Location: Warmwater Aquaculture Research UnitTitle: Chronic pathology and longevity of Drepanocephalus spathans infections in juvenile channel catfish Author
Submitted to: Journal of Aquatic Animal Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2014
Publication Date: 9/17/2014
Citation: Griffin, M.J., Khoo, L.H., Steadman, J.M., Ware, C., Quiniou, S., Mischke, C.C., Terrence, G.E., Wise, D.J. 2014. Chronic pathology and longevity of Drepanocephalus spathans infections in juvenile channel catfish. Journal of Aquatic Animal Health. 26(4):210-218. Interpretive Summary: Drepanocephalus spathans (D.s.) is a common parasite of the double-crested cormorant. One of D. spathans life stages (cercariae) have been shown infective to juvenile channel catfish (Ictalurus punctatus). A subsequent life stage (metacercariae) often occlude blood vessels in the gills resulting in death of some fish. This study established that the infection with D. spathans is transient and does not appear to persist longer than 2 months.
Technical Abstract: Drepanocephalus spathans (Digenea: Echinostomatidae) is a common parasite of the double-crested cormorant (Phalacrocorax auritus). The cercariae of D. spathans have been shown infective to juvenile channel catfish (Ictalurus punctatus). The developing metacercariae concentrate in the cranial regions, often occluding blood vessels at the base of the branchial arch, resulting in death of some fish. The purpose of this study was to determine how long D. spathans metacercariae persist in experimentally challenged channel catfish. Two separate infectivity trials were conducted. In both trials, metacercariae persisted at least 49 days post-infection, although infection prevalence and intensity decreased over time. In the first trial, juvenile catfish (1-3 g) were exposed over 3 consecutive days to 100, 100 and 80 cercariae/fish/day, respectively. Fish were sampled seven days after the final exposure, and developing metacercariae were observed in 83.3% (5 of 6) of challenged fish. Twenty-one days post-exposure, metacercariae were present in only 50% of exposed fish (3 of 6). No metacercariae were observed in fish sampled at 35 days, however, metacercariae were present in 1 of 6 (16.7%) fish sampled on days 49 and 70, respectively. A second challenge consisted of a 24-hour pooled exposure of 500 cercariae/fish. Again, metacercariae were present in most (85.7%; 6 of 7) fish sampled 7 days post-exposure. At 21 days post-exposure, metacercariae were only evident in 1 of the 7 (14.3%) sampled fish. No metacercariae were in any fish at 35 days post-challenge, yet 1 of 7 (14.3%) fish was positive at 49 days post-challenge. The second study was terminated at 63 days post-challenge, as all fish sampled (n=14) were negative for metacercariae. This study supports D. spathans is infective to juvenile channel catfish, although the infection does not appear to persist longer than 2 months.