EXPERIMENTAL VIBRIO-HARVEYI INFECTIONS IN PENAEUS-VANNAMEI LARVAE

A culture of Vibrio harveyi, isolated from diseased Penaeus vannamei, was pathogenic in penaeid shrimp larvae when used in a bath at 10(5) c ells ml(-1) for 2 h. The resultant disease had characteristics of Boli tas negricans, as observed in Ecuadorian hatcheries, namely the develo pment of bioluminescence, reduced feeding and retarded development, sl uggish swimming, reduced escape mechanisms, degeneration of hepatopanc reatic tissue with resultant formation of necrotic bundles, and increa sed mortality. Koch's Postulates were confirmed by reisolation and ide ntification of the organism. Histopathology showed the presence of dis tinctive melanotic tissue aggregates within the hepatopancreas, with i mmunohistochemistry confirming the presence of large numbers of V. har veyi in the intestine and hepatopancreas. These results indicate a sui table infection protocol, which can be used to test the pathogenicity of putative pathogens of penaeid shrimp larvae.