TWENTY-FIFTH ANNUAL EASTERN FISH HEALTH WORKSHOP MARCH 10-13, 2000   The Catfish Trematode Bolbophorus confusus And The Control Of Its Intermediate Snail Host Planorbella trivolvus     Andrew J. Mitchell   Harry K. Dupree Stuttgart National Aquaculture Research Center, U.S. Department of Agriculture, Agricultural Research Service, P. O. Box 860, Stuttgart, AR 72160   There are at least thirty digenetic trematodes that infect channel catfish Ictalurus punctatus.  Recently a digenetic trematode, tentatively identified as Bolbophorus confusus, has caused problems on about 15 catfish farms in Arkansas, Louisiana, and Mississippi.  The trematode is vectored by pelicans Pelecanus spp., the definitive hosts, and snails Planorbella trivolvus, the first intermediate host. Bolbophorus confusus infections, while usually not serious, have been known to can kill over 90% of the catfish in ponds in less than a week. The parasite infects the muscle tissues and is usually found in the caudal peduncle. The metacercarial and adult forms are characterized by the presence of lateral pseudosuckers, a clear cyst of parasite origin, interconnecting excretory channels, a tribocytic organ, and distinct hind- and forebody regions.  The length of metacercarial and adult trematodes usually ranges from 1 to 2 mm and 2 to 3.5 mm, respectively. The furcocercous cercariae is about 310µ in total length with the head region, anterior caudal portion, and furca all approximately the same length. Various molluscicides were tested against the snails that carry the catfish trematode.  Metaldehyde pellets applied at 375 mg/141cm2 of bottom area, the highest level tested, showed no adverse affect on the snails in 7 days.  HydrotholÒ 191, applied as an indefinite water treatment, caused an immediate death-like state in the snails but they recovered by the third day with 60% of the snails surviving at 8 mg/L, a rate too high for practical consideration. Niclosamide, also applied as an indefinite treatment, showed promise killing all the P. trivolvus in less than 72 hours at 0.3 mg/L but not at 0.1 mg/L.  Niclosamide, however, is toxic to channel catfish at 0.8 mg/L.  In addition, two chemicals were tested as potential pond shoreline treatments. Preliminary tests in jars were run with niclosamide (3 mg/L) and a copper sulfate/citric acid combination (30 and 3 mg/L respectively) for 30 min.  No snails were killed with niclosamide but 80% were killed in the copper sulfate/citric acid combination treatment. The copper sulfate/citric acid combination was then tested against snails in a pond. Copper sulfate (4.5 kg) and citric acid (0.45 kg) were added to about 265 L of water and sprayed into the pond water along the shore line in a 2 m band over 76.25 linear meters. The treatment appeared quite promising, eliminating 86% of the live snails in 96 h while not harming fish in the pond.     Return to 25th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page