Evaluation of plasma fibrinogen concentration as a diagnostic indicator of inflammation in red-eared sliders (Trachemys scripta elegans)

• Autores: A. Russell Moore
• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 246, Nº. 2, 2015, págs. 245-253
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Objective—To critically evaluate plasma fibrinogen concentration as a diagnostic indicator of inflammation in red-eared sliders (Trachemys scripta elegans).

    Design—Prospective induced-disease model and prospective cross-sectional study.

    Sample—Plasma samples from 12 purpose-bred red-eared sliders and 153 farm-raised red-eared sliders.

    Procedures—A modification of the Jacobsson method was developed to measure fibrinogen concentration in platelet-poor plasma from red-eared sliders. Purpose-bred turtles had been inoculated with a ranavirus (n = 4) or sterile PBS solution (8) as part of another study. Farm-raised red-eared sliders were categorized as healthy (n = 138) or overtly ill (15) on the basis of physical examination findings at the time of blood sample collection. Samples from 124 of the 138 healthy red-eared sliders were used to establish a fibrinogen concentration reference interval as measured by the modified Jacobsson method. Fibrinogen concentrations in ranavirus-infected and physically ill turtles were compared with those of healthy turtles to determine whether fibrinogen concentration would be a useful diagnostic indicator of inflammation in red-eared sliders.

    Results—The modified Jacobsson method was reliably used to measure fibrinogen concentration. The fibrinogen concentration reference interval from healthy reproductively active female red-eared sliders was right skewed. Fibrinogen concentration did not differ significantly between healthy red-eared sliders and ranavirus-infected or overtly ill red-eared sliders.

    Conclusions and Clinical Relevance—A reference interval for red-eared slider plasma fibrinogen concentration was established and partitioned by sex to account for considerable right skewing observed for females. Fibrinogen concentration was not a useful indicator of inflammation in red-eared sliders with ranavirus infection or other overt illnesses.

    The acute phase response includes fever, behavioral modification, and plasma protein changes and is a programmed biological reaction that mediates tissue damage and promotes a return to homeostasis following inflammation, neoplasia, and stress.1 In reptiles, diagnosis of inflammation is challenging; several diagnostic methods have failed to reliably detect disease. For example, WBC counts are not accurate indicators of an acute phase response in chelonians.2 Mild alterations in plasma protein concentrations have been detected in ill loggerhead sea turtles (Caretta caretta) and red-eared sliders by plasma protein electrophoresis, but additional studies are needed.3,4 Inflammation induced by Aeromonas hydrophila infection in Chinese softshell turtles (Pelodiscus sinensis) was associated with changes in hepatic expression of several APP transcripts consistent with a mammalian acute phase response, including increases in fibrinogen RNA transcripts.5 Having a reliable diagnostic indicator of inflammation in turtles would be beneficial for monitoring disease in many species.

    Several methods can be used to measure fibrinogen concentration. The gravimetric method, which defines plasma fibrinogen concentration as the mass of the fibrin clot isolated from a plasma sample, is the gold standard for fibrinogen measurement but requires a large volume of plasma.6 The Clauss method compares thrombin-induced clot time to a standard curve to determine fibrinogen concentration.7 However, an increased concentration of plasma heparin-like molecules seen in red-eared sliders during torpor affects the results of the Clauss method.8,9 The heat precipitation method measures changes in total plasma solids concentration after precipitation of fibrinogen at 58°C. Fibrinogen and other heat-precipitating components, including fibrinogen degradation products, are measured by use of this protocol.6,10 Lastly, the Jacobsson method begins similarly to the gravimetric method, but the clot is dissolved and OD at 280 nm of the solution is used to calculate fibrinogen concentration.11 In mammals, the best correlation with the gravimetric method is attained with the Clauss or Jacobsson methods.6,12 In green iguanas (Iguana iguana), the Clauss and heat precipitation methods correlated poorly with the gravimetric method and were deemed inappropriate for use in that species.6 The FV3-like virus is a ranavirus that causes clinical signs of oral discharge, stomatitis, and respiratory distress; heterophilic splenitis, vasculitis, pneumonia, and fibrinoid necrosis can be found histologically.13 Ranavirus infection in amphibians is designated as a reportable disease by the World Organization for Animal Health and has been associated with high morbidity and mortality rates in wild reptile and amphibian populations.14 Red-eared sliders infected with FV3-like virus have clinically and histologically confirmed inflammation; however, WBC counts are not affected.13 Interestingly, at the time of PCR assay–based confirmation of viremia, changes in plasma protein concentrations consistent with an acute phase response were observed in the ranavirus-infected red-eared sliders, including decreases in total plasma protein and albumin concentrations and an increased β-globulin percentage.13,15 The objective of the study reported here was to evaluate plasma fibrinogen concentration as a diagnostic indicator of inflammation in red-eared sliders. Our aims were to validate the measurement of plasma fibrinogen concentration with a modification of the Jacobsson method and determine the diagnostic utility of this assay in red-eared sliders. We hypothesized that plasma fibrinogen concentration would increase as part of the acute phase response to ranavirus infection and would be identified as a useful biomarker of inflammation in chelonians.