Abstract

A two month old female harbor seal pup was collected from Prince William Sound, AK in July 2005 by the Alaska SeaLife Center (ASLC) and held with seven other harbor seal pups for nutrition and growth studies. In December 2007, she was retired from research because of persistent gastrointestinal problems which included aerophagia, regurgitation, vomiting, diarrhea, bloat, abdominal pain, and occasional inappetance. Multiple supplemental diagnostic tests were pursued as part of the clinical workup of these problems. Gastric fluid was negative for Helicobacter pylori. Bile acids were within normal limits. Serum cortisol was consistently the highest when compared to the other juvenile harbor seals in the study. Serial biopsies obtained endoscopically from the stomach, rectum, colon, and ileum over the course of two years were found to have varying degrees of lymphoplasmocytic, eosinophilic, neutrophilic, and catarrhal gastritis and colitis/proctitis with crypt abscesses consistent with chronic, relatively intense but nonspecific antigenic stimulation. No infectious agents, ova, or parasites were seen in examined sections and some gastric biopsies were normal. Contrast radiography in August 2008 confirmed previously suspected megaesophagus. Treatment included diet management and various gastrointestinal therapies which reduced the incidence and severity of her clinical signs but did not resolve them. A combination of simethicone, Culturelle © (Lactobacillus); and mirtazapine appeared to provide fair control of her symptoms and occasional flare ups were short, usually 1 to 2 days, but she was smaller and had less weight gain than other juvenile harbor seals. She was found dead in the pool in December 2010 and gross necropsy revealed septic peritoneal effusion with severe congestion and necrosis of the small intestine secondary to a 360 degree volvulus of the mesenteric root and multiple focal chronic lesions of mesenteric fibrosis. Histopathological findings included severe chronic proliferative and erosive esophagitis at the cardiac sphincter and myofiber necrosis and fibrosis with associated megaesophagus and esophageal serosal adhesions as well as acute severe hemorrhage, congestion, edema, and necrosis of the small intestine and chronic adhesions of serosal membranes in the abdominal cavity.

Similar chronic aerophagia, regurgitation, bloating and abdominal discomfort had been observed in a male harbor seal collected as a weaned pup in Canada in 1996 and transferred first to ASLC in 1998 then to Milwaukee County Zoo in 2005. Due to his history of abnormal digestive function, he was maintained on a limited stable diet plus omeprazole and simethicone orally. Following a relatively asymptomatic period, he was found dead in his pool in July 2009. Necropsy revealed diffuse small intestinal 540 degree clockwise mesenteric torsion with massive acute intestinal hemorrhagic necrosis (infarction), severe acute fibrinous peritonitis, and severe locally extensive aboral esophageal dilatation with no observed histopathological abnormalities of the esophageal tissues. Although it was unclear whether the esophageal dilation was chronic or agonal in this male harbor seal, the similarity and chronic nature of the other digestive difficulties suggest that the volvulus / mesenteric torsion may have been related to aerophagia and abnormal intestinal function in both seals.