Gastrointestinal Helminths in the Hawaiian Monk Seal (Monachus schauinslandi): Associations with Body Size, Hematology, and Serum Chemistry

Abstract: Gastrointestinal helminth parasites are found commonly in the Hawaiian monk seal (Monachus schauinslandi), the most endangered seal in the United States and one of the world’s most endangered pinnipeds. We studied potential associations between gastrointestinal helminth infections and body size, and hematologic and serum chemistry variables in a sample of 282 monk seals captured between 1998 and 2002 as part of a population health assessment. Based on the presence of eggs in feces, the highest prevalence of infection (78%) was for cestodes belonging to a complex of several Diphyllobothrium spp. Infections with the nematode Contracaecum turgidum were found in 29% of samples tested. Eggs of the acanthocephalan Corynosoma rauschi were found in 4% of seals examined; and the feces of four weanling seals on the French Frigate Shoals contained eggs of the recently described trematode, Heterophyopsis hawaiiensis. We used a general linear model and analysis of variance techniques with adjustment for subpopulation and age to determine whether infections with Diphyllobothrium spp. or C. turgidum were associated with changes in hematologic or serum chemistry variables and found little evidence of an effect when we compared infected with negative seals or seals in the highest quartile of egg counts with negative seals. We also conducted analyses of associations between infection and morphometric values in adjusted, age-stratified data. Infection with Diphyllobothrium spp. was associated with a decrease in axillary girth and an increase in dorsal standard length/axillary girth ratio in seals less than 2 y of age, with the effects most pronounced in seals less than 1 y of age. After adjustment for Diphyllobothrium spp., C. turgidum infection was not associated with morphometric parameters. Co-infection with Diphyllobothrium spp. and C. turgidum was not associated with differences in body size greater than those found with diphyllobothriid tapeworm infection alone. These findings suggest that intervention strategies to reduce the prevalence of tapeworm infections in immature Hawaiian monk seals should be considered as a conservation measure for this highly endangered marine mammal.

Key Words: Hawaiian monk seal, Monachus schauinslandi, hematology, serum chemistry, Diphyllobothrium spp., Contracaecum turgidum, Corynosoma rauschi, Heterophyopsis hawaiiensis, gastrointestinal helminthes

Document Type: Research article

DOI: 10.1578/AM.32.2.2006.157

Page Numbers: 157-167

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