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J Stone - One of the best experts on this subject based on the ideXlab platform.
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environmental effects of the anti sea lice copepoda caligidae therapeutant Emamectin benzoate under commercial use conditions in the marine environment
Aquaculture, 2006Co-Authors: Trevor C Telfer, Donald J Baird, J G Mchenery, J Stone, I Sutherland, P WislockiAbstract:Abstract Sea lice infestation can pose a particular problem to intensive cage aquaculture of salmonids. It is most often treated by therapeutants added to the water or incorporated into fish feed. This study investigated the environmental effects of one such in-feed treatment, Emamectin benzoate, under commercial use conditions. Atlantic salmon were fed the commercial preparation of Emamectin benzoate at a production fish farm on the west coast of Scotland. Sediment dwelling fauna, large mobile fauna and sentinel organisms were monitored for potential impacts over a 1 year post-treatment period (23 September 1997 to 23 September 1998). Additionally, sediment and water samples, transplanted blue mussels and captured large fauna were analysed for accumulated Emamectin benzoate and its desmethylamino metabolite to investigate the long term environmental fate of Emamectin benzoate. Results from analysis of sediments suggested that limited deposition of Emamectin benzoate took place during and up to 1 week post-treatment, and may have continued up to 4 months of post-treatment. This was consistent with the release of the active ingredient from fish excretion and defecation after treatment. Quantifiable amounts of Emamectin benzoate were found 10 m from the cages 12 months after treatment. However, clear reduction in overall sediment concentrations indicated that the deposited Emamectin was degrading over time. Emamectin benzoate was not detected in water samples during the field trial. Quantifiable concentrations of Emamectin benzoate were found in blue mussels deployed up to 100 m from the treatment cages at 1 week post treatment, but found only at 10 m from the cages at 1 month post-treatment. This suggests that while mussels were actively accumulating Emamectin benzoate immediately after treatment by 1 month this had largely been depurated. Macrobenthic faunal analysis indicated that there was no evidence that the occurrence of Emamectin benzoate, or its desmethylamino metabolite, in sediments around fish farm cages after treatment had any toxic impacts on organisms in either water column or sediments.
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safety and efficacy of Emamectin benzoate administered in feed to atlantic salmon salmo salar l smolts in freshwater as a preventative treatment against infestations of sea lice lepeophtheirus salmonis kroyer
Aquaculture, 2002Co-Authors: J Stone, I H Sutherland, Christina Sommerville, H W Ferguson, Richard G EndrisAbstract:The safety and efficacy of Emamectin benzoate, administered in-feed to Atlantic salmon smolts, Salmo salar L., held in freshwater, was evaluated as a preventative treatment against sea lice, Lepeophtheirus salmonis, following transfer of fish to seawater. In the safety study, salmon smolts held in freshwater were fed with diets containing Emamectin benzoate at nominal doses of 0 (control), 50 (recommended dose) and 250 (5× recommended dose) μg kg−1 fish day−1 for 7 days (days 0–6). Actual dose rates, based on measured concentrations of Emamectin benzoate in feed, differences in fish weight, and feed consumed, were 0, 54, and 272 μg kg−1 day−1, respectively. On day 9, fish were transferred to seawater and observed for 14 days. No differences in feeding response, coordination, behaviour, gross and histological appearance were observed between control fish and those that received 54 μg kg−1 day−1. Among smolts that received 272 μg kg−1 day−1, approximately 50% exhibited darker coloration, and one fish (1%) exhibited uncoordinated swimming behaviour. No pathognomonic signs of Emamectin benzoate toxicity were identified. In the efficacy study, smolts held in freshwater were fed an unmedicated ration (control group) or Emamectin benzoate at 50 μg kg−1 day−1 (treated group) for 7 days (days 0–6). On day 9, fish were re-distributed to eight seawater tanks, each holding 30 control and 30 treated fish. On days 28, 56, 77 and 109, respectively, control and treated fish in two tanks were challenged with L. salmonis copepodites. When lice in each group reached chalimus stage IV, fish were sampled and the numbers of lice were recorded. Fish challenged at day 109 were sampled for the second time when lice were at the adult stage. Efficacy was calculated as the reduction in the mean number of lice on treated fish relative to the mean on control fish. Treatment with Emamectin benzoate resulted in an efficacy of 85.0–99.8% in fish challenged at days 28–77, from the start of treatment, and lice counts were significantly lower (P<0.001) on treated fish than on controls. When fish challenged at day 109 were sampled at day 128, efficacy was 44.3%, but survival of chalimus to adult lice on treated fish was lower, and at day 159, efficacy had increased to 73%. These results demonstrate that treatment of salmon smolts with Emamectin benzoate in freshwater was well tolerated and highly effective in preventing sea lice infestation following transfer of fish to seawater.
