Experimental feeding of Hydrilla verticillata colonized by stigonematales cyanobacteria induces vacuolar myelinopathy in painted turtles (Chrysemys picta).
Vacuolar myelinopathy (VM) is a neurologic disease primarily found in birds that occurs when wildlife ingest submerged aquatic vegetation colonized by an uncharacterized toxin-producing cyanobacterium (hereafter "UCB" for "uncharacterized cyanobacterium"). Turtles are among the closest extant relatives of birds and many species directly and/or indirectly consume aquatic vegetation. However, it is unknown whether turtles can develop VM. We conducted a feeding trial to determine whether painted turtles (Chrysemys picta) would develop VM after feeding on Hydrilla (Hydrilla verticillata), colonized by the UCB (Hydrilla is the most common "host" of UCB). We hypothesized turtles fed Hydrilla colonized by the UCB would exhibit neurologic impairment and vacuolation of nervous tissues, whereas turtles fed Hydrilla free of the UCB would not. The ability of Hydrilla colonized by the UCB to cause VM (hereafter, "toxicity") was verified by feeding it to domestic chickens (Gallus gallus domesticus) or necropsy of field collected American coots (Fulica americana) captured at the site of Hydrilla collections. We randomly assigned ten wild-caught turtles into toxic or non-toxic Hydrilla feeding groups and delivered the diets for up to 97 days. Between days 82 and 89, all turtles fed toxic Hydrilla displayed physical and/or neurologic impairment. Histologic examination of the brain and spinal cord revealed vacuolations in all treatment turtles. None of the control turtles exhibited neurologic impairment or had detectable brain or spinal cord vacuolations. This is the first evidence that freshwater turtles can become neurologically impaired and develop vacuolations after consuming toxic Hydrilla colonized with the UCB. The southeastern United States, where outbreaks of VM occur regularly and where vegetation colonized by the UCB is common, is also a global hotspot of freshwater turtle diversity. Our results suggest that further investigations into the effect of the putative UCB toxin on wild turtles in situ are warranted.
D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, United States of America; Southeastern Cooperative Wildlife Disease Study (SCWDS), Department of Population Health, Wildlife Health Building, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
Albert D
AD
Mercurio
D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, United States of America; Southeastern Cooperative Wildlife Disease Study (SCWDS), Department of Population Health, Wildlife Health Building, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
Sonia M
SM
Hernandez
D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, United States of America.
John C
JC
Maerz
D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, United States of America; Southeastern Cooperative Wildlife Disease Study (SCWDS), Department of Population Health, Wildlife Health Building, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
Michael J
MJ
Yabsley
The Athens Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
Angela E
AE
Ellis
D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, United States of America.
Amanda L
AL
Coleman
The University of Georgia College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
Leslie M
LM
Shelnutt
Southeastern Cooperative Wildlife Disease Study (SCWDS), Department of Population Health, Wildlife Health Building, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
John R
JR
Fischer
D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, United States of America.
Susan B
SB
Wilde
D000821:Animal Feed; D000818:Animals; D001921:Brain / Q000382:microbiology / Q000473:pathology; D002493:Central Nervous System Diseases / Q000382:microbiology* / Q000473:pathology*; D000458:Cyanobacteria / Q000378:metabolism*; D005618:Fresh Water; D031321:Hydrocharitaceae / Q000382:microbiology*; D009186:Myelin Sheath / Q000382:microbiology / Q000473:pathology*; D013116:Spinal Cord / Q000382:microbiology / Q000473:pathology; D014426:Turtles / Q000382:microbiology*; D014617:Vacuoles / Q000382:microbiology / Q000473:pathology*