STUDIES ON INFECTION VARIATION OF FISH TO Argulus japonicus AND TRIAL FOR ARGULOSIS TREATMENT

The present study aimed at identifying susceptibility pattern of experimental infestation of fishes to Argulus japonicus and effective control measures against Argulosis.  Fish from 7 species (Labeo rohita, Catla catla, Cyprinus carpio, Carassius auratus, Oreochromis niloticus, Pangasianodon hypophthalmus, Trichogaster trichopterus), were used for the study. Fishes were acclimatized for a week in the tanks before challenged with 50 A. japonicus individual/fish in triplicate. There was no water exchange or removal of faecal matter from the tanks during initial 5 dpi (Days post infestation) to prevent accidental removal of free living parasites. Based on the observed parasite load on each species, P. hypophthalmus, followed by L. rohita, C. catla and C. auratus were found to be the most susceptible and O. niloticus and T. trichopterus least infected species. There were signs of reddening spot on the fish skin surface following infection by lice. In all the infested fishes, base of fins especially at the caudal fin were found to be the preferential site of attachment. Once fishes were heavily infected, we went for controlling the parasitized Argulus (Argulosis) by different methods viz. potassium permanganate, table salt, methylene blue, formalin and mechanical. Among all the controlling measures mechanical treatment by rubbing the skin with soft nylon net as most effective means of detaching the parasite from fish. The present findings will helpful for understanding the infection pattern of freshwater louse and its effective prophylactic measures.

Argulus, an obligate macroectoparasite, infests a wide range of fishes causing severe economic loss to aquaculture industry. It has also been suggested that argulids make use of chemosensory capability to locate. Variation of susceptibility to Argulus can provide comprehensive understanding of A. japonicus infection. Results of the present study indicated that artificial infection to various fishes pangasius catfish is most susceptible species whereas an ornamental fish, blue gourami is least susceptible (Table 1)