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Efficacy Of Various Chemotherapeutic Agents On The Growth Of Spironucleus Vortens, An Intestinal Parasite Of The Freshwater Angelfish
Somboon Sangmaneedet and Stephen A. Smith Department of
Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of
Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
Spironucleus spp. are
diplomonad flagellates frequently found in the digestive tract of freshwater,
brackish and saltwater fish. These motile parasites may cause cellular damage
in the intestinal tract of infected fishes and in heavy infections may
interfere with normal growth of the host. These parasites have been reported as
pathogens causing enteritis and mortalities in salmonids, cyprinids and
ornamental tropical aquarium fish. Thus, treatment and control of these
organisms are important to both the foodfish and tropical fish industry. Seven
chemotherapeutic agents (dimetridazole, metronidazole, pyrimethamine,
albendazole, fenbendazole, mebendazole and magnesium sulfate) were evaluated
for their inhibition of growth on the in vitro cultivation of Spironucleus
vortens, an intestinal parasite of the freshwater angelfish, Pterophyllum
scalare. Dimetridazole and metronidazole were effective in inhibiting the
growth of the parasite at concentrations of 1 µg ml-1 or higher. At
24 hours post-exposure, 33% of the parasites demonstrated inhibited growth when
exposed to either dimetridazole or metronidazole at concentrations of 2 and 4
µg ml-1, respectively. Dimetridazole at 4 µg ml-1 or higher
concentrations decreased the number of organisms to 50% or less after 48 hours
of exposure. During the same period of time, metronidazole at 6 µg ml-1 or
higher concentrations decreased the number of parasites to 50% or less.
Pyrimethamine at concentrations of 1 to 10 µg ml-1 was not effective
in inhibiting the growth of the parasite. Albendazole and fenbendazole were
similar in inhibiting the growth of the organism. Both compounds significantly
suppressed the growth of the parasite at concentrations of 1.0 µg ml-1
or higher after 24 hours of exposure. Mebendazole inhibited the parasite's
growth at concentrations of 0.5 µg ml-1 or higher. At 72 hours post-
exposure, 45-50% of the parasites demonstrated inhibited growth when exposed to
mebendazole at concentrations higher than 0.5 µg ml-1. Magnesium
sulfate at concentrations of 70 mg ml-1 or higher also suppressed the growth of
the parasite after 24 hours of
exposure. These results suggest that dimetridazole, metronidazole and
mebendazole are the most effective chemotherapeutic agents at inhibiting the in
vitro growth of S. vortens.
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