Sensitivity assessment of Caligus rogercresseyi to emamectin benzoate in Chile (original) (raw)
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Aquaculture, 2012
Caligus royercresseyi (Boxshall and Bravo, 2000) has been one of the greatest challenges for the salmon farming industry in Chile since 1997. A field study was carried out in four areas of Region X in the period 2006-2007 to obtain information about the efficacy of emamectin benzoate in the control of C. rogercresseyi in farmed Atlantic salmon (Salmo salar), one of the susceptible salmon species reared in Chile. The results obtained in this study show that the differences observed in the values of prevalence and abundance between the four areas in Region X were mainly caused by the oceanographic conditions and not as a consequence of the number of treatments with emamectin benzoate applied in the period of study, which on average ranged between 8 and 14 treatments by area.
The toxicity of emamectin benzoate, an aquaculture pesticide, to planktonic marine copepods
Aquaculture, 2003
The acute and sublethal toxicity of emamectin benzoate to non-target planktonic marine copepods was determined. Emamectin benzoate is the active ingredient in SliceR, an in-feed pesticide formulation used to control parasitic sea lice in salmon aquaculture. The comparative sensitivity of three life stages (nauplii, copepodites, adults) of four common marine copepods (Acartia clausi, Pseudocalanus elongatus, Temora longicornis and Oithona similis) was assessed in 48-h exposures followed by a recovery period in toxicant-free sea water. The calanoid copepods responded similarly to emamectin benzoate and EC50 values were significantly lower than those for the cyclopoid O. similis. Nauplii and copepodite 48-h EC50 values were generally lower than those for the adults. EC50 values ranged from 0.12 Ag/l (P. elongatus nauplii) to 232 Ag/l (O. similis adults). The primary toxic effect, immobilisation, was generally irreversible. A 7-day sublethal test with adult A. clausi females measured a significant reduction in egg production at higher concentrations. The noobserved-effect-concentration (NOEC) and lowest-observed-effect-concentration (LOEC) values were 0.05 and 0.158 Ag/l, respectively. Concentrations causing toxicity to planktonic copepods were considerably higher than Predicted Environmental Concentrations (PEC) in the vicinity of treated salmon farms and suggest that the use of emamectin benzoate for lice control is unlikely to adversely affect planktonic copepods. D
Journal of Fish Diseases
Caligus rogercresseyi is the dominant sea louse parasite affecting the salmon and trout industry in southern Chile (Carvajal, González, & George-Nascimento, 1998). The parasitic life cycle includes eight developmental stages each separated by a moult (González & Carvajal, 2003; González, Marín, & Vargas-Chacoff, 2015). It inhabits marine waters of southern Chile, having a wide range of fish host species (Carvajal et al., 1998; Marín, Martin, & Lewis, 2015). Due to the serious crisis of 2007, the Chilean National Fisheries and Aquaculture Service implemented a Caligidosis Surveillance and Control Program (PSEVC-Caligidosis), which establishes the abundance threshold that triggers control measures. However, this programme does not consider the evaluation of parasite susceptibility to antiparasitic treatments as a mandatory activity. Currently, in Chile the antiparasitic treatments with deltamethrin, cypermethrin, azamethiphos and hydrogen peroxide are authorized for use by bath immersion, in addition to oral treatments such as diflubenzuron, lufenuron and emamectin benzoate (SERNAPESCA, 2017). However, despite these ranges of treatments, the salmon farming industry is threatened by the loss of efficacy of the routine chemotherapeutic substances, from which the antiparasitic treatments are not excluded. The latter could be related to the potential development of resistance occurring in C. rogercresseyi populations. Resistance can be defined as the selection of a strain or population that is capable of surviving the exposure to a control agent dose that should be lethal to the majority of individuals from a susceptible population (Ffrench-Constant, Daborn, & Goff, 2004; Sevatdal & Horsberg, 2003). This phenomena can be identified and characterized through susceptibility evaluations by using bioassays, in which the parasites are exposed to a gradient of increasing concentrations of the antiparasitic treatment (SEARCH, 2006). A traditional sea louse susceptibility evaluation bioassay considers the exposition of
Aquaculture, 2000
The ectoparasitic copepod, Caligus flexispina, is causing increasing problems in farmed salmonids in southern Chile. Field and experimental approaches were used to assess whether any of the three host species, rainbow trout Oncorhynchus mykiss, atlantic salmon Salmo salar and coho salmon Oncorhynchus kisutch, is preferentially colonized. Prevalence, abundance, density and developmental stages attained by the parasite in three host species were compared. Results clearly revealed that rainbow trout is the most susceptible species: under field conditions, C. flexispina is more prevalent and abundant and there is a higher proportion of adult stages. No ovigerous females were found in coho salmon. In experimental infestations, rainbow trout were more heavily colonized by infective copepodids, and these were more likely to reach the adult stage. A mixture of factors inherent to each host-parasite relationship is considered to play a role in these observations because coho salmon is also colonized by copepodids but a low proportion of the parasites reach the adult stage. However, atlantic salmon is less suitable for colonizing larva.
