Restoration of reproductive potential following expiration or removal of melengestrol acetate contraceptive implants in golden lion tamarins (Leontopithecus rosalia)

Infant survival is significantly impacted by dam- and management-related factors in zoo-managed Eulemur populations

Due to their potential impact on population growth, many studies have investigated factors affecting infant survival in mammal populations under human care. Here we used more than 30 years of Association of Zoos and Aquariums (AZA) studbook data and contraception data from the AZA Reproductive Management Center, along with logistic regression models, to investigate which factors affect infant survival in four Eulemur species managed as Species Survival Plans® in AZA. Across species, infant survival to 1 month ranged from 65% to 78%. Previous experience producing surviving offspring was positively correlated to infant survival in collared (Eulemur collaris), crowned (Eulemur coronatus), and mongoose (Eulemur mongoz) lemurs. Both dam age and previous use of contraception were negatively correlated to infant survival for collared lemurs, though our results suggest the latter may be confounded with other factors. Blue-eyed black lemurs (Eulemur flavifrons) were affected by birth location, suggesting differences in husbandry that may affect infant survival. These results can be used to assist in reproductive planning or to anticipate the likelihood of breeding success. Population managers may also be able to focus their reproductive planning on younger dams or those with previous experience to predict successful births. Future studies should seek to determine what aspects of previous dam success are most important to infant survival, investigate sire-related factors, and examine factors related to cause of death in infants that may lead to differential survival. Our hope is to present a framework that may be useful for investigating infant survival in other mammal species' breeding programs.

Oral immunocontraceptive vaccines: A novel approach for fertility control in wildlife

The overabundant populations of wildlife have caused many negative impacts, such as human-wildlife conflicts and ecological degradation. The existing approaches like injectable immunocontraceptive vaccines and lethal methods have limitations in many aspects, which has prompted the advancement of oral immunocontraceptive vaccine. There is growing interest in oral immunocontraceptive vaccines for reasons including high immunization coverage, easier administration, frequent boosting, the ability to induce systemic and mucosal immune responses, and cost-effectiveness. Delivery systems have been developed to protect oral antigens and enhance the immunogenicity, including live vectors, microparticles and nanoparticles, bacterial ghosts, and mucosal adjuvants. However, currently, no effective oral immunocontraceptive vaccine is available for field trials because of the enormous development challenges, including biological and physicochemical barriers of the gastrointestinal tract, mucosal tolerance, pre-existing immunity, antigen residence time in the small intestine, species specificity and other safety issues. To overcome these challenges, this article summarizes achievements in delivery systems and contraceptive antigens in oral immunocontraceptive vaccines and explores the potential barriers for future vaccine design and application.

Reproductive one health in primates

One Health is a collaborative trans-disciplinary approach to health; integrating human, animal, and environmental health. The focus is often on infection disease transmission and disease risk mitigation. However, One Health also includes the multidisciplinary and comparative approach to disease investigation and health of humans, animals, and the environment. One key aspect of environmental/ecosystem health is conservation, the maintenance of healthy, actively reproducing wildlife populations. Reproduction and reproductive health are an integral part of the One Health approach: the comparative aspects of reproduction can inform conservation policies or breeding strategies (in situ and ex situ) in addition to physiology and disease. Differences in reproductive strategies affect the impact poaching and habitat disruption might have on a given population, as well as ex situ breeding programs and the management of zoo and sanctuary populations. Much is known about chimpanzees, macaques, and marmosets as these are common animal models, but there is much that remains unknown regarding reproduction in many other primates. Examining the similarities and differences between and within taxonomic groups allows reasonable extrapolation for decision-making when there are knowledge gaps. For example: (1) knowing that a species has very low reproductive rates adds urgency to conservation policy for that region or species; (2) identifying species with short or absent lactation anestrus allows ex situ institutions to better plan contraception options for specific individuals or prepare for the immediate next pregnancy; (3) recognizing that progestin contraceptives are effective contraceptives, but may be associated with endometrial hyperplasia in some species (in Lemuridae but not great apes) better guides empirical contraceptive choice; (4) recognizing the variable endometriosis prevalence across taxa improves preventive medicine programs. A summary of anatomical variation, endocrinology, contraception, pathology, and diagnostics is provided to illustrate these features and aid in routine physical and postmortem examinations as well as primate management.

Melengestrol acetate contraceptive implant use in colobus monkeys (Colobus guereza): Patterns through time and differences in reproductive potential and live births

Melengestrol acetate (MGA) implants are progestin-based reversible contraceptives used to manage fertility in zoo populations. Although it is recommended that MGA implants should be replaced every 2 years, the duration of efficacy has not been systematically evaluated in most species. Anecdotal reports for Old World monkeys indicate that reproduction may be suppressed longer if the implant is not removed. This study uses Guereza colobus monkey (Colobus guereza) as a model Old World monkey species to examine the effects of MGA implants on reproductive potential. In particular, we investigate whether the probability of reproducing (pR) and rates of stillbirth differ among (1) non-implanted females, (2) females who have had MGA implants removed, and (3) females whose implants were left in past expiration. We found no significant difference in pR between non-implanted and implant-removed groups, but when implants were left in past expiration, the pR was significantly lower than in other groups. Both parity and age significantly impacted pR for the non-implanted group (i.e., younger females and those who were parous increased pR), but neither were significant factors for the implant-removed group. Stillbirth rates were significantly higher post-contraception as compared with pre-contraception. These results support similar analyses in other taxa that show a shorter time to reversal after MGA contraception when implants are removed, making this a good contraceptive option for females likely to receive a breeding recommendation, especially when a more predictable time to reversal is important.

