TRANSMISSION OF LOMA-SALMONAE (MICROSPOREA) TO CHINOOK SALMON IN SEA-WATER

Transmission studies were conducted to determine if Loma salmonae was transmissible in sea water. Transmission of L. salmonae to chinook sal mon (Oncorhynchus tshawytscha) held in sea water was achieved by expos ing fish to macerated, infected gill tissue, Fish were exposed in seaw ater in a flow-through aquarium, and the infection was detected as soo n as 5 wk after exposure, Heavily infected fish exhibited numerous xen omas in the branchial arteries, central venous sinusoids, and within t he blood channels of the lamellae. The pathological changes were simil ar to those seen in pen-reared salmon with L. salmonae infections. The infection was not observed in Atlantic salmon (Salmo salar), Pacific herring (Clupea pallasi, family Clupeidae), or shiner perch (Cymatogas ter aggregata, family Embiotocidae), experimentally exposed using iden tical methods. This study suggests that L. salmonae is transmissible t o chinook salmon in seawater netpens. Fish farmers and fish health spe cialists should consider this possibility when developing and implemen ting strategies to control the infection.