Cetacea

Verminous bronchitis and pneumonia by nasal trematodes in Greater Caribbean manatees from Puerto Rico

Five adult Greater Caribbean manatees Trichechus manatus manatus were found stranded on various coasts of Puerto Rico; 2 stranded alive and 3 stranded dead. Clinical signs observed in live-stranded manatees included emaciation, weakness, bradypnea, arrhythmia, and nasal mucus discharge. Postmortem examinations revealed serosanguinous, mucohemorrhagic, or suppurative exudate in bronchi associated with luminal adult Pulmonicola cochleotrema (range: 18-182 trematodes), accompanied by pulmonary abscesses in 2 cases. Histologically, we observed eosinophilic bronchopneumonia of varying severity (n = 4) and chronic erosive to eosinophilic tracheobronchitis (n = 4) with squamous metaplasia (n = 3) and intralesional trematodes and eggs. The trematode identity was confirmed and compared through molecular analysis for the amplified 18S rDNA fragment. Comorbidities included enteric chiorchosis (n = 5), gastric heterocheilosis (n = 4), malnutrition (n = 4), trauma related to watercraft collision (n = 3), systemic toxoplasmosis (n = 1), acute bacterial peritonitis (n = 1), and interstitial nephritis (n = 1), suggesting that immunosuppression was a predisposing factor for lower respiratory tract pulmonicolosis. Based on lesion severity, clinical signs, and the presence and absence of other findings to explain death, this condition was considered the primary cause of death in 1 manatee, a contributory cause of death in 3 manatees, and an incidental finding in 1 individual. These clinicopathological descriptions will facilitate the diagnosis and clinical management of pulmonicolosis in T. manatus, a species endangered with extinction.

Systemic Erysipelas Outbreak among Free-Ranging Bottlenose Dolphins, San Diego, California, USA, 2022

We diagnosed fatal Erysipelothrix rhusiopathiae sepsis in 3 stranded bottlenose dolphins (Tursiops truncatus) during summer 2022, in San Diego, California, USA. The previously undetected disease in this relatively small, regional population of dolphins most likely indicates an environmental or biological change in the coastal ocean or organisms.

Viral skin diseases in odontocete cetaceans: gross, histopathological, and molecular characterization of selected pathogens

Fifty-five skin lesions from 31 stranded cetaceans along the Canary coasts (2011-2021) were submitted to macroscopic, histological, and molecular analyses to confirm infection by cetacean poxvirus, herpesvirus and cetacean morbillivirus. They were macroscopically categorized into eight categories with respective subcategories according to their color, shape, size, and consistency. Cetacean poxvirus was detected in 54.54% of the skin lesions through real-time and conventional PCRs based on the DNA polymerase gene. Additionally, herpesvirus and morbillivirus were currently detected from 43.63 and 1.82% of the cutaneous lesions, respectively. Coinfection of poxvirus and herpesvirus was detected in nine of them (16.36%), which makes the present study the first to report coinfection by both pathogens in skin lesions in cetaceans. A plausible approach to histopathological characterization of poxvirus-and herpesvirus-positive skin lesions was established. Hyperkeratosis, acanthosis, ballooning degeneration, and intracytoplasmic inclusion bodies in vacuolized keratinocytes through the stratum spinosum were common findings in poxvirus skin lesions. Alphaherpesvirus was associated with a prominent acanthotic epidermis, moderate necrosis, multifocal dyskeratosis, and irregular keratinocytes with both cellular and nuclei pleomorphism. The common histopathological findings of both pathogens were observed in coinfection lesions. However, those associated with herpesvirus were considerably more remarkable. Relationships between molecular and microscopic findings were observed for the lesions that showed tattoo-like and tortuous patterns. Further multidisciplinary diagnostic studies of infected skin lesions are needed to understand the epidemiology of these emerging infectious diseases.

Congenital defects and herpesvirus infection in beluga whale Delphinapterus leucas calves from the Critically Endangered Cook Inlet population

Cook Inlet beluga whales (CIBs) Delphinapterus leucas are Critically Endangered and genetically distinct from other beluga populations in Alaska. CIBs are exposed to numerous natural and anthropogenic sources of mortality and morbidity. This study describes congenital defects observed in 2 CIB calves. The first case, an aborted fetus, was characterized by lack of a peduncle and flukes, anorectal and genitourinary dysgenesis, and probable biliary dysplasia. The second case, a male calf, had a perineal groove defect and suspected secondary peritonitis; it also had a systemic herpesvirus infection. Further studies are needed to determine if such defects are due to genetic mutation, infectious diseases, nutritional imbalances, or contaminant exposure.

