Investigating the Contribution of Major Drug-Metabolising Enzymes to Possum-Specific Fertility Control

The potential to improve the effectiveness and efficiency of potential oestrogen-based oral contraceptives (fertility control) for possums was investigated by comparing the inhibitory potential of hepatic CYP3A and UGT2B catalytic activity using a selected compound library (CYP450 inhibitor-based compounds) in possums to that of three other species (mouse, avian, and human). The results showed higher CYP3A protein levels in possum liver microsomes compared to other test species (up to a 4-fold difference). Moreover, possum liver microsomes had significantly higher basal p-nitrophenol glucuronidation activity than other test species (up to an 8-fold difference). However, no CYP450 inhibitor-based compounds significantly decreased the catalytic activity of possum CYP3A and UGT2B below the estimated IC₅₀ and 2-fold IC₅₀ values and were therefore not considered to be potent inhibitors of these enzymes. However, compounds such as isosilybin (65%), ketoconazole (72%), and fluconazole (74%) showed reduced UGT2B glucuronidation activity in possums, mainly at 2-fold IC₅₀ values compared to the control (p < 0.05). Given the structural features of these compounds, these results could provide opportunities for future compound screening. More importantly, however, this study provided preliminary evidence that the basal activity and protein content of two major drug-metabolising enzymes differ in possums compared to other test species, suggesting that this could be further exploited to reach the ultimate goal: a potential target-specific fertility control for possums in New Zealand.

The koala gut microbiome is largely unaffected by host translocation but rather influences host diet

Introduction

Translocation is a valuable and increasingly used strategy for the management of both threatened and overabundant wildlife populations. However, in some instances the translocated animals fail to thrive. Differences in diet between the source and destination areas may contribute to poor translocation outcomes, which could conceivably be exacerbated if the animals' microbiomes are unsuited to the new diet and cannot adapt.

Methods

In this study we tracked how the faecal microbiome of a specialist Eucalyptus folivore, the koala (Phascolarctos cinereus), changed over the course of a year after translocation. We assessed microbiome composition by 16S rRNA amplicon sequencing of faecal pellets.

Results

We found no significant overall changes in the faecal microbiomes of koalas post-translocation (n = 17) in terms of microbial richness, diversity or composition when compared to the faecal microbiomes of koalas from an untranslocated control group (n = 12). This was despite the translocated koalas feeding on a greater variety of Eucalyptus species after translocation. Furthermore, while differences between koalas accounted for half of the microbiome variation, estimated diets at the time of sampling only accounted for 5% of the variation in the koala microbiomes between sampling periods. By contrast, we observed that the composition of koala faecal microbiomes at the time of translocation accounted for 37% of between koala variation in post-translocation diet. We also observed that translocated koalas lost body condition during the first month post-translocation and that the composition of the koalas' initial microbiomes were associated with the magnitude of that change.

Discussion

These findings suggest that the koala gut microbiome was largely unaffected by dietary change and support previous findings suggesting that the koala gut microbiome influences the tree species chosen for feeding. They further indicate that future research is needed to establish whether the koalas' gut microbiomes are directly influencing their health and condition or whether aspects of the koala gut microbiomes are an indicator of underlying physiological differences or pathologies. Our study provides insights into how animal microbiomes may not always be affected by the extreme upheaval of translocation and highlights that responses may be host species-specific. We also provide recommendations to improve the success of koala translocations in the future.

Breeding dynamics of overabundant koala (Phascolarctos cinereus) populations subject to fertility-control management

Abstract ContextThe koala (Phascolarctos cinereus) sometimes occurs as an overabundant folivore in south-eastern Australia, where high-density populations have caused defoliation of preferred food trees, threatening habitat. Kangaroo Island, South Australia and Budj Bim National Park, Victoria, are two regions where such eruptive population dynamics have arisen. One way of mitigating their damage is through management via fertility control. AimsThis paper examines the outcomes of fertility control (surgical sterilisation and treatment with levonorgestrel implants) on breeding dynamics at the population level, using data obtained from two separate koala management programs conducted by State Government wildlife agencies, South Australia Department for Environment and Water and Parks Victoria. MethodsThe relationships between female body condition, reproductive status, fertility control, age and population density were examined using linear mixed effects models. Population density (koalas/ha) was estimated using annual census data and modelled in a Bayesian framework. Key resultsBody condition was a key influence on breeding success in female koalas, with sexual maturity being defined by both age and body condition, whereas the effect of reproductive experience was minimal. It is likely that reduced densities have led to decreased intraspecific competition for food resources and territory, leading to increased breeding success at one management site (BBNP) and by allowing females to begin breeding at a lower overall body condition. The reduction in densities to sustainable levels at both management sites, despite differing fertility-control methods, supports the use of the less invasive and more cost-effective levonorgestrel implants as the preferred fertility-control method. ConclusionsIn addition to contraceptive effects, broad-scale fertility control may have resulted in a compensatory higher breeding success in the untreated population, possibly in response to decreasing densities, increased resource availability or behavioural responses to population management. ImplicationsAlthough compensatory breeding mechanisms can reduce the effectiveness of fertility control at the population level, ongoing fertility-control management can still be successful at reducing overabundant koala populations to sustainable levels with significant long-term commitment, provided that annual control targets are continuously met.

