The intraspecific variability of E. ictaluri isolates from different origins was investigated. Isolates were recovered from farm-raised catfish (Ictalurus punctatus) in Mississippi, USA, tilapia (Oreochromis niloticus) cultured in the Western Hemisphere and zebrafish (Danio rerio) propagated in Florida, USA. These isolates were phenotypically homologous and antimicrobial profiles were largely similar. Genetically, isolates possessed differences that could be exploited by repetitive-sequence-mediated PCR and gyrB sequence, which identified three distinct E. ictaluri genotypes: one associated with catfish, one from tilapia and a third from zebrafish. Plasmid profiles were also group specific and correlated with rep-PCR and gyrB sequences. The catfish isolates possessed profiles typical of those described for E. ictaluri isolates; however, plasmids from the zebrafish and tilapia isolates differed in both composition and arrangement. Furthermore, some zebrafish and tilapia isolates were PCR negative for several E. ictaluri virulence factors. Isolates were serologically heterogenous, as serum from a channel catfish exposed to a catfish isolate had reduced antibody activity to tilapia and zebrafish isolates. This work identifies three genetically distinct strains of E. ictaluri from different origins using rep-PCR, 16S, gyrB and plasmid sequencing, in addition to antimicrobial and serological profiling.

Abstract. From 2001to 2003 farms in Florida, California, and South Carolina experienced epizootics of a systemic disease causing mortality. The fish exhibited lethargy, occasional exophthalmia, and skin petechia. The gills were often necrotic, with a patchy white and red appearance. Grossly, the spleen and kidneys were granular with whitish irregular nodules throughout. Granulomatous infiltrates were observed in kidney, spleen, testes, and ovary tissues, but not in the liver. The granulomas contained pleomorphic coccoid bacteria, measuring 0.57 Ϯ 0.1 ϫ 0.8 Ϯ 0.2 m, that were Giemsa-positive, acid-fast-negative, and Gram-negative. The bacteria had a double cell wall, variable electron-dense and -lucent areas, and were present in the cytoplasm and within phagolysosomes. The syndrome was associated with cold stress and poor water conditions. These findings are consistent with an infectious process caused by a Piscirickettsia-like bacterium described previously in tilapia in Taiwan and Hawaii. This report involves the first identified cases of a piscirickettsiosis-like syndrome affecting tilapia in the continental United States.Key words: Piscirickettsiosis; Piscirickettsia-like organisms; piscirickettsiosis-like syndrome; Tilapia.Since the identification of Piscirickettsia salmonis as the first rickettsia-like organism recognized as a fish pathogen, 9 a number of Piscirickettsia-like organisms (PLOs) have been observed microscopically or isolated in cell culture from a variety of marine and fresh-water piscine species from locations worldwide. 5,11,12,16 Piscirickettsiosis or piscirickettsiosis-like syndromes can be severe, resulting in high mortality and significant economic losses.The number of reports of piscirickettsiosis, with significant associated economic losses, have been increasing for the last 5-10 years in British Columbia, 2,8 Ireland, 16 and Scotland. 10 PLOs have also been observed in and isolated from seabass in Europe 1,7 and California 3 during epizootics characterized by high mortality and severe economic losses. Tilapia in Taiwan 4,6 and Hawaii 15 have also been severely affected by PLO epizootics. Here we report on the first identified cases of PLO epizootics in tilapia in the continental United States.Between 2001 and 2003, 3 facilities in the continental United States (California, South Carolina, and Florida) reported epizootics with signs consistent with a piscirickettsiosis-like syndrome. All 3 facilities had increased mortalities during times of fish stress due to lowered temperature or water quality. The fish appeared lethargic, with darkened color, and would crowd toward the middle of the pond or tank. Occasionally, petechia were observed on the sides of the fish. Fins had light fraying, some exophthalmia was observed, and gills were necrotic, with a patchy white and red appearance. Internally, the spleen and kidneys were extremely granular with whitish irregular nodules throughout. The liver was a pale reddish tan with patchy lighter areas.In hematoxylin and eosin (HE) sections, the spl...

Since 2012, low-to-moderate mortality associated with an Erysipelothrix sp. bacterium has been reported in ornamental fish. Histological findings have included facial cellulitis, necrotizing dermatitis and myositis, and disseminated coelomitis with abundant intralesional Gram-positive bacterial colonies. Sixteen Erysipelothrix sp. isolates identified phenotypically as E. rhusiopathiae were recovered from diseased cyprinid and characid fish. Similar clinical and histological changes were also observed in zebrafish, Danio rerio, challenged by intracoelomic injection. The Erysipelothrix sp. isolates from ornamental fish were compared phenotypically and genetically to E. rhusiopathiae and E. tonsillarum isolates recovered from aquatic and terrestrial animals from multiple facilities. Results demonstrated that isolates from diseased fish were largely clonal and divergent from E. rhusiopathiae and E. tonsillarum isolates from normal fish skin, marine mammals and terrestrial animals. All ornamental fish isolates were PCR positive for spaC, with marked genetic divergence (<92% similarity at gyrB, <60% similarity by rep-PCR) between the ornamental fish isolates and other Erysipelothrix spp. isolates. This study supports previous work citing the genetic variability of Erysipelothrix spp. spa types and suggests isolates from diseased ornamental fish may represent a genetically distinct species.

