Infection Dynamics of Cryptosporidium parvum (Apicomplexa: Cryptosporiidae) in Neonatal Mice (Mus musculus)

Abstract

maintained alive in a dechlorinated city water supply. Based on their size and immaturity, the hosts collected in the 1982 survey likely had not spent any time at sea. Anadromous fishes, such as eulachon (Thaleichthys pacificus (Richardson)) or possibly salmonids, that had returned to fresh water to spawn after a period of marine life were probably the source of the marine parasites found in the sturgeon. Semakula and Larkin (1968, loc. cit.) noted that eulachon form an important part of the diet of Fraser River white sturgeon. As mentioned above, Becker (1970, loc. cit.) offered a similar explanation for the occurrence of T. lindbergi in Columbia River white sturgeon. For reasons unexplainable at present, Corynosoma strumosum was found only in female sturgeon (9/21 examined), the difference in prevalence of infection between the sexes being statistically significant (Fisher's exact probability test, P = 0.0083). There were no statistically significant host sex differences in prevalence of the other parasite species encountered. The present report represents the first on parasites of the Fraser River stock of white sturgeon, which is one of the major stocks of this North American sturgeon species. Voucher specimens of the parasites reported herein have been deposited in the National Museum of Natural Sciences, Invertebrate Collection (Parasites), Ottawa, Canada, and bear the following numbers: Crepidostomum auriculatum, NMIC(P) 1985-0115; Diphyllobothrium sp., NMIC(P) 1985-0116; Amphilina bipunctata, NMIC(P) 1985-0117; Corynosoma strumosum, NMIC(P) 1985-0118; Cystoopsis acipenseris, NMIC(P) 1985-0119; Anisakis simplex, NMIC(P) 1985-0120; undetermined nematode larvae, NMIC(P) 1985-0121. In addition, 4 specimens of C. auriculatum have been deposited in the Harold W. Manter Laboratory, University of Nebraska State Museum, Lincoln, Nebraska (No. 22983), and specimens of all species, except Diphyllobothrium sp. and A. bipunctata, are retained in the collection of the Pacific Biological Station. Specimens of A. bipunctata were given to Dr. G. Malmberg, University of Stockholm. We are pleased to acknowledge the assistance of Dr. Mary Hanson Pritchard and Dr. Janine Caira (Harold W. Manter Laboratory, University of Nebraska) in verifying the identification of C. auriculatum.