KLAUS KNOPF1, A. P. EKANEM2
1Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Department of Inland Fisheries, Germany
2University of Calabar, Institute of Oceanography, Nigeria
The ciliate Ichthyophthirius multifiliis is one of the most pathogenic parasites of fish, and it constitutes a major disease problem in aquaculture. The most effective treatment of I. multifiliis was achieved by use of malachite green, but meanwhile its use for the treatment of disease in food fish has been discouraged due to its potential mutagenic and teratogenic properties. Recently, there have been increased research activities into the utilisation of traditional plant-based medicines to control bacterial and parasitic infections in human and animal medicine. However, the use of medical plant extracts for the treatment of parasitic diseases in fish has rarely been reported.
In the present study, the effects of the crude methanolic extract of leaves of Mucuna pruriens and the petroleum ether extract of seeds of Carica papaya against I. multifiliis were investigated. Goldfish (Carassius auratus auratus) infected with the parasites were immersed for 72 h in baths with M. pruriens extract, and for 96 h in baths with C. papaya extract. There was a 90% reduction in numbers of I. multifiliis on fish in 200 mg l -1 baths of each plant extract compared to untreated control. Consequently, parasite-induced fish mortality was reduced significantly. A complete interruption of trophont recruitment was achieved by immersion in the M. pruriens extract. In vitro tests led to a 100% mortality of I. multifiliis in 150 mg l -1 M. pruriens extract, and in 200 mg l -1 of C. papaya extract after 6 h. Although the active constituents of the medicinal plant extracts are still unknown, we have demonstrated that they have potential for effective control of I. multifiliis.
Keywords: Ichthyophthirius multifiliis, methanolic extract, Mucuna pruriens