Trait-Based Vaccination of Individual Meerkats (Suricata suricatta) against Tuberculosis Provides Evidence to Support Targeted Disease Control

Individuals vary in their potential to acquire and transmit infections, but this fact is currently underexploited in disease control strategies. We trialled a trait-based vaccination strategy to reduce tuberculosis in free-living meerkats by targeting high-contact meerkats (socially dominant individuals) in one study arm, and high-susceptibility individuals (young subordinates) in a second arm. We monitored infection within vaccinated groups over two years comparing the results with untreated control groups. Being a member of a high-contact group had a protective effect on individuals’ survival times (Hazard Ratio = 0.5, 95% Confidence Interval, CI: 0.29–0.88, p = 0.02) compared to control groups. Over the study, odds of testing positive for tuberculosis increased more than five-fold in control groups (Odds Ratio = 5.40, 95% CI = 0.94–30.98, p = 0.058); however, no increases were observed in either of the treatment arms. Targeted disease control approaches, such as the one described in this study, allow for reduced numbers of interventions. Here, trait-based vaccination was associated with reduced infection rates and thus has the potential to offer more efficient alternatives to traditional mass-vaccination policies. Such improvements in efficiency warrant further study and could make infectious disease control more practically achievable in both animal (particularly wildlife) and human populations.

Neuroanatomical and Immunohistological Study of the Main and Accessory Olfactory Bulbs of the Meerkat (Suricata suricatta)

We approached the study of the main (MOB) and accessory olfactory bulbs (AOB) of the meerkat (Suricata suricatta) aiming to fill important gaps in knowledge regarding the neuroanatomical basis of olfactory and pheromonal signal processing in this iconic species. Microdissection techniques were used to extract the olfactory bulbs. The samples were subjected to hematoxylin-eosin and Nissl stains, histochemical (Ulex europaeus agglutinin, Lycopersicon esculentum agglutinin) and immunohistochemical labelling (Gαo, Gαi2, calretinin, calbindin, olfactory marker protein, glial fibrillary acidic protein, microtubule-associated protein 2, SMI-32, growth-associated protein 43). Microscopically, the meerkat AOB lamination pattern is more defined than the dog’s, approaching that described in cats, with well-defined glomeruli and a wide mitral-plexiform layer, with scattered main cells and granular cells organized in clusters. The degree of lamination and development of the meerkat MOB suggests a macrosmatic mammalian species. Calcium-binding proteins allow for the discrimination of atypical glomerular subpopulations in the olfactory limbus between the MOB and AOB. Our observations support AOB functionality in the meerkat, indicating chemosensory specialization for the detection of pheromones, as identified by the characterization of the V1R vomeronasal receptor family and the apparent deterioration of the V2R receptor family.

A practical guide for generating unsupervised, spectrogram-based latent space representations of animal vocalizations

The manual detection, analysis, and classification of animal vocalizations in acoustic recordings is laborious and requires expert knowledge. Hence, there is a need for objective, generalizable methods that detect underlying patterns in these data, categorize sounds into distinct groups, and quantify similarities between them. Among all computational methods that have been proposed to accomplish this, neighborhood-based dimensionality reduction of spectrograms to produce a latent-space representation of calls stands out for its conceptual simplicity and effectiveness. Using a dataset of manually annotated meerkat (Suricata suricatta) vocalizations, we demonstrate how this method can be used to obtain meaningful latent space representations that reflect the established taxonomy of call types. We analyze strengths and weaknesses of the proposed approach, give recommendations for its usage and show application examples, such as the classification of ambiguous calls and the detection of mislabeled calls. All analyses are accompanied by example code to help researchers realize the potential of this method for the study of animal vocalizations.

Combining Analytical Approaches and Multiple Sources of Information to Improve Interpretation of Diagnostic Test Results for Tuberculosis in Wild Meerkats

Diagnostic tests are used to classify individual animals’ infection statuses. However, validating test performance in wild animals without gold standard tests is extremely challenging, and the issue is further complicated in chronic conditions where measured immune parameters vary over time. Here, we demonstrate the value of combining evidence from different diagnostic approaches to aid interpretation in the absence of gold standards, large sample sizes, and controlled environments. Over a two-year period, we sampled 268 free-living meerkats (Suricata suricatta) longitudinally for Mycobacterium suricattae (a causative agent of tuberculosis), using three ante-mortem diagnostic tests based on mycobacterial culture, and antigen-specific humoral and cell-mediated immune responses, interpreting results both independently and in combination. Post-mortem cultures confirmed M. suricattae infection in 22 animals, which had prior ante-mortem information, 59% (13/22) of which were test-positive on a parallel test interpretation (PTI) of the three ante-mortem diagnostic assays (95% confidence interval: 37–79%). A similar ability to detect infection, 65.7% (95% credible interval: 42.7–84.7%), was estimated using a Bayesian approach to examine PTI. Strong evidence was found for a near doubling of the hazard of death (Hazard Ratio 1.75, CI: 1.14–2.67, p = 0.01), associated with a positive PTI result, thus demonstrating that these test results are related to disease outcomes. For individual tests, small sample sizes led to wide confidence intervals, but replication of conclusions, using different methods, increased our confidence in these results. This study demonstrates that combining multiple methodologies to evaluate diagnostic tests in free-ranging wildlife populations can be a useful approach for exploiting such valuable datasets.

