Abstract
Mortality in the first 3 months after birth is a serious problem in captive bottlenose dolphins (Tursiops truncatus), and it is difficult to take appropriate actions to improve the situation due to undetermined cause of death.2,5 For improving our knowledge in this field, a case of Group B Streptococcus (GBS) infection, possibly related to lack of maternally acquired immunity, in a captive bottlenose dolphin calf is reported. A female bottlenose dolphin calf was born on June 4, 2014. Due to the failure of maternal nursing, artificial milk was given on the 5th day after birth. Increased white blood cell (WBC) count (27,600/µl) was noted on June 12 with other abnormal parameters, including fibrinogen (336 mg/dl), iron (84 mcg/dl) and alkaline phosphatase (1,588 U/l).1 Therefore, a serial medical treatment was performed, with ceftriazone (20 mg/kg/day, IM) given to the calf for 6 days followed by amikacin (10 mg/kg/day, IM) until June 24, when the results of blood examination were back to reference range. During July 3 to July 17, no remarkable findings were noted by blood examination except increased WBC count, but it was back to reference range on July 18. On July 19, the respiratory rate of the calf had increased slowly since 2:00 pm. Then, she was injected with cefovecin (8 mg/kg, IM; CONVENIA®) at 5:00 pm because of tachypnea and vomiting. This calf was dead at 8:00 pm. Carcass of the animal was necropsied with systemic examination at 3 hours after death. Samples for histopathology were collected and preserved in 10% neutral buffered formalin. Bacteriological samples were also collected based on the standard procedures and were obtained from lung, liver, spleen, kidney, and heart by swabs with appropriate transport media. The animal was in good nutritional condition with multiple pinholes of tail flukes. Upon opening the body cavity, 40 to 50 ml of cloudy yellow ascites was found. Bilateral lungs were wet, heavy and reddish with multifocal hemorrhages. Multifocal hemorrhages on the coronary sulcus of heart were noted. Microscopically, multifocal eosinophilic and pyknotic myocardiocytes with dense clumps of basophilic bacteria were noted. Focal hemorrhage was found on visceral pleura and multifocal alveoli revealed collapse, emphysema, hemorrhage and edema with small amount of neutrophil infiltration in alveolar walls. Fibrillar eosinophilic substances were multifocally deposited in the sinusoids of red pulp in spleen. GBS was isolated from all tissue specimens by bacteriological examination. In the present case, GBS infection was diagnosed and could be associated with the lack of maternal immunity (failure to nurse). Furthermore, GBS infection of the calf should be categorized as late-onset disease by using the criteria of human GBS infection, and hence the source of infection is unlikely related to the mother.3,4 Therefore, ascending infection of gastrointestinal tract (contaminated feeding equipment and artificial milk) and contamination of external wounds such as pinholes through environment should be considered as possible sources of infection. Finally, GBS is also pathogenic for normal human, and thus the risk of zoonotic transmission should be expected.
Acknowledgements
The authors would like to thank Mr. Billy Hurley of Georgia Aquarium, Dr. I-Hua Chen, research assistant at aquatic animal medicine laboratory of National Chiayi University, and all Farglory Ocean Park members who did help and support in this case.
* Presenting author
Literature Cited
1. Bossart GD, Reidarson TH, Dierauf LA, Duffield DA. Clinical pathology. In: Dierauf LA, Gulland FMD, eds. CRC Handbook of Marine Mammal Medicine: Health, Disease, and Rehabilitation. 2nd ed. Boca Raton, FL: CRC Press; 2001: 383–436.
2. Duffield DA, Shell ED, Dudley M. Demographic analysis of breeding bottlenose dolphins in North American zoological facilities: 1976–1998. In: Duffield D, Robeck TR, eds. The Bottlenose Dolphin Breeding Workshop. Silver Springs, MD: AZA Marine Mammal Taxon Advisory Group; 2000:139–155.
3. Eskandarian N, Neela V, Ismail Z, Puzi SM, Hamat RA, Desa MN, Nordin SA. Group B streptococcal bacteremia in a major teaching hospital in Malaysia: a case series of eighteen patients. Int J Infect Dis. 2013:17(9):e777–780.
4. Filleron A, Lombard F, Jacquot A, Jumas-Bilak E, Rodière M, Cambonie G, Marchandin H. Group B streptococci in milk and late neonatal infections: an analysis of cases in the literature. Arch Dis Child Fetal Neonatal Ed. 2014:99(1):F41–47.
5. van Elk CE, van Dep Bildt MW, Martina BE, Osterhaus AD, Kuiken T. Escherichia coli septicemia associated with lack of maternally acquired immunity in a bottlenose dolphin calf. Vet Pathol. 2007:44(1):88–92.