Epidemiological connectivity between humans and animals across an urban landscape.

Urbanization is predicted to be a key driver of disease emergence through human exposure to novel, animal-borne pathogens. However, while we suspect that urban landscapes are primed to expose people to novel animal-borne diseases, evidence for the mechanisms by which this occurs is lacking. To address this, we studied how bacterial genes are shared between wild animals, livestock, and humans (n = 1,428) across Nairobi, Kenya-one of the world's most rapidly developing cities. Applying a multilayer network framework, we show that low biodiversity (of both natural habitat and vertebrate wildlife communities), coupled with livestock management practices and more densely populated urban environments, promotes sharing of Escherichia coli-borne bacterial mobile genetic elements between animals and humans. These results provide empirical support for hypotheses linking resource provision, the biological simplification of urban landscapes, and human and livestock demography to urban dynamics of cross-species pathogen transmission at a landscape scale. Urban areas where high densities of people and livestock live in close association with synanthropes (species such as rodents that are more competent reservoirs for zoonotic pathogens) should be prioritized for disease surveillance and control.

High-fat diet, microbiome-gut-brain axis signaling, and anxiety-like behavior in male rats.

Obesity, associated with the intake of a high-fat diet (HFD), and anxiety are common among those living in modern urban societies. Recent studies suggest a role of microbiome-gut-brain axis signaling, including a role for brain serotonergic systems in the relationship between HFD and anxiety. Evidence suggests the gut microbiome and the serotonergic brain system together may play an important role in this response. Here we conducted a nine-week HFD protocol in male rats, followed by an analysis of the gut microbiome diversity and community composition, brainstem serotonergic gene expression (tph2, htr1a, and slc6a4), and anxiety-related defensive behavioral responses. We show that HFD intake decreased alpha diversity and altered the community composition of the gut microbiome in association with obesity, increased brainstem tph2, htr1a and slc6a4 mRNA expression, including in the caudal part of the dorsomedial dorsal raphe nucleus (cDRD), a subregion previously associated with stress- and anxiety-related behavioral responses, and, finally, increased anxiety-related defensive behavioral responses. The HFD increased the Firmicutes/Bacteroidetes ratio relative to control diet, as well as higher relative abundances of Blautia, and decreases in Prevotella. We found that tph2, htr1a and slc6a4 mRNA expression were increased in subregions of the dorsal raphe nucleus in the HFD, relative to control diet. Specific bacterial taxa were associated with increased serotonergic gene expression in the cDRD. Thus, we propose that HFD-induced obesity is associated with altered microbiome-gut-serotonergic brain axis signaling, leading to increased anxiety-related defensive behavioral responses in rats.

Immunization with a heat-killed preparation of Mycobacterium vaccae NCTC 11659 enhances auditory-cued fear extinction in a stress-dependent manner.

