 that induces rapid and complete infertility in BALB/c mice has been produced. The onset of infertility is temporally related to the presence of antibody sequestered into ovarian follicles and binding to the ZP of infected mice and the loss of mature follicles. When this vaccine was inoculated into immunoglobulin-deficient BALB/c mice with a null mutation in the immunoglobulin mu chain gene Igh-6, fertility was unaffected. Passive transfer of serum containing ZP3 antibodies also elicited transient infertility. Electron microscopy of ovarian tissue collected from ZP3-immunized immunocompetent mice demonstrated significant focal thinning of the zona pellucida (ZP) with reduced length and concentration of transzonal processes and many oocytes displayed evidence of injury. None of these changes were found in vaccinated immunoglobulin-deficient mice. These data confirm that ZP3-reactive antibody is necessary and sufficient to induce autoimmune-mediated follicular depletion and fertility suppression following the inoculation of this vaccine, and suggest that this is due to impaired zona pellucida formation. These findings have relevance in understanding the etiology of autoimmune ovarian disease in woman where anti-ZP antibodies are likely to have a causal role in infertility.

Does contraceptive treatment in wildlife result in side effects? A review of quantitative and anecdotal evidence

The efficacy of contraceptive treatments has been extensively tested, and several formulations are effective at reducing fertility in a range of species. However, these formulations should minimally impact the behavior of individuals and populations before a contraceptive is used for population manipulation, but these effects have received less attention. Potential side effects have been identified theoretically and we reviewed published studies that have investigated side effects on behavior and physiology of individuals or population-level effects, which provided mixed results. Physiological side effects were most prevalent. Most studies reported a lack of secondary effects, but were usually based on qualitative data or anecdotes. A meta-analysis on quantitative studies of side effects showed that secondary effects consistently occur across all categories and all contraceptive types. This contrasts with the qualitative studies, suggesting that anecdotal reports are insufficient to investigate secondary impacts of contraceptive treatment. We conclude that more research is needed to address fundamental questions about secondary effects of contraceptive treatment and experiments are fundamental to conclusions. In addition, researchers are missing a vital opportunity to use contraceptives as an experimental tool to test the influence of reproduction, sex and fertility on the behavior of wildlife species.

Contraceptive potential of porcine and feline zona pellucida A, B and C subunits in domestic cats

Feral cat populations are a major problem in many urban regions throughout the world, threatening biodiversity. Immunocontraception is considered as an alternative and a more humane means to control overpopulation of pest animals than current methods including trapping, poisoning and shooting. In this study, we evaluate porcine zona pellucida (ZP) polypeptide (55 kDa) and feline ZP A, B and C subunits expressed by plasmid vectors as candidate vaccines against fertility in the female domestic cat. Cats were injected subcutaneously with three doses of the ZP vaccines. Vaccinated cats were compared with naïve cats for ZP-antibody response, ovarian histology and fertility after mating. Vaccination with native porcine ZP 55 kDa polypeptide induced anti-porcine ZP antibodies detected by ELISA. However, these antibodies did not cross-react with feline ZP as assessed by immunohistochemistry and no effect on fertilityin vivowas observed after mating. However, vaccination of cats with feline ZPA or feline ZPB+C DNA vectors elicited circulating antibodies specific for feline ZP as assessed by ELISA, with reactivity to native feline ZP in ovarian folliclesin situ. Vaccination with feline ZPA and ZPB+C DNA did not elicit changes in ovarian histology. Although sample sizes were small, conception rates in mated females were 25 and 20% in the ZPA and ZPB+C vaccinated groups respectively, compared with 83% in the control group. We conclude that feline ZPA and ZPB+C subunits are potential candidate antigens for immunocontraceptive vaccines in the domestic cat.

