Abstract:
Ichthyophthirius multifiliis (a ciliate), Gyrodactylus spp. and Dactylogyrus
spp. are common, external, harmful parasites of goldfish, Carassius auratus. Bath
treatments with different chemicals that could be harmful to the environment as
well as to the fish are used by Sri Lankan farmers to control these parasites. The
present study was planned to investigate the efficacy of row garlic (Allium
sativum) extract in controlling I. multifiliis, Gyrodactylus spp. and Dactylogyrus
spp. on goldfish.
In vitro test was carried out with different concentrations of row garlic
extract to find out the effective minimum concentration required to kill I.
multifiliis; toxicity of the extract on healthy goldfish was tested at a range of
concentrations closer to this effective minimum concentration. In vivo test was
performed at different concentrations of garlic extract and random samples of
fish were observed for the presence of parasites two times a day. Anti-parasitic
efficacy of the plant extract on I. multifiliis and both flukes were calculated.
The effective minimum concentration of row garlic extract to kill I.
multi(iliis in vitro experiment was 2S0 mgr' at exposure time of 3.5 hours. In vivo
experiment revealed that garlic extract at concentration of 260 mgr' and 270
mgr' could kill/ remove aliI. multifiliis and both monogenean flukes respectively
from the body and gills of goldfish in 3 days of exposure at 24°C-27°C;
antiparasitic efficacy (1.S7l:t0.00) recorded for garlic extract at the respective
concentrations on I. multifiliis and monogenean flukes were not significantly
different (P>O.OS) from the antiparasitic efficacy recorded for formalin at 200
mgr' at 4 hours of exposure time, which was the positive control. Histopathology
revealed that the effect of formalin treatment on gill tissues of treated fish was
greater compared to the effect of treatment with garlic extract.