Contraception of prepubertal young can increase cost effectiveness of management of overabundant koala populations

Context With limited resources for wildlife management and conservation, it is vital that the effectiveness of management programs is maximised and costs reduced. Koala populations need to be reduced in locations where they are locally overabundant and over-browsing their food trees. Subcutaneous contraceptive implants containing levonorgestrel are currently used to control koala fertility to assist in reducing population densities. Dependent young are caught with their mothers, so are also available for contraception. Aims The overall aim was to investigate whether the effectiveness of koala contraception programs can be improved by administering levonorgestrel implants to female young along with their mothers. This was achieved by: (1) determining if implanting females before sexual maturation affects their fertility, growth and pouch development; and (2) developing a stage-structured population growth model to compare two management scenarios. Methods Juvenile female koalas (11–17 months old) were treated with either a control (n = 5) or 70 mg levonorgestrel implant (n = 5). Koalas were caught every 4 to 6 weeks for 15 months, then every 3 to 12 months for 5 years. Koalas were weighed and head length measured. Pouches were checked for young. Pouch development was assessed as a proxy for sexual maturation. A stage-based population model simulating koala population growth was developed to compare different management scenarios: no treatment; treatment of adults only; and treatment of adults plus their dependent young. Key results Levonorgestrel implants prevented births with no effect on growth, survival or timing of sexual maturation. Population growth simulations indicate that treating dependent young with their mothers results in earlier population reduction. Conclusions The treatment of prepubertal female koalas with levonorgestrel implants is a safe and effective method that increases the effectiveness of koala contraception programs. Implications Development of novel strategies may provide opportunities to increase the efficiency and cost-effectiveness of management programs with constrained resources.

Survival and movements of koalas translocated from an over-abundant population

Abstract Context At some sites in southern Victoria, browsing pressure caused by high-density koala populations can result in defoliation of preferred browse trees. In extreme cases, this over-browsing can lead to widespread tree death and starvation of koalas. To reduce the potential for mortality of trees and koalas, a management strategy that includes fertility control of females and translocation of healthy individuals (male and female) has been adopted. AimsTo compare the short- to medium-term survival and body condition of koalas translocated from over-browsed habitat and released into unoccupied (or nearly so) habitat with that of koalas left in situ in compromised habitat. Methods We monitored survival and body condition of 36 translocated koalas for 4–5 months after translocation relative to that of a control group (24 animals) left in situ. Koalas were recaptured and body condition measured (as a scaled body-mass index) ~40 and 137 days after translocation. Additionally, GPS loggers were used to investigate patterns of koala movement. Key resultsSurvival rates of translocated koalas were not different from those of controls and females in both groups showed slightly higher survival rates than did males. After 137 days, control animals had lower scaled body mass, whereas translocated animals, after an initial reduction, had mostly regained, or increased their scaled body mass. Translocated females regained their original scaled body mass faster than did translocated males. Male koalas in both control and translocated groups had higher rates of movement than did females, and translocated koalas had slightly higher rates of movement than did control koalas. Translocated koalas moved farther from their release location than control koalas. ConclusionsOn the basis of the scaled body-mass index, translocated koalas fared better than those left in situ in compromised habitat, even though the density of koalas in the over-browsed habitat had been reduced by a wider salvage translocation program. The process used to identify potential release sites, including a spatial koala-habitat index, accurately predicted suitable koala habitat. ImplicationsThe current management strategy of translocating koalas out of over-browsed habitat is supported and could be more widely applied.

Treatment of Adenomyosis with Subcutaneous Etonogestrel Implants: A Clinical Observational Study in 17 Patients

Background

Adenomyosis is a cause of chronic pelvic pain in women of reproductive age. The aim of this study was to investigate the effects of subcutaneous etonogestrel implantation on adenomyosis.

