Dried leaves of Rosmarinus officinalis as a treatment for streptococcosis in tilapia

D. Zilberg, A. Tal, N. Froyman, S. Abutbul, N. Dudai, A. Golan-Goldhirsh

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


Dietary application of dried Rosmarinus officinalis (rosemary) leaves as a treatment for streptococcal infection was studied in tilapia, Oreochromis sp. Feeding with dried rosemary leaves significantly reduced mortality following infection with Streptococcus iniae: 44% mortality in the group fed 8% rosemary, similar to oxytetracycline treatment (43% mortality), and significantly lower than the control (65%). Dietary administration of 16% rosemary significantly reduced mortality because of Streptococcus agalactiae infection in 44 g fish (62% and 76% in 16% rosemary and control, respectively), but not in a similar experiment conducted with 5.5 g fish. The antibacterial effect of rosemary on S. iniae was studied. Activity of rosemary cultivar Israel was reduced during the winter, but there was no significant change in cultivars Oranit and Star. Storage of powdered rosemary leaves at 50 °C resulted in fourfold and eightfold higher MIC24 h values after 3 and 4.5 months, respectively. Storage at -20 °C, 4 °C and 25 °C and autoclaving (120 °C) each resulted in a twofold increase in MIC24 h. Repeated exposures of S. iniae to rosemary did not affect minimal inhibitory concentration, suggesting no development of resistance to rosemary.

Original languageEnglish
Pages (from-to)361-369
Number of pages9
JournalJournal of Fish Diseases
Issue number4
StatePublished - 1 Apr 2010


  • Bacteria
  • Disease
  • Fish
  • Rosemary
  • Streptococcus agalactiae
  • Streptococcus iniae
  • Tilapia

ASJC Scopus subject areas

  • Aquatic Science
  • Veterinary (miscellaneous)


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