A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia
Vita. A streptococcal disease affecting hybrid tilapia (Tilapia nilotica x T aurea) at a commercial aquaculture facility in central Texas was investigated. The causative agent was identified as a biotype of Streptococcus iniae, based both on phenotypic characteristics and RRNA sequencing. The 0-hemo...
Main Author: | |
---|---|
Format: | Thesis |
Language: | English |
Published: |
Texas A&M University. Libraries
1995
|
Subjects: | |
Online Access: | https://hdl.handle.net/1969.1/DISSERTATIONS-1560130 |
id |
fttexasamuniv:oai:oaktrust.library.tamu.edu:1969.1/DISSERTATIONS-1560130 |
---|---|
record_format |
openpolar |
spelling |
fttexasamuniv:oai:oaktrust.library.tamu.edu:1969.1/DISSERTATIONS-1560130 2023-07-16T04:00:41+02:00 A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia Perera, Ramesh Poshitha 1995 xi, 75 leaves electronic application/pdf reformatted digital https://hdl.handle.net/1969.1/DISSERTATIONS-1560130 eng eng Texas A&M University. Libraries https://hdl.handle.net/1969.1/DISSERTATIONS-1560130 35024925 This thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use. http://rightsstatements.org/vocab/InC/1.0/ Major wildlife and fisheries sciences 1995 Dissertation P474 Thesis dissertations text 1995 fttexasamuniv 2023-06-27T22:20:45Z Vita. A streptococcal disease affecting hybrid tilapia (Tilapia nilotica x T aurea) at a commercial aquaculture facility in central Texas was investigated. The causative agent was identified as a biotype of Streptococcus iniae, based both on phenotypic characteristics and RRNA sequencing. The 0-hemolytic bacterium grew better at 37'C than at 10, 25 or 40'C, and its growth was inhibited at pH 9.6, in 6.5 % NaCl, and in 40 % bile. The pathogen was resistant to ampicillin and furazolidone but was susceptible to several antibiotics including tetracycline and sulfadimethoxineormetoprim (5: 1). After suspension of the bacteria in distilled water, viable cocci were recovered for up to 5 days at 5'C and < 24 h at 25'C. Gross signs of disease in tilapia included loss of orientation, exophthalmia, corneal opacity, petechiae around the mouth, vent and pectoral fin margins, and enlargement of the liver, spleen and kidney. Histology revealed cellular infiltration and numerous cocci in the eye, brain, liver, kidney and spleen. Cocci were also present in the blood. Monitoring of hematological parameters showed changes in the hematocrit, erythrocyte count, erythrocyte integrity and blood hemoglobin with disease progress. The 96-h and 168-h LD50 values in 30-90 g fish injected intraperitoneally were measured to be 4.9 x 10' and 3.18 x 10' cells, respectively. Artificial infection was achieved by dipping fish in water containing the bacteria and by oral administration. Greater rates of mortality were observed in artificially infected tilapia maintained at 20 than at 15, 25, 30 or 35'C; and at pH 9 compared to more acidic water. Hybrid striped bass were found susceptible whilst red drum and channel catfish were resistant to artificial infection. Size exclusion gel separation of cell-free media (Todd Hewitt broth, pH 7, supplemented with 10% fetal calf serum) produced three hemolytic fractions corresponding to molecular weights of 21,700, 2,200 and 125 daltons with respective isoelectric points of 4.1, 6; 3.5-4, 8; and 3.5, 8. Thesis Red drum Texas A&M University Digital Repository Todd ENVELOPE(-85.933,-85.933,-78.050,-78.050) |
institution |
Open Polar |
collection |
Texas A&M University Digital Repository |
op_collection_id |
fttexasamuniv |
language |
English |
topic |
Major wildlife and fisheries sciences 1995 Dissertation P474 |
spellingShingle |
Major wildlife and fisheries sciences 1995 Dissertation P474 Perera, Ramesh Poshitha A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia |
topic_facet |
Major wildlife and fisheries sciences 1995 Dissertation P474 |
description |
Vita. A streptococcal disease affecting hybrid tilapia (Tilapia nilotica x T aurea) at a commercial aquaculture facility in central Texas was investigated. The causative agent was identified as a biotype of Streptococcus iniae, based both on phenotypic characteristics and RRNA sequencing. The 0-hemolytic bacterium grew better at 37'C than at 10, 25 or 40'C, and its growth was inhibited at pH 9.6, in 6.5 % NaCl, and in 40 % bile. The pathogen was resistant to ampicillin and furazolidone but was susceptible to several antibiotics including tetracycline and sulfadimethoxineormetoprim (5: 1). After suspension of the bacteria in distilled water, viable cocci were recovered for up to 5 days at 5'C and < 24 h at 25'C. Gross signs of disease in tilapia included loss of orientation, exophthalmia, corneal opacity, petechiae around the mouth, vent and pectoral fin margins, and enlargement of the liver, spleen and kidney. Histology revealed cellular infiltration and numerous cocci in the eye, brain, liver, kidney and spleen. Cocci were also present in the blood. Monitoring of hematological parameters showed changes in the hematocrit, erythrocyte count, erythrocyte integrity and blood hemoglobin with disease progress. The 96-h and 168-h LD50 values in 30-90 g fish injected intraperitoneally were measured to be 4.9 x 10' and 3.18 x 10' cells, respectively. Artificial infection was achieved by dipping fish in water containing the bacteria and by oral administration. Greater rates of mortality were observed in artificially infected tilapia maintained at 20 than at 15, 25, 30 or 35'C; and at pH 9 compared to more acidic water. Hybrid striped bass were found susceptible whilst red drum and channel catfish were resistant to artificial infection. Size exclusion gel separation of cell-free media (Todd Hewitt broth, pH 7, supplemented with 10% fetal calf serum) produced three hemolytic fractions corresponding to molecular weights of 21,700, 2,200 and 125 daltons with respective isoelectric points of 4.1, 6; 3.5-4, 8; and 3.5, 8. |
format |
Thesis |
author |
Perera, Ramesh Poshitha |
author_facet |
Perera, Ramesh Poshitha |
author_sort |
Perera, Ramesh Poshitha |
title |
A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia |
title_short |
A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia |
title_full |
A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia |
title_fullStr |
A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia |
title_full_unstemmed |
A study of the pathology, epizootiology and toxicology of Streptococci found causing mortality in tilapia |
title_sort |
study of the pathology, epizootiology and toxicology of streptococci found causing mortality in tilapia |
publisher |
Texas A&M University. Libraries |
publishDate |
1995 |
url |
https://hdl.handle.net/1969.1/DISSERTATIONS-1560130 |
long_lat |
ENVELOPE(-85.933,-85.933,-78.050,-78.050) |
geographic |
Todd |
geographic_facet |
Todd |
genre |
Red drum |
genre_facet |
Red drum |
op_relation |
https://hdl.handle.net/1969.1/DISSERTATIONS-1560130 35024925 |
op_rights |
This thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use. http://rightsstatements.org/vocab/InC/1.0/ |
_version_ |
1771549716986724352 |