Stress-related psychiatric disorders including anxiety disorders, mood disorders, and trauma and stressor-related disorders, such as posttraumatic stress disorder (PTSD), affect millions of people world-wide each year. Individuals with stress-related psychiatric disorders have been found to have poor immunoregulation, increased proinflammatory markers, and dysregulation of fear memory. The "Old Friends" hypothesis proposes that a lack of immunoregulatory inputs has led to a higher prevalence of inflammatory disorders and stress-related psychiatric disorders, in which inappropriate inflammation is thought to be a risk factor. Immunization with a soil-derived saprophytic bacterium with anti-inflammatory and immunoregulatory properties, Mycobacterium vaccae NCTC 11659, can lower proinflammatory biomarkers, increase stress resilience, and, when given prior to or after fear conditioning in a rat model of fear-potentiated startle, enhance fear extinction. In this study, we investigated whether immunization with heat-killed M. vaccae NCTC 11659 would enhance fear extinction in contextual or auditory-cued fear conditioning paradigms and whether M. vaccae NCTC 11659 would prevent stress-induced exaggeration of fear expression or stress-induced resistance to extinction learning. Adult male Sprague Dawley rats were immunized with M. vaccae NCTC 11659 (subcutaneous injections once a week for three weeks), and underwent either: Experiment 1) one-trial contextual fear conditioning; Experiment 2) two-trial contextual fear conditioning; Experiment 3) stress-induced enhancement of contextual fear conditioning; Experiment 4) stress-induced enhancement of auditory-cued fear conditioning; or Experiment 5) stress-induced enhancement of auditory-cued fear conditioning exploring short-term memory. Immunizations with M. vaccae NCTC 11659 had no effect on one- or two-trial contextual fear conditioning or contextual fear extinction, with or without exposure to inescapable stress. However, inescapable stress increased resistance to auditory-cued fear extinction. Immunization with M. vaccae NCTC 11659 prevented the stress-induced increase in resistance to auditory-cued fear extinction learning. Finally, in an auditory-cued fear conditioning paradigm exploring short-term memory and fear acquisition, immunization with M. vaccae did not prevent fear acquisition, either with or without exposure to inescapable stress, consistent with the hypothesis that M. vaccae NCTC 11659 has no effect on fear acquisition but enhances fear extinction. These data are consistent with the hypothesis that increased immunoregulation following immunization with M. vaccae NCTC 11659 promotes stress resilience, in particular by preventing stress-induced resistance to fear extinction, and may be a potential therapeutic intervention for trauma- and stressor-related disorders such as PTSD.

Genomic epidemiology of Escherichia coli: antimicrobial resistance through a One Health lens in sympatric humans, livestock and peri-domestic wildlife in Nairobi, Kenya.

BACKGROUND: Livestock systems have been proposed as a reservoir for antimicrobial-resistant (AMR) bacteria and AMR genetic determinants that may infect or colonise humans, yet quantitative evidence regarding their epidemiological role remains lacking. Here, we used a combination of genomics, epidemiology and ecology to investigate patterns of AMR gene carriage in Escherichia coli, regarded as a sentinel organism. METHODS: We conducted a structured epidemiological survey of 99 households across Nairobi, Kenya, and whole genome sequenced E. coli isolates from 311 human, 606 livestock and 399 wildlife faecal samples. We used statistical models to investigate the prevalence of AMR carriage and characterise AMR gene diversity and structure of AMR genes in different host populations across the city. We also investigated household-level risk factors for the exchange of AMR genes between sympatric humans and livestock. RESULTS: We detected 56 unique acquired genes along with 13 point mutations present in variable proportions in human and animal isolates, known to confer resistance to nine antibiotic classes. We find that AMR gene community composition is not associated with host species, but AMR genes were frequently co-located, potentially enabling the acquisition and dispersal of multi-drug resistance in a single step. We find that whilst keeping livestock had no influence on human AMR gene carriage, the potential for AMR transmission across human-livestock interfaces is greatest when manure is poorly disposed of and in larger households. CONCLUSIONS: Findings of widespread carriage of AMR bacteria in human and animal populations, including in long-distance wildlife species, in community settings highlight the value of evidence-based surveillance to address antimicrobial resistance on a global scale. Our genomic analysis provided an in-depth understanding of AMR determinants at the interfaces of One Health sectors that will inform AMR prevention and control.

Great ape health watch: Enhancing surveillance for emerging infectious diseases in great apes.

Infectious diseases have the potential to extirpate populations of great apes. As the interface between humans and great apes expands, zoonoses pose an increasingly severe threat to already endangered great ape populations. Despite recognition of the threat posed by human pathogens to great apes, health monitoring is only conducted for a small fraction of the world's wild great apes (and mostly those that are habituated) meaning that outbreaks of disease often go unrecognized and therefore unmitigated. This lack of surveillance (even in sites where capacity to conduct surveillance is present) is the most significant limiting factor in our ability to quickly detect and respond to emerging infectious diseases in great apes when they first appear. Accordingly, we must create a surveillance system that links disease outbreaks in humans and great apes in time and space, and enables veterinarians, clinicians, conservation managers, national decision makers, and the global health community to respond quickly to these events. Here, we review existing great ape health surveillance programs in African range habitats to identify successes, gaps, and challenges. We use these findings to argue that standardization of surveillance across sites and geographic scales, that monitors primate health in real-time and generates early warnings of disease outbreaks, is an efficient, low-cost step to conserve great ape populations. Such a surveillance program, which we call "Great Ape Health Watch" would lead to long-term improvements in outbreak preparedness, prevention, detection, and response, while generating valuable data for epidemiological research and sustainable conservation planning. Standardized monitoring of great apes would also make it easier to integrate with human surveillance activities. This approach would empower local stakeholders to link wildlife and human health, allowing for near real-time, bidirectional surveillance at the great ape-human interface.

