Clostridium perfringens septicemia in a long-beaked common dolphin Delphinus capensis: an etiology of gas bubble accumulation in cetaceans

Anthropic Pressure on Cetaceans Stranded Along the Ligurian Coast Within the Pelagos Sanctuary: A Case Series

Data collected by C. Re. Di. Ma over a 3-year period (2020-2022) were considered to assess anthropic pressure on cetaceans living in the Ligurian sea. Out of a total of 37 stranded cetaceans, a complete post mortem examination was performed on 23 cases. Of these, 14 were further selected considering at least one of these conditions: (i) confirmed, probable, or suspected interaction with fishing activities through the application of a standardized diagnostic framework (7/14; 50%), (ii) toxicological stress through the evaluation of OCs hazardous levels (14/14; 100%), and (iii) terrestrial pathogen-associated disease (systemic infection and/or associated lesions) (7/14; 50%). For 9 animals out of a total of 14 selected, the cause of death was classified as natural (6/14; 42,8%), anthropic (3/14; 21,4%), or not determined (5/14; 35,7%) based on gross and histological pathology and ancillary testing. These findings extend our knowledge of the anthropic pressure to which cetaceans stranded along the Ligurian coastline are subjected from a multidisciplinary point of view.

Illustrated cross-sectional computed tomography of the cetacean abdomino-pelvic organs

BACKGROUND

Computed tomography (CT) is a non-invasive diagnostic imaging modality which can be used to study the anatomy and morphology of live or deceased animals in-situ. In cetaceans, existing CT anatomy studies mostly focused on the head and thoracic regions. Using postmortem CT (PMCT) scans of Indo-Pacific finless porpoises (Neophocaena phocaenoides), this study describes the cross-sectional imaging anatomy of the cetacean abdomino-pelvic organs for the first time.

METHODS

PMCT scans of finless porpoises stranded in Hong Kong waters were reviewed, of which two freshly dead cases, one male and one female, were selected for illustration. In addition, a contrast-enhanced PMCT scan was performed on the female subject as a trial for a PMCT-angiography study (PMCTA) in cetaceans. A total of 18 axial PMCT images were acquired at selected vertebral levels in the abdomen and supplemented with a series of corresponding labeled anatomical diagrams.

RESULTS

By applying different image rendering techniques, most osseous and soft tissue structures in the finless porpoise abdomen were successfully depicted and annotated on PMCT, including the male and female reproductive organs in the pelvic region. The application of contrast medium in PMCT created artificial radiodensity differences which improved the ability to visualize and differentiate soft organs and vasculature. The merits and limitations of CT compared to other imaging modalities, as well as the future directions of PMCT in stranding investigation, were discussed.

CONCLUSIONS

The findings from this study significantly enhance the applications of CT in cetaceans by assisting researchers and veterinarians in the interpretation of cetacean abdomino-pelvic CT for morphological and pathological assessment during clinical or postmortem examination.

Case Report: Ambergris coprolite and septicemia in a male sperm whale stranded in La Palma (Canary Islands)

On the 21st of May 2023, a dead adult male sperm whale (Physeter macrocephalus) of 13 m in length and estimated weight of around 18,000 kg was reportedly stranded at Playa Los Nogales, La Palma, Canary Islands, Spain. A necropsy was performed 48hpm. A 50 cm diameter and 9.5 kg coprolite was found obstructing the caudal colon-rectal lumen. Necro-hemorrhagic lesions were found in heart muscles and three different bacteria of intestinal origin were isolated and identified (Edwarsiella tarda, Hathewaya limosa and Clostridium perfringens). It is reported a lethal septicemia of intestinal origin associated with ambergris coprolite as cause of death in this sperm whale.

