Molecular epidemiology and pathology of spirorchiid infection in green sea turtles (Chelonia mydas).
Spirorchiid blood fluke infections affect endangered turtle populations globally, and are reported as a common cause of mortality in Queensland green sea turtles. Both the flukes and their ova are pathogenic and can contribute to the stranding or death of their host. Of particular interest are ova-associated brain lesions, which have been associated with host neurological deficits. Accurate estimations of disease frequency and the relative effect of infection relating to different spirorchiid species are made difficult by challenges in morphological identification of adults of some genera, and a lack of species-level identifying features for ova. A new specifically designed molecular assay was used to detect and identify cryptic spirorchiids and their ova in Queensland green sea turtle tissues collected from 2011 to 2014 in order to investigate epidemiology, tissue tropisms and pathology. Eight spirorchiid genotypes were detected in 14 distinct tissues, including multiple tissues for each. We found no evidence of a characteristic pathway of the eggs to the exterior; instead the results suggest that a high proportion of eggs become lost in dead-end tissues. The most common lesions observed were granulomas affecting most organs with varying severity, followed by arteritis and thrombi in the great vessels. The number of spirorchiid types detected increased with the presence and severity of granulomatous lesions. However, compared with other organs the brain showed relatively low levels of spirorchiid diversity. An inverse relationship between host age and spirorchiid diversity was evident for the liver and kidneys, but no such relationship was evident for other organs. Molecular data in this study, the first of its kind, provides the first species-level examination of spirorchiid ova and associated pathology, and paves the way for the future development of targeted ante-mortem diagnosis of spirorchiidiasis.
Veterinary-Marine Animal Research, Teaching and Investigation, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Phoebe A
PA
Chapman
Veterinary-Marine Animal Research, Teaching and Investigation, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Helen
H
Owen
Veterinary-Marine Animal Research, Teaching and Investigation, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia; School of Forest Resources and Conservation, University of Florida, The Florida Aquarium's Center for Conservation, Apollo Beach, FL, USA.
Mark
M
Flint
UQ Spatial Epidemiology Laboratory, School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia; Children's Health and Environment Program, Child Health Research Centre, The University of Queensland, South Brisbane, Queensland, Australia.
Ricardo J
RJ
Soares Magalhães
Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia.
Rebecca J
RJ
Traub
School of Biological Science, The University of Queensland, St Lucia, Queensland, Australia.
Thomas H
TH
Cribb
Veterinary-Marine Animal Research, Teaching and Investigation, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Myat T
MT
Kyaw-Tanner
Veterinary-Marine Animal Research, Teaching and Investigation, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Paul C
PC
Mills
Chelonia mydas; Epidemiology; Pathology; Spirorchiidiasis; Terminal restriction fragment length polymorphism; Tissue tropisms