Radiographic measurement of the cardiac silhouette is a survey diagnostic test that is commonly used in conjunction with physical examination to determine whether a patient likely has cardiac disease. However, physical examination of avians has limitations because of the high heart rate of most species, which makes it difficult to evaluate birds for murmurs or arrhythmias. Radiographs are commonly obtained and evaluated in avian species, but differences among species limit the usefulness of the few reference values currently available.
Radiographic measurements of the cardiac silhouette in avian species were first reported for Amazon parrots in 19941 and have since been determined for other psittacine species (African grey parrots [Psittacus erythacus], Senegal parrots [Poicephalus senegalis], orange-winged Amazon parrots [Amazona amazonica], Spix macaws [Cyanopsitta spixii], and budgerigars [Melopsittacus undulatus]),2–4 select falconry species (common kestrels [Falco tinnunculus], red-tailed hawks [Buteo jamaicensis], Harris hawks [Parabuteo unicinctus], peregrine falcons [Falco cherrug], and lanner falcons [Falco biarmicus])5–8 and other wildlife avian species (screech owls [Otus asio] and Canada geese [Branta canadensis]).7 Ventrodorsal measurements of bald eagles (Haliaeetus leucocephalus) have also been reported.a
Radiographic measurements have been established to provide standards by which to determine cardiomegaly. Common causes of cardiomegaly in wild avian patients include congenital abnormalities (iron storage disease),9 viral disease (avipoxvirus),10 endoparasitism (Plasmodium spp),11 and toxins (fumonisin B1 and moniliformin).12
Ospreys (Pandion haliaetus) are piscivorous raptors in the family Pandionidae of the order Accipitriformes.13 Similar to most of the other species in that order, ospreys are diurnal birds that rely on sight to hunt prey. They have been used as a sentinel species for monitoring aquatic environmental changes since the 1960s because they are apex predators in the piscivorous food chain, have a long life span (the oldest osprey was reportedly 25 years and 2 months old)14 and thus a long-term opportunity for bioaccumulation of lipophilic contaminants, can adapt to nest disturbances and human encroachment, and are found in almost all countries.15 However, the authors are not aware of any reported standards for radiographic measurements of the cardiac silhouette of ospreys. The purpose of the study reported here was to determine reference values for the cardiac silhouette in this species to enable monitoring of diseases and conditions attributable to toxins that may affect ospreys and the ecosystems they inhabit.
The authors did not receive any extrainstitutional funding or support for this study and have no conflicts of interest to report.
Lecona IG, Barncord K, Stauthammer C. Cardiac evaluation in the bald eagle (Haliaeetus leucocephalus) (abstr), in Proceedings. ExoticsCon 2015;143–144.
Vet-Ray Digital Vet DX system, Sedecal, Buffalo Grove, Ill.
QXVue software, Sedecal, Buffalo Grove, Ill.
SAS, version 9.4, SAS Institute, Cary, NC.
1. McMillan M. Imaging techniques. In: Ritchie BW, Harrison GJ, Harrison LR, eds. Avian medicine: principles and applications. Lake Worth, Fla: Wingers Publishing, 1994;246–326.
2. Straub J, Pees M, Krautwald-Junghanns ME. Measurement of the cardiac silhouette in psittacines. J Am Vet Med Assoc 2002;221:76–79.
3. Rettmer H, Watson R, Hatt JM, et al. Radiographic measurement of internal organs in Spix's macaws (Cyanopsitta spixii). J Avian Med Surg 2011;25:254–258.
4. Velayati M, Mirshahi A, Razmyar J, et al. Radiographic reference limits for cardiac width of budgerigars (Melopsittacus undulatus). J Zoo Wildl Med 2015;46:34–38.
5. Barbon AR, Smith S, Forbes N. Radiographic evaluation of cardiac size in four falconiform species. J Avian Med Surg 2010;24:222–226.
6. Lumeij JT, Shaik MAS, Ali M. Radiographic reference limits for cardiac width in peregrine falcons (Falco peregrinus). J Am Vet Med Assoc 2011;238:1459–1463.
7. Hanley CS, Murray HG, Torrey S, et al. Establishing cardiac measurement standards in three avian species. J Avian Med Surg 1997;11:15–19.
8. Mirshahi A, Shariatzaden M, Razmyar J, et al. Evaluation of cardiac size in the common kestrel (Falco tinnunculus) based on radiographic measurements. J Avian Med Surg 2016;30:345–349.
9. Klasing KC, Dierenfeld ES, Koutsos EA. Avian iron storage disease: variations on a common theme? J Zoo Wildl Med 2012;43:S27–S34.
10. Niemeyer C, Favero CM, Kolesnikovas CKM, et al. Two different avipoxviruses associated with pox disease in Magellanic penguins (Spheniscus magellanicus) along the Brazilian coast. Avian Pathol 2013;42:546–551.
11. Vanstreels RET, Kolesnikovas CKM, Sandri S, et al. Outbreak of avian malaria associated to multiple species of Plasmodium in Magellanic penguins undergoing rehabilitation in Southern Brazil. PLoS One 2014;9:e94994.
12. Sharma D, Asrani RK, Ledoux DR, et al. Toxic interaction between fumonisin B1 and moniliformin for cardiac lesions in Japanese quail. Avian Dis 2012;56:545–554.
13. United States Geological Survey. Integrated taxonomic information system on-line database. Pandion haliaetus. Available at: www.itis.gov. Accessed Mar 29, 2019.
14. United States Geological Survey. Longevity records of North American birds. Available at: www.pwrc.usgs.gov/bbl/longevity/longevity_main.cfm. Accessed Mar 29, 2019.
15. Grove RA, Henny CJ, Kaiser JL. Osprey: worldwide sentinel species for assessing and monitoring environmental contamination in rivers, lakes, reservoirs, and estuaries. J Toxicol Environ Health Part B Crit Rev 2009;12:25–44.
16. Cornell Laboratory of Ornithology. Osprey identification. Available at: www.allaboutbirds.org/guide/Osprey/id. Accessed Dec 17, 2018.
17. Virginia Institute of Marine Science. How to identify an osprey. Available at: www.vims.edu/bayinfo/ospreycam/about/identification/index.php. Accessed Dec 17, 2018.
18. Lumeij JT, Ritchie BW. Cardiology. In: Ritchie BW, Harrison GJ, Harrison LR, eds. Avian medicine: principles and application. Lake Worth, Fla: Wingers Publishing, 1994;695–722.
20. Daigneault M, Harr KE, Dean KM, et al. Assay validation of the cardiac isoform of troponin I in double crested cormorant (Phalacrocorax auritus) plasma for diagnosis of cardiac damage. Ecotoxicol Environ Saf 2017;141:52–56.