Amylin, Aß42, and Amyloid in Varicella Zoster Virus Vasculopathy Cerebrospinal Fluid and Infected Vascular Cells.

BACKGROUND: Varicella zoster virus (VZV) vasculopathy is characterized by persistent arterial inflammation leading to stroke. Studies show that VZV induces amyloid formation that may aggravate vasculitis. Thus, we determined if VZV central nervous system infection produces amyloid. METHODS: Aß peptides, amylin, and amyloid were measured in cerebrospinal fluid (CSF) from 16 VZV vasculopathy subjects and 36 stroke controls. To determine if infection induced amyloid deposition, mock- and VZV-infected quiescent primary human perineurial cells (qHPNCs), present in vasculature, were analyzed for intracellular amyloidogenic transcripts/proteins and amyloid. Supernatants were assayed for amyloidogenic peptides and ability to induce amyloid formation. To determine amylin's function during infection, amylin was knocked down with small interfering RNA and viral complementary DNA (cDNA) was quantitated. RESULTS: Compared to controls, VZV vasculopathy CSF had increased amyloid that positively correlated with amylin and anti-VZV antibody levels; Aß40 was reduced and Aß42 unchanged. Intracellular amylin, Aß42, and amyloid were seen only in VZV-infected qHPNCs. VZV-infected supernatant formed amyloid fibrils following addition of amyloidogenic peptides. Amylin knockdown decreased viral cDNA. CONCLUSIONS: VZV infection increased levels of amyloidogenic peptides and amyloid in CSF and qHPNCs, indicating that VZV-induced amyloid deposition may contribute to persistent arterial inflammation in VZV vasculopathy. In addition, we identified a novel proviral function of amylin.

Transcriptional profiling reveals potential involvement of microvillous TRPM5-expressing cells in viral infection of the olfactory epithelium.

BACKGROUND: Understanding viral infection of the olfactory epithelium is essential because the olfactory nerve is an important route of entry for viruses to the central nervous system. Specialized chemosensory epithelial cells that express the transient receptor potential cation channel subfamily M member 5 (TRPM5) are found throughout the airways and intestinal epithelium and are involved in responses to viral infection. RESULTS: Herein we performed deep transcriptional profiling of olfactory epithelial cells sorted by flow cytometry based on the expression of mCherry as a marker for olfactory sensory neurons and for eGFP in OMP-H2B::mCherry/TRPM5-eGFP transgenic mice (Mus musculus). We find profuse expression of transcripts involved in inflammation, immunity and viral infection in TRPM5-expressing microvillous cells compared to olfactory sensory neurons. CONCLUSION: Our study provides new insights into a potential role for TRPM5-expressing microvillous cells in viral infection of the olfactory epithelium. We find that, as found for solitary chemosensory cells (SCCs) and brush cells in the airway epithelium, and for tuft cells in the intestine, the transcriptome of TRPM5-expressing microvillous cells indicates that they are likely involved in the inflammatory response elicited by viral infection of the olfactory epithelium.

Socio-ecological drivers of vertebrate biodiversity and human-animal interfaces across an urban landscape.

