Parasitism of a Herring Gull by the duck leech

Published on 01 September 1954 in Main articles

O N February 13th, 1954, an adult Herring Gull (Larus argentatus) was found at the edge of Blagdon lake, north Somerset, unable to fly and gaping continuously. It was kept in captivity, but died the following day after being forcibly fed with sardine. A detailed post mortem was performed 24 hours later. The gull was an adult female in summer plumage weighing 720 g m . with massive subcutaneous and mesenteric fat depots. An examination of the bill showed a specimen of the Duck Leech (Theromyzon tessulatum) occluding the left nasal cavity and considerable blood stained mucus covering the posterior narial apertures. Fragments of sardine were present in the mouth and one piece was blocking the opening into the larynx causing the death of the gull by asphyxiation. The atria of the heart were greatly dilated with blood and engorged blood vessels were prominent on the surface of the shrunken ventricles. The rest of the organs appeared normal in the gross. No pathogenic bacteria were isolated from the intestinal contents. These findings suggest that the gull was a normal healthy adult before the leech entered the nasal cavity. The leech, measuring 25 mm. in length when fully extended, was filled with blood and at the site of attachment to the wall of the nasal cavity, there was some haemorrhage. The right nasal cavity and trachea were not blood stained indicating that these sites had not recently been occupied by other leeches which may have left the host after a blood

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