Carnivorans are an important study object for comparative neuroscience, as they exhibit a wide range of behaviours, ecological adaptations, and social structures. Previous studies have mainly examined relative brain size, but a comprehensive understanding of brain diversity requires the investigation of other aspects of their neuroanatomy. Here, we obtained primarily post-mortem brain scans from 26 species of the order Carnivora, spanning across eight families with diverse representatives and including additional individuals for selected species, to create the largest carnivoran brain collection to date. We reconstructed their cortical surfaces and examined neocortical sulcal anatomy to establish a framework for systematic interspecies comparisons, revealing distinct regional variations in sulcal anatomy, potentially related to the species’ behaviour and ecology. Arctoidea species with pronounced forepaw dexterity exhibited complex sulcal configurations in the presumed somatosensory cortex but low sulcal complexity in the presumed visual and auditory occipitotemporal cortex. Canidae had the largest number of unique major sulci, including one in the occipital cortex and highly social canids featuring an additional frontal cortex sulcus. We also observed differentially complex occipitotemporal sulcal patterns in Felidae and Canidae, indicative of changes in auditory and visual areas that may be related to foraging strategies and social behaviour. In conclusion, this study presents an inventory of the sulcal anatomy of a number of rarely studied carnivoran brains including detailed digital atlases and establishes a framework and novel avenues for further investigations employing a variety of neuroimaging modalities to reveal more about carnivoran brain diversity.

Mosquito-borne viruses are emerging in new regions with increasing regularity. Shifting climatic envelopes, especially in temperate regions, and altered enzootic cycles are changing likelihoods of persistence, meaning new approaches are required to predict and monitor establishment. Usutu virus (USUV) is a mosquito-borne viral zoonosis, which was first recorded in the United Kingdom in wild birds and mosquitoes in 2020. By developing a multidisciplinary approach, incorporating enhanced passive and active surveillance of wild birds, we discovered previously unrecorded introductions and identified USUV persistence and geographic expansion. By combining molecular and serological testing with citizen science derived datasets, we show an associated marked decline in a common, widespread, and highly susceptible host species (Eurasian Blackbird, Turdus merula). However, the clearest continuous signal of host population decline remains localised to a large urban area, despite the much wider virus distribution. This may be a consequence of an urban heat island effect and associated increase in length of the mosquito active season. Our results indicate that the establishment and impact of future mosquito-borne pathogens in temperate zones, anticipated under climate change, may first be most apparent in urban areas. Consequently, enhanced surveillance efforts in urban areas could provide an efficient mechanism for detecting novel pathogen emergence. The epidemiology of emerging vector-borne diseases, especially in temperate areas, depends on the interplay between climate, land-use and available hosts; therefore, considering each in isolation will not be sufficient to reliably inform surveillance or response planning. ### Competing Interest Statement The authors have declared no competing interest. UK Research and Innovation, https://ror.org/001aqnf71, BB/X017990/1 Department for Environment Food and Rural Affairs, https://ror.org/00tnppw48, SV3045 Garfield Weston Foundation, https://ror.org/00rm5fa18 Universities Federation for Animal Welfare, https://ror.org/00qy2eq52

Sex is an important driver of variation in behaviour, ecology and physiology. Sex identification in the Critically Endangered European eel (Anguilla anguilla) currently requires fish sacrifice, or the use of morphological differences such as body length, which can be inaccurate in certain habitats and at intermediate body lengths. Non-lethal tools for accurate sex identification in this species are therefore required. Here, we test the efficacy of two minimally invasive methods of sex identification: (1) ultrasonography and (2) molecular markers taken from pectoral fin clips. Both methodologies were applied to riverine European silver eel and compared to histological sex identification. Ultrasonography accurately identified the gonads in female eel, with males identified by the absence of detectable gonadal structures. The level of expression of three molecular markers (dcn, LOC111853410, kera) previously used to identify sex in Japanese eel (Anguilla japonica) were evaluated. There was no significant differential expression of the three molecular markers between sexes, suggesting that these markers cannot be accurately used to identify sex in European eel. Our findings suggest that minimally invasive imaging using ultrasonography can be a reliable tool for identifying sex in early-stage adult migratory European eels, with particular use at intermediate sizes (400-500 mm) and animals in habitats where migration potential is limited and may regularly exceed typical growth sizes. This technique can be highly valuable for studies that address ecological, behavioural, conservation and management issues in this Critically Endangered species.

