PARASITE EPIZOOTIC IN SEA OTTERS INEASTERN PRINCE WILLIAM SOUND
In winter of 1996, sea otters were reported dying in eastern Prince William Sound. We were able to necropsy several of the dead animals and found the same cause of death for all: septic peritonitis caused by gastrointestinal perforations due to heavy parasitism. The exact identification of the parasite is still being determined, but it is most likely Anisakis. An epizootic of a roundworm (Porrocaecum) that appears to be identical was described many years ago in sea otters from the Aleutian Islands in western Alaska (Rausch 1953).
Sea otter biologists had determined that the population of sea otters in eastern Prince William Sound was too large for the available resources. They were waiting for something to happen that would correct the population. People reported sea otters eating fish and remains of fish, sometimes from fish packing plants or fish cleaning stations. Fish are an intermediate host of this parasite.
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When the stomachs of the sea otters were opened during necropsy, large colonies of the nematode, a type of roundworm, were found attached to the lining. The dark areas in the photograph on the left show the colonies. Many loose worms were also present. |
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Most of the dead sea otters had colonies of the same parasite present in their intestines (the dark area in the center of the loop of intestine). Some of these colonies had perforated the intestinal wall, contaminating the abdomen and producing a peritonitis. |
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Some of the colonies in the intestines were large enough to cause an obstruction. The peristaltic waves continuing to push along the intestinal wall, working against the obstruction. As a result, the intestine folded in on itself, much like pushing the toe of a sock back into the interior of the sock. Some otters had more than a dozen of these "intussusceptions". |
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The bacteria that escaped from the intestines, through the bowel perforations, into the abdomen, produced an extensive infectious peritonitis. The omentum from such a case is shown here. It has become blackened and necrotic. |
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The Anisakis/Porrocaecum parasite is not the typical kind of worm we find in sea otters.
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ç Some animals contain huge burdens of tapeworms, here seen filling the lumen of the small intestines.è Most sea otters contain an acanthocephalan parasite about 11/2 cm long. Sometimes there are many thousands of these present in the sea otters. |
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Rausch,R. 1953. Studies on the helminth fauna of Alaska. XIII. Disease in the sea otter, with special reference to helminth parasites. Ecology 34(3):584-604.
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