Post-Mortem Computed Tomography Pulmonary Findings in Harbor Porpoises (Phocoena phocoena)

Simple Summary

The use of cross-sectional imaging techniques to examine the cause of death and health status of deceased animals is increasing in both veterinary and wildlife conservation programs, including species of whales and dolphins. Lung disease is common in harbor porpoises (Phocoena phocoena), a small whale species that regularly washes up on the coast in North Sea-bordering countries. This study aimed to describe lung changes visible in computed tomographic (CT) images of recently deceased harbor porpoises before pathological dissection was performed, including comparison of these two examination methods. Despite frequently visible signs of body decomposition, several lung abnormalities (collapsed lung, fluid in the airways, lung mineralization) were more often seen on the CT images. In general, lung changes could be described in more detail compared to gross dissection. CT images of lungs of recently deceased harbor porpoises can therefore be used to guide gross dissection, leading to more specific findings and potentially a more complete understanding of the circumstances leading to the death of the porpoise, assessment of the population, and ultimately, ecosystem health.

Abstract

The application of whole-body post-mortem computed tomography (PMCT) in veterinary and wildlife post-mortem research programs is advancing. A high incidence of pulmonary pathology is reported in the harbor porpoise (Phocoena phocoena). In this study, the value of PMCT focused on pulmonary assessment is evaluated. The objectives of this study were to describe pulmonary changes as well as autolytic features detected by PMCT examination and to compare those findings with conventional necropsy. Retrospective evaluation of whole-body PMCT images of 46 relatively fresh harbor porpoises and corresponding conventional necropsy reports was carried out, with a special focus on the respiratory tract. Common pulmonary PMCT findings included: moderate (24/46) to severe (19/46) increased pulmonary soft tissue attenuation, severe parasite burden (17/46), bronchial wall thickening (30/46), and mild autolysis (26/46). Compared to conventional necropsy, PMCT more frequently identified pneumothorax (5/46 vs. none), tracheal content (26/46 vs. 7/46), and macroscopic pulmonary mineralization (23/46 vs. 11/46), and provided more information of the distribution of pulmonary changes. These results indicate that PMCT adds information on pulmonary assessment and is a promising complementary technique for necropsy, despite the frequent presence of mild autolytic features.

Dietary effects on urinary physicochemistry in Navy bottlenose dolphins (Tursiops truncatus) for the prevention of ammonium urate kidney stones

Bottlenose dolphins are susceptible to developing ammonium urate (NH₄U) kidney stones. The current study was designed to test the hypothesis that diet influences the urinary physicochemistry risk factors associated with nephrolithiasis in dolphins. A comprehensive nutrient analysis was performed revealing that the baseline diet (BD) commonly fed to dolphins under professional care had a greater purine content and a more negative dietary cation-anion difference (DCAD) when compared with a model diet consumed by free-ranging dolphins. A modified diet (MD) was formulated to include free-ranging diet fish species and achieve a more positive DCAD. The BD had a more negative DCAD (-52 mEq/Mcal metabolizable energy) when compared with the MD (+51 mEq/Mcal ME), which more closely approximated the DCAD of the free-ranging model diet (+152 mEq/Mcal ME). Six dolphins (with stones) were fed the BD followed by the MD for a minimum of 4 wk. At the end of each feeding trial, a 6-h continuous urine collection was performed to compare urine parameters of dolphins fed the BD versus MD. Dolphins consuming the MD demonstrated a significant decrease in urinary ammonium, net acid excretion, saturation index of ammonium urate, and phosphorous, and a significant increase in urinary citrate and net gastrointestinal (GI) alkali absorption, as compared with urine parameters assessed when fed the BD. Increasing the proportion of free-ranging diet fish species and optimizing the DCAD positively influenced some of the risk factors believed to be associated with NH₄U kidney stone development in bottlenose dolphins under professional care.