Fecal and skin microbiota of two rescued Mediterranean monk seal pups during rehabilitation

IMPORTANCE

This study showed that during the rehabilitation of two rescued Mediterranean monk seal pups (Monachus monachus), the skin and fecal bacterial communities showed similar succession patterns between the two individuals. This finding means that co-housed pups share their microbiomes, and this needs to be considered in cases of infection outbreaks and their treatment. The housing conditions, along with the feeding scheme and care protocols, including the admission of antibiotics as prophylaxis, probiotics, and essential food supplements, resulted in bacterial communities with no apparent pathogenic bacteria. This is the first contribution to the microbiome of the protected seal species of M. monachus and contributes to the animal's conservation practices through its microbiome.

Marine biological injuries and their medical management: A narrative review

The marine environment can be extremely dangerous, and the harm caused by marine organisms when they contact the human body can be especially harmful, even deadly. Contact includes stings, bites, wounds, and consumption as food. In this article, the characteristics of the common marine biological injuries are summarized, the major marine organisms causing damage in China’s marine waters are described, and injury prevention and treatment methods are discussed.

Vitamin B12 biosynthesis of Cetobacterium ceti isolated from the intestinal content of captive common bottlenose dolphins (Tursiops truncatus)

In comparison with terrestrial mammals, dolphins require a large amount of haemoglobin in blood and myoglobin in muscle to prolong their diving time underwater and increase the depth they can dive. The genus Cetobacterium is a common gastrointestinal bacterium in dolphins and includes two species: C. somerae and C. ceti. Whilst the former produces vitamin B₁₂, which is essential for the biosynthesis of haem, a component of haemoglobin and myoglobin, but not produced by mammals, the production ability of the latter remains unknown. The present study aimed to isolate C. ceti from dolphins and reveal its ability to biosynthesize vitamin B₁₂. Three strains of C. ceti, identified by phylogenetic analyses with 16S rRNA gene and genome-based taxonomy assignment and biochemical features, were isolated from faecal samples collected from two captive common bottlenose dolphins (Tursiops truncatus). A microbioassay using Lactobacillus leichmannii ATCC 7830 showed that the average concentration of vitamin B₁₂ produced by the three strains was 11 (standard deviation: 2) pg ml^-1. The biosynthesis pathway of vitamin B₁₂, in particular, adenosylcobalamin, was detected in the draft genome of the three strains using blastKOALA. This is the first study to isolate C. ceti from common bottlenose dolphins and reveal its ability of vitamin B₁₂ biosynthesis, and our findings emphasize the importance of C. ceti in supplying haemoglobin and myoglobin to dolphins.

Characterisation of Crassicauda fuelleborni nematode infection in Indo-Pacific finless porpoises (Neophocaena phocaenoides) using postmortem computed tomography

Nematodes of the genus Crassicauda are parasites that infect various body tissues of cetaceans, including the mammary glands which can influence the reproductive output and hence threaten the survival of endangered cetacean populations. In this study, postmortem computed tomography (PMCT) was used to characterise lesions related to Crassicauda fuelleborni infections in stranded Indo-Pacific finless porpoises (Neophocaena phocaenoides) from Hong Kong waters. Using PMCT and subsequently verified by conventional necropsy, Crassicauda-related lesions were found in 52% of finless porpoises examined (n = 13/25), including both males and females. These parasitic lesions were mostly located in the ventral abdominal muscles in both sexes and situated in proximity to the mammary glands in females. C. fuelleborni infections were also found in the male reproductive organs, which to our knowledge have not been reported in this cetacean species previously. PMCT characteristics of the lesions were also correlated with the gross appearance observed at necropsy and the chronicity of the parasitic infections. In conclusion, this study established the use of virtopsy, particularly PMCT, to characterise C. fuelleborni infections in stranded finless porpoises for the first time, which is non-invasive and can be used prior to conventional necropsy to aid disease diagnosis and targeted sampling. This technique can be extended to other species of cetaceans and parasites, as well as being used in the retrospective analysis of past PMCT scans to deepen our understanding of the prevalence, health impacts, and ecological implications of parasitic infection in cetaceans.

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Computed tomography descriptions of cetacean mammary glands and adjacent musculature.

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Detection and characterisation of Crassicauda-related lesions using virtopsy.