Urbanization can have profound impacts on the distributional ecology of wildlife and livestock, with implications for biodiversity conservation, ecosystem services and human health. A wealth of studies have assessed biotic responses to urbanization in North America and Europe, but there is little empirical evidence that directly links human activities to urban biodiversity in the tropics. Results from a large-scale field study conducted in Nairobi, Kenya, are used to explore the impact of human activities on the biodiversity of wildlife and livestock with which humans co-exist across the city. The structure of sympatric wildlife, livestock and human populations are characterized using unsupervised machine learning, and statistical modelling is used to relate compositional variation in these communities to socio-ecological drivers occurring across the city. By characterizing landscape-scale drivers acting on these interfaces, we demonstrate that socioeconomics, elevation and subsequent changes in habitat have measurable impacts upon the diversity, density and species assemblage of wildlife, livestock and humans. Restructuring of wildlife and livestock assemblages (both in terms of species diversity and composition) has important implications for the emergence of novel diseases at urban interfaces, and we therefore use our results to generate a set of testable hypotheses that explore the influence of urban change on microbial communities. These results provide novel insight into the impact of urbanization on biodiversity in the tropics. An understanding of associations between urban processes and the structure of human and animal populations is required to link urban development to conservation efforts and risks posed by disease emergence to human health, ultimately informing sustainable urban development policy.

Varicella-Zoster Virus Infection of Primary Human Spinal Astrocytes Produces Intracellular Amylin, Amyloid-ß, and an Amyloidogenic Extracellular Environment.

BACKGROUND: Herpes zoster is linked to amyloid-associated diseases, including dementia, macular degeneration, and diabetes mellitus, in epidemiological studies. Thus, we examined whether varicella-zoster virus (VZV)-infected cells produce amyloid. METHODS: Production of intracellular amyloidogenic proteins (amylin, amyloid precursor protein [APP], and amyloid-ß [Aß]) and amyloid, as well as extracellular amylin, Aß, and amyloid, was compared between mock- and VZV-infected quiescent primary human spinal astrocytes (qHA-sps). The ability of supernatant from infected cells to induce amylin or Aß42 aggregation was quantitated. Finally, the amyloidogenic activity of viral peptides was examined. RESULTS: VZV-infected qHA-sps, but not mock-infected qHA-sps, contained intracellular amylin, APP, and/or Aß, and amyloid. No differences in extracellular amylin, Aß40, or Aß42 were detected, yet only supernatant from VZV-infected cells induced amylin aggregation and, to a lesser extent, Aß42 aggregation into amyloid fibrils. VZV glycoprotein B (gB) peptides assembled into fibrils and catalyzed amylin and Aß42 aggregation. CONCLUSIONS: VZV-infected qHA-sps produced intracellular amyloid and their extracellular environment promoted aggregation of cellular peptides into amyloid fibrils that may be due, in part, to VZV gB peptides. These findings suggest that together with host and other environmental factors, VZV infection may increase the toxic amyloid burden and contribute to amyloid-associated disease progression.

Acute zoster plasma contains elevated amyloid, correlating with Aß42 and amylin levels, and is amyloidogenic.

Herpes zoster is associated with an increased dementia and neovascular macular degeneration risk and a decline in glycemic control in diabetes mellitus. Because amyloid is present and pathogenic in these diseases, we quantified amyloid, Aß40, Aß42, and amylin in 14 zoster and 10 control plasmas. Compared with controls, zoster plasma had significantly elevated amyloid that correlated with Aß42 and amylin levels and increased amyloid aggregation with addition of exogenous Aß42 or amylin. These results suggest that zoster plasma contains factor(s) that promotes aggregation of amyloidogenic peptides, potentially contributing to the toxic amyloid burden and explaining accelerated disease progression following zoster.

Evidence that preimmunization with a heat-killed preparation of Mycobacterium vaccae reduces corticotropin-releasing hormone mRNA expression in the extended amygdala in a fear-potentiated startle paradigm.