Establishment of breeding programs in zoo-housed Humboldt penguin (Spheniscus humboldti) colonies often takes several years and breeding success is generally perceived as poor. Husbandry and pathology records of eggs laid since the establishment of London Zoo's colony were retrospectively analyzed. Following a barren period from arrival of the first birds in May 2011, the first egg to hatch was laid in December 2013 and egg laying was consistent over the following 10 yr. A total of 823 eggs were laid by male-female pairs, so from 2018 onwards some newly-laid eggs were removed in order to limit population growth. Of the 556 eggs incubated by 61 pairs, 289 (52.0%) hatched. Individual females laid between one and 56 eggs across this period; over 40% of which were laid in March, generally as their first clutch of the year. Hatching was significantly affected by the time of year (p = 0.004), the laying order in the clutch (p < 0.001), and the nest type (p = 0.004), but not by the year, size of the clutch, parental age, or whether either parent had been parent or hand-reared. Postmortem examination of eggs that failed to hatch only identified embryos in 27.2%, covering a range of developmental stages. However, half of the remainder were too autolyzed for a meaningful diagnosis. More detailed, microscopic examination of 78 of the eggs from 2019-20 revealed that only six of 71 eggs (8.5%) that were diagnosed as suspect infertile on gross examination were truly infertile. In addition, two of the seven eggs suspected to be fertile on gross examination had no microscopic evidence of fertility. These findings highlight the importance of microscopic examination of unhatched eggs for accurate fertility assessment.

Encephalomyocarditis virus (EMCV-1) is a known cause of fatal myocarditis in captive nonhuman primates, but subclinical infection has not previously been documented. This retrospective study investigated evidence of subclinical EMCV-1 infection in 29 individuals representing four primate species—white-naped mangabey (Cercocebus lunulatus), Kikuyu black-and-white colobus monkey (Colobus guereza kikuyuensis), northern plains gray langur (Semnopithecus entellus), and Sulawesi crested macaque (Macaca nigra)—housed at Zoological Society of London, London Zoo. Thirty-nine serum samples were tested for EMCV-1-specific immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies using ELISA. Thirteen samples from 11 individuals tested positive for EMCV-1 IgM and/or IgG. Notably, three individuals were IgG-positive despite no history of clinical disease, indicative of prior subclinical infection and seroconversion. Postmortem EMCV PCR was performed on tissues from four seropositive individuals that died of unrelated causes. One individual was PCR-positive for EMCV-1, confirming active subclinical infection at the time of death, with no clinical signs or histopathological lesions attributable to EMCV-1. These findings provide the first evidence of natural subclinical EMCV-1 infection in captive nonhuman primates and highlight the importance of serological surveillance in zoo populations.

Mosquito-borne virus transmission continues to increase in Europe, with the emergence of Usutu virus (USUV) in the United Kingdom (UK) in 2020 and the geographical expansion of West Nile virus (WNV) to more northerly latitudes. Other mosquito-borne viruses also circulate throughout mainland Europe, including Batai virus (BATV), leading to seropositivity in a range of vertebrate species, including humans, livestock and birds. A panel of archived sera from birds housed within a zoological collection in Central London was investigated for antibodies raised against the mosquito-borne viruses USUV, WNV and BATV. Orthoflavivirus seropositivity was detected in several birds, along with antibodies raised against BATV, an orthobunyavirus previously not reported in the UK. Furthermore, seropositivity in birds bred in captivity provides evidence of cryptic transmission of mosquito-borne viruses. This study highlights the utility of zoological collection birds as sentinels for VBD detection.