Early adolescent Depo-Provera exposure increases stillbirths in adult sooty mangabeys

The 3-month injectable contraceptive medroxyprogesterone acetate (MPA; Depo-Provera) is a synthetic progestin that protects against pregnancy by suppressing ovulation. Studies have focused on the resumption of ovulation after MPA-treatment cessation but neglected potential long-term effects of MPA exposure on future successful reproduction. MPA is frequently administered to adolescent girls; however, long-term fertility effects of adolescent MPA exposure have not been explored. We investigated fertility after extended MPA exposure in a species of old world primate, the sooty mangabey (Cercocebus atys). Female sooty mangabeys (n=31) received chronic MPA-treatment for 4–8 years. At MPA-treatment onset, subjects were either parous adults (n=14) or nulliparous adolescents (n=17), with adolescent-treated subjects being further divided into those who had reached first ovulation (n=10) and those who had not (n=7). After MPA-treatment cessation, adolescent-treated females had a significantly higher incidence of stillbirth than did age-matched and parity-matched controls, whereas adult-treated females did not differ from their matched controls. Females placed on MPA-treatment prior to first ovulation had a significantly higher incidence of stillbirth post-treatment than did females placed on MPA-treatment after first ovulation. Diabetic females had an increased incidence of stillbirth as compared to nondiabetic females; however, when controlling for diabetes, MPA exposure prior to first ovulation was still a significant positive predictor of stillbirth. These findings suggest that the post-treatment fertility effects of chronic MPA exposure vary with the developmental timing of treatment onset and raise concern about the use of MPA as a contraceptive for adolescent girls.

Fertility control to mitigate human–wildlife conflicts: a review

As human populations grow, conflicts with wildlife increase. Concurrently, concerns about the welfare, safety and environmental impacts of conventional lethal methods of wildlife management restrict the options available for conflict mitigation. In parallel, there is increasing interest in using fertility control to manage wildlife. The present review aimed at analysing trends in research on fertility control for wildlife, illustrating developments in fertility-control technologies and delivery methods of fertility-control agents, summarising the conclusions of empirical and theoretical studies of fertility control applied at the population level and offering criteria to guide decisions regarding the suitability of fertility control to mitigate human–wildlife conflicts. The review highlighted a growing interest in fertility control for wildlife, underpinned by increasing numbers of scientific studies. Most current practical applications of fertility control for wild mammals use injectable single-dose immunocontraceptive vaccines mainly aimed at sterilising females, although many of these vaccines are not yet commercially available. One oral avian contraceptive, nicarbazin, is commercially available in some countries. Potential new methods of remote contraceptive delivery include bacterial ghosts, virus-like particles and genetically modified transmissible and non-transmissible organisms, although none of these have yet progressed to field testing. In parallel, new species-specific delivery systems have been developed. The results of population-level studies of fertility control indicated that this approach may increase survival and affect social and spatial behaviour of treated animals, although the effects are species- and context-specific. The present studies suggested that a substantial initial effort is generally required to reduce population growth if fertility control is the sole wildlife management method. However, several empirical and field studies have demonstrated that fertility control, particularly of isolated populations, can be successfully used to limit population growth and reduce human–wildlife conflicts. In parallel, there is growing recognition of the possible synergy between fertility control and disease vaccination to optimise the maintenance of herd immunity in the management of wildlife diseases. The review provides a decision tree that can be used to determine whether fertility control should be employed to resolve specific human–wildlife conflicts. These criteria encompass public consultation, considerations about animal welfare and feasibility, evaluation of population responses, costs and sustainability.

Re-assessing the reversibility of melengestrol acetate (MGA) implants in golden-headed lion tamarins (Leontopithecus chrysomelas): a comparison with golden lion tamarins (L. rosalia)

The reversibility and flexibility of contraceptive methods generally allow for improved genetic and demographic management of captive populations. Earlier studies have produced conflicting results regarding the restoration of reproduction after using melengestrol acetate (MGA) implants in golden-headed (Leontopithecus chrysomelas, GHLT) and golden lion tamarins (L. rosalia, GLT): two closely related species that are physiologically and genetically very similar. The present study investigates the nature of this inter-species difference, presents new data on GHLTs and compares this with published data on GLTs. Analyses showed that around 34% of the GHLTs resumed breeding after their MGA implants were removed or had expired. Non-implanted GHLTs (control group) were significantly more likely to reproduce than females previously treated with an MGA implant, regardless of whether the implant was removed or left to expire. Younger and parous female GHLTs in the control group were more likely to start reproducing. In implanted females, only parity had an impact, with parous females being more likely to resume breeding than non-parous females. In contrast, data published on GLTs indicate that 75% of GLT females resume breeding, and that removing the implant increases the probability of reproduction occurring. Available data suggest that the observed inter-specific differences are related to differences in the weights of the implants used for the two species. For GHLTs, adjusting MGA doses and/or the sizes of the implants currently administered may be required in order to preserve the reproductive potential of individuals. Apart from potentially negative medical and welfare consequences for individual GHLTs, the reduced reversibility of MGA implants also impacts on management practices used to achieve the objectives of conservation breeding programmes. Finally, this study stresses the importance of evaluating the suitability of contraceptive methods at a species-specific level.