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Crassicauda-related lesions found in 52% of finless porpoises examined in Hong Kong.

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Virtopsy features correlated with necropsy findings and chronicity of infection.

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Virtopsy can be used to study the prevalence and impact of parasitic infection in cetaceans.

A Review and Case Study of 3D Imaging Modalities for Female Amniote Reproductive Anatomy

Recent advances in non-invasive imaging methods have revitalised the field of comparative anatomy, and reproductive anatomy has been no exception. The reproductive systems of female amniotes present specific challenges, namely their often internal "hidden" anatomy. Quantifying female reproductive systems is crucial to recognising reproductive pathologies, monitoring menstrual cycles, and understanding copulatory mechanics. Here we conduct a review of the application of non-invasive imaging techniques to female amniote reproductive anatomy. We introduce the commonly used imaging modalities of computed tomography (CT) and magnetic resonance imaging (MRI), highlighting their advantages and limitations when applied to female reproductive tissues, and make suggestions for future advances. We also include a case study of micro CT and MRI, along with their associated staining protocols, applied to cadavers of female adult stoats (Mustela erminea). In doing so, we will progress the discussion surrounding the imaging of female reproductive anatomy, whilst also impacting the fields of sexual selection research and comparative anatomy more broadly.

Suppurative necrotizing bronchopneumonia caused by Nocardia cyriacigeorgica infection in a stranded striped dolphin (Stenella coeruleoalba) in Japan

On a coastline in Miyazaki Prefecture, Japan, a wild subadult female striped dolphin was found dead. Necropsy revealed poor nutritional status and bilateral pneumonia, which was histologically diagnosed as severe suppurative necrotizing bronchopneumonia. Special staining detected numerous intralesional filamentous, branching bacteria, which was identified as Nocardia cyriacigeorgica by sequencing of 16S ribosomal RNA and gyrB genes. Other main histological findings included lymphoid depletion in the spleen and superficial cervical and pulmonary lymph nodes. Suppurative nocardiosis without a granulomatous reaction is uncommon, and it is assumed its pathogenesis was related to the host's immune status. This paper discusses the variable inflammatory response to nocardiosis and describes the first case of N. cyriacigeorgica infection in a wild striped dolphin in Japan.

The Gut Microbial Community Structure of the North American River Otter (Lontra canadensis) in the Alberta Oil Sands Region in Canada: Relationship with Local Environmental Variables and Metal Body Burden

The Alberta Oil Sands Region in Canada is home to one of the largest oil bitumen deposits in the world. The North American river otter (Lontra canadensis) is a top predator with a small home range and is sensitive to disturbances; it has been designated as a sentinel species for the potential impacts of the natural resource exploitation on freshwater ecosystems in the Alberta Oil Sands Region. With an increasing interest in noninvasive biomarkers, recent studies suggest that gut microbiota can be used as a potential biomarker of early biological effects on aquatic wildlife. The goal of the present study was to determine the river otter gut microbial structure related to environmental variables characterizing mining activities and metal body burden. We obtained 18 trapped animals from and surrounding the surface mineable area of the Alberta Oil Sands Region. The gut microbial community structure was characterized using high-throughput sequencing of 16S rRNA gene amplicon analyses. Trace metal concentrations in the liver were measured by inductively coupled plasma-mass spectrometry. Our study revealed that the gut bacteria of river otters in the Alberta Oil Sands Region clustered in 4 groups dominated by Peptostreptococcaceae, Carnobacteriaceae, Enterobacteriaceae, Clostridiaceae, and Nostocaceae. We show that arsenic, barium, rubidium, liver-body weight ratio, and δ¹⁵ N were associated with each cluster. When comparing affected versus less affected sites, we show that river otter gut bacterial community and structure are significantly related to trophic level of the river otter but not to Alberta Oil Sands Region mining activities. Our study reveals that the gut bacterial dynamics can provide insights into the diet and habitat use of river otters but that more work is needed to use it as a pollution biomarker. Environ Toxicol Chem 2020;39:2516-2526. © 2020 SETAC.