Posttraumatic stress disorder (PTSD) is a trauma and stressor-related disorder that is characterized by dysregulation of glucocorticoid signaling, chronic low-grade inflammation, and impairment in the ability to extinguish learned fear. Corticotropin-releasing hormone (Crh) is a stress- and immune-responsive neuropeptide secreted from the paraventricular nucleus of the hypothalamus (PVN) to stimulate the hypothalamic-pituitary-adrenal (HPA) axis; however, extra-hypothalamic sources of Crh from the central nucleus of the amygdala (CeA) and bed nucleus of the stria terminalis (BNST) govern specific fear- and anxiety-related defensive behavioral responses. We previously reported that preimmunization with a heat-killed preparation of the immunoregulatory environmental bacterium Mycobacterium vaccae NCTC 11659 enhances fear extinction in a fear-potentiated startle (FPS) paradigm. In this follow-up study, we utilized an in situ hybridization histochemistry technique to investigate Crh, Crhr1, and Crhr2 mRNA expression in the CeA, BNST, and PVN of the same rats from the original study [Fox et al., 2017, Brain, Behavior, and Immunity, 66: 70-84]. Here, we demonstrate that preimmunization with M. vaccae NCTC 11659 decreases Crh mRNA expression in the CeA and BNST of rats exposed to the FPS paradigm, and, further, that Crh mRNA expression in these regions is correlated with fear behavior during extinction training. These data are consistent with the hypothesis that M. vaccae promotes stress-resilience by attenuating Crh production in fear- and anxiety-related circuits. These data suggest that immunization with M. vaccae may be an effective strategy for prevention of fear- and anxiety-related disorders.

Treatment with a heat-killed preparation of Mycobacterium vaccae after fear conditioning enhances fear extinction in the fear-potentiated startle paradigm.

The hygiene hypothesis or "Old Friends" hypothesis proposes that inflammatory diseases are increasing in modern urban societies, due in part to reduced exposure to microorganisms that drive immunoregulatory circuits and a failure to terminate inappropriate inflammatory responses. Inappropriate inflammation is also emerging as a risk factor for anxiety disorders, affective disorders, and trauma-and stressor-related disorders, including posttraumatic stress disorder (PTSD), which is characterized as persistent re-experiencing of the trauma after a traumatic experience. Traumatic experiences can lead to long-lasting fear memories and fear potentiation of the acoustic startle reflex. The acoustic startle reflex is an ethologically relevant reflex and can be potentiated in both humans and rats through Pavlovian conditioning. Mycobacterium vaccae is a soil-derived bacterium with immunoregulatory and anti-inflammatory properties that has been demonstrated to enhance fear extinction in the fear-potentiated startle paradigm when given prior to fear conditioning. To determine if immunization with M. vaccae after fear conditioning also has protective effects, adult male Sprague Dawley rats underwent fear conditioning on days -37 and -36 followed by immunizations (3x), once per week beginning 24 h following fear conditioning, with a heat-killed preparation of M. vaccae NCTC 11659 (0.1 mg, s.c., in 100 µl borate-buffered saline) or vehicle, and, then, 3 weeks following the final immunization, were tested in the fear-potentiated startle paradigm (n = 12 per group). Rats underwent fear extinction training on days 1 through 6 followed by spontaneous recovery 14 days later (day 20). Rats were euthanized on day 21 and brain tissue was sectioned for analysis of Tph2, Htr1a, Slc6a4, Slc22a3, and Crhr2 mRNA expression throughout the brainstem dorsal and median raphe nuclei. Immunization with M. vaccae did not affect fear expression on day 1. However, M. vaccae-immunized rats showed enhanced enhanced within-session fear extinction on day 1 and enhanced between-session fear extinction beginning on day 2, relative to vehicle-immunized controls. Immunization with M. vaccae and fear-potentiated startle had minimal effects on serotonergic gene expression when assessed 42 days after the final immunization. Together with previous studies, these data are consistent with the hypothesis that immunoregulatory strategies, such as immunization with M. vaccae, have potential for both prevention and treatment of trauma- and stressor-related psychiatric disorders.

Immunization with a heat-killed preparation of the environmental bacterium Mycobacterium vaccae promotes stress resilience in mice.

