Effects of Caligus rogercresseyi (Boxshall & Bravo 2000) chalimus stage condition (dead, moribund, live) on the estimates of Cypermethrin BETAMAX® efficacy
2015
Marín, Sandra L. | Martin, Roberto | Lewis, Rodrigo
To maintain antiparasitics against caligids copepods over time, accurate information is necessary to estimate efficacy. The objective of this study was to experimentally evaluate cypermethrin BETAMAX®efficacy on chalimus I and II combined of Caligus rogercresseyi (Boxshall & Bravo, 2000) using two approaches to estimate chalimus abundance: dead + moribund + live parasites, and only live parasites. Forty‐eight Oncorhynchus mykiss (Wallbaum) were distributed in four 100‐L tanks (two control and two treated) and exposed to 60 copepodids per fish. Parasite abundance by developmental stage and condition (dead, moribund, live) was determined 7 days post infection. Treatment with cypermethrin was applied and after 48 h, fish were euthanized to estimate parasite abundance per developmental stage and condition. Live, moribund and dead parasites were observed at 67.8%, 26.0% and 6.2% respectively. Mortality of chalimus I and II combined due to treatment, after discounting mortality of lice on the control fish, was 54.8%. Treatment efficacy against was 16.5% and 94.6% when estimating parasite abundance as dead + moribund + live, and only live parasites respectively. Results from laboratory experiments provide valuable information regarding effects of the chemotherapeutants that are not easy to detect on farms (time of parasite detachment).
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