Multinucleate parietal cells and cytoplasmic inclusion bodies in the gastric epithelium of callitrichids

Inclusion bodies (IBs) and multinucleate cells can be associated with viral infections; however, IBs and multinucleate cells have been described in normal tissue and with non-viral disease processes in multiple species. We examined fundic stomach from 50 callitrichids histologically for bi- and multinucleate parietal cells and cytoplasmic IBs in gastric epithelial cells. Callitrichids represented included 6 genera: Saguinus (4 spp.), Leontopithecus (1 sp.), Mico (3 spp.), Cebuella (1 sp.), Callithrix (1 sp.), Callimico (1 sp.), and 13 unspecified marmosets. Gastric epithelial IBs were present in 46 of 47 (98%) of the callitrichids from which the stomach was sufficiently well preserved to identify IBs. Cytoplasmic IBs were identified in gastric surface pit epithelial cells (43 of 44, 98%), mucous neck cells (43 of 44, 98%), parietal cells (43 of 44, 98%), and chief cells (43 of 44, 98%). The IBs were eosinophilic, ovoid, round, elongate, or variably indented, sometimes slightly refractile, and 1-6 × 1-13 µm. IBs were sometimes perinuclear and molded around the nucleus. Electron microscopy of the gastric epithelium of one marmoset indicated that IBs were composed of intermediate filaments. The IBs did not stain with immunohistochemical markers for cytokeratin AE1/AE3 or vimentin. Binucleate parietal cells were found in 49 of 50 (98%) callitrichids, and multinucleate parietal cells were observed in 40 of 49 (82%) callitrichids. Gastric epithelial cytoplasmic IBs and bi- and multinucleate parietal cells are likely a normal finding in callitrichids, and, to our knowledge, have not been reported previously.

CEREBROSPINAL FLUID SAMPLING IN A BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) UNDER GENERAL ANESTHESIA

Brucella ceti, associated with neurobrucellosis, has been isolated from cerebrospinal fluid (CSF) of postmortem cetaceans. A 106-kg, stranded female bottlenose dolphin (Tursiops truncatus) presented with serum antibodies to Brucella spp. via competitive enzyme-linked immunosorbent assay and fluorescence polarization assay. Polymerase chain reaction (PCR) and culture of whole blood, bronchoalveolar fluid, and rectal, nasal, and genital swabs for Brucella spp. were consistently negative. Serial computed tomography revealed mild focal dilatation of brain ventricles. CSF sampling was warranted to exclude neurobrucellosis. Sedation was achieved with 30 mg diazepam (0.28 mg/kg) orally 2.5 hours prior to arrival in hospital, followed by 5.3 mg midazolam (0.05 mg/kg) intramuscularly, and anesthetic induction with 2.5 mg midazolam (0.02 mg/kg) and 200 mg propofol (2 mg/kg) administered slowly intravenously, followed by intubation and maintenance on sevoflurane using controlled mechanical and apneustic anesthesia ventilation. The atlanto-occipital joint was opened by flexing the upper cervical region with the animal in left lateral recumbency. A 20-ga × 6-inch spinal needle was advanced into the cisterna magna using radiographic guidance. CSF was collected successfully with no neurological deficits appreciable on recovery. Brucella spp. was not identified via PCR or culture. This represents the first report of an antemortem CSF tap in a cetacean.

Standardization of Dolphin Cardiac Auscultation and Characterization of Heart Murmurs in Managed and Free-Ranging Bottlenose Dolphins (Tursiops truncatus)

Cardiac auscultation is an important, albeit underutilized tool in aquatic animal medicine due to the many challenges associated with in-water examinations. The aims of this prospective study were to (1) establish an efficient and repeatable in-water cardiac auscultation technique in bottlenose dolphins (Tursiops truncatus), (2) describe the presence and characterization of heart murmurs detected in free-ranging and managed dolphins, and (3) characterize heart murmur etiology through echocardiography in free-ranging dolphins. For technique development, 65 dolphins cared for by the Navy Marine Mammal Program (Navy) were auscultated. The techniques were then applied to two free-ranging dolphin populations during capture-release health assessments: Sarasota Bay, Florida (SB), a reference population, and Barataria Bay, LA (BB), a well-studied population of dolphins impacted by the Deepwater Horizon oil spill. Systolic heart murmurs were detected at a frequent and similar prevalence in all dolphin populations examined (Navy 92%, SB 89%, and BB 88%), and characterized as fixed or dynamic. In all three populations, sternal cranial and left cranial were the most common locations for murmur point of maximal intensity (PMI). An in-water transthoracic echocardiogram technique was refined on a subset of Navy dolphins, and full echocardiographic exams were performed on 17 SB dolphins and 29 BB dolphins, of which, 40 had murmurs. Spectral Doppler was used to measure flow velocities across the outflow tracts, and almost all dolphins with audible murmurs had peak outflow velocities ≥1.6 m/s (95%, 38/40); three dolphins also had medium mitral regurgitation which could be the source of their murmurs. The presence of audible murmurs in most of the free-ranging dolphins (88%) was attributed to high velocity blood flow as seen on echocardiography, similar to a phenomenon described in other athletic species. These innocent murmurs were generally characterized as Grade I-III systolic murmurs with PMI in the left or sternal cranial region. This study is the first to describe an efficient technique for in-water dolphin cardiac auscultation, and to present evidence that heart murmurs are common in bottlenose dolphins.

