Abstract

Piscirickettsiosis is an important pathological condition of salmonids described in Chile since 1989. The aetiological agent is a rickettsial organism named Piscirickettsia salmonis and it has been described in all species of salmonids reared in Chile. The transmission mechanisms of piscirickettsiosis have not been established. Cvitanich et al. (1991) described a horizontal transmission in experimental conditions in saltwater and freshwater aquariums. Vertical transmission for piscirickettsiosis has scarcely been studied. In the present report, male (M+) and female (F+) brooders were inoculated via an intraperitoneal injection (IP) with P. salmonis, while other groups, corresponding to the negative control brooders (M-, F-), were injected with PBS. 50 days later, eggs and semen were separately collected and pooled from each fish group. Four types of crossings were obtained according to the source of eggs and semen (i.e., 1=M+H+, 2=M+H-, 3=M-H+4=M-H-). Approximately 10% of the fertilized ova obtained from one or both parent brooders inoculated with the rickettsia were positive to the presence of the agent by IFAT at 18 days of incubation. The microorganism was mainly observed inside the yolk. These results suggest that a vertical transmission is a possible event in natural diseases.