Erysipelas with preferential brain and skin involvement in a Mediterranean bottlenose dolphin Tursiops truncatus.

Infections by Erysipelothrix rhusiopathiae occur in domestic animals and cause the disease known as 'erysipelas'. The ubiquity of Erysipelothrix spp. makes infection possible in a wide range of vertebrates and invertebrates. Cetaceans are highly susceptible to erysipelas, especially those under human care. The number of cases documented in wild cetaceans is low, the pathogenesis is incompletely understood, and the full spectrum of lesions is not well defined. The possible serotypes and species of the genus that can cause disease are unknown. In October 2022, a common bottlenose dolphin Tursiops truncatus stranded in Vilassar de Mar (Catalonia) showing skin lesions consistent with 'diamond skin disease', a characteristic lesion of erysipelas shared by swine and cetaceans. Necropsy was performed following standardized procedures, and multiple samples were taken for histopathology and bacteriology. Erysipelothrix sp. grew in pure culture in many tissue samples. Genetic characterization by multi-locus sequence analysis identified the species as E. rhusiopathiae. Histologically, the main lesions were an intense suppurative vasculitis of leptomeningeal arteries and veins with abundant intramural Gram-positive bacilli and meningeal hemorrhages. Meningeal lesions were considered the cause of death. The affected skin showed moderate suppurative dermatitis. Herein we document a case of erysipelas in a Mediterranean common bottlenose dolphin with unusual lesions in the leptomeningeal vessels and marked skin tropism. To our knowledge, this is the first case of severe brain involvement in erysipelas in a cetacean. We also provide a review of available cases in wild cetaceans, to highlight the characteristics of the disease and improve future diagnosis.

Tension pneumothorax in small odontocetes.

Pneumothorax, the accumulation of air in the pleural cavity, occurs when air enters the pleural space by the pleuro-cutaneous, pleuro-pulmonary, or pleuro-oesophageal-mediastinal route. Tension pneumothorax is an infrequent and severe form of pneumothorax where a positive pressure in the pleural space is built up during at least part of the respiratory cycle, with compression of both lungs and mediastinal vessels, and, if unilateral, with midline deviation towards the unaffected hemithorax. We describe 9 cases of tension pneumothorax in 3 species of small cetaceans (striped dolphin Stenella coeruleoalba, common dolphin Delphinus delphis, and common bottlenose dolphin Tursiops truncatus) from the western Mediterranean coast of Spain, and one case from a dolphinarium. Computed tomography (CT) imaging performed in 2 carcasses before necropsy showed lung compression, midline deviation, and pressure on the diaphragm, which was caudally displaced. Tension pneumothorax was recognized at necropsy by the presence of pressurized air in one of the hemithoraces. Seven of the pneumothorax cases were spontaneous (2 primary and 5 secondary to previous lung pathology). In the other 2 dolphins, the pneumothorax was traumatic, due to oesophageal-pleural perforation or rib fractures. We hypothesize that pneumothorax in dolphins is predominantly tensional because of their specific anatomical and physiological adaptations to marine life and the obligate exposure to extreme pressure changes as diving mammals.

Needle tract seeding and malignant transformation of hepatocellular adenoma into well-differentiated hepatocellular carcinoma in a dog.

An 11-year-old neutered female Golden Retriever was referred for investigation of marked increases in liver enzyme activities. Abdominal ultrasound revealed a large pedunculated liver mass. Diagnosis of hepatocellular adenoma (HCA) was made when the mass was excised after a first unsuccessful attempt through ultrasound-guided core-needle biopsy. One and a half years after presentation, a nodule embedded between muscles of the abdominal wall appeared. The mass was first diagnosed as a well-differentiated hepatocellular carcinoma (HCC) through cytologic examination, which was later confirmed with histopathology. Ki 67 immunostaining of the abdominal wall nodule showed an increased immunoreactivity compared with the liver mass. Therefore, the present case documents the first needle-tract seeding of a hepatocellular epithelial tumor with possible malignant transformation of HCA into a well-differentiated HCC in a dog.

Activation of hippocampal postsynaptic muscarinic receptors is involved in long-term spatial memory formation.

Spatial memory has been strongly associated with hippocampal function. There are several reports of the participation of this structure in acquisition and consolidation of spatial tasks. In this study, we evaluated the effects of selective and non-selective muscarinic antagonists in the dorsal hippocampus of rats during acquisition and encoding of a spatial task. Rats were trained in a Morris water maze for 4 days with identical daily sessions, and tested for long-term memory (LTM) 1 week after training. The animals were injected bilaterally in the dorsal hippocampus 20 min before the start of every day of training. The results showed that the non-selective muscarinic antagonist, scopolamine, disrupted acquisition of water maze memory formation. Moreover, microinjections of a selective postsynaptic muscarinic antagonist, pirenzepine, disrupted LTM, whereas it did not affect acquisition. Conversely, a selective presynaptic muscarinic antagonist, AFDX-116, did not disrupt either water maze acquisition or LTM formation. Combination of AFDX-116 and pirenzepine had similar effects as scopolamine, partially blocking acquisition and impairing long-term spatial memory. These results support the view that muscarinic receptors are involved in spatial learning and that postsynaptic muscarinic receptors in the dorsal hippocampus are particularly involved in long-term spatial memory formation.