Material/Methods

A clinical observational study included 17 women with adenomyosis who were treated with subcutaneous etonogestrel implants and followed-up for 12 months. Imaging and clinical observations were undertaken in the 17 patients at baseline (time 0), and at 3 months, 6 months, and 12 months following subcutaneous etonogestrel implantation. The following imaging and clinical findings were compared between baseline (time 0) and 12-month follow-up: menstrual bleeding pattern, dysmenorrhea, visual analog scale (VAS) pain score, uterine volume, serum cancer antigen 125 (CA125) levels, hemoglobin, follicle-stimulating hormone (FSH) levels, luteinizing hormone levels, serum estradiol levels, and any treatment side effects.

Results

All 17 patients treated with etonogestrel implants completed the 12-month follow-up, at which time, the mean hemoglobin level (127.08±2.56 g/L) was significantly higher compared with that at baseline (94.54±5.47 g/L; P<0.01); uterine volume, serum CA125, and VAS score for dysmenorrhea at 12 months (118.03±12.83 cm³, 34.58±9.66 U/mL, and 1.45±0.35, respectively) were significantly lower when compared with baseline (198.53±39.47 cm³, 100.41±49.89 U/mL, and 7.62±0.74, respectively) (P<0.01, for all). However, changes in bleeding pattern and amenorrhoea occurred after treatment in some women.

Conclusions

Subcutaneous etonogestrel was effective in reducing some symptoms and signs of adenomyosis, including dysmenorrhea, anemia, serum CA125, and uterine volume.

A role for selective contraception of individuals in conservation

Contraception has an established role in managing overabundant populations and preventing undesirable breeding in zoos. We propose that it can also be used strategically and selectively in conservation to increase the genetic and behavioral quality of the animals. In captive breeding programs, it is becoming increasingly important to maximize the retention of genetic diversity by managing the reproductive contribution of each individual and preventing genetically suboptimal breeding through the use of selective contraception. Reproductive suppression of selected individuals in conservation programs has further benefits of allowing animals to be housed as a group in extensive enclosures without interfering with breeding recommendations, which reduces adaptation to captivity and facilitates the expression of wild behaviors and social structures. Before selective contraception can be incorporated into a breeding program, the most suitable method of fertility control must be selected, and this can be influenced by factors such as species life history, age, ease of treatment, potential for reversibility, and desired management outcome for the individual or population. Contraception should then be implemented in the population following a step-by-step process. In this way, it can provide crucial, flexible control over breeding to promote the physical and genetic health and sustainability of a conservation dependent species held in captivity. For Tasmanian devils (Sarcophilus harrisii), black-flanked rock wallabies (Petrogale lateralis), and burrowing bettongs (Bettongia lesueur), contraception can benefit their conservation by maximizing genetic diversity and behavioral integrity in the captive breeding program, or, in the case of the wallabies and bettongs, by reducing populations to a sustainable size when they become locally overabundant. In these examples, contraceptive duration relative to reproductive life, reversibility, and predictability of the contraceptive agent being used are important to ensure the potential for individuals to reproduce following cessation of contraception, as exemplified by the wallabies when their population crashed and needed females to resume breeding.

Recent advances in tools and technologies for monitoring and controlling ovarian activity in marsupials

Components of assisted reproduction technologies (ART), such as sperm cryopreservation, artificial insemination, superovulation and pouch young surrogacy, have been developed for a range of Australian and American marsupials. However, methods to effectively control ovarian function, arguably the key limiting factors in applying and integrating ART as a practical tool in conservation management, remain poorly developed. This is largely due to unique characteristics of the marsupial corpus luteum and its failure to respond to agents used to synchronize ovarian function in eutherian mammals. This paper presents an overview of relevant aspects of marsupial reproductive biology across marsupial taxonomic groups including information on the long-established technique of removal of suckling young to activate ovarian cycles. Ovarian monitoring tools for marsupials are reviewed and their usefulness for ART assessed (laparotomy, hormone cycling, vaginal cytology, laparoscopy and ultrasonography). We also discuss promising recent work examining the potential of manipulating hypothalamic-pituitary function using GnRH agonists and antagonists as the basis of ovarian control (female synchronization) strategies.