Host phylogeny and life history stage shape the gut microbiome in dwarf (Kogia sima) and pygmy (Kogia breviceps) sperm whales

Gut microbiomes perform crucial roles in host health and development, but few studies have explored cetacean microbiomes especially deep divers. We characterized the gut microbiomes of stranded dwarf (Kogia sima) and pygmy (K. breviceps) sperm whales to examine the effects of phylogeny and life stage on microbiome composition and diversity. 16S rRNA gene sequence analysis revealed diverse gut communities (averaging 674 OTUs) dominated by a few symbiont taxa (25 OTUs accounted for 64% of total relative abundance). Both phylogeny and life stage shaped community composition and diversity, with species-specific microbiome differences present early in life. Further analysis showed evidence of microbiome convergence with host maturity, albeit through different processes: symbiont 'accumulation' in K. sima and 'winnowing' in K. breviceps, indicating different methods of community assembly during host development. Furthermore, culture-based analyses yielded 116 pure cultures matching 25 OTUs, including one isolate positive for chitin utilization. Our findings indicate that kogiid gut microbiomes are highly diverse and species-specific, undergo significant shifts with host development, and can be cultivated on specialized media under anaerobic conditions. These results enhance our understanding of the kogiid gut microbiome and may provide useful information for symbiont assessment in host health.

Molecular Hydrogen Metabolism: a Widespread Trait of Pathogenic Bacteria and Protists

Pathogenic microorganisms use various mechanisms to conserve energy in host tissues and environmental reservoirs. One widespread but often overlooked means of energy conservation is through the consumption or production of molecular hydrogen (H2). Here, we comprehensively review the distribution, biochemistry, and physiology of H2 metabolism in pathogens. Over 200 pathogens and pathobionts carry genes for hydrogenases, the enzymes responsible for H2 oxidation and/or production. Furthermore, at least 46 of these species have been experimentally shown to consume or produce H2 Several major human pathogens use the large amounts of H2 produced by colonic microbiota as an energy source for aerobic or anaerobic respiration. This process has been shown to be critical for growth and virulence of the gastrointestinal bacteria Salmonella enterica serovar Typhimurium, Campylobacter jejuni, Campylobacter concisus, and Helicobacter pylori (including carcinogenic strains). H2 oxidation is generally a facultative trait controlled by central regulators in response to energy and oxidant availability. Other bacterial and protist pathogens produce H2 as a diffusible end product of fermentation processes. These include facultative anaerobes such as Escherichia coli, S Typhimurium, and Giardia intestinalis, which persist by fermentation when limited for respiratory electron acceptors, as well as obligate anaerobes, such as Clostridium perfringens, Clostridioides difficile, and Trichomonas vaginalis, that produce large amounts of H2 during growth. Overall, there is a rich literature on hydrogenases in growth, survival, and virulence in some pathogens. However, we lack a detailed understanding of H2 metabolism in most pathogens, especially obligately anaerobic bacteria, as well as a holistic understanding of gastrointestinal H2 transactions overall. Based on these findings, we also evaluate H2 metabolism as a possible target for drug development or other therapies.

Advances in research on the impacts of anti-submarine sonar on beaked whales

Mass stranding events (MSEs) of beaked whales (BWs) were extremely rare prior to the 1960s but increased markedly after the development of naval mid-frequency active sonar (MFAS). The temporal and spatial associations between atypical BW MSEs and naval exercises were first observed in the Canary Islands, Spain, in the mid-1980s. Further research on BWs stranded in association with naval exercises demonstrated pathological findings consistent with decompression sickness (DCS). A 2004 ban on MFASs around the Canary Islands successfully prevented additional BW MSEs in the region, but atypical MSEs have continued in other places of the world, especially in the Mediterranean Sea, with examined individuals showing DCS. A workshop held in Fuerteventura, Canary Islands, in September 2017 reviewed current knowledge on BW atypical MSEs associated with MFAS. Our review suggests that the effects of MFAS on BWs vary among individuals or populations, and predisposing factors may contribute to individual outcomes. Spatial management specific to BW habitat, such as the MFAS ban in the Canary Islands, has proven to be an effective mitigation tool and mitigation measures should be established in other areas taking into consideration known population-level information.