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the efficacy of Emamectin benzoate as an oral treatment of sea lice lepeophtheirus salmonis kroyer infestations in atlantic salmon salmo salar l
Journal of Fish Diseases, 2002Co-Authors: J Stone, I H Sutherland, Christina Sommerville, R H Richards, Kanwal J VarmaAbstract:The efficacy of Emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (KrOyer), infestations in Atlantic salmon, Salmo salar L., was evaluated in a dose titration study and two dose confirmation studies. Replicated groups of salmon with induced infestations of sea lice were given Emamectin benzoate on pelleted feed at doses of 0, 25, 50 and 100 μg kg−1 biomass day−1 for seven consecutive days. Sea lice were counted at 7, 14 and 21 days from the start of treatment, and comparisons made with control fish given the same diet without Emamectin benzoate. Total numbers of sea lice were significantly reduced at all doses in all three studies when compared to control fish. There was no significant difference between doses of 50 and 100 μg kg−1, but the 50 μg kg−1 dose resulted in significantly fewer lice than the 25 μg kg−1 dose. Emamectin benzoate was highly effective in reducing numbers of preadult and adult lice and prevented the maturation of chalimus to motile stages. The optimum therapeutic dose was selected as 50 μg kg−1 day−1 for seven days. Treatment reduced the incidence of epidermal damage by sea lice and, in one study, survival of treated fish was 48% higher than in control groups. No fish mortalities or adverse effects were attributed to treatment with Emamectin benzoate at any of the doses tested.
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field trials to evaluate the efficacy of Emamectin benzoate in the control of sea lice lepeophtheirus salmonis kroyer and caligus elongatus nordmann infestations in atlantic salmon salmo salar l
Aquaculture, 2000Co-Authors: J Stone, I H Sutherland, Christina Sommerville, R H Richards, Kanwal J VarmaAbstract:Abstract Three field trials were conducted to evaluate the efficacy of Emamectin benzoate as a treatment for sea lice, Lepeophtheirus salmonis (Kroyer) and Caligus elongatus (Nordmann), infestations on Atlantic salmon Salmo salar (L.). Trials were carried out at sea temperatures of 13.0–15.5°C and 7.2–8.5°C. 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 −1 or −2, 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 μg kg −1 biomass day −1 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 third trial, both control pens were treated with hydrogen peroxide owing to heavy lice burdens. However, L. salmonis numbers rapidly increased again and at day 55, fish treated only with Emamectin benzoate still had 80% fewer lice than control fish. In the two summer trials, large numbers of C. elongatus were rapidly reduced by treatment with 82–84% efficacy by day 21. Despite the potential for continuous re-infestation, oral treatment with Emamectin benzoate presented an effective means of controlling all parasitic stages of L. salmonis and C. elongatus on farmed salmon, and in one trial, numbers remained lower on treated fish for at least 55 days.
Kanwal J Varma - One of the best experts on this subject based on the ideXlab platform.
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the efficacy of Emamectin benzoate as an oral treatment of sea lice lepeophtheirus salmonis kroyer infestations in atlantic salmon salmo salar l
Journal of Fish Diseases, 2002Co-Authors: J Stone, I H Sutherland, Christina Sommerville, R H Richards, Kanwal J VarmaAbstract:The efficacy of Emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (KrOyer), infestations in Atlantic salmon, Salmo salar L., was evaluated in a dose titration study and two dose confirmation studies. Replicated groups of salmon with induced infestations of sea lice were given Emamectin benzoate on pelleted feed at doses of 0, 25, 50 and 100 μg kg−1 biomass day−1 for seven consecutive days. Sea lice were counted at 7, 14 and 21 days from the start of treatment, and comparisons made with control fish given the same diet without Emamectin benzoate. Total numbers of sea lice were significantly reduced at all doses in all three studies when compared to control fish. There was no significant difference between doses of 50 and 100 μg kg−1, but the 50 μg kg−1 dose resulted in significantly fewer lice than the 25 μg kg−1 dose. Emamectin benzoate was highly effective in reducing numbers of preadult and adult lice and prevented the maturation of chalimus to motile stages. The optimum therapeutic dose was selected as 50 μg kg−1 day−1 for seven days. Treatment reduced the incidence of epidermal damage by sea lice and, in one study, survival of treated fish was 48% higher than in control groups. No fish mortalities or adverse effects were attributed to treatment with Emamectin benzoate at any of the doses tested.
