Resumen

SANCHEZ RONCANDO, C. O.  y  FONSECA DE FREITAS, R. T.. Survival observed in three families of Nile tilapia (Oreochromis niloticus) infected with Streptococcus agalactiae. Rev. Med. Vet. Zoot. [online]. 2022, vol.69, n.3, pp.236-244.  Epub 12-Ene-2023. ISSN 0120-2952.  https://doi.org/10.15446/rfmvz.v69n3.103804.

Streptococcosis is one of the main diseases in freshwater fish that causes high mortality rates. The objective of this study was to evaluate the survival response to Streptococcus agalactiae infection in three families of tilapia. The experiment was carried out at the Laboratory of Fish Diseases of the Federal University of Lavras. Fish weighing 93.7 ± 5.4 g from three different families (FA, FB, and FC) were used. 36 fish were used in each experimental unit, intraperitoneally inoculated with 107 CFU/mL of Streptococcus agalactiae per fish and a control group per family with 9 fish with 1 mL of BHI broth (Brain Heart Infusion) evaluated for 15 days. There was no mortality in the control group. The three evaluated families exposed to the pathogen observed the presence of exophthalmia, dark coloration throughout the body, lethargy, and abdominal dilation before death. The Kaplan-Meier nonparametric estimator was used to observe the survival curves. During the 15 days of the challenge, the average survival time of an individual in the FA, FB, and FC families was 9.4, 6.90, and 8.14 days, respectively. Log-rank and Peto & Peto test to evaluate the difference between the survival curves showed no significant differences between the assessed families (P=0.08 and P= 0.09), respectively.

Palabras clave : streptococcus; Streptococcus agalactiae; Oreochromis niloticus; tilapia; Kaplan-Meier.

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