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Comparative efficacies of sodium percarbonate, peracetic acid, and formaldehyde for control of Ichthyobodo necator—an ectoparasitic flagellate from rainbow trout

100%

Jaafar R. M. , Kuhn J. A. , Chettri J. K. , Buchmann K.

Acta Ichthyologica et Piscatoria

2013

tom 43

nr 2

Background. Ichthyobodosis (“costiosis”) is induced by the flagellate Ichthyobodo necator in both wild and cultured host populations. Fish farmers for decades have been using formaldehyde (FA) for control but this compound is problematic due to its carcinogenic and allergenic nature. Alternative auxiliary substances for bath treatment are needed and therefore we decided to compare efficacies of sodium percarbonate (SPC), peracetic acid (PAA), and hydrogen peroxide (HP) for control of ichthyobodosis in rainbow trout, Oncorhynchus mykiss. Materials and Methods. An experimental infection of Ichthyobodo necator on rainbow trout (2–3 g) was established (total parasite population up to 142 000 flagellates per fish) and duplicated controlled water bath treatments were conducted with specified water quality criteria. Four compounds: SPC (40, 80, and 120 mg · L–1), PAA (0.1, 0.2, and 0.3 mg · L–1), HP (15 and 30 mg · L–1), and FA (40 and 80 mg · L–1) were tested. The compounds were applied for 2 h (as static freshwater bath treatments at 13°C) in 20-L aerated tanks (containing 10 L of the treatment solution). Results. FA at a concentration of 80 mg · L–1 and PAA at 0.3 mg · L–1 showed almost complete elimination of parasites but it was found that also SPC at a concentration of the 120 mg · L– was highly effective in eliminating I. necator. In addition, SPC and PAA (80 mg · L–1 and 0.2 mg · L–1, respectively) also significantly reduced the parasite load compared to untreated control fish. HP significantly reduced parasite populations at a concentration of 30 mg · L–1, but the compound elicited adverse reactions in fish. Conclusion. It is suggested that SPC and PAA may serve as alternatives to formaldehyde for control of ichthyobodosis in rainbow trout farms.

Annual and spatial variability in endo- and ectoparasite infections of North Sea cod (Gadus morhua Linnaeus, 1758) larvae, post-larvae and juveniles

75%

Mehrdana F. , Bahlool Q. Z. M. , Skovgaard A. , Kuhn J. A. , Kania P. W. , Munk P. , Buchmann K.

Acta Parasitologica

2014

tom 59

nr 2

A parasitological investigation was performed on a total of 5380 Atlantic cod larvae, post-larvae and small juveniles sampled from the North Sea during a period of five years. The copepod Caligus elongatus (Von Nordmann, 1832) and the nematode Hysterothylacium aduncum (Rudolphi, 1802) were found at a relatively high prevalence of infection (4.6% and 5.2%, respectively). The infection by both parasites showed annual and spatial variability. C. elongatus showed a higher prevalence in 1992 compared to the following years, whereas the prevalence of H. aduncum increased from 1992 to 2001.We observed a relation between parasite distribution and parameters such as latitude and water depth. Adult digeneans (Lecithaster gibbosus and Derogenes varicus) and larval cestodes were also found with lower infection rates. Since changes of infection levels coincided with increasing North Sea water temperature in the studied period, it is hypothesized that temperature may affect parasite population levels. However, it is likely that other environmental factors may contribute to the observed variations. Absence of infection intensities higher than one nematode per fish in small larvae and post-larvae suggests that host survival may be affected by a high infection pressure. The relatively high levels of infection in the younger stages of cod, and the annual/spatial variability of these infections should be considered in the understanding of the early life dynamics of the species.