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field trials to evaluate the efficacy of Emamectin benzoate in the control of sea lice lepeophtheirus salmonis kroyer and caligus elongatus nordmann infestations in atlantic salmon salmo salar l
Aquaculture, 2000Co-Authors: J Stone, I H Sutherland, Christina Sommerville, R H Richards, Kanwal J VarmaAbstract:Abstract Three field trials were conducted to evaluate the efficacy of Emamectin benzoate as a treatment for sea lice, Lepeophtheirus salmonis (Kroyer) and Caligus elongatus (Nordmann), infestations on Atlantic salmon Salmo salar (L.). Trials were carried out at sea temperatures of 13.0–15.5°C and 7.2–8.5°C. 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 −1 or −2, 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 μg kg −1 biomass day −1 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 third trial, both control pens were treated with hydrogen peroxide owing to heavy lice burdens. However, L. salmonis numbers rapidly increased again and at day 55, fish treated only with Emamectin benzoate still had 80% fewer lice than control fish. In the two summer trials, large numbers of C. elongatus were rapidly reduced by treatment with 82–84% efficacy by day 21. Despite the potential for continuous re-infestation, oral treatment with Emamectin benzoate presented an effective means of controlling all parasitic stages of L. salmonis and C. elongatus on farmed salmon, and in one trial, numbers remained lower on treated fish for at least 55 days.
Sarfraz Ali Shad - One of the best experts on this subject based on the ideXlab platform.
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characterization of phenacoccus solenopsis tinsley homoptera pseudococcidae resistance to Emamectin benzoate cross resistance patterns and fitness cost analysis
Neotropical Entomology, 2016Co-Authors: M B S Afzal, Sarfraz Ali ShadAbstract:Cotton mealybug Phenacoccus solenopsis (Tinsley) (Homoptera: Pseudococcidae) is a sucking pest of worldwide importance causing huge losses by feeding upon cotton in various parts of the world. Because of the importance of this pest, this research was carried out to select Emamectin resistance in P. solenopsis in the laboratory to study cross-resistance, stability, realized heritability, and fitness cost of Emamectin resistance. After selection from third generation (G3) to G6, P. solenopsis developed very high Emamectin resistance (159.24-fold) when compared to a susceptible unselected population (Unsel pop). Population selected to Emamectin benzoate conferred moderate (45.81-fold), low (14.06-fold), and no cross-resistance with abamectin, cypermethrin, and profenofos, respectively compared to the Unsel pop. A significant decline in Emamectin resistance was observed in the resistant population when not exposed to Emamectin from G7 to G13. The estimated realized heritability (h 2) for Emamectin resistance was 0.84. A high fitness cost was associated with Emamectin resistance in P. solenopsis. Results of this study may be helpful in devising insecticide resistance management strategies for P. solenopsis.
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resistance inheritance and mechanism to Emamectin benzoate in phenacoccus solenopsis homoptera pseudococcidae
Crop Protection, 2015Co-Authors: Muhammad Afzal, Sarfraz Ali ShadAbstract:Cotton mealybug Phenacoccus solenopsis Tinsley (Homoptera: Pseudococcidae) is an economic pest in many agricultural crops including cotton. Insecticide resistance in P. solenopsis has led to field failures. A study was conducted in the laboratory on selection, inheritance and mechanism of Emamectin resistance in P. solenopsis. After four selection cycles, high resistance (159-fold) was measured and resistance ratios for reciprocal crosses F1 and F1′ were 84 and 54-fold respectively. Dominance values for the resistance trait were determined to be 0.87 and 0.78, respectively. The number of genes controlling Emamectin resistance was calculated to be more than one. Synergism tests indicated the possible involvement of cytochrome P-450 mono-oxygenases and esterases in the expression of Emamectin resistance. It was concluded that Emamectin resistance in the experimental strain of P. solenopsis was autosomal, incompletely dominant and polygenic. Furthermore, Emamectin resistance in P. solenopsis could be due to enhanced metabolic detoxification mechanism. These findings have important practical application in managing insecticide resistance in P. solenopsis.