An intergenerational androgenic mechanism of female intrasexual competition in the cooperatively breeding meerkat

Female intrasexual competition can be intense in cooperatively breeding species, with some dominant breeders (matriarchs) limiting reproduction in subordinates via aggression, eviction or infanticide. In males, such tendencies bidirectionally link to testosterone, but in females, there has been little systematic investigation of androgen-mediated behaviour within and across generations. In 22 clans of wild meerkats (Suricata suricatta), we show that matriarchs 1) express peak androgen concentrations during late gestation, 2) when displaying peak feeding competition, dominance behaviour, and evictions, and 3) relative to subordinates, produce offspring that are more aggressive in early development. Late-gestation antiandrogen treatment of matriarchs 4) specifically reduces dominance behaviour, is associated with infrequent evictions, decreases social centrality within the clan, 5) increases aggression in cohabiting subordinate dams, and 6) reduces offspring aggression. These effects implicate androgen-mediated aggression in the operation of female sexual selection, and intergenerational transmission of masculinised phenotypes in the evolution of meerkat cooperative breeding.

Discrimination of Acoustic Stimuli and Maintenance of Graded Alarm Call Structure in Captive Meerkats

Animals living in human care for several generations face the risk of losing natural behaviors, which can lead to reduced animal welfare. The goal of this study is to demonstrate that meerkats (Suricata suricatta) living in zoos can assess potential danger and respond naturally based on acoustic signals only. This includes that the graded information of urgency in alarm calls as well as a response to those alarm calls is retained in captivity. To test the response to acoustic signals with different threat potential, meerkats were played calls of various animals differing in size and threat (e.g., robin, raven, buzzard, jackal) while their behavior was observed. The emitted alarm calls were recorded and examined for their graded structure on the one hand and played back to them on the other hand by means of a playback experiment to see whether the animals react to their own alarm calls even in the absence of danger. A fuzzy clustering algorithm was used to analyze and classify the alarm calls. Subsequently, the features that best described the graded structure were isolated using the LASSO algorithm and compared to features already known from wild meerkats. The results show that the graded structure is maintained in captivity and can be described by features such as noise and duration. The animals respond to new threats and can distinguish animal calls that are dangerous to them from those that are not, indicating the preservation of natural cooperative behavior. In addition, the playback experiments show that the meerkats respond to their own alarm calls with vigilance and escape behavior. The findings can be used to draw conclusions about the intensity of alertness in captive meerkats and to adapt husbandry conditions to appropriate welfare.

Diurnal oscillations in gut bacterial load and composition eclipse seasonal and lifetime dynamics in wild meerkats

Circadian rhythms in gut microbiota composition are crucial for metabolic function, yet the extent to which they govern microbial dynamics compared to seasonal and lifetime processes remains unknown. Here, we investigate gut bacterial dynamics in wild meerkats (Suricata suricatta) over a 20-year period to compare diurnal, seasonal, and lifetime processes in concert, applying ratios of absolute abundance. We found that diurnal oscillations in bacterial load and composition eclipsed seasonal and lifetime dynamics. Diurnal oscillations were characterised by a peak in Clostridium abundance at dawn, were associated with temperature-constrained foraging schedules, and did not decay with age. Some genera exhibited seasonal fluctuations, whilst others developed with age, although we found little support for microbial senescence in very old meerkats. Strong microbial circadian rhythms in this species may reflect the extreme daily temperature fluctuations typical of arid-zone climates. Our findings demonstrate that accounting for circadian rhythms is essential for future gut microbiome research.

Neoplasia ovárica (Luteoma) en una Suricata (Suricata suricatta)

En este artículo se describe el caso de una Suricata suricatta de 5 años, hembra, nacida bajo cuidado humano en el Zoológico de Cali, Colombia, que presentó reporte de comportamiento anormal. Al examen clínico se observó alopecia multifocal y simétrica bilateral con costras. Se realizó una evaluación ultrasonográfica que determinó la presencia de quistes ováricos. Como alternativa terapéutica se realizó una ovariohisterctomía (OVH) con biopsia escisional de ambos ovarios, que fueron remitidos al laboratorio de patología. Los hallazgos histopatológicos concluyeron una neoplasia del ovario izquierdo consistente con un Luteoma. El ovario derecho no presentó lesiones significativas. Durante la cirugía se tomaron muestras de sangre que indicaron que el paciente presentaba anemia regenerativa, química sanguínea con aumento del BUN y proteínas totales asociados a una hiperglobulinemia indicativos de un proceso inflamatorio crónico. La paciente se recuperó satisfactoriamente de la cirugía y tras dos semanas posteriores al procedimiento, las lesiones dermatológicas remitieron, así como los problemas de comportamiento previamente reportados.