The Disease

Introduction
Since 1963 when Pasteurellosis was first detected in striped bass and white perch in the United States, this disease has become a worldwide concern in aquaculture. Photobacterium damsela subsp. piscicida was known until recently as Pasteurella piscicida. It is a gram-negative rod which causes a disease in fish known either as Pseudotuberculosis or Fish Pasteurellosis.

This serious problem in Japanese yellowtail culture can result in losses on individual farms of up to 50%. The bacterium's taxonomic position as a bonafide Pasteurella has been questioned for a number of years and based on small subunit ribosomal ribonucleic acid (rRNA) sequences; whole deoxyribonucleic acid (DNA) relatedness and biochemical characterization, Gauthier et al. (1995) have reassigned the bacterium to a subspecies of P. damsela. Some fish farmers and scientists may still refer to the disease as Pasteurellosis.

Etiology
Photobacterium damsela subsp. piscicida is a Gram-negative, pleomorphic, non-motile bacterium that grows slowly on NaCl-supplemented media.

Serologically, the strains found all over the world are highly homogeneous and there seems to be only one serotype. However, ribotyping revealed genetic variation of different geographical isolates.


Disease reprinted courtesy of OIE Diagnostic Manual for Aquatic Animal Diseases, OIE (World Organisation for Animal Health), Paris, France.