Aquaculture, 2000
Three field trials were conducted to evaluate the efficacy of emamectin benzoate as a treatment Ž. Ž. for sea lice, Lepeophtheirus salmonis Krøyer and Caligus elongatus Nordmann , infestations on Ž. Atlantic salmon Salmo salar L.. Trials were carried out at sea temperatures of 13.0-15.58C and 7.2-8.58C. Salmon naturally infested with sea lice, with mean weights of 438, 513 and 2662 g, respectively, were held in experimental pens on commercial sites. At day y1 or y2, 20 or 30 fish were sampled from each pen to determine pre-treatment numbers of lice. Emamectin benzoate was administered in-feed at a dose of 50 mg kg y1 biomass day y1 for 7 consecutive days. Sea lice were counted again on days 7, 14 and 21, and comparisons made with untreated control fish. Treatment with emamectin benzoate was effective against chalimus and motile stages of sea lice. In all three trials, treated groups were surrounded by pens of heavily infested fish and L. salmonis numbers increased over time on control fish by 87-284%, whereas over the same period, L. salmonis were reduced on treated fish by 68-98%. In the low temperature trial, reductions were slower but numbers were still 90% lower than on control fish at day 21. At the end of the
2006
The genus Lernanthropus de Blainville, 1822 (Copepoda: Lernanthropidae) comprises more than 100 species of parasites of the gills of marine fishes, most of them inhabiting warm water (1-3). L. kroyeri causes gill lamellar necrosis, asphyxia, anemia, and secondary bacterial infections in sea bass, Dicentrarchus labrax (4-6). Some copepodid parasites, such as Lepeophtheirus salmonis (Kroyer) and Caligus elongates Nordman, can be treated with hydrogen peroxide (7,8), cypermethrin, deltamethrin, dichlorvos, and azamethiphos (9,10). Even though some successful results have been reported with bath treatments, immersion treatments of billions of fish are impractical and stressful to the fish. As a result of these limitations, treatments are being developed that can be administered in feed.
Acute toxicity of emamectin benzoate (SLICEtm) in fish feed to American lobster, Homarus americanus
Aquaculture Research, 2004
SLICE TM (active ingredient 0.2% emamectin benzoate (EMB)), a feed premix developed by Schering-Plough Animal Health for the control of sea lice on cultured salmonids, is registered for use in several countries and is being prescribed on an emergency basis in Canada and the United States. The concentration of EMB in feed administered to farmed salmon ranges from 1 to 25 mg g À1 . To determine the acute toxicity of the compound to juvenile and adult American lobster (Homarus americanus), commercial salmon feed was coated with SLICE TM at a range of concentrations and provided to the animals for 7 d in the laboratory. The LC 50 is estimated to be 644 mg g À1 (95% CI 5 428, 1275) for adult lobsters and 4589 mg g À1 for stage V and VI juvenile lobsters. The consumption of medicated pellets by adult lobsters decreased signi¢cantly with increasing concentration of EMB. Adult lobsters that died during the study had a signi¢cantly greater concentration of emamectin B1a in their muscle tissue than those that survived. These results support the conclusion that salmon feed medicated with EMB at the concentrations used by the aquaculture industry is unlikely to pose an acute lethal threat to adult and small juvenile American lobsters.
Diseases of Aquatic Organisms, 2000
Two trials were conducted at commercial salmon farms to evaluate the efficacy of emamectin benzoate (Slicem. 0.2 % aquaculture p r e-M , Schering-Plough Animal Health) as a treatment for sea lice Lepeophthe~rus salmonjs (Krayer) and Caligus elongatus Nordmann infestations in Atlantic salmon Salmo salar L. Tnals were carried out in 15 m2 commercial sea pens, at temperatures of 5.5 to 7.5"C and 10.8 to 13.8"C. Each pen was stocked with 14 000 to 17 500 fish with mean weights of 0.44 to 0.74 and 1.33 to 1.83 kg. Fish were naturally infested with sea hce at the start of each trial. At Day-1, samples of 10 or 15 fish were taken from each pen to determine pre-treatment numbers of lice. Emamectin benzoate was administered in feed, to 4 replicate pens, at a dose of 50 pg kg-' biomass d-' for 7 consecutive days (Days 0 to 6). Sea lice were counted again, between Days 7 and 77, and comparisons made with untreated control fish. Despite adverse weather conditions, wide vanations in fish weights and exposure to new infestations, treatment was effective against challmus and motile stages of L. salmon~s. In the autumn tnal, efficacy at Day 27 was 89%, and lice numbers remained lower on treated fish than on control fish 64 d from the start of treatment. In the winter trial, reductions in lice numbers at low temperatures were slower but good efficacy was achieved by Day 35. Although control fish had to be treated with hydrogen peroxide at Day 21, fish treated only with emamectin benzoate on Days 0 to 6 still had 89% fewer lice than control fish at Day 35. There were very few C. elongatus present, but at the end of both trials numbers were lower on treated fish. No adverse effects were associated with treatment of fish with emamectin benzoate. KEY WORDS: Sea lice. Lepeophtheirus salmonls. Caligus elongatus. Salmo salar. Emamectin benzoate O Inter-Research 2000 Resale of full article not permitted