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United States Department of Agriculture

Agricultural Research Service

Title: Survival and Virulence of Streptococcus Agalactiae and Its Transmission from Nile Tilapia (Oreochromis Niloticus) to Sheepshead Minnows (Cyprinodon Variegatus) When Exposed to Different Water Microcosms and Temperatures

Authors
item Garcia, Julio
item Klesius, Phillip
item Evans, Joyce

Submitted to: Southern Conference of Researchers in Aquatic Diseases
Publication Type: Abstract Only
Publication Acceptance Date: January 9, 2004
Publication Date: February 8, 2004
Citation: Garcia, J.C., Klesius, P.H., Evans, J.J. Survival and virulence of streptococcus agalactiae and its transmission from nile tilapia (oreochromis niloticus) to sheepshead minnows (cyprinodon variegatus) when exposed to different water microcosms and temperatures. 6th Annual Meeting of the Southern Conference of Researchers in Aquatic Diseases. 9th Biennial Meeting of the Fish Diagnostician's Workshop. 55th Annual Meeeting of the Animal Disease Research Workers in Southern States. 19th Annual Meeting of the Southern Conference on Animal Parasites. February 8-10, 2004. Biloxi, Mississippi. 2004.

Technical Abstract: Streptococcus agalactiae is the causative agent of warmwater streptococcal disease in cultured and wild species of fish of both fresh and sea waters, worldwide. Disease outbreaks of S. agalactiae results in significant losses of fish and aquaculture profits. The objective of the present study was to determine the survival capacity of S. agalactiae in laboratory conditions at different salinities and temperatures and to determine the virulence of starving S.agalactiae cells. The results indicated that S. agalactiae survived in 0, 15 and 40 ppt salinity at 0, 10, 25, 35, and 45°C and these cells were cultivable after starvation for 10 days. High salinity (40 ppt) and temperature (35°C) resulted in only slight reduction in the number of cultivable cells after 10 days of starvation. The challenge experiments indicated that the virulence of starving S. agalactiae cells for tilapia was maintained for 10 days in 0, 15 and 40 ppt salinity at 25°C. Also the possibility of transmission of S. agalactiae, from Nile tilapia to sheepshead minnows was studied in laboratory cohabitation trials. Tilapia infected with S.agalactiae by either intraperitoneal (I.P.) injection of bath immersion were infectious for healthy sheepshead minnows in cohabitation experiments where either both species were cohabitated together or separated by a screen barrier in the same aquarium at 15 ppt salinity and 32°C. The results suggested that S. agalactiae infected fish can be directly or indirectly infectious to other species of fish in close proximity.

Last Modified: 9/22/2014
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