Detailed Research Information

Detailed project information for
Study Plan Number 01072-02

Branch : Fish Health Branch

Study Plan Number : 01072-02

Study Title : Fish heal parameters associated with ecological survival of Atlantic salmon (Salmo salar) and their subsequent restoration in New England Rivers. Study 2: Detection of covert Aeromonas salmonicida infection in Atlantic salmon and other salmonids

Starting Date : 08/01/1996

Completion Date : 09/30/1999

Principal Investigator(s) : Cipriano, Rocco C.

Primary PI : Cipriano, Rocco C.

Telephone Number : (304) 724-4432

Email Address : rocco_cipriano@usgs.gov

SIS Number : 5003022

Primary Program Element : Fisheries and Aquatic Resources

Second Program Element : Application of Science Information to Management

Status : Completed

Abstract : Accurate detection of salmonids covertly infected with Aeromonas salmonicida subsp. salmonicida, cause of furunculosis disease, is a problem that causes concern in fish health inspection and resource management programs. In this study, populations of salmonids that previously sustained natural episodes of furunculosis were examined, therefore, survivors were presumed to harbor latent infections. Mucus, gill, liver, kidney, heart, spleen and intestine samples (n=100 fish per population) were processed and examined by (1) direct dilution counts and (2) quadrant streaking after a 48 hour pre-enrichment in tryptic soy broth. Another subsample of fish from each population was then subjected to stress inducible furunculosis tests. Results indicated that the stress tests were more definitive than either method of culture and provided the most accurate detection of the pathogen. Although pre-enrichment in tryptic soy broth enhanced detection in some organs, the assay was not as accurate as direct dilution counts from mucus, gill and intestinal samples. Prevalences of infection did not appear to be affected by using either the hydrochloride or hemmisuccinate form of prenisolone acetate were used in the stress tests. In another part of the study, two A. salmonicida specific PCR tests, and one A. salmonicida subspecies salmonicida specific PCR test, were used to screen salmonid populations that were either overtly or covertly infected with A. salmonicida subspecies salmonicida. It was demonstrated that these PCR assays could be used to replace the biochemical testing currently employed to confirm the identity of A. salmonicida isolates cultured from overtly and covertly infected fish. The AP and PAAS PCR assays were also capable of direct detection of A. salmonicida in overtly infected fish, with mucus, gill and kidney samples most likely to yield a positive result. Culture was a more reliable and sensitive method for the direct detection of A. salmonicida in covertly infected salmonids than was the direct PCR testing of tissue samples, with the AP and PAAS PCRs having a lower detection limit (LDL) of approximately 4 x 105 CFU/g sample.

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Branch :	Fish Health Branch
Study Plan Number :	01072-02
Study Title :	Fish heal parameters associated with ecological survival of Atlantic salmon (Salmo salar) and their subsequent restoration in New England Rivers. Study 2: Detection of covert Aeromonas salmonicida infection in Atlantic salmon and other salmonids
Starting Date :	08/01/1996
Completion Date :	09/30/1999
Principal Investigator(s) :	Cipriano, Rocco C.
Primary PI :	Cipriano, Rocco C.
Telephone Number :	(304) 724-4432
Email Address :	rocco_cipriano@usgs.gov
SIS Number :	5003022
Primary Program Element :	Fisheries and Aquatic Resources
Second Program Element :	Application of Science Information to Management
Status :	Completed
Abstract :	Accurate detection of salmonids covertly infected with Aeromonas salmonicida subsp. salmonicida, cause of furunculosis disease, is a problem that causes concern in fish health inspection and resource management programs. In this study, populations of salmonids that previously sustained natural episodes of furunculosis were examined, therefore, survivors were presumed to harbor latent infections. Mucus, gill, liver, kidney, heart, spleen and intestine samples (n=100 fish per population) were processed and examined by (1) direct dilution counts and (2) quadrant streaking after a 48 hour pre-enrichment in tryptic soy broth. Another subsample of fish from each population was then subjected to stress inducible furunculosis tests. Results indicated that the stress tests were more definitive than either method of culture and provided the most accurate detection of the pathogen. Although pre-enrichment in tryptic soy broth enhanced detection in some organs, the assay was not as accurate as direct dilution counts from mucus, gill and intestinal samples. Prevalences of infection did not appear to be affected by using either the hydrochloride or hemmisuccinate form of prenisolone acetate were used in the stress tests. In another part of the study, two A. salmonicida specific PCR tests, and one A. salmonicida subspecies salmonicida specific PCR test, were used to screen salmonid populations that were either overtly or covertly infected with A. salmonicida subspecies salmonicida. It was demonstrated that these PCR assays could be used to replace the biochemical testing currently employed to confirm the identity of A. salmonicida isolates cultured from overtly and covertly infected fish. The AP and PAAS PCR assays were also capable of direct detection of A. salmonicida in overtly infected fish, with mucus, gill and kidney samples most likely to yield a positive result. Culture was a more reliable and sensitive method for the direct detection of A. salmonicida in covertly infected salmonids than was the direct PCR testing of tissue samples, with the AP and PAAS PCRs having a lower detection limit (LDL) of approximately 4 x 105 CFU/g sample.
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U.S. Department of the Interior \|\| U.S. Geological Survey 11700 Leetown Road, Kearneysville, WV 25430, USA URL: http://www.lsc.usgs.gov Maintainer: lsc_webmaster@usgs.gov Last Modified: October 21, 2002 dwn Privacy Policy and Disclaimers \|\| FOIA \|\| Accessibility