Neoparamoebic gill infections: host response and physiology in salmonids

• Main Authors: Powell, MD, Leef, MJ, Roberts, SD, Jones, MA
• Format: Article in Journal/Newspaper
• Language: English
• Published: Blackwell Publishing Ltd 2008
• Subjects: Agricultural and Veterinary Sciences; Fisheries Sciences; Aquaculture; Norway; Salmo salar
• Online Access: https://doi.org/10.1111/j.1095-8649; http://ecite.utas.edu.au/77771

Neoparamoebic gill infections: host response andphysiology in salmonidsM. D. POWELL*, M. J. LEEF, S. D. ROBERTS AND M. A. JONESk*Department of Fisheries and Natural Sciences, Bod University College, Bod 8049,Norway, National Institute of Water and Atmospheric Research Ltd, Ruakaka 0250, NewZealand, South Australian Research and Development Institute, Aquatic Sciences,Adelaide, South Australia and kNational Centre for Marine Conservation and ResourceSustainability, University of Tasmania, Launceston, TAS 7250, AustraliaAmoebic gill diseases (AGD) caused primarily by the amphizoic Neoparamoeba spp. have beenidentified as significant to fish health in intensive aquaculture. These diseases have consequentlyreceived significant attention with regard to disease pathophysiology. Neoparamoeba peruranshas been putatively identified as the aetiological agent in salmonids, with other species such asturbot Psetta maxima and sea bass Dicentrarchus labrax also affected. Similarly, Neoparamoebaspp. have also been identified in co-infections with other gill diseases in salmonids. Whileinfection of the gills results in an acute multifocal hyperplastic host response, reduced gill surfacearea and increased mucous cell densities, ion regulation and respiration in terms of blood gassesare only marginally affected. This may be partially attributed to reserve respiratory capacity anda reduction in mucous viscosity allowing for a greater flushing of the gill, so reducing the gillmucus boundary layer. Clinical and acute infections result in significant cardiovascularcompromise with increases in aortic blood pressure, and systemic vascular resistance in Atlanticsalmon, Salmo salar, which are not seen in rainbow Oncorhynchus mykiss and brown trout Salmotrutta. Increases in vascular resistance appear to be due to vascular constriction potentiallyreducing blood flow to the heart in compromised fishes, the overall effect being to lead toa compensatory tissue remodelling and change in cardiac shape in chronically infected fishes.The combined effect of reduced gill surface area and cardiovascular compromise leads toa significant reduction in swimming performance and increases in the routine metabolic ratethat lead to an increase in the overall metabolic cost of disease.