Hematology of Wild Lake Erie Watersnakes (Nerodia sipedon insularum) with Natural Ophidiomycosis
Habitat loss, human persecution, and infectious diseases all threaten declining reptile populations. Lake Erie watersnakes (Nerodia sipedon insularum, LEWS), once classified as an endangered species in part due to human persecution, have recovered to stable population levels but have been observed with a high prevalence of ophidiomycosis. Strategies are needed to mitigate the current disease threat, including assessing overall wellness. Hematologic analysis provides information about the presence of inflammation and infection and thus informs health-based conservation efforts, but has not been previously performed in LEWS. The objective of this study was to evaluate hematologic parameters in LEWS and identify differences based on ophidiomycosis status. Blood was drawn from wild-caught snakes at nine sites in 2018 and 2019 and complete blood counts were performed in 180 individuals. For apparently healthy snakes, packed cell volume was significantly higher in males (median = 32.5%) compared to females (median = 26.5%; P = 0.03). Animals classified as having possible or apparent ophidiomycosis, or those with skin lesions, had a relative azurophilia and lymphopenia compared to individuals classified as negative or Ophidiomyces present, or those without skin lesions (P < 0.01). This is the first study to investigate hematology in a free-ranging population of LEWS and will serve as a baseline for future investigations that aim to improve conservation efforts through population health monitoring.Abstract
Photomicrography at 1,000 × of blood cells from Lake Erie watersnakes (Nerodia sipedon insularum) stained with Hema 3: (A) azurophil, (B) basophil, (C) azurophil (black arrow) and basophil (red arrow), (D) heterophil, (E) lymphocyte, (F) monocyte (black arrow) and lymphocyte (red arrow).
Box and whisker plot of packed cell volume (PCV; %) in male and female Lake Erie watersnakes (Nerodia sipedon insularum) in the ophidiomycosis negative category. Snakes were sampled in 2018 and 2019. There was a significant difference in PCV by sex (P = 0.03).
Box and whisker plots showing estimated WBC count (cells/µl) in Lake Erie watersnakes (Nerodia sipedon insularum) testing quantitative PCR positive and negative for O. ophidiicola DNA in 2018 and 2019. Estimated WBC count was significantly higher in animals with positive qPCR results (P < 0.01). Black dots indicate outliers more than 1.5 times the interquartile range away from the first or third quartiles.
Box and whisker plot of azurophils (top graph) and lymphocytes (bottom graph) based on presence or absence of lesions in Lake Erie watersnakes (Nerodia sipedon insularum) in 2018 and 2019. Black dots indicate outliers more than 1.5 times the interquartile range away from the first or third quartiles.
Box and whisker plots of percent azurophils (top graph) and percent lymphocytes (bottom graph) based on ophidiomycosis categories in Lake Erie watersnakes (Nerodia sipedon insularum) in 2018 and 2019. Black dots indicate outliers more than 1.5 times the interquartile range away from the first or third quartiles.