Analysis of our results with the outlier species removed

All of the PGLS regressions done with the exception of the multivariate analysis. The multivariate analysis is included as a separate file S41

A geriatric southern white rhinoceros ( Ceratotherium simum simum ) held at a zoological institution was euthanased following persistent dysmastication and decreasing body condition. A postmortem examination revealed marked calculi on the surfaces of the maxillary and mandibular molars with associated severe gingival recession, fetid material within diastemas and periodontal pockets, and multiple markedly mobile teeth. Postmortem computed tomography of the head found advanced periodontitis and apical periodontitis. Maceration of the skull showed severe vertical alveolar bone loss. The narrow oral cavity of the rhinoceros and the risk of general anaesthesia make dental examination difficult; however, the importance of such procedures to monitor and improve animal welfare is evident in the face of the advanced nature of the presented periodontal disease. Consequently, successful oral examinations have been performed on conspecifics at the same zoological institution. Details and recommendations for performing dental examinations on white rhinoceros are provided.

Cell line collection and passage number information for the functional cell assays

List of veterinarian diagnoses used as the data dictionary

The hazel dormouse (Muscardinus avellanarius) population in the UK continues to decline due to habitat loss, despite reintroductions of captive-bred individuals being conducted nationally for over 30 years. Disease surveillance of captive-bred and wild dormice is performed to identify novel and existing disease threats which could impact populations. In this study, we firstly investigated cause of death in seven hazel dormice found dead in England, through next-generation sequencing identifying a virus closely related to a wood mouse encephalomyocarditis virus-2 (EMCV-2). Subsequently, lung tissue samples from 35 out of 44 hazel dormice tested positive for EMCV-2 RNA using a reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and Sanger sequencing methods developed in this study. Formalin-fixed tissues available for nine hazel dormice which tested positive for EMCV-2 RNA were examined microscopically. Three cases showed moderate interstitial pneumonia with minimal to mild lymphoplasmacytic myocarditis, but no evidence of encephalitis. However, the presence of possible alternative causes of death in these cases means that the lesions cannot be definitively attributed to EMCV-2. Here, we report the first detection of EMCV-2 in hazel dormice and conclude that EMCV-2 is likely to be endemic in the hazel dormouse population in England and may be associated with clinical disease.

Entamoebiasis is a significant disease in non-human primates (NHPs), causing a spectrum of clinical presentations ranging from asymptomatic carriage to severe, necrotizing colitis and life-threatening extraintestinal dissemination. This study examined entamoebiasis in captive NHPs across nine zoological collections from 2004 to 2020. A total of 28 cases, spanning nine Old World (OW) and four New World (NW) primate species, were confirmed via histopathology and Entamoeba histolytica immunohistochemistry. Entamoebiasis caused intra- and extraintestinal disease, including necrotizing colitis and hepatitis, with characteristic gross and histological lesions including well-demarcated transmural 'flask-like' mucosal ulceration and necrotizing hepatitis with intralesional amoebic trophozoites. Rare cases presented with pneumonia, peritonitis and orchitis. OW primates, particularly Colobinae species, were more frequently affected. This study expands the known host range of entamoebiasis providing the first reports in emperor tamarin (Saguinus imperator), king colobus (Colobus polykamos), grizzled leaf (Presbytis comata), black howler (Alouatta caraya), brown spider (Ateles hybridus) and white-faced saki (Pithecia pithecia) monkeys. No seasonal trends were observed, and cases involved both sexes and all age groups, predominantly adults. Species-specific differences were noted, with OW primates having more frequent transmural colitis. These findings emphasize the importance of entamoebiasis in differential diagnoses for NHPs with gastrointestinal signs, and include recommendations for routine collection of fresh, frozen and formalin-fixed tissues during necropsy, prioritizing gastrointestinal and hepatic samples. Regular health assessments and surveillance for Entamoeba species in NHPs are crucial for detecting subclinical carriers, enabling early, targeted interventions and minimizing negative impacts on NHP populations and conservation efforts.

