Escherichia coli Septicemia Associated with Lack of Maternally Acquired Immunity in a Bottlenose Dolphin Calf

Case report: Fatal neonatal sepsis associated with Escherichia fergusonii infection in a common bottlenose dolphin (Tursiops truncatus)

A 25-day-old male common bottlenose dolphin (Tursiops truncatus) died suddenly while swimming at a dolphinarium. The gross examination revealed ulceration on the dorsal and pectoral fins and rostrum. Severe congestion, hemorrhage, and edema were observed in the gastrointestinal tract, liver, mesenteric lymph nodes, lungs, and kidneys. Fibrinosuppurative arthritis of the atlantooccipital joint and extension of fibrin into the spinal canal caused compression of the spinal cord. Histopathological examination revealed tracheitis, fibrinosuppurative bronchopneumonia and enteritis. In the central nervous system, meningeal vessel congestion in the brain, and intraparenchymal hemorrhages with neurodegeneration were observed in the spinal cord. Based on the histopathological findings, representative samples, including lung, liver, mesenteric lymph node, blood obtained from the jugular vein, and fluid sample of the ascites, were inoculated on tryptic soy agar and blood agar for routine bacterial isolation. Each isolated bacterial colony was streaked aseptically onto tryptic soy agar and blood agar for pure culture. After then, polymerase chain reaction (PCR) was performed for further identification of pathogenic microorganisms. PCR identified Escherichia fergusonii, Shewanella haliotis, Enterococcus faecalis, and Staphylococcus schleiferi. E. fergusonii was considered the primary etiologic agent in this case since it was the only species identified in all representative samples. The cause of death in this animal was E. fergusonii sepsis. To the best of our knowledge, this is the first case of neonatal sepsis associated with E. fergusonii infection in a dolphin, and suggests E. fergusonii as an opportunistic pathogen associated with sepsis in dolphins.

A case of meconium aspiration syndrome in a bottlenose dolphin (Tursiops truncatus) calf

Stillbirth and neonatal mortality are significant problems in captive breeding of dolphins, however, the causes of these problems are not fully understood. Here, we report a case of meconium aspiration syndrome (MAS) in a male neonate of bottlenose dolphin (Tursiops truncates) who died immediately after birth. At necropsy, a true knot was found in the umbilical cord. The lungs showed diffuse intraalveolar edema, hyperemic congestion and atelectasis due to meconium aspiration with mild inflammatory cell infiltration. Although the exact cause of MAS in this case was unknown, fetal hypoxia due possibly to the umbilical knot might have been associated with MAS, which is the first report in dolphins. MAS due to perinatal asphyxia should be taken into account as a possible cause of neonatal mortality and stillbirth of dolphin calves.