Inoculation of female American black bears (Ursus americanus) with partially purified porcine zona pellucidae limits cub production

The present 2-year study investigated the feasibility of using porcine zona pellucidae (pZP) as antigen for immunocontraception in American black bears. Sows, 3–6 years of age, were administered either two doses of 250 µg pZP with Freund’s adjuvant (n = 10) or adjuvant alone (n = 5), one in April and one in May, and were kept away from the boars until June. Serum samples were collected before injections and before denning (November). The presence of sows with cubs at side was observed during premature emergence from denning. First-year results indicated that anti-pZP antibody titres in vaccinated sows were 2.5–9.0-fold (range) higher compared with non-vaccinated sows and that the vaccinated sows were threefold less likely to become pregnant (P = 0.167). Control and vaccinated bears produced 1.6 and 0.2 cubs per sow, respectively (P = 0.06). The second-year study investigated the feasibility of using pZP sequestered in a controlled-release pellet and a water-soluble adjuvant (QS-21) to avoid regulatory problems associated with Freund’s adjuvant. Sows in the treatment group (n = 22) were administered a single dose of an emulsion of 250 µg pZP and 150 μg QS-21 plus a pellet containing 70–90 µg pZP for delayed release as booster dose. Control sows (n = 5) received the QS-21 adjuvant in pellet alone. Serum samples were collected before inoculations (April) and before denning (November). Seven cubs were born to the five control sows, but none was born to the 22 vaccinated sows (P < 0.001). Anti-pZP antibody mean absorbance ratios in control sows remained at background levels, whereas vaccinated sows had ratios fourfold higher than controls. Two-dimensional polyacrylamide gel electrophoresis and immunohistochemical localisation confirmed immunoreactivity of sera from inoculated bears. We conclude that cub production in the American black bear can be effectively limited with either two injections of 250 μg pZP or a single inoculation of partially purified pZP sequestered in controlled-release pellets.

Immunocontraception of mammalian wildlife: ecological and immunogenetic issues

Immunocontraception involves stimulating immune responses against gametes or reproductive hormones thus preventing conception. The method is being developed for the humane control of pest and overabundant populations of mammalian wildlife. This paper examines three fundamental issues associated with its use: (1) the difficulties of obtaining responses to self-antigens, (2) the likely evolution of genetically based non-response to immunocontraceptive agents, and (3) the possible changes in the array of pathogens possessed by the target species after generations of immunocontraception. Our review of the literature demonstrates that the barriers to an effective immunocontraceptive are at present very basic. Should they be overcome, the effects of immunocontraception on the immunogenetic constitution of wildlife populations through the selection for non-responders must be examined. We suggest that the attempt to use the animal’s own immune system to modulate reproduction may be incompatible with the basic biological function of protection against infectious disease. Research programs on mammalian immunocontraception should involve measurement of the heritability of non-response and an assessment of the likely change in the response of the contracepted population to possible pathogens.

Contraception in felids

Contraceptives are used for reversible reproductive control in genetically valuable wild felids, as permanent reproductive control in generic wild felids, and as an economically practicable means to control feral cats. The progestin contraceptives, megestrol acetate, melengesterol acetate, medroxyprogesterone acetate, and levonorgestrol (administered orally, in implants, or as depot injections), are effective in preventing pregnancy. However, long-term use is associated with endometrial hyperplasia, endometrial cancer, and mammary cancer. Gonadotropin releasing hormone analogs or luteinizing hormone vaccines that achieve contraception by suppressing ovarian or testicular function, do not have the adverse health effects of progestins. However, reliable reversibility has not been demonstrated, and male secondary sex characteristics may be suppressed. Bisdiamines also inhibit spermatogenesis and lower circulating testosterone concentrations in treated male cats. Porcine zona pellucida vaccines are ineffective contraceptives in felids and may cause serious health problems when combined with some adjuvants. Because of the limited availability of non-progestin contraceptives and side effects associated with some agents, widespread application of contraception to felids has been curtailed. More non-steroidal methods of contraception should be tested in the future to provide alternatives for controlling reproduction in felids. Furthermore, all empirical information on contraceptive safety and efficacy should be assembled in a database to provide the knowledge needed by veterinarians and managers to determine benefits/risks of currently available contraceptives in felids, both domestic and wild.