Killing effect of various treatments on the monogenean Heterobothrium okamotoi eggs and oncomiracidia and the ciliate Cryptocaryon irritans cysts and theronts
2003
Hirazawa, N. | Goto, T. | Shirasu, K.
The effect of chlorine (12, 60, and 120 ppm available chlorine concentrations), benzalkonium chloride (100 ppm), freshwater, heat (40 °C), and drying on the hatching ability of Heterobothrium okamotoi eggs and Cryptocaryon irritans cysts was examined. The eggs and cysts at an early stage (1-16 h after spawning or leaving the host for H. okamotoi and C. irritans, respectively) and at a late stage (72-87 h) were exposed to each treatment for 1 or 24 h. Hatching of H. okamotoi eggs and C. irritans cysts was completely suppressed at both early and late stages when they were exposed to heat for 1 h. Exposure to chlorine at a concentration of more than 60 ppm available chlorine or to drying for 24 h was also effective in preventing hatching completely. However, freshwater had limited effect on preventing hatching of both parasites. Although benzalkonium chloride treatment for 1 h prevented hatching of C. irritans cysts completely, it was not effective against H. okamotoi eggs. One-hour treatments with chlorine (2.4 and 12 ppm) or benzalkonium chloride (100 ppm),or heat (40 °C) killed hatched H. okamotoi oncomiracidia and C. irritans theronts. These methods would be useful to prevent the horizontal infection with these parasites from used equipment, tanks, and wastewater in fish-rearing facilities.
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