Abstract: Cardiomyopathy (CMP) has been documented as a disease associated with stranded pygmy (Kogia breviceps) and dwarf (Kogia sima) sperm whales in the United States and Asia. In this study, hearts from 27 pygmy and two dwarf sperm whales stranded in the coastal U.S. Atlantic Ocean and Gulf of Mexico from 1999 to 2006 were analyzed. Gross and microscopic examinations were conducted according to a standardized protocol designed to ensure systematic examination of tissue and data recording. Hearts were weighed and specific measurements made for selected tissues. Fourteen (48.3%) pygmy sperm whales had a microscopic diagnosis of CMP, 12 (41.4%) showed evidence of mild myocardial degeneration (MCD), one (3.4%) had moderate myocarditis and two (6.9%) had no pathological lesions. One dwarf sperm whale had CMP, and the other had mild MCD. The majority of stranded Kogia spp. with cardiac lesions came from the southeast Atlantic region (19/27, 70.3%). Cardiomyopathy and MCD lesions were found predominantly among adult whales. An excess of males was found for CMP and MCD (approximately 75% of both groups). The predominant histological lesions found in both disorders were anisokaryosis with karyomegaly and nuclear rowing, followed in frequency by interstitial edema. Cardiac weight, ventricular wall thickness, and valve circumference were compared between pygmy sperm whales with CMP and those with MCD. The largest differences were found for heart weight and intraventricular septum wall thickness, but none of the differences were statistically significant. Further adjustment for sex and body length did not alter the results. In the aggregate, these findings suggest that CMP in Kogia spp. is a chronic, progressive condition that represents a continuum from MCD to the more severe forms of the disorder. The etiology of this complex disorder remains unknown.

Key Words: PYGMY SPERM WHALE; KOGIA BREVICEPS; DWARF SPERM WHALE; KOGIA SIMA; CARDIOMYOPATHY; MYOCARDIAL DEGENERATION; STRANDING; U.S. ATLANTIC OCEAN AND GULF OF MEXICO

Document Type: Research article

DOI: 10.1578/AM.33.2.2007.214

Page Numbers: 214 - 222

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