RESOLUTION OF A HYPERPROLACTINEMIA IN A WESTERN LOWLAND GORILLA (GORILLA GORILLA GORILLA)

The elusive role of prolactin in the sociality of the naked mole-rat

Despite decades of research into the evolutionary drivers of sociality, we know relatively little about the underlying proximate mechanisms. Here we investigate the potential role of prolactin in the highly social naked mole-rat. Naked mole-rats live in large social groups but, only a small number of individuals reproduce. The remaining non-breeders are reproductively suppressed and contribute to burrow maintenance, foraging, and allo-parental care. Prolactin has well-documented links with reproductive timing and parental behaviour, and the discovery that non-breeding naked mole-rats have unusually high prolactin levels has led to the suggestion that prolactin may help maintain naked mole-rat sociality. To test this idea, we investigated whether urinary prolactin was correlated with cooperative behaviour and aggression. We then administered the prolactin-suppressing drug Cabergoline to eight female non-breeders for eight weeks and assessed the physiology and behaviour of the animals relative to controls. Contrary to the mammalian norm, and supporting previous findings for plasma, we found non-breeders had elevated urinary prolactin concentrations that were similar to breeding females. Further, prolactin levels were higher in heavier, socially dominant non-breeders. Urinary prolactin concentrations did not explain variation in working behaviour or patterns of aggression. Furthermore, females receiving Cabergoline did not show any behavioural or hormonal (progesterone) differences, and urinary prolactin did not appear to be suppressed in individuals receiving Cabergoline. While the results add to the relatively limited literature experimentally manipulating prolactin to investigate its role in reproduction and behaviour, they fail to explain why prolactin levels are high in non-breeding naked mole-rats, or how female non-breeding phenotypes are maintained.

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.

UNDERSTANDING PROLACTIN REGULATION AND DETERMINING THE EFFICACY OF CABERGOLINE AND DOMPERIDONE TO MITIGATE PROLACTIN-ASSOCIATED OVARIAN CYCLE PROBLEMS IN ZOO AFRICAN ELEPHANTS (LOXODONTA AFRICANA )

Perturbations in serum prolactin secretion, both over- and underproduction, are observed in zoo African elephants (Loxodonta africana) that exhibit abnormal ovarian cycles. Similar prolactin problems are associated with infertility in other species. Pituitary prolactin is held under constant inhibition by a hypothalamic-derived neurotransmitter, dopamine; thus, regulation by exogenous treatment with agonists or antagonists may be capable of reinitiating normal ovarian cycles. This study tested the efficacy of oral administration of cabergoline (agonist) and domperidone (antagonist) as possible treatments for hyperprolactinemia or chronic low prolactin, respectively. Hyperprolactinemic (overall mean prolactin, >30 ng/ml), acyclic elephants were administered oral cabergoline (2 mg, n = 4) or placebo (dextrose capsule, n = 4) twice weekly. Overall mean prolactin concentration decreased in treated females compared with controls (32.22 ± 14.75 vs 77.53 ± 0.96 ng/ml; P = 0.01). Interestingly, overall mean progestagen concentrations also increased slightly (P < 0.05) in treated females (0.15 ± 0.01 ng/ml) compared with controls (0.07 ± 0.01 ng/ml), but no reinitation of normal cyclic patterns was observed. Chronic low prolactin (overall mean prolactin, <10 ng/ml), acyclic females were orally administered domperidone (2 g/day, n = 4) or placebo (dextrose capsule, n = 4) for 4 wk, followed by 8 wk of no treatment (four cycles) to simulate the prolactin pattern observed in normal cycling elephants. Overall mean prolactin concentrations increased (P = 0.005) during domperidone treatment (21.77 ± 3.69 ng/ml) compared with controls (5.77 ± 0.46 ng/ml), but progestagen concentrations were unaltered. Prolactin regulation by dopamine was confirmed by expected responses to dopamine agonist and antagonist treatment. Although prolactin concentrations were successfully reduced by cabergoline, and domperidone initiated the expected cyclic prolactin pattern, neither treatment induced normal ovarian activity.

