Current practices in the chemotherapeutic control of sea lice infestations in aquaculture: a review

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Abstract
This review surveys the available literature on the efficacy and ecotoxicology of chemotherapeutic agents for the control of sea lice (Copepoda: Caligidae) infestations in marine aquaculture. To date, treatment for the disease has relied almost exclusively on the use of the organophosphorus pesticides, trichlorfon and dichlorvos. While use of dichlorvos and trichlorfon appears to have little, if any, environmental impact, protracted use in some areas has led to reduced efficacy. Compounds proposed for sea lice control currently under field evaluation include azamethiphos (organophosphate), ivermectin (avermectin), pyrethrum (pyrethrin) and hydrogen peroxide. Although all of these compounds are effi cacious, at present published information on marine environmental toxicology is scarce and is limited to in vitro toxicity testing. Other compounds that have been considered for sea lice control include formalin, malathion (organophosphate), carbaryl (carbamate), diflubenzuron (insect growth regulator) and natural remedies (i.e. onions and garlic). In general, formaldehyde (aldehyde), malathion and natural compounds show either poor efficacy or unsuitable therapeutic margins. Although carbaryl and diflubenzuron are both efficacious and exhibit suitable therapeutic margins, available data suggests that the compounds, due to undesirable environmental toxicological characteristics, would be unsuitable for sea lice control.