Caracterización clínica y patobiológica de la infección experimental con Edwardsiella tarda Y Edwardsiella anguillarum en alevinos de tilapia (Oreochromis sp.)

Abstract

Edwardsiellosis is a systemic granulomatous disease that affects a wide range of terrestrial and aquatic hosts, including tilapia (Oreochromis sp). Recently, Edwardsiella tarda was phylogenetically reclasiffied in three species: E. tarda, E. anguillarum and E. piscicida. The purpose of this research was to characterize clinically and pathobiologically the experimental infection with E. tarda and E. anguillarum in tilapia fingerlings. An experimental study was carried out with 19 groups, each with two replications, as follows: immersion inoculum (INM) and intragastric (IG) in doses 106 , 107 and 108 cfu/ml for each bacteria (E. anguilllarum and E. tarda) (12 groups), intraperitoneal inoculum (IP) at doses 106 and 107 cfu/ml equally for both microorganisms (4 groups), and three (3) negative control groups with inoculation of sterile physiological buffered solution (PBS) by the respective routes inoculation (IP, IG, or IMM). During the experimental period (30 days) the fish were clinically evaluated (signs and gross lesions). The fingerlings were weighed at three times: at day 0 start of the experiment, at day 15 (first phase) and at day 30, culmination of the experiment (second phase). The fish inoculated with E. anguillarum (18-355) and with E. tarda (18- 294) by IP route after day 4PI and 7PI presented ascites, whitish masses in the peritoneum and spleen, hepatomegaly, splenomegaly, absence of food in the intestine and gallbladder distention. By the IG route with E. anguillarum, 25% of mortality was presented with 106 cfu/ml, 33% with 107 cfu/ml and 58% with 108 cfu/ml; with this same bacterium by the INM route with 106 cfu/ml there was no mortality during the first 15 days, with 107 cfu/ml it was 50% and with 108 cfu/ml it was 55%. With E. tarda by inoculation via IG and INM for a period of 1 to 15 days PI there was no mortality, and during days 15 to 30 PI the fish inoculated by INM with 108 cfu/ml had 43% mortality. At day 30 PI, significant differences (P