A SYSTEMATIC REVIEW OF THE LITERATURE RELATING TO CAPTIVE GREAT APE MORBIDITY AND MORTALITY

Wild bonobos (Pan paniscus), chimpanzees (Pan troglodytes), Western gorillas (Gorilla gorilla), and orangutans (Pongo pygmaeus, Pongo abelii) are threatened with extinction. In order to help maintain a self-sustaining zoo population, clinicians require a sound understanding of the diseases with which they might be presented. To provide an up-to-date perspective on great ape morbidity and mortality, a systematic review of the zoological and veterinary literature of great apes from 1990 to 2014 was conducted. This is the first review of the great ape literature published since 1990 and the first-ever systematic literature review of great ape morbidity and mortality. The following databases were searched for relevant articles: CAB Abstracts, Web of Science Core Collection, BIOSIS Citation Index, BIOSIS Previews, Current Contents Connect, Data Citation Index, Derwent Innovations Index, MEDLINE, SciELO Citation Index, and Zoological Record. A total of 189 articles reporting on the causes of morbidity and mortality among captive great apes were selected and divided into comparative morbidity-mortality studies and case reports-series or single-disease prevalence studies. The content and main findings of the morbidity-mortality studies were reviewed and the main limitations identified. The case reports-case series and single-disease prevalence studies were categorized and coded according to taxa, etiology, and body system. Subsequent analysis allowed the amount of literature coverage afforded to each category to be calculated and the main diseases and disorders reported within the literature to be identified. This review concludes that reports of idiopathic and infectious diseases along with disorders of the cardiovascular, respiratory, and gastrointestinal body systems were particularly prominent within the great ape literature during 1990-2014. However, recent and accurate prevalence figures are lacking and there are flaws in those reviews that do exist. There is therefore a critical need for a robust, widespread, and more up-to-date review of mortality among captive great apes.

Comparative Pathology of Aging Great Apes: Bonobos, Chimpanzees, Gorillas, and Orangutans

The great apes (chimpanzees, bonobos, gorillas, and orangutans) are our closest relatives. Despite the many similarities, there are significant differences in aging among apes, including the human ape. Common to all are dental attrition, periodontitis, tooth loss, osteopenia, and arthritis, although gout is uniquely human and spondyloarthropathy is more prevalent in apes than humans. Humans are more prone to frailty, sarcopenia, osteoporosis, longevity past reproductive senescence, loss of brain volume, and Alzheimer dementia. Cerebral vascular disease occurs in both humans and apes. Cardiovascular disease mortality increases in aging humans and apes, but coronary atherosclerosis is the most significant type in humans. In captive apes, idiopathic myocardial fibrosis and cardiomyopathy predominate, with arteriosclerosis of intramural coronary arteries. Similar cardiac lesions are occasionally seen in wild apes. Vascular changes in heart and kidneys and aortic dissections in gorillas and bonobos suggest that hypertension may be involved in pathogenesis. Chronic kidney disease is common in elderly humans and some aging apes and is linked with cardiovascular disease in orangutans. Neoplasms common to aging humans and apes include uterine leiomyomas in chimpanzees, but other tumors of elderly humans, such as breast, prostate, lung, and colorectal cancers, are uncommon in apes. Among the apes, chimpanzees have been best studied in laboratory settings, and more comparative research is needed into the pathology of geriatric zoo-housed and wild apes. Increasing longevity of humans and apes makes understanding aging processes and diseases imperative for optimizing quality of life in all the ape species.

Prolactin levels in Western Lowland gorillas

Hyperprolactinemia is known to cause menstrual irregularity and infertility in humans. However, little is known about the role of prolactin in menstruation and fertility in Western Lowland gorillas. To create a database of prolactin values in gorillas, we have performed immunoassays on serum specimens dating back to 1983 from nine female gorillas at the Brookfield Zoo. We matched these samples with documented behavioral data to correlate menstrual timing. In addition, we ran other reproductive hormones both to aid in determining the phase of the menstrual cycle and to evaluate the effect of the prolactin on suppression of these hormones during the premenarchal and postpartum phases. We found that values for luteinizing hormone, follicle-stimulating hormone, estradiol and progesterone cycle in very similar patterns to humans. Based on the 59 available samples, prolactin was found to be higher in gorillas than in humans in nearly every phase of the menstrual cycle (range 49.9-93.7 ng/mL) and such levels do not appear to alter the reproductive axis as it does in humans. Thus, prolactin may have a different impact on fertility in gorillas than it does in humans.