Phylogeography of the Koala, (Phascolarctos cinereus), and Harmonising Data to Inform Conservation

The Australian continent exhibits complex biogeographic patterns but studies of the impacts of Pleistocene climatic oscillation on the mesic environments of the Southern Hemisphere are limited. The koala (Phascolarctos cinereus), one of Australia’s most iconic species, was historically widely distributed throughout much of eastern Australia but currently represents a complex conservation challenge. To better understand the challenges to koala genetic health, we assessed the phylogeographic history of the koala. Variation in the maternally inherited mitochondrial DNA (mtDNA) Control Region (CR) was examined in 662 koalas sampled throughout their distribution. In addition, koala CR haplotypes accessioned to Genbank were evaluated and consolidated. A total of 53 unique CR haplotypes have been isolated from koalas to date (including 15 haplotypes novel to this study). The relationships among koala CR haplotypes were indicative of a single Evolutionary Significant Unit and do not support the recognition of subspecies, but were separated into four weakly differentiated lineages which correspond to three geographic clusters: a central lineage, a southern lineage and two northern lineages co-occurring north of Brisbane. The three geographic clusters were separated by known Pleistocene biogeographic barriers: the Brisbane River Valley and Clarence River Valley, although there was evidence of mixing amongst clusters. While there is evidence for historical connectivity, current koala populations exhibit greater structure, suggesting habitat fragmentation may have restricted female-mediated gene flow. Since mtDNA data informs conservation planning, we provide a summary of existing CR haplotypes, standardise nomenclature and make recommendations for future studies to harmonise existing datasets. This holistic approach is critical to ensuring management is effective and small scale local population studies can be integrated into a wider species context.

Comparative efficacy of levonorgestrel and deslorelin contraceptive implants in free-ranging eastern grey kangaroos (Macropus giganteus)

Context Fertility control of females with levonorgestrel or deslorelin implants shows promise for managing populations of overabundant eastern grey kangaroos (Macropus giganteus). Although these implants have been tested separately in captive and free-ranging kangaroos, there has been no direct comparison under equivalent field conditions. Aims We investigated the long-term efficacy of levonorgestrel and deslorelin implants, together with the cost of treatment, ease of administration, and the welfare of the animals, in a side-by-side trial under realistic management conditions. Methods We captured 65 adult female kangaroos over 11 days at a golf course in Anglesea, Victoria, Australia. We assigned each female to one of the following three experimental groups: levonorgestrel (210 mg, n = 18), deslorelin (9.4 mg, n = 24) or procedural control (n = 23). We monitored reproductive success for 8 years, by observing young in the pouch in winter and spring. Key results Natural fertility was high; in most years, less than 20% of control females failed to reproduce. For deslorelin-treated females, the odds of failing to reproduce were four times higher than for the control group; for levonorgestrel-treated females, these odds were 74 times higher. Deslorelin was ineffective after 3 years, whereas levonorgestrel was effective for at least 5 years. Conclusions Levonorgestrel was markedly superior in efficacy, as shown by a stronger contraceptive effect persisting for longer. In other respects, the two implants were comparable, being similar in cost and ease of delivery, and equally safe. Implications Only levonorgestrel implants fulfill their promise for non-lethal, long-term control of kangaroo populations. Deslorelin implants cannot be recommended for this purpose.

The use of a synthetic progesterone, levonorgestrel (LNG), to control the oestrous cycle in the koala

This study investigated the efficacy of a synthetic progestogen, levonorgestrel (LNG), to control koala ovarian activity for the purposes of oestrous synchronisation. Captive koalas were administered either saline control or a 70-mg LNG implant on Day 2 of oestrus. Urogenital cytology, oestrous behaviour and plasma oestradiol-17β and LH concentrations were monitored over a 6-week period. After LNG implant removal females were monitored to determine if the return to oestrus was synchronised. LNG-treated koalas immediately ceased displaying oestrous behaviour, showed no evidence of cornified epithelial cells in smears of urogenital cytology and exhibited low plasma oestradiol-17β concentrations throughout the implantation period. In contrast, oestradiol-17β levels in control koalas showed evidence of continued cyclic activity associated with behavioural oestrus and increased cornified epithelial cells in urogenital smears on Days 33 to 35 after saline injection. After implant removal, LNG-treated koalas exhibited oestrus at 13, 14, 17 and 30 days after implant removal. Plasma LH concentrations varied throughout the study period with no significant time (P = 0.49) or treatment (P = 0.13) effect. Overall results from this study suggest that LNG implants in koalas can inhibit oestrous behaviour and reduce circulating oestradiol-17β levels before oestrus, most likely by preventing development of the pre-ovulatory follicle. However, there was no evidence of LH suppression by the LNG implants. Removal of LNG implants resulted in the synchronous return to oestrus in three of the four treated koalas. Further studies on a larger population are required to validate these findings.

Fertility control in wildlife: review of current status, including novel and future technologies

Overpopulation of selected groups of animals is widely recognised as an issue that can have adverse effects on several current global problems, such as animal and human health, conservation and environmental changes. This review will, therefore, focus on recent novel contraception together with future technologies that may provide additional contraceptive methods.