Pathologic findings in cetacean skeletal muscle

Abstract

Jncidcncc and c-haracterization of ske!ctal muscle lesions in strnmled cetaceans is unknown. Toe purpose ofthe currcnt stndy was to detennine the prevalence and nature of skeletal muscle lesions in cetaceans. Histopatbologic evaluation of skeletal muscle was pcrfonned in 162 stranded cetaccans belong to 21 different spccics, undergoing posl-mortem e:wmination in Canmy lslands between 1996 and 2008. Skeletal musc!e samplcs were taken from the middle portion of Longissimus dorsi {near the as\ thoracic vertcbrne). Muscle samples were fixed in fonnalin, processcd routinely, and staincd with haematoxylin and eosin, Phosphotungstic Acid Haematoxylin, periodic acid-Schiff for glucogen, and Von Kossa for calcium. Samples were al¡¡o postfüed in Osmium tetrm;.idc for lipids. In addition, immunohistochemical cxamination was perfonned using primary monoclonal (fast and anti-s!ow myosin hcavy chain) and polyclonal antlbodies {myoglobin and fibrinogcn). Skelctal musde lesions were 1.-·,mmmu in stranded cetm:eans examined al post-mortem (88.8%). In our opinion, consecutive longitudinal and transverse scctions staincd with n combh1a1ion of different histological, his1ochcmical and immunohistochemical techniques were neccssary to cstnblish a definitive morphologic diagnosis in musc:uJ.ir palhology of strandcd cc\llceans. Acule to subacute segmcntary myonccrosis represented the mafo finding (51 .8%) und lt was related to the stress of active stmnding. Olher common causes included septicnemia, fühery intcractions and ship collision. Chronic myopathic e han ges including excessive fibre siz.e variation, interna] nuc:lei. yuxtanuclear lipofuscin-!ike pigment, and different stnges of myofibre regenemtion were also a frequent group of muscular changes {13.5%). These are non-spedfic findings and can be a.􀸪sociatcd with a variety ofncuromuscu!ar disordefS, and a!so with increasing age in cetuccans. Genera!ized or focal atrophy rcpresented the J 1% and was rc!atcd to a poor body condi1ion or scnility. Other findings were myositis (1 .8%), ring fibres (1 .23%), libre spliuing (2.46%) and presence of intramyofibre sarcocystis sp. (8%). Finally, intr:unyofibre protowa (To.wp/asmo. sp.) wme only detectcd in one animal.