Cetaceans have evolved from herbivorous terrestrial artiodactyls closely related to ruminants and hippopotamuses. Delphinidae, a family included in this order, represent an extreme and successful re-adaptation of mammalian physiology to the marine habitat and piscivorous diet. The anatomical aspects of Delphinidae success are well understood, whereas some physiological aspects of their environmental fitness are less defined, such as the gut microbiota composition and its adaptation to their dietary niche. Here, we explored the faecal microbiota structure of nine adult bottlenose dolphins (Tursiops truncatus) and one breast-fed calf living in a controlled environment. According to our findings, dolphins possess a unique microbiota profile within the Mammalia class, highly resembling that of carnivorous marine fishes. The breast-fed calf showed a distinctive compositional structure of the gut microbial ecosystem, which partially overlaps with the mother's milk microbiota. Taken together, our data indicate that in dolphins the adaptation to the marine niche and piscivorous diet involved the convergence of their gut microbiota structure with that of marine fishes, overcoming the gut microbiota phylogenetic inertia previously described in terrestrial mammalians.
Fecal glucocorticoid measurement is an important noninvasive tool to monitor animal health. A radioimmunoassay (RIA) method was developed to measure fecal cortisol in bottlenose dolphins under human care. The method was used to measure baseline hormone levels and evaluate the adrenal response to environmental challenges in a small number of individual dolphins. The method was validated by precision and accuracy tests and by comparison with liquid chromatography‐mass spectrometry (LC‐MS). The parallelism test suggested few matrix interferences. The assay showed a good degree of precision within assay (CV = 5.4%) and between assays (CV = 4.1%). The RIA significantly correlated with the LC‐MS method (r = 0.838, P < 0.01). The recovery test and the comparison between RIA and LC‐MS suggested that the RIA slightly underestimates fecal cortisol concentrations, although the degree of accuracy was good. This study established that bottlenose dolphins excrete appreciable amounts of fecal cortisol (healthy subjects: 0.2–9.5 ng/g). Therefore, chronic HPA axis activation may be monitored in fecal samples by immunoassays after validating a suitable extraction protocol. The RIA could discriminate conditions of stimulation (pregnancy, parturition, isolation, transportation) and inhibition (diazepam administration) of the HPA axis and may, therefore, be useful for monitoring dolphin well‐being.
The present study describes the isolation of Methicillin-resistant Staphylococcus aureus (MRSA) from respiratory tract of 2 dolphins of different origin, a stranded juvenile Risso's dolphin (Grampus griseus) and a captive born common bottlenose dolphin (Tursiops truncatus) calf, which died in the same institution at 1-month distance from the other. A complete microbiological and genetic investigation confirmed the presence of MRSA clone-complex 8, sequence type (ST) 8, spa-type t008 in both individuals. This strain differs from the one previously reported in walruses and dolphins and has never been described in dolphins before, but it is randomly isolated from Italian human patients. Vertical transmission of the infection may also occurs in other species and considering the description and location of the pathological lesions, this seems to be the most likely route of transmission implied in the young bottlenose dolphin. Staphylococcus aureus is known as an opportunistic agent, usually secondary to other pathogens, but its multiple antibiotic resistance and its zoonotic implications suggest a thorough and strict application of animal management hygiene protocols.
This case reports the presence of meticillin-resistant Staphylococcus aureus (MRSA) in a colony of cetaceans maintained under human care. MRSA isolates of the same strain were cultured from multiple organs of two dolphins that died with septicaemia. Following these mortalities and in consideration of the zoonotic potential of this pathogen, a decolonisation protocol was developed and applied to reduce the risk of exposure to humans and animals. After monitoring for MRSA presence in the animals, environment and staff, a strict sanitation protocol was applied for 15 months, with the aim of controlling MRSA. This protocol reduced the incidence of this pathogen and its involvement in acute clinical cases. The transmission between cetaceans and the implication of human reservoirs are discussed as important issues for veterinarians, facility managers and public health officials.
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