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Effect of Emamectin benzoate on life history traits and relative fitness of Spodoptera litura (Lepidoptera: Noctuidae)
Phytoparasitica, 2014Co-Authors: Syed Muhammad Zaka, Sarfraz Ali Shad, Naeem Abbas, Rizwan Mustafa ShahAbstract:Emamectin benzoate, a semisynthetic bioinsecticide, has been used frequently for the management of lepidopteran pests of cotton worldwide. To assess the resistance risk and design strategy for resistance management, life history traits were established for Emamectin benzoate-resistant, unselected and susceptible S. litura strains based on the laboratory observations. Bioassay results showed that the Emamectin benzoate-selected strain developed a resistance ratio of 911-fold compared with that of the susceptible strain. The Emamectin-selected strain had a relative fitness of 0.37 and lower prepupal and pupal weights, prolonged larval duration and development time, lower fecundity and hatchability compared with the susceptible strain. Mean population growth rates, such as intrinsic rate of population increase and biotic potential, were lower for the Emamectin-selected strain compared with the susceptible strain. Development of resistance can cost considerable fitness for the Emamectin-selected strain. The present study provided useful information for determining potential management strategies to overcome development of resistance.
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Increased fitness and realized heritability in Emamectin benzoate-resistant Chrysoperla carnea (Neuroptera: Chrysopidae)
Ecotoxicology, 2013Co-Authors: Muhammad Mudassir Mansoor, Sarfraz Ali Shad, Naeem Abbas, Attaullah Khan Pathan, Muhammad RazaqAbstract:The common green lacewing Chrysoperla carnea is a key biological control agent employed in integrated pest management (IPM) programs for managing various insect pests. A field collected population of C. carnea was selected for Emamectin benzoate resistance in the laboratory and fitness costs and realized heritability were investigated. After five generations of selection with Emamectin benzoate, C. carnea developed a 318-fold resistance to the insecticide. The resistant population had a relative fitness of 1.49, with substantially higher emergence rate of healthy adults, fecundity and hatchability and shorter larval duration, pupal duration, and development time compared to the susceptible population. Mean population growth rates; such as the intrinsic rate of natural population increase and biotic potential were higher for the Emamectin benzoate selected population compared to the susceptible population. The realized heritability ( h ^2) value of Emamectin benzoate resistance was 0.34 in Emamectin benzoate selected population of C. carnea . Chrysoperla species which show resistance to insecticides makes them compatible with those IPM systems where Emamectin benzoate is employed.
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cross resistance mode of inheritance and stability of resistance to Emamectin in spodoptera litura lepidoptera noctuidae
Pest Management Science, 2010Co-Authors: Sarfraz Ali Shad, Ali H Sayyed, Mushtaq A SaleemAbstract:BACKGROUND:Spodoptera litura (F.) is a cosmopolitan pest that has developed resistance to several insecticides. The aim of the present study was to establish whether an Emamectin-selected (Ema-SEL) population could render cross-resistance to other insecticides, and to investigate the genetics of resistance. RESULTS: Bioassays at G1 gave resistance ratios (RRs) of 80-, 2980-, 3050- and 2800-fold for Emamectin, abamectin, indoxacarb and acetamiprid, respectively, compared with a laboratory susceptible population Lab-PK. After three rounds of selection, resistance to Emamectin in Ema-SEL increased significantly, with RRs of 730-fold and 13-fold compared with the Lab-PK and unselected (UNSEL) population respectively. Further studies revealed that three generations were required for a tenfold increase in resistance to Emamectin. Resistance to abamectin, indoxacarb, acetamiprid and Emamectin in UNSEL declined significantly compared with the field population at G1. Furthermore, selection with Emamectin reduced resistance to abamectin, indoxacarb and acetamiprid on a par with UNSEL. Crosses between Ema-SEL and Lab-PK indicated autosomal and incomplete dominance of resistance. A direct test of a monogenic model and Land's method suggested that resistance to Emamectin was controlled by more than one locus. CONCLUSION: Instability of resistance and lack of cross-resistance to other insecticides suggest that insecticides with different modes of action should be recommended to reduce Emamectin selection pressure. Copyright © 2010 Society of Chemical Industry
Crawford W Revie - One of the best experts on this subject based on the ideXlab platform.
