Abstract

Rearing a new species in captivity presents special veterinary challenges as the animals grow and develop. When this species is a continually active giant pelagic gelativore, the challenges multiply. Captive juvenile leatherback turtles (Dermochelys coriacea) raised from hatchlings in a closed recirculating seawater system displayed a variety of lesions and disease entities at various points over a two year period. These included: early wasting /failure to thrive, rostral abrasion, ulcerative dermatitis of the cranial "pink spot", and bronchopneumonia with septicemic sequelae.

Early wasting

A number of newly hatched juveniles failed to thrive and feed properly, did not gain weight in normal fashion after hatch, displayed anomalies in carapace shape, mandibular foreshortening and other abnormal physical traits of undefined etiology which may have related to incubation conditions or congenital defects. The majority of these animals were weak, did not swim with the same speed, regularity or energy as conspecifics and died within the first 8 weeks of hatching, terminally developing white skin lesions positive for fungal hyphae, on necropsy displaying hepatic lipidosis and acute bronchopneumonia, culturing Aeromonas salmonicida and Shewanella putrifaciens sensitive to enrofloxacin from lung tissue in one case.

Rostral abrasions

Rostral abrasions involving the bones of the maxillary region and causing changes in the gross structure of the external nares, resulted when juveniles broke the restraint tether, leading to osteomyelitis, successfully treated with enrofloxacin 5 mg/kg IM SID for 7-10 days; however, permanent remodeling of the rostral region frequently resulted, and changes in structure of the external nares predisposed to pneumonia.

Pink Spot ulcerative dermatitis

In 1-2 kg juveniles the skin overlying the pineal "pink spot" developed localized inflammation and erosion with subsequent formation of brown granulating exudates, also seen in axillary folds and in the skin folds under the chin of some animals. This syndrome coincided with increasing stocking density and bacterial load in seawater and resolved with systemic enrofloxacin 5 mg/kg IM SID, topical cleaning with povidone iodine solution, and improved water quality.

Bronchopneumonia

Leatherback turtle juveniles were more susceptible to water-borne bacterial pathogens than adult green sea turtles (Chelonia mydas) kept under near identical conditions in separate housing in the same facility, which may reflect in part the offshore pelagic habit and immune system function of juvenile leatherbacks. Hatchlings were susceptible to a complex of symptoms that originated with primary bacterial pneumonia leading to secondary bacteremia, septicemia and multiple organ involvement after aspirating or ingesting bacteria-laden seawater. Gram negative bacteria isolated from lesions at necropsy included Vibrio damsela, Vibrio vulnificus, Pseudomonas aeruginosa, Aeromonas salmonicida, Shewanella putrifaciens, Klebsiella pneumoniae and Citrobacter freundii. Vibrio damsela has been previously isolated from a stranded leatherback turtle with multiple system infection, although the putative route of infection was via the GI tract.¹ Lesions ranged from severe acute hemorrhagic pneumonia to chronic granulomatous pneumonia. Secondary syndromes following primary pneumonia included interstitial nephritis, hepatitis, splenitis, epicarditis and coelomitis. Prolonged treatment of affected animals with parenteral antibiotics based on culture and sensitivity results was successful using enrofloxacin 5 mg/kg SID IM up to 21 days, alternately amikacin sulfate 2.5-5 mg/kg IM every three days for 5 treatments together with ampicillin trihydrate injectable 20 mg/kg SID for 7 days. Early identification of sick animals (decreased food intake, hemorrhagic foci on plastron, development of edema in any visible area, listing) prompted immediate treatment. Enrofloxacin treatment of leatherback turtles was associated with plateaus in weight gain, a side effect which has been characterized in growing juvenile mammalian species due to arthropathy;² however, arthropathy had not been recognized histologically in treated leatherback juveniles.

Acknowledgements

The authors wish to thank Mervin Hastings, Arthur VanDerhorst, David Jones, and the many leatherback turtle husbandry volunteers for their dedication and support of this study, which was supported by NSERC and the Department of Fisheries, Government of British Virgin Islands.

References

1.  Obendorf D.L, J. Carson, and T.J. McManus. 1987. Vibrio damsela infection in a stranded leatherback turtle (Dermochelys coriacea). J Wildl Dis 23(4): 666-668.

2.  Mitchell M.A. 2006. Therapeutics. In: D.R. Mader (ed). Reptile Medicine and Surgery. W.B. Saunders, Philadelphia; Pp.649-651.