BACKGROUND:Sindbis virus (SINV) and Batai virus (BATV) are emerging zoonotic arboviruses with a growing number of detections in Europe. Recent SINV outbreaks in northern Europe and high BATV seroprevalence in sheep, goats, and cattle in Germany emphasise the threat they pose to both animal and human health. Despite their presence in countries of similar latitude and climate, neither of these viruses have been detected in the UK. METHODS:Zoos are strategic sentinel sites for disease surveillance because they are well monitored and possess a high diversity of animal species. Located in southeast England, where the climate and vector prevalence may provide suitable conditions for viral emergence, London Zoo was selected as the sampling site for SINV and BATV prevalence in mosquito samples between September 2022 and January 2024. In 2020, it was also the first location where Usutu virus was detected in the UK. Adult mosquitoes were collected during host-seeking and overwintering seasons while larvae were collected in the summer months. RESULTS:A total of 8477 mosquito specimens were analysed, representing all mosquito stages, i.e. including host-seeking and overwintering mosquitoes as well as adults that had emerged from larvae. Mosquitoes of the Culex pipiens/Culex torrentium complex were the most abundant, accounting for 97.5% of the total. Molecular analysis using quantitative polymerase chain reaction was performed to test for SINV and BATV; however, none of the samples tested positive. CONCLUSIONS:These results suggest that neither SINV nor BATV actively circulated in the sampled area during the study period. The findings provide baseline data for arbovirus surveillance in the UK, particularly at London Zoo, which is home to diverse bird populations that might be potential sentinel populations for viral emergence. Future studies that obtain molecular and serological data on birds or mammals housed at the zoo would complement our surveillance efforts on the emergence or prevalence of SINV and BATV in the UK. This study focused on a single location, but extending sampling and monitoring to other sites across the UK, especially in the southeast, is crucial to strengthening the UK's preparedness and response strategies in case SINV and BATV emerge in the country in the future.

Toxoplasma gondii is a globally distributed apicomplexan protozoan of zoonotic importance. Domestic cats (Felis catus) and related felids constitute its sole definitive hosts, while numerous warm-blooded species serve as intermediate hosts. Infection outcomes for intermediate hosts range from latent toxoplasmosis to behaviour alteration and fatal systemic disease. Oocysts, the lifecycle environmental stage, are often washed into watercourses, making river-dwelling species like Eurasian beavers (Castor fiber) particularly at risk. To investigate the presence and impact of T. gondii on beavers in the United Kingdom, archived brain, heart, and liver from 23 beavers necropsied between 2021 and 2023 were screened for T. gondii DNA by nested- and quantitative PCR. Positive samples were genotyped using a panel of six published PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) assays and amplicon sequencing. Sequences were aligned with those reported previously from UK and other wildlife species to assess the occurrence of shared genotypes. Toxoplasma gondii DNA was detected in 19/23 (83%) Eurasian beavers; all consistent with PCR-RFLP ToxoDB#3 with limited genetic diversity, concurring with findings from previous surveillance of UK wildlife species. Following histopathological screening non-suppurative toxoplasmosis was characterised in 3/6 tissues selected from two animals. These results demonstrate a high occurrence of T. gondii infection in UK beavers

Abstract Cancer is pervasive across multicellular species, but what explains the differences in cancer prevalence across species? Using 16,049 necropsy records for 292 species spanning three clades of tetrapods (amphibians, sauropsids, and mammals), we found that neoplasia and malignancy prevalence increases with adult mass (contrary to Peto’s paradox) and somatic mutation rate but decreases with gestation time. The relationship between adult mass and malignancy prevalence was only apparent when we controlled for gestation time. Evolution of cancer susceptibility appears to have undergone sudden shifts followed by stabilizing selection. Outliers for neoplasia prevalence include the common porpoise (<1.3%), the Rodrigues fruit bat (<1.6%), the black-footed penguin (<0.4%), ferrets (63%), and opossums (35%). Discovering why some species have particularly high or low levels of cancer may lead to a better understanding of cancer syndromes and novel strategies for the management and prevention of cancer. Significance: Evolution has discovered mechanisms for suppressing cancer in a wide variety of species. By analyzing veterinary necropsy records, we can identify species with exceptionally high or low cancer prevalence. Discovering the mechanisms of cancer susceptibility and resistance may help improve cancer prevention and explain cancer syndromes. See related commentary by Metzger, p. 14