title: Infection and pathology in Queensland grouper, Epinephelus lanceolatus, (Bloch), caused by exposure to Streptococcus agalactiae via different routes.
abstract: Since 2007, 96 wild Queensland groupers, Epinephelus lanceolatus, (Bloch), have been found dead in NE Australia. In some cases, Streptococcus agalactiae (Group B Streptococcus, GBS) was isolated. At present, a GBS isolate from a wild grouper case was employed in experimental challenge trials in hatchery-reared Queensland grouper by different routes of exposure. Injection resulted in rapid development of clinical signs including bilateral exophthalmia, hyperaemic skin or fins and abnormal swimming. Death occurred in, and GBS was re-isolated from, 98% fish injected and was detected by PCR in brain, head kidney and spleen from all fish, regardless of challenge dose. Challenge by immersion resulted in lower morbidity with a clear dose response. Whilst infection was established via oral challenge by admixture with feed, no mortality occurred. Histology showed pathology consistent with GBS infection in organs examined from all injected fish, from fish challenged with medium and high doses by immersion, and from high-dose oral challenge. These experimental challenges demonstrated that GBS isolated from wild Queensland grouper reproduced disease in experimentally challenged fish and resulted in pathology that was consistent with that seen in wild Queensland grouper infected with S. agalactiae.
authors.affiliation: School of Biological Sciences and Centre for Marine Science, The University of Queensland, Brisbane, Qld, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Delamare-Deboutteville
authors.affiliation: Biosecurity Queensland, Department of Agriculture Fisheries & Forestry, Townsville, Qld, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Bowater
authors.affiliation: Biosecurity Queensland, Department of Agriculture Fisheries & Forestry, Townsville, Qld, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Condon
authors.affiliation: Northern Fisheries Centre (NFC), Department of Agriculture Fisheries & Forestry, Cairns, Qld, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Reynolds
authors.affiliation: Biosecurity Queensland, Department of Agriculture Fisheries & Forestry, Townsville, Qld, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Fisk
authors.affiliation: School of Biological Sciences and Centre for Marine Science, The University of Queensland, Brisbane, Qld, Australia.
authors.forename: F
authors.initials: F
authors.lastname: Aviles
authors.affiliation: School of Biological Sciences and Centre for Marine Science, The University of Queensland, Brisbane, Qld, Australia.
authors.forename: A C
authors.initials: AC
authors.lastname: Barnes
mesh_terms: D000818:Animals; D001492:Bass / Q000382:microbiology*; D005393:Fish Diseases / Q000209:etiology / Q000382:microbiology* / Q000473:pathology; D016133:Polymerase Chain Reaction / Q000662:veterinary; D013290:Streptococcal Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D013292:Streptococcus agalactiae
keywords: Epinephelus lanceolatus; Streptococcus agalactiae; bacteriology; his-topathology; immunohistochemistry; polymerase chain reaction