A series of fungal cases in hatchery-reared juvenile and young adult Siberian sturgeon Acipenser baerii and white sturgeon A. transmontanus occurred at production facilities in Florida and California, USA, respectively. Affected fish exhibited abnormal orientation and/or buoyancy, emaciation, coelomic distension, exophthalmos, cutaneous erythema, and ulcerative skin and eye lesions. Necropsies revealed haemorrhage throughout the coelom, serosanguinous coelomic effusion and organomegaly with nodular or cystic lesions in multiple organs. Fungal hyphae were observed in 27 fish (24 A. baerii and 3 A. transmontanus) via microscopic examination of tissue wet mounts and on slides prepared from colonies grown on culture media. Histopathological examination of these infected tissues revealed extensive infiltration by melanised fungal hyphae that were recovered in culture. Phenotypic characteristics and sequencing of the fungal isolates with the use of the internal transcribed spacer region and 28S rRNA gene confirmed the aetiological agent as Veronaea botryosa. To our knowledge, this is the first documentation of V. botryosa infection in fish, although melanised fungi of the closely related genus Exophiala are well-known pathogens of freshwater and marine fishes.

Ovaprim is a commercial product used as a spawning aid in fishes and contains a salmon gonadotropin‐releasing hormone analog and a dopamine antagonist. Since 2005, the use of Ovaprim in commercial ornamental fish production has been through enrollment with the University of Florida Tropical Aquaculture Laboratory in an Investigational New Animal Drug (INAD) study. A database is maintained to provide information to the U.S. Food and Drug Administration on product effectiveness and target animal safety. There were 25 fish species in 17 genera and 10 families in the INAD database. Ostariophysan fishes constituted 84% of the species and 99.9% of the individuals. The goldfish Carassius auratus was numerically the dominant species (80% of individuals). Nearly 40,000 fish in total were injected with Ovaprim; ovulation was induced in 92% of females and spermiation was induced in 96% of males, primarily reflecting extensive use in cyprinid fishes. Conversely, average success rates across all species were moderate (50% ovulation and 54% spermiation), and some species had low success rates (range = 0–100%). Mortality after injection was 1.3% of overall individuals but varied by species (mean = 2.7%; range = 0–36%). Ovaprim was most used by producers of ornamental cyprinids.

Francisella noatunensis is an emerging pathogen of fish that has been isolated from several cultured species worldwide. Here presented is a case involving several hundred marine grunts that were caught near the Florida Keys for display in public aquaria. These fish were maintained in a recirculating system where they began to experience mortalities approximately two weeks post-stocking. Postmortem examination revealed disseminated systemic granulomatous disease most severely affecting spleen and kidney. Splenic and renal tissue homogenates inoculated in modified Thayer Martin agar media yielded colonies consistent with F. noatunensis 4 days post inoculation. Bacterial colonies and tissues were confirmed positive after real-time PCR amplification of the intracellular growth loci gene (iglC) specific for F. noatunensis subspecies orientalis. Consequently, multiple novel host species for this pathogen were identified, including the French grunt (Haemulon flavolineatum) and the Caesar grunt (Haemulon carbonarium).

Mycobacterium marinum isolates cultivated from tissue containing granulomatous lesions in Florida pompano Trachinotus carolinus and from biofilm samples collected from their tank and water recirculating system had identical (L1 of 11 bands) repetitive-sequence-based polymerase chain reaction (rep-PCR) DNA fingerprints. A second M. marinum clone sharing 4 of 11 rep-PCR bands with the first clone was isolated from some fish tissues but not from system samples. Water samples yielded low numbers of colonies of mycobacteria (0.08-1.3/mL), but high numbers were recovered from biofilms (260-12,000/swab) and filters (63-21,000/ filter). Mycobacterium hemophilum, M. chelonae, M. trivale, M. gastri, and M. gordonae were isolated from system samples alone.

Revised! FA-16, a 5-page illustrated fact sheet by Ruth Francis-Floyd, Craig Watson, Denise Petty, and Deborah B. Pouder, informs aquarists, aquaculturists, and hobbyists about this important water quality parameter, its effect on fish health, the nitrogen cycle that eliminates ammonia from water, how to test for ammonia, and how to manage an ammonia problem. Includes references. Published by the UF School of Forest Resources and Conservation, Program in Fisheries and Aquatic Sciences, February 2009. FA16/FA031: Ammonia in Aquatic Systems (ufl.edu)