Whale Beachings Linked to Mysterious Heart Defect

John Pickrell in England
for National Geographic News
August 6, 2003

Typically known for suddenly killing otherwise healthy, young human athletes, a deadly heart condition with mysterious causes is affecting populations of two whales species found in both U.S. Atlantic waters and the Gulf of Mexico. Already this year more than three times the typical number of diseased whales found in an entire year have beached in the U.S. Southeast.

The increase in the number of stranded dwarf sperm whales, Kogia simus, and pygmy sperm whales, Kogia breviceps, with the heart defect is "disturbing, worrisome, and something we want to investigate," said marine mammal veterinarian and pathologist Gregory Bossart, director of Harbor Branch Oceanographic Institution's Marine Mammal Research and Conservation Division, in Fort Pierce, Florida.

A workshop on the disease, dilated cardiomyopathy, was held at Harbor Branch last month. The meeting united both human and marine mammal researchers and medics, hoping to better understand the heart defect with the help of medical techniques usually used by physicians on humans.

Increasingly Common

The disease has been found in more than three-quarters of stranded dwarf and pygmy sperm whales beached so far in the Southeast this year, said Bossart, and has been known as one cause of beaching since the 1980s.

On average over the last five years just 12 diseased whales beached and died in the region annually, said Blair Mase, the Southeast Marine Mammal Stranding Coordinator, based at the National Oceanic and Atmospheric Administration (NOAA) Southeast Fisheries Science Center in Miami. However, already this year, 38 diseased whales have washed up on to Southeast beaches. The figures should be treated with caution, however, warned Dann Odell, stranding expert with the Hubbs-Seaworld Research institute in Orlando, Florida. Stranding figures can show great variation from year to year, he said. Several more years' data may be required to prove an increase in stranding frequencies due to the heart defect.

Dilated cardiomyopathy was first documented in both species by Bossart and colleagues in 1985, after 29 beached whales were found to have a heart defect. Little research into causes and treatments has been carried out since then, but this year's mysterious increase in stranding has spurred Bossart's team into action.

Cardiomyopathy is characterized by enlargement and ensuing weakening of the heart. The dilated form is due to the expansion of the lower chambers of the heart (the right side alone in both Kogia species). A thickening of the walls of these chambers causes hypertrophic cardiomyopathy, the more common disease in humans. Both diseases can cause the heart to deteriorate until it is unable to function.

The human version of the disease—nearly always due to inherited genetic defects—is thought to be responsible in many cases where young footballers, basketball players, and other athletes drop dead unexpectedly, said George Hensley, a retired human pathologist formerly of the University of Miami Jackson Memorial Hospital. Hensley is aiding in applying knowledge of the related human heart defect to recognizing and studying the whale disease. According to a recent news article in the journal Science, cardiomyopathies may claim more than 27,000 human lives each year in the U.S.

Deep Ocean "Extra-Terrestrials"

In addition to limited knowledge of the heart defect, very little is known about these species of whale. They've never been kept in captivity, and were deemed too small for commercial whaling purposes, said Bossart. "They're like little extra-terrestrials."

And little they are, compared to their giant sibling species the sperm whale, Physeter catadon, made famous as Moby Dick in Herman Melville's classic novel. The sperm whale can reach over 60 feet (18.2 meters) in length and has a heart "large enough to walk inside of," said Bossart.

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