Occurrence of anthropozoonotic parasitic infections and faecal microbes in free-ranging sperm whales (Physeter macrocephalus) from the Mediterranean Sea

Sperm whales (Physeter macrocephalus) are the largest toothed whales and only living member of family Physeteridae. Present survey represents first report on cultivable faecal microbes and gastrointestinal helminths and protozoans infecting free-ranging sperm whales inhabiting Mediterranean Sea waters surrounding Balearic Archipelago, Spain. Twenty-five individual sperm whale scat samples, including one calf, were collected without disturbance of animals during the summer of 2016. Parasitological diagnostic methods, such as sodium acetate acetic formalin (SAF) method, carbol fuchsin-stained faecal smears, Giardia/Cryptosporidium coproantigen ELISAs and an Anisakis-specific PCR were applied for further identification. Five bacterial genera, i.e. Acinetobacter, Clostridium, Enterococcus, Staphylococcus and Streptococcus, and one fungus namely Cladosporium were identified. Parasitological infections included seven different parasite species with some of them bearing anthropozoonotic potential. Thus, four of these parasites were zoonotic, i.e. Anisakis, Balantidium, Diphyllobothriidae gen. sp. and Giardia. Additionally, Zalophotrema curilensis eggs, spirurid-like eggs and Cystoisospora-like oocysts were identified. Molecular characterization identified Anisakis physeteris as the species infecting these whales. This survey provides first records on occurrence of two zoonotic enteropathogenic protozoan parasites (Giardia and Balantidium) and of facultative pathogenic bacteria (Clostridium and Enterococcus) in sperm whales. Presented data should be considered as a baseline study for future monitoring surveys on anthropozoonotic pathogens affecting free-living sperm whale populations and enhance investigations on possible impact on public health as well as on isolated Mediterranean sperm whale subpopulation.

Discrimination between bycatch and other causes of cetacean and pinniped stranding

The challenge of identifying cause of death in discarded bycaught marine mammals stems from a combination of the non-specific nature of the lesions of drowning, the complex physiologic adaptations unique to breath-holding marine mammals, lack of case histories, and the diverse nature of fishing gear. While no pathognomonic lesions are recognized, signs of acute external entanglement, bulging or reddened eyes, recently ingested gastric contents, pulmonary changes, and decompression-associated gas bubbles have been identified in the condition of peracute underwater entrapment (PUE) syndrome in previous studies of marine mammals. We reviewed the gross necropsy and histopathology reports of 36 cetaceans and pinnipeds including 20 directly observed bycaught and 16 live stranded animals that were euthanized between 2005 and 2011 for lesions consistent with PUE. We identified 5 criteria which present at significantly higher rates in bycaught marine mammals: external signs of acute entanglement, red or bulging eyes, recently ingested gastric contents, multi-organ congestion, and disseminated gas bubbles detected grossly during the necropsy and histologically. In contrast, froth in the trachea or primary bronchi, and lung changes (i.e. wet, heavy, froth, edema, congestion, and hemorrhage) were poor indicators of PUE. This is the first study that provides insight into the different published parameters for PUE in bycatch. For regions frequently confronted by stranded marine mammals with non-specific lesions, this could potentially aid in the investigation and quantification of marine fisheries interactions.

Frequency of decompression illness among recent and extinct mammals and "reptiles": a review

The frequency of decompression illness was high among the extinct marine "reptiles" and very low among the marine mammals. Signs of decompression illness are still found among turtles but whales and seals are unaffected. In humans, the risk of decompression illness is five times increased in individuals with Patent Foramen Ovale; this condition allows blood shunting from the venous circuit to the systemic circuit. This right-left shunt is characteristic of the "reptile" heart, and it is suggested that this could contribute to the high frequency of decompression illness in the extinct reptiles.