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a fixed dose approach to conducting Emamectin benzoate tolerance assessments on field collected sea lice lepeophtheirus salmonis
Journal of Fish Diseases, 2013Co-Authors: Shona K Whyte, J D Westcott, Ahmed M Elmoslemany, K L Hammell, Crawford W RevieAbstract:In New Brunswick, Canada, the sea louse, Lepeophtheirus salmonis, poses an on-going management challenge to the health and productivity of commercially cultured Atlantic salmon, Salmo salar. While the in-feed medication, Emamectin benzoate (SLICE®; Merck), has been highly effective for many years, evidence of increased tolerance has been observed in the field since late 2008. Although bioassays on motile stages are a common tool to monitor sea lice sensitivity to Emamectin benzoate in field-collected sea lice, they require the collection of large numbers of sea lice due to inherent natural variability in the gender and stage response to chemotherapeutants. In addition, sensitive instruments such as EC50 analysis may be unnecessarily complex to characterize susceptibility subsequent to a significant observed decline in efficacy. This study proposes an adaptation of the traditional, dose-response format bioassay to a fixed-dose method. Analysis of 657 bioassays on preadult and adult stages of sea lice over the period 2008-2011 indicated a population of sea lice in New Brunswick with varying degrees of susceptibility to Emamectin benzoate. A seasonal and spatial effect was observed in the robustness of genders and stages of sea lice, which suggest that mixing different genders and stages of lice within a single bioassay may result in pertinent information being overlooked. Poor survival of adult female lice in bioassays, particularly during May/June, indicates it may be prudent to consider excluding this stage from bioassays conducted at certain times of the year. This work demonstrates that fixed-dose bioassays can be a valuable technique in detecting reduced sensitivity in sea lice populations with varying degrees of susceptibility to Emamectin benzoate treatments.
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the efficacy of Emamectin benzoate against infestations of lepeophtheirus salmonis on farmed atlantic salmon salmo salar l in scotland 2002 2006
PLOS ONE, 2008Co-Authors: F Lees, Mark Baillie, G Gettinby, Crawford W RevieAbstract:Infestations of the parasitic copepod Lepeophtheirus salmonis, commonly referred to as sea lice, represent a major challenge to commercial salmon aquaculture. Dependence on a limited number of theraputants to control such infestations has led to concerns of reduced sensitivity in some sea lice populations. This study investigates trends in the efficacy of the in-feed treatment Emamectin benzoate in Scotland, the active ingredient most widely used across all salmon producing regions. Study data were drawn from over 50 commercial Atlantic salmon farms on the west coast of Scotland between 2002 and 2006. An epi-informatics approach was adopted whereby available farm records, descriptive epidemiological summaries and statistical linear modelling methods were used to identify factors that significantly affect sea lice abundance following treatment with Emamectin benzoate (SLICEH, Schering Plough Animal Health). The results show that although sea lice infestations are reduced following the application of Emamectin benzoate, not all treatments are effective. Specifically there is evidence of variation across geographical regions and a reduction in efficacy over time. Reduced sensitivity and potential resistance to currently available medicines are constant threats to maintaining control of sea lice populations on Atlantic salmon farms. There is a need for on-going monitoring of Emamectin benzoate treatment efficacy together with reasons for any apparent reduction in performance. In addition, strategic rotation of medicines should be encouraged and empirical evidence for the benefit of such strategies more fully evaluated.
I H Sutherland - One of the best experts on this subject based on the ideXlab platform.
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safety and efficacy of Emamectin benzoate administered in feed to atlantic salmon salmo salar l smolts in freshwater as a preventative treatment against infestations of sea lice lepeophtheirus salmonis kroyer
Aquaculture, 2002Co-Authors: J Stone, I H Sutherland, Christina Sommerville, H W Ferguson, Richard G EndrisAbstract:The safety and efficacy of Emamectin benzoate, administered in-feed to Atlantic salmon smolts, Salmo salar L., held in freshwater, was evaluated as a preventative treatment against sea lice, Lepeophtheirus salmonis, following transfer of fish to seawater. In the safety study, salmon smolts held in freshwater were fed with diets containing Emamectin benzoate at nominal doses of 0 (control), 50 (recommended dose) and 250 (5× recommended dose) μg kg−1 fish day−1 for 7 days (days 0–6). Actual dose rates, based on measured concentrations of Emamectin benzoate in feed, differences in fish weight, and feed consumed, were 0, 54, and 272 μg kg−1 day−1, respectively. On day 9, fish were transferred to seawater and observed for 14 days. No differences in feeding response, coordination, behaviour, gross and histological appearance were observed between control fish and those that received 54 μg kg−1 day−1. Among smolts that received 272 μg kg−1 day−1, approximately 50% exhibited darker coloration, and one fish (1%) exhibited uncoordinated swimming behaviour. No pathognomonic signs of Emamectin benzoate toxicity were identified. In the efficacy study, smolts held in freshwater were fed an unmedicated ration (control group) or Emamectin benzoate at 50 μg kg−1 day−1 (treated group) for 7 days (days 0–6). On day 9, fish were re-distributed to eight seawater tanks, each holding 30 control and 30 treated fish. On days 28, 56, 77 and 109, respectively, control and treated fish in two tanks were challenged with L. salmonis copepodites. When lice in each group reached chalimus stage IV, fish were sampled and the numbers of lice were recorded. Fish challenged at day 109 were sampled for the second time when lice were at the adult stage. Efficacy was calculated as the reduction in the mean number of lice on treated fish relative to the mean on control fish. Treatment with Emamectin benzoate resulted in an efficacy of 85.0–99.8% in fish challenged at days 28–77, from the start of treatment, and lice counts were significantly lower (P<0.001) on treated fish than on controls. When fish challenged at day 109 were sampled at day 128, efficacy was 44.3%, but survival of chalimus to adult lice on treated fish was lower, and at day 159, efficacy had increased to 73%. These results demonstrate that treatment of salmon smolts with Emamectin benzoate in freshwater was well tolerated and highly effective in preventing sea lice infestation following transfer of fish to seawater.
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the efficacy of Emamectin benzoate as an oral treatment of sea lice lepeophtheirus salmonis kroyer infestations in atlantic salmon salmo salar l
Journal of Fish Diseases, 2002Co-Authors: J Stone, I H Sutherland, Christina Sommerville, R H Richards, Kanwal J VarmaAbstract:The efficacy of Emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (KrOyer), infestations in Atlantic salmon, Salmo salar L., was evaluated in a dose titration study and two dose confirmation studies. Replicated groups of salmon with induced infestations of sea lice were given Emamectin benzoate on pelleted feed at doses of 0, 25, 50 and 100 μg kg−1 biomass day−1 for seven consecutive days. Sea lice were counted at 7, 14 and 21 days from the start of treatment, and comparisons made with control fish given the same diet without Emamectin benzoate. Total numbers of sea lice were significantly reduced at all doses in all three studies when compared to control fish. There was no significant difference between doses of 50 and 100 μg kg−1, but the 50 μg kg−1 dose resulted in significantly fewer lice than the 25 μg kg−1 dose. Emamectin benzoate was highly effective in reducing numbers of preadult and adult lice and prevented the maturation of chalimus to motile stages. The optimum therapeutic dose was selected as 50 μg kg−1 day−1 for seven days. Treatment reduced the incidence of epidermal damage by sea lice and, in one study, survival of treated fish was 48% higher than in control groups. No fish mortalities or adverse effects were attributed to treatment with Emamectin benzoate at any of the doses tested.
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field trials to evaluate the efficacy of Emamectin benzoate in the control of sea lice lepeophtheirus salmonis kroyer and caligus elongatus nordmann infestations in atlantic salmon salmo salar l
Aquaculture, 2000Co-Authors: J Stone, I H Sutherland, Christina Sommerville, R H Richards, Kanwal J VarmaAbstract:Abstract Three field trials were conducted to evaluate the efficacy of Emamectin benzoate as a treatment for sea lice, Lepeophtheirus salmonis (Kroyer) and Caligus elongatus (Nordmann), infestations on Atlantic salmon Salmo salar (L.). Trials were carried out at sea temperatures of 13.0–15.5°C and 7.2–8.5°C. 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 −1 or −2, 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 μg kg −1 biomass day −1 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 third trial, both control pens were treated with hydrogen peroxide owing to heavy lice burdens. However, L. salmonis numbers rapidly increased again and at day 55, fish treated only with Emamectin benzoate still had 80% fewer lice than control fish. In the two summer trials, large numbers of C. elongatus were rapidly reduced by treatment with 82–84% efficacy by day 21. Despite the potential for continuous re-infestation, oral treatment with Emamectin benzoate presented an effective means of controlling all parasitic stages of L. salmonis and C. elongatus on farmed salmon, and in one trial, numbers remained lower on treated fish for at least 55 days.