HEARTWORM, ACANTHOCHEILONEMA-SPIROCAUDA (LEIDY, 1858), INFECTIONS IN CANADIAN PHOCID SEALS

Heartworm, Acanthocheilonema spirocauda, was observed in four of six s pecies of seals (19 seals of 701) examined from the Atlantic coast of Canada including the Canadian Arctic. Fourteen of 221 ringed seals (Ph oca hispida), 2 of 18 harbour seals (Phoca vitulina), 2 of 186 harp se als (Phoca groenlandica) (new host record), and the only hooded seal e xamined (Cystophora cristata) were infected with A. spirocauda. Intens ity of infection ranged from 1 to 31. Infected seals were age 0 to 14, but 8 of the 14 infected ringed seals were age 0. All worms were foun d in the right ventricle except in three cases. In one ringed seal and one harp seal, worms were found in the pulmonary artery, and in anoth er ringed seal, worms were found deep within the lungs. No infections were found in grey seals (Halichoerus grypus) (N=271) or bearded seals (Erignathus barbatus) (N=4). Heartworm is primarily a parasite of you ng seals. Its apparent absence in grey seals examined to date suggests either that a much larger sample of young seals from a broad geograph ic area is needed or that grey seals are refractory to infection or do not survive infections.