Dermal exposure to weathered MC252 crude oil results in echocardiographically identifiable systolic myocardial dysfunction in double-crested cormorants ( Phalacrocorax auritus )

Abstract

During the Deepwater Horizon Natural Resource Damage Assessment, gross morphologic cardiac abnormalities, including softer, more distensible musculature, were noted upon gross necropsy in hearts from laughing gulls and double-crested cormorants exposed to weathered MC252 crude oil. A species specific, echocardiographic technique was developed for antemortem evaluation of function that was used to evaluate and better characterize cardiac dysfunction. Control (n=12) and treated (n=13) cormorant groups of similar sex-ratio and ages were dermally treated with approximately 13ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages. This resulted in a low to moderate external exposure. Upon visualization and clinical assessment of the hearts of all test subjects, comprehensive diagnostic cardiographic measurements were taken twice, prior to oil application and after a 21day dermal oil exposure. Oil-treated birds showed a decrease in cardiac systolic function, as characterized by an increased left ventricular internal dimension-systole and left ventricular stroke volume as well as concurrent decreased left ventricular ejection fraction and left ventricular fractional shortening when compared to both control birds' and the treated birds' time zero values. These changes are indicative of a possible dilative cardiomyopathy induced by oil exposure, although further elucidation of possible collagen damage is recommended. Arrhythmias including tachycardia in two treated birds and bradycardia in all treated birds were documented, indicating further clinically significant abnormalities induced by MC252 oil that warrant further investigation. A statistically significant increase in free calcium concentration, important to muscular and neurologic function in treated birds was also noted. This study documents that weathered MC252 oil caused clinically significant cardiac dysfunction that could result in mortality and decrease recruitment.

Development of methods for avian oil toxicity studies using the double crested cormorant ( Phalacrocorax auritus )

“…Results associated with endpoints assessed in the oral and external dosing studies with DCCOs that are not covered in the present report include oil-induced increases in CYP1A protein expression and catalytic activity (Alexander, submitted for publication et al, this issue), changes in CBC estimates and plasma chemistry and electrophoresis endpoints (Dean et al, 2017b, this issue), hemolytic anemia as indicated by decreased PCV, relative reticulocytosis with an inadequate regenerative response, and presence of Heinz bodies (Harr et al, 2017a, this issue), and increases in liver and kidney weights and the presence of lesions in kidney, liver, heart and thyroid gland (Harr et al, 2017b, this issue). Results related to a decrease in cardiac systolic function and internal body temperature and heat loss in externally dosed DCCOs are presented in Harr et al (2017c) and Mathewson et al (2017), respectively. Results related to changes in oxidative stress endpoints in orally dosed DCCOs are presented in (Pritsos et al, 2017, this issue).…”

“…However, these results are specific for the source of oil, the species, and age class of the birds, the dosing methodology, and the husbandry employed, and should be used with caution. New findings from the oral dosing study included cardiovascular abnormalities documented upon gross necropsy that prompted further diagnostic evaluation in the external dosing study (Harr et al, 2017c). Evidence of coagulopathy found on gross necropsy has not been reported before in oil-dosed birds and has been minimally investigated using MC252 oil in any species.…”

“…External body temperature was taken just prior to initial oiling and every six days thereafter (on days 3, 9, 15 and 20) with a handheld scanning thermograph camera (FLIR ThermoCAM T640; FLIR Systems, Boston, MA, USA) (Mathewson, submitted for publication et al,). Echocardiograms were used to evaluate DCCO cardiac structure and function (Harr et al, 2017c, this issue).…”

Changes in white cell estimates and plasma chemistry measurements following oral or external dosing of double-crested cormorants, Phalacocorax auritus , with artificially weathered MC252 oil

“…There were additional signs and symptoms of this toxicity reported in other manuscripts describing these studies (Alexander et al, 2017;Cunningham et al, 2017;Harr et a, 2017a, c, d;Pritsos et al, 2017). These include increases in relative organ weight, hypertrophy and histopathological changes at necropsy, development of hemolytic anemia, inflammation and atrophy (Harr et al, 2017a(Harr et al, , 2017c, as well as newly documented clotting dysfunction, cardiomyopathy and associated functional losses (Harr et al, 2017d). However, there was a confounding variable for the orally dosed birds in that they developed some food aversion or gastrointestinal irritation that reduced their food intake overall and caused weight loss, while externally dosed birds did not lose weight, and in fact increased food consumption .…”

Magnetic Resonance Imaging (MRI) reveals high cardiac ejection fractions in red-footed tortoises (Chelonoidis carbonarius)

“…Under normal conditions, the ejection fraction (EF)the proportion of blood ejected in each beat [EF=(EDV−ESV)/EDV]ranges from 40% to 70% in mammals, meaning that 30-60% of EDV resides in the ventricle at the end of each contraction (Hoffmann et al, 2014;Lang et al, 2015). Similar values apply in birds, although considerably less is known about their cardiac function (Harr et al, 2017;Pees et al, 2004). In contrast to these endothermic hearts, EFs of 80-100% have been measured using echocardiography in fish (Coucelo et al, 2000;Franklin and Davie, 1992;Lai et al, 1998Lai et al, , 2004.…”