Efficacy of SLICE Premix (0.2% Emamectin Benzoate) for Reducing Infestations of Salmincola spp. on Freshwater‐Reared Rainbow Trout

Abstract

Salmincola spp. are ectoparasites of major concern in wild and cultured salmonids. These parasites can cause respiratory distress and facilitate the entry of secondary pathogens. Of particular concern in the United States is S. californiensis, which can infest all Oncorhynchus spp. and is restricted largely to freshwater. Bath treatments with formalin and hydrogen peroxide have traditionally been used to control infestations of some parasitic copepods in cultured salmonids; however, these treatments can be difficult to apply, expensive, and stressful to fish and have not been shown to be effective against S. californiensis. A more effective and efficient treatment method needs to be developed. SLICE (0.2% emamectin benzoate [EB]) is a commercial in-feed treatment that has been shown to be effective for the control of sea lice infestations in seawater-reared farmed salmon and trout. We postulated that EB might also be efficacious for the control of parasitic copepods such as S. californiensis on freshwater-reared salmonids. Four trials were conducted to evaluate the effectiveness of SLICE-medicated feed administered at a target dosage of 50 µg EB·kg fish −1 ·d −1 for seven consecutive days to control infestations of S. californiensis on freshwater-reared rainbow trout. At the end of each trial (after either a 30-or 42-d posttreatment period), copepod prevalence in treated tanks was substantially reduced compared with the pretrial prevalence recorded in the reference populations. Additionally, a significant difference was detected in mean abundance between treated and control groups, with a 79-96% reduction in mean abundance among fish offered the EB-medicated feed. Based on the results of these trials, it was concluded that SLICE was efficacious in reducing infestations of S. californiensis on freshwater-reared rainbow trout.Copepods are the most prevalent of the parasitic crustaceans affecting a wide range of marine and freshwater finfish worldwide (Lester and Hayward 2006). Salmincola spp. are parasitic copepods of major concern in wild and cultured salmonids. It has been reported that the incidence and spread of these parasites can be exacerbated by degraded environmental conditions such as increased water temperature, high organic loading, low dissolved oxygen, and overcrowding (Sutherland and Wittrock 428 CONTROL OF Salmincola ON RAINBOW TROUT

Effects of emamectin benzoate on pharmacokinetic profiles, bioavailability, and serum biochemical indices in crucian carp (Carassius carassius) following oral administration with multiple dosage levels

“…The levels of ALT and AST content proved that in the range of 50–500 μg/kg bw EMB stimulated the crucian carp, but the content became normal over time, indicating that there was no substantial damage caused to the body, meanwhile, it was also proved in previous studies ( 12 , 19 , 48 ).…”

“…and AST levels obviously projected EMB as an inducer of hepatic dysfunction in Nile tilapia possibly due to damage of hepatic cells, disrupted Kreb's cycle, and other hepato-cellular damage (46, 47). The levels of ALT and AST content proved that in the range of 50-500 µg/kg bw EMB stimulated the crucian carp, but the content became normal over time, indicating that there was no substantial damage caused to the body, meanwhile, it was also proved in previous studies (12,19,48).…”

Observational data on the effects of infection by the copepod Salmincola californiensis on the short- and long-term viability of juvenile Chinook salmon (Oncorhynchus tshawytscha) implanted with telemetry tags

“…Damage to gill filaments of the host due to the presence of the parasite has been associated with loss of fitness due to impairment of gas exchange from a reduction in functional gill tissue and has been described affecting fecundity and temperature tolerance [8,12,13]. Several control measures have been described for cultured populations [14][15][16].…”

Assessment of the effect of sub-lethal acute toxicity of Emamectin benzoate in Labeo rohita using multiple biomarker approach

“…Additionally EMB was employed for parasites control in aquaculture like; Argulus sp. in koi carp and goldfish [ 8 ]; Argulus coregoni in rainbow trout ( Oncorhynchus mykiss ) [ 9 ]; sea lice ( Lepeophtheirus salmonis ) in Atlantic salmon [ [10] , [11] , [12] ]; Salmincolacaliforniensis in rainbow trout [ 13 , 14 ]; sea louse (Caligusminimus) in Asian sea bass (Lates calcarifer) [ 15 ]; Anguillicoloides crassus in American eels ( Anguilla rostrata ) [ 16 ]. Acute or chronic exposure to pesticides even at low concentrations alters the physiological and biochemical parameters in fish [ [17] , [18] , [19] , [20] ].…”