The Viability of Ichthyophthirius multifiliis Maintained at Low Temperature.

Abstract

The ciliate Ichthyophthirius multifiliis, an obligat fish parasite, was maintained at low temperature as attempt to prolong its life span and reduce the number of fish hosts required in its laboratory propagation. The experiments were conducted using trophont stage of parasite which originally isolated from any outbreaks of white spot disease. Briefly, parasites were subjected at optimal temperature 25- 28°C (control) and at low temperature 9°C for 14 consecutive days of observation. The survival rate, encystation rate, excystation rate, and the abnormality of descendants which produced by maintained parasites were examined at the last day of observation. Here the infectivity of parasites then performed by means of infecting the animal model either black moly Poecilia sphenops or red belly pacu Colossoma macropomum with escaping theronts which collected during excystation. The results revealed that the survival rate and the excystation rate of parasites were decreased, while the encystation rate and the abnormality increased as maintaining period increased. Spesifically, the final rate of survival, encystation, and excystation of parasites were 35%, 100%, and 33,33% respectively. Additionally, the descendants came out with highly abnormality recognized by their weak mobility and their lower infectivity (40-50%) compared to the control (80-100%). Overall, from the study concluded that, it is possible to maintain I. multifiliis at low temperature without its host for 14 days, where it still gain its infectivity, eventhough being decreased.