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Erysipelothrix spp., including E. rhusiopathiae, are zoonotic bacterial pathogens that can cause morbidity and mortality in mammals, fish, reptiles, birds, and humans. The southern sea otter (SSO; Enhydra lutris nereis) is a federally-listed threatened species for which infectious disease is a major cause of mortality. We estimated the frequency of detection of these opportunistic pathogens in dead SSOs, described pathology associated with Erysipelothrix infections in SSOs, characterized the genetic diversity and antimicrobial susceptibility of SSO isolates, and evaluated the virulence of two novel Erysipelothrix isolates from SSOs using an in vivo fish model. From 1998 to 2021 Erysipelothrix spp. were isolated from six of >500 necropsied SSOs. Erysipelothrix spp. were isolated in pure culture from three cases, while the other three were mixed cultures. Bacterial septicemia was a primary or contributing cause of death in five of the six cases. Other pathology observed included suppurative lymphadenopathy, fibrinosuppurative arteritis with thrombosis and infarction, bilateral uveitis and endophthalmitis, hypopyon, petechia and ecchymoses, mucosal infarction, and suppurative meningoencephalitis and ventriculitis. Short to long slender Gram-positive or Gram-variable bacterial rods were identified within lesions, alone or with other opportunistic bacteria. All six SSO isolates had the spaA genotype-four isolates clustered with spaA E. rhusiopathiae strains from various terrestrial and marine animal hosts. Two isolates did not cluster with any known Erysipelothrix spp.; whole genome sequencing revealed a novel Erysipelothrix species and a novel E. rhusiopathiae subspecies. We propose the names Erysipelothrix enhydrae sp. nov. and Erysipelothrix rhusiopathiae ohloneorum ssp. nov. respectively. The type strains are E. enhydrae UCD-4322-04 and E. rhusiopathiae ohloneorum UCD-4724-06, respectively. Experimental injection of tiger barbs (Puntigrus tetrazona) resulted in infection and mortality from the two novel Erysipelothrix spp. Antimicrobial susceptibility testing of Erysipelothrix isolates from SSOs shows similar susceptibility profiles to isolates from other terrestrial and aquatic animals. This is the first description of the pathology, microbial characteristics, and genetic diversity of Erysipelothrix