Comparative susceptibility of carp fingerlings to Lernaea cyprinacea infection.

Study was conducted to find out the comparative susceptibility of fingerlings of seven species of carps (Labeo fimbriatus, L. rohita, L. calbasu, Catla catla, Ctenopharyngodon idella, Cyprinus carpio and Hypophthamichthys molitrix) grown under both mono and polyculture to Lernaea cyprinacea infection. Under monoculture, C. carpio, L. rohita and L. calbasu, did not acquire Lernaea infection and were thus considered resistant, whereas C. idella, H. molitrix, C. catla and L. fimbriatus were susceptible. Even challenge with higher infective doses of copepodids under monoculture did not result in infection in the resistant fish species. The resistance of L. rohita and C. carpio to Lernaea infection under monoculture was not sustained when these two fish species were maintained in polyculture along with susceptible fish species. Labeo calbasu, even under polyculture, however, did not acquire Lernaea infection indicating that this fish species is the most resistant and least preferred host for this parasite. Similarly, C. carpio, L. rohita and L. calbasu when grown together in polyculture and exposed to a higher infective dose (120 copepodids/fish) also did not develop the infection. The possible reasons for differences in susceptibility shown by these carp species in monoculture and the loss of resistance by rohu and common carp while in polyculture with susceptible species are discussed. The ability of resistant fish species to prevent establishment of anchor worms on them under monoculture can be utilized to control this parasitic infection commonly encountered in culture ponds.

Efficacy of doramectin against natural and experimental infections of Lernaea cyprinacea in carps.

Efficacy of doramectin administered via oral and parenteral routes against experimentally induced and natural infections of the copepod parasite Lernaea cyprinacea in carps was studied. Administration of doramectin incorporated in feed at 1mg/kg b.wt. of fish for 10 days effectively controlled experimentally induced Lernaea infection in Labeo fimbriatus fingerlings within an average of 19 days of post-treatment as compared to the normal course of 41 days. Similarly, doramectin given through feed at 1mg/kgb.wt. of fish for 10 days was equally effective in controlling natural infection of this parasite in the underyearlings of Catla catla and L. fimbriatus. Intramuscular administration of doramectin at 200microg/kgb.wt. of fish effectively removed adult Lernaea infection in L. fimbriatus as early as 18 days of treatment as compared to the time period of 43 days taken by the untreated fish to get rid of the infection. Single intramuscular administration of the drug was more effective against the parasite than its administration in multiple divided doses. In all cases, doramectin did not cause any noticeable adverse reactions or toxicity to the fish host. In view of the handling associated stress and other operational difficulties involved, a single intramuscular administration of the drug at 200microg/kgb.wt. is suggested for treatment of heavily infected adults and brood stock of carps. Doramectin incorporated in feed at 1mg/kgb.wt. of fish is best suited for treatment of Lernaea infection in young fish including fingerlings. However, detailed studies on the toxicity and pharmacokinetics of doramectin upon its administration to aquatic organisms and the environmental impact of its usage are required to be undertaken before finally recommending the safe use of this drug for control of parasitic infections of aquatic organisms.

Repeated use of oil for frying fish. Effects of feeding the fried fish to rats.

Four groups of weanling male albino rats (Wistar strain) were fed isonitrogenous diet (10% protein) identical in all respects except in the nature of the protein source, for 4 weeks. Control group (group 1) had steamed mackerel meat as the protein source, whereas groups 2, 3 and 4 had mackerel fried on the 1st, 3rd and 4th days in the same coconut oil repeatedly used for frying each day. Four groups of adult male rats weighing around 130 g were fed on the same diet for 12 weeks. Weanlings fed on fish fried on the 4th day showed significantly lower feed consumption and weight gain compared to the other three groups. All the three groups of adult rats fed on fried fish compared well with control rats in weight gain and hepatosomatic index. There was a decrease in the total lipid and cholesterol content of the liver of rats fed with fried fish in comparison with the control rats. The total lipid and cholesterol in heart and serum cholesterol levels increased significantly from control rats through group 4. The C22:6/C20:5 ratio in the heart lipid showed a very high value compared to the dietary lipids. Histopathological examination showed initial stages of cell damage in the liver and kidney of rats fed with fish fried on the 4th day. In-vitro digestibility of proteins of fried fish were lower than that of steamed fish, but the difference in this respect between proteins of fish fried on different days was not significant.