[Prophylactic and therapeutic studies on intestinal giant-cystic disease of the Israel carp caused by Thelohanellus kitauei. II. Effects of physical and chemical factors on T. kitauei spores in vitro].

In a basic attempt to develop the prophylactic and therapeutic measures on intestinal giant-cystic disease of the Israel carp, Cyprinus carpio nudus, the effects of physical and chemical factors on viability or survival of the spores of Thelohanellus kitauei were checked in vitro by means of extrusion test on the polar filament. When the fresh spores suspended with 0.45% and 0.9% sodium chloride solution and distilled water were laid at 5 degrees C and 28 degrees C for short terms, the extrusion rates increased until the 3rd day, meanwhile when some of them were suspended with Tyrode's solution at -70 degrees C the rates increased gradually until the 8th day. Viabilities of the spores suspended with 0.9% saline and added antibiotics to the suspension at 5 degrees C for long terms lasted for 997 days and 1,256 days (presumed values) at maximum, respectively. The spores suspended with distilled water at 28 degrees C for long terms survived 152.4 days, but the spores suspended with Tyrode's solution at -70 degrees C for long terms showed almost the same viable pattern as early freezing stages up to 780 days. The spores suspended with Tyrode's solution, frozen at -70 degrees C and thawed at 5 degrees C, showed the highest rate of extrusion of the polar filament. In the case of frozen spores, the extrusion rates during heating tend to become higher in accordance with the increase of frozen period, and the critical points of 180 day-frozen spores to be killed were generally 78.5 hr. at 60 degrees C, 23.4 hr. at 70 degrees C, 189.1 min. at 80 degrees C or 10.5 min. at 90 degrees C. The longer the spores were frozen, the more time was needed for the death of spores after thawing; 20 days-17.4 days, 100 days-33.2 days, and 400 days-37.8 days. The longer the spores were frozen, the more time was needed for the death of spores at a conventional when they were dried air drying condition, 540 days-23.5 days, 160 days-21.0 days, and 20 days-14.4 days. On the other hand, the longer the spores were frozen, the more spores were dead rapidly when they were irradiated with 10W UV-ray; 100 days-26.0 hr, 300 days-21.9 hr, and 540 days-13.9 hr. The time needed for killing 200 days-frozen spores by various disinfectants at 1,000 ppm was 5.2 min. by calcium oxide, 10.4 min. by potassium permanganate, 27.8 min. by malachite green and 14.3 hr. by formalin.(ABSTRACT TRUNCATED AT 400 WORDS)