Histopathological Differential Diagnosis of Meningoencephalitis in Cetaceans: Morbillivirus, Herpesvirus, Toxoplasma gondii, Brucella sp., and Nasitrema sp

Infectious and inflammatory processes are among the most common causes of central nervous system involvement in stranded cetaceans. Meningitis and encephalitis are among the leading known natural causes of death in stranded cetaceans and may be caused by a wide range of pathogens. This study describes histopathological findings in post-mortem brain tissue specimens from stranded cetaceans associated with five relevant infectious agents: viruses [Cetacean Morbillivirus (CeMV) and Herpesvirus (HV); n = 29], bacteria (Brucella sp.; n = 7), protozoa (Toxoplasma gondii; n = 6), and helminths (Nasitrema sp.; n = 1). Aetiological diagnosis was established by molecular methods. Histopathologic evaluations of brain samples were performed in all the cases, and additional histochemical and/or immunohistochemical stains were carried out accordingly. Compared with those produced by other types of pathogens in our study, the characteristic features of viral meningoencephalitis (CeMV and HV) included the most severe and frequent presence of malacia, intranuclear, and/or intracytoplasmic inclusion bodies, neuronal necrosis and associated neuronophagia, syncytia and hemorrhages, predominantly in the cerebrum. The characteristic features of Brucella sp. meningoencephalitis included the most severe and frequent presence of meningitis, perivascular cuffing, cerebellitis, myelitis, polyradiculoneuritis, choroiditis, ventriculitis, vasculitis, and fibrinoid necrosis of vessels. The characteristic features of T. gondii meningoencephalitis included lymphocytic and granulomatous encephalitis, tissue cysts, microgliosis, and oedema. In the case of Nasitrema sp. infection, lesions are all that we describe since just one animal was available. The results of this study are expected to contribute, to a large extent, to a better understanding of brain-pathogen-associated lesions in cetaceans.

Neurobrucellosis in a common bottlenose dolphin (Tursiops truncatus) stranded in the Canary Islands

Background

Brucella spp. isolation is increasingly reported in cetaceans, although associated pathologies, including lesions of the musculoskeletal and nervous systems, are less frequently described. Concerning the nervous system, Brucella sp. infection causing meningitis, meningoencephalitis or meningoencephalomyelitis have been extensively reported in striped dolphins (Stenella coeruleoalba), and less frequently in other cetacean species.

Case presentation

A juvenile female common bottlenose dolphin (Tursiops truncatus) was found stranded alive in Lanzarote (Canary Islands, Spain) in 2005, but died shortly after. On physical examination, the dolphin showed a moderate body condition and was classified as code 2 (fresh dead) at the time of necropsy. The main gross findings were severe multiorgan parasitism, thickened and congested leptomeninges, and (sero)fibrino-suppurative and proliferative arthritis of the shoulder joint. Histopathological examination revealed the distinct features of a sub-acute systemic disease associated with Cetacean Morbillivirus (CeMV) infection. However, brain lesions diverged from those reported in systemic CeMV infection. This led to suspect that there was a coinfecting pathogen, based on the characteristics of the inflammatory response and the lesion distribution pattern in the central nervous system. Brucella sp. was detected in the brain tissue by PCR and Brucella antigen was demonstrated by immunohistochemistry in the brain and shoulder joint lesions.

Conclusions

The zoonotic potential of marine mammal strains of Brucella has been demonstrated both in natural and laboratory conditions. In this study, PCR detected Brucella sp. in the brain of a common bottlenose dolphin stranded in the Canary Islands; the dolphin was also co-infected with CeMV. This is the first detection of Brucella sp. infection in a stranded cetacean in this archipelago. Therefore, we stress the importance of taking adequate measures during the handling of these species to prevent the transmissions of the infection to humans.