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Lesions induced in Seriola dumerili following exposure to Streptococcus dysgalactiae by oral treatment or immersion

H Hagiwara1, R Takano, N Noguchi

  • 1Advanced Technology Development Center, Kyoritsu Seiyaku Corporation, Takamihara, Tsukuba, Ibaraki 300-1252, Japan. jerzy.kaleczyc@uwm.edu.pl

Journal of Comparative Pathology
|June 24, 2010
PubMed

Insights

This study found that immersing greater amberjack (Seriola dumerili) in water with Streptococcus dysgalactiae caused moderate mortality. Immersion is a more effective infection route than oral dosing for this fish pathogen.

Area of Science:

  • Aquatic Animal Health
  • Fish Pathology
  • Bacteriology

Background:

  • Streptococcus dysgalactiae is a significant pathogen in marine fish.
  • Understanding infection routes is crucial for disease management in aquaculture.

Purpose of the Study:

  • To compare the efficacy of oral dosing versus immersion for experimentally infecting greater amberjack (Seriola dumerili) with Streptococcus dysgalactiae.
  • To characterize the lesions and antigen distribution following experimental infection.

Main Methods:

  • Greater amberjack were experimentally infected via oral gavage or immersion in bacterial suspensions.
  • Mortality rates, lesion development, and S. dysgalactiae antigen distribution were assessed.
  • Histopathology and immunohistochemistry were used to identify bacterial antigen in tissues.

Main Results:

  • Immersion resulted in moderate mortality regardless of bacterial dose.
  • Oral challenge efficacy was dose-dependent.
  • Characteristic lesions included microabscesses and pyogranulomatous inflammation in various tissues (caudal peduncle, fins, heart, olfactory region).
  • S. dysgalactiae antigen was detected in necrotic foci across all infected sites and exposure routes.

Conclusions:

  • Immersion is a more effective and natural route for Streptococcus dysgalactiae infection in greater amberjack compared to oral challenge.
  • The observed lesions and antigen distribution highlight key target sites for this pathogen in fish.

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