The prevalence of inflammatory diseases is increasing in modern urban societies. Inflammation increases risk of stress-related pathology; consequently, immunoregulatory or antiinflammatory approaches may protect against negative stress-related outcomes. We show that stress disrupts the homeostatic relationship between the microbiota and the host, resulting in exaggerated inflammation. Repeated immunization with a heat-killed preparation of Mycobacterium vaccae, an immunoregulatory environmental microorganism, reduced subordinate, flight, and avoiding behavioral responses to a dominant aggressor in a murine model of chronic psychosocial stress when tested 1-2 wk following the final immunization. Furthermore, immunization with M. vaccae prevented stress-induced spontaneous colitis and, in stressed mice, induced anxiolytic or fear-reducing effects as measured on the elevated plus-maze, despite stress-induced gut microbiota changes characteristic of gut infection and colitis. Immunization with M. vaccae also prevented stress-induced aggravation of colitis in a model of inflammatory bowel disease. Depletion of regulatory T cells negated protective effects of immunization with M. vaccae on stress-induced colitis and anxiety-like or fear behaviors. These data provide a framework for developing microbiome- and immunoregulation-based strategies for prevention of stress-related pathologies.

Preimmunization with a heat-killed preparation of Mycobacterium vaccae enhances fear extinction in the fear-potentiated startle paradigm.

The hygiene hypothesis or "Old Friends" hypothesis proposes that inflammatory diseases are increasing in modern urban societies, due in part to reduced exposure to microorganisms that drive immunoregulatory circuits, and a failure to terminate inappropriate inflammatory responses. Inappropriate inflammation is also emerging as a risk factor for trauma-related, anxiety, and affective disorders, including posttraumatic stress disorder (PTSD), which is characterized as persistent re-experiencing of the trauma after a traumatic experience. Traumatic experiences can lead to long-lasting fear memories and exaggerated fear potentiation of the acoustic startle reflex. The acoustic startle reflex is an ethologically relevant reflex and can be potentiated in both humans and rats through Pavlovian conditioning. Mycobacterium vaccae NCTC 11659 is a soil-derived bacterium with immunoregulatory and anti-inflammatory properties that has been demonstrated to confer stress resilience in mice. Here we immunized adult male Sprague Dawley rats 3×, once per week, with a heat-killed preparation of M. vaccae NCTC 11659 (0.1mg, s.c., in 100µl borate-buffered saline) or vehicle, and, then, 3weeks following the final immunization, tested them in the fear-potentiated startle paradigm; controls were maintained under home cage control conditions throughout the experiment (n=11-12 per group). Rats were tested on days 1 and 2 for baseline acoustic startle, received fear conditioning on days 3 and 4, and underwent fear extinction training on days 5-10. Rats were euthanized on day 11 and brain tissue was sectioned for analysis of mRNA expression for genes important in control of brain serotonergic signaling, including tph2, htr1a, slc6a4, and slc22a3, throughout the brainstem dorsal and median raphe nuclei. Immunization with M. vaccae had no effect on baseline acoustic startle or fear expression on day 5. However, M. vaccae-immunized rats showed enhanced between-session and within-session extinction on day 6, relative to vehicle-immunized controls. Immunization with M. vaccae and fear-potentiated startle altered serotonergic gene expression in a gene- and subregion-specific manner. These data are consistent with the hypothesis that immunoregulatory strategies, such as preimmunization with M. vaccae, have potential for prevention of stress- and trauma-related psychiatric disorders.

Activation of 5-HT1A receptors in the rat dorsomedial hypothalamus inhibits stress-induced activation of the hypothalamic-pituitary-adrenal axis.

Acute activation of the hypothalamic-pituitary-adrenal (HPA) axis, leading to the release of corticosteroid hormones into the circulation, is an adaptive response to perceived threats. Persistent activation of the HPA axis can lead to impaired physiological or behavioral function with maladaptive consequences. Thus, efficient control and termination of stress responses is essential for well-being. However, inhibitory control mechanisms governing the HPA axis are poorly understood. Previous studies suggest that serotonergic systems, acting within the medial hypothalamus, play an important role in inhibitory control of stress-induced HPA axis activity. To test this hypothesis, we surgically implanted chronic jugular cannulae in adult male rats and conducted bilateral microinjection of vehicle or the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide (8-OH-DPAT; 8 nmol, 0.2 µL, 0.1 µL/min, per side) into the dorsomedial hypothalamus (DMH) immediately prior to a 40 min period of restraint stress. Repeated blood sampling was conducted using an automated blood sampling system and plasma corticosterone concentrations were determined using enzyme-linked immunosorbent assay. Bilateral intra-DMH microinjections of 8-OH-DPAT suppressed stress-induced increases in plasma corticosterone within 10 min of the onset of handling prior to restraint and, as measured by area-under-the-curve analysis of plasma corticosterone concentrations, during the 40 min period of restraint. These data support an inhibitory role for serotonergic systems, acting within the DMH, on stress-induced activation of the HPA axis. Lay summary: Inhibitory control of the hypothalamic-pituitary-adrenal (HPA) stress hormone response is important for well-being. One neurochemical implicated in inhibitory control of the HPA axis is serotonin. In this study we show that activation of serotonin receptors, specifically inhibitory 5-HT1A receptors in the dorsomedial hypothalamus, is sufficient to inhibit stress-induced HPA axis activity in rats.

Morbidity and mortality in infant mountain gorillas (Gorilla beringei beringei): A 46-year retrospective review.

Long-term studies of morbidity and mortality in free-ranging primates are scarce, but may have important implications for the conservation of extant populations. Infants comprise a particularly important age group, as variation in survival rates may have a strong influence on population dynamics. Since 1968, the Mountain Gorilla Veterinary Project (MGVP, Inc.) and government partners have conducted a comprehensive health monitoring and disease investigation program on mountain gorillas (Gorilla beringei beringei) in Rwanda, Uganda, and the Democratic Republic of the Congo. In an effort to better understand diseases in this species, we reviewed reliable field reports (n = 37), gross post-mortem (n = 66), and histopathology (n = 53) reports for 103 infants (less than 3.5 years) mountain gorillas in the Virunga Massif. Our aim was to conduct the first comprehensive analysis of causes of infant mortality and to correlate histological evidence with antemortem morbidity in infant mountain gorillas. Causes of morbidity and mortality were described, and compared by age, sex, and over time. Trauma was the most common cause of death in infants (56%), followed by respiratory infections and aspiration (13%). Gastrointestinal parasitism (33%), atypical lymphoid hyperplasia (suggestive of infectious disease) (31%), and hepatic capillariasis (25%) were the most significant causes of antemortem morbidity identified post-mortem. Identifying the causes of mortality and morbidity in infants of this critically endangered species will help to inform policy aimed at their protection and guide ante- and post-mortem health monitoring and clinical decision-making in the future.

Serotonergic responses to stress are enhanced in the central amygdala and inhibited in the ventral hippocampus during amphetamine withdrawal.

Withdrawal from amphetamine increases anxiety and reduces the ability to cope with stress, which are factors that are believed to contribute to drug relapse. Stress-induced serotonergic transmission in the central nucleus of the amygdala is associated with anxiety states and fear. Conversely, stress-induced increases in ventral hippocampal serotonin (5-HT) levels have been linked to coping mechanisms. The goal of this study was to investigate the neurobiological changes induced by amphetamine that contribute to stress sensitivity during withdrawal. We tested the hypothesis that limbic serotonergic responses to restraint stress would be altered in male Sprague-Dawley rats chronically pretreated with amphetamine (2.5 mg/kg, intraperitoneal) and then subjected to 2 weeks of withdrawal. Amphetamine withdrawal resulted in increased stress-induced behavioral arousal relative to control treatment, suggesting that drug withdrawal induced greater sensitivity to the stressor. When microdialysis was used to determine the effects of restraint on extracellular 5-HT, stress-induced increases in 5-HT levels were abolished in the ventral hippocampus and augmented in the central amygdala during amphetamine withdrawal. Reverse dialysis of the glucocorticoid receptor antagonist mifepristone into the ventral hippocampus blocked the stress-induced increase in 5-HT levels in saline-pretreated rats, suggesting that glucocorticoid receptors mediate stress-induced increases in 5-HT levels in the ventral hippocampus. However, mifepristone had no effect on stress-induced increases in 5-HT levels in the central amygdala, indicating that stress increases 5-HT levels in this region independently of glucocorticoid receptors. During amphetamine withdrawal, the absence of stress-induced increases in ventral hippocampal 5-HT levels combined with enhanced stress-induced serotonergic responses in the central amygdala may contribute to drug relapse by decreasing stress-coping ability and heightening stress responsiveness.

Neural circuits for the adaptive regulation of fear and extinction memory.

The regulation of fear memories is critical for adaptive behaviors and dysregulation of these processes is implicated in trauma- and stress-related disorders. Treatments for these disorders include pharmacological interventions as well as exposure-based therapies, which rely upon extinction learning. Considerable attention has been directed toward elucidating the neural mechanisms underlying fear and extinction learning. In this review, we will discuss historic discoveries and emerging evidence on the neural mechanisms of the adaptive regulation of fear and extinction memories. We will focus on neural circuits regulating the acquisition and extinction of Pavlovian fear conditioning in rodent models, particularly the role of the medial prefrontal cortex and hippocampus in the contextual control of extinguished fear memories. We will also consider new work revealing an important role for the thalamic nucleus reuniens in the modulation of prefrontal-hippocampal interactions in extinction learning and memory. Finally, we will explore the effects of stress on this circuit and the clinical implications of these findings.

Pharmacological stimulation of infralimbic cortex after fear conditioning facilitates subsequent fear extinction.

The infralimbic (IL) division of the medial prefrontal cortex (mPFC) is a crucial site for extinction of conditioned fear memories in rodents. Recent work suggests that neuronal plasticity in the IL that occurs during (or soon after) fear conditioning enables subsequent IL-dependent extinction learning. We therefore hypothesized that pharmacological activation of the IL after fear conditioning would promote the extinction of conditioned fear. To test this hypothesis, we characterized the effects of post-conditioning infusions of the GABAA receptor antagonist, picrotoxin, into the IL on extinction of auditory conditioned freezing in male and female rats. In four experiments, we found that picrotoxin injections performed immediately, 24 hours, or 13 days after fear conditioning reduced conditioned freezing to the auditory conditioned stimulus (CS) during both extinction training and extinction retrieval; this effect was observed up to two weeks after picrotoxin infusions. Interestingly, inhibiting protein synthesis inhibition in the IL immediately after fear conditioning prevented the inhibition of freezing by picrotoxin injected 24 hours later. Our data suggest that the IL encodes an inhibitory memory during the consolidation of fear conditioning that is necessary for future fear suppression.

Data release: targeted systematic literature search for tick and tick-borne pathogen distributions in six countries in sub-Saharan Africa from 1901 to 2020.

BACKGROUND: Surveillance data documenting tick and tick-borne disease (TBD) prevalence is needed to develop risk assessments and implement control strategies. Despite extensive research in Africa, there is no standardized, comprehensive review. METHODS: Here we tackle this knowledge gap, by producing a comprehensive review of research articles on ticks and TBD between 1901 and 2020 in Chad, Djibouti, Ethiopia, Kenya, Tanzania, and Uganda. Over 8356 English language articles were recovered. Our search strategy included 19 related MeSH terms. Articles were reviewed, and 331 met inclusion criteria. Articles containing mappable data were compiled into a standardized data schema, georeferenced, and uploaded to VectorMap. RESULTS: Tick and pathogen matrixes were created, providing information on vector distributions and tick-pathogen associations within the six selected African countries. CONCLUSIONS: These results provide a digital, mappable database of current and historical tick and TBD distributions across six countries in Africa, which can inform specific risk modeling, determine surveillance gaps, and guide future surveillance priorities.