Health Surveillance of Stranded Green Turtles in Southern Queensland, Australia (2006-2009): An Epidemiological Analysis of Causes of Disease and Mortality

Causes of disease and mortality in marine turtles are frequently based on opportunistic investigations producing results that may not contribute to knowledge on how to protect their survival rate. Over a 4-year period (2006-2009), the major causes of stranding and morbidity in 100 green turtles (Chelonia mydas) from southern Queensland on the east coast of Australia were determined by comprehensive postmortem examination. Lesions were characterized for analysis using descriptive and probability statistics. Spirorchiid parasitism was found to be the most frequently occurring cause of mortality (41.8%), followed by gastrointestinal impaction (11.8%), microbiological infectious diseases (5.2%), and trauma (5.2%). Spirorchiid parasitism with associated inflammation (75%) was the most frequently occurring disease, followed by gastrointestinal impaction (5.1%). All other diseases were observed at a low prevalence. Assessment of the likelihood of disease being influenced by risk factors (season, maturity, and gender) showed that: (i) there were more observed cases of spirorchiid infection in summer when compared with the other seasons (P = 0.029); (ii) immature turtles had more severe spirorchiid parasite infections than mature turtles (P = 0.032); and (iii) respiratory disorders were more likely (P = 0.01) in summer and autumn than winter or spring. Number of observed cases and severity of spirorchiid lesions were highest in the brain compared with other histologically examined organ systems (all P > 0.1). Further investigation is required to build on these findings, aid management decisions, and determine the significance of these diseases for green turtle survivorship in Queensland.