Diplomonad flagellates of some ornamental fish cultured in Thailand

The study on diplomonad flagellates infection in some ornamental fishes in the family cichlidae i.e., angelfish(Pterophyllum scalare), oscar (Astronotus ocellatus), blue mbuna (Labeotropheus fuelleborni) and the family osphronemidaei.e., Siamese fighting fish (Betta splendens) revealed that this parasite infected three out of four ornamental fish species,angelfish, oscar and blue mbuna. The highest infection was recorded in angelfish (90%) followed by oscar (75.4%) and bluembuna (61%), respectively. Identification of diplomonad flagellates from angelfish by means of morphological studies underlight and electron microscopes indicated that the parasite was Spironucleus vortens. The 14–days LD50 of S. vortens inangelfish was 2.99x103 cells. Histopathological changes of infected angelfish revealed granulomatous liver, numerousnumbers of melanomacrophage in the spleen and inflammation of the intestine. Susceptibility study of S. vortens to goldfish(Carassius auratus), guppy (Poecilia reticulata) and platy (Xiphophorus maculatus) indicated that they were resistant toartificial infection. In vitro examination of the growth inhibition assay of S. vortens indicated that dimetridazole and metronidazolewere effective in inhibiting parasite growth after 48 hrs exposure at concentrations of >4.0 μg/ml and >6.0 μg/ml,respectively. Magnesium sulfate at a concentration of >60 mg/ml inhibited the parasite growth after 72 hrs exposure. In vivoexamination of the dimetridazole efficiency on S. vortens infection indicated that dimetridazole at 4.0 μg/ml provided thehighest efficiency which could be used for treatment of spironucleosis in angelfish.