Ultrasound stimulated cavitation for ectoparasite reduction in fish: The State of the Art

Sea louse (in particular Lepeophtheirus salmonis) infestation is estimated to cost the Atlantic salmon industry some $1 billion in losses each year. The lice are highly adaptable and quickly evolve to develop resistance to [bio-]chemical and pharmaceutical treatment approaches. Alternative strategies are thus demanded, and with the explicit parallel needs to minimize environmental impact whilst affecting treatment in an ethically acceptable fashion and that is non-invasive to the host fish. We previously mooted the possibility of exploiting ultrasound stimulated cavitation as a physical means of treating generic aquatic parasites [1,2], and report here on the results of preliminary laboratory, and field-station-based, assessments towards that goal. Essentially, bubbles can be targeted on the louse which then respond to ultrasound stimulation and lead to either direct lysis or downstream incapacitation of the parasites. The mechanism whereby damage occurs is suggested and discussed in comparison with parallel studies emerging in the literature. The longer-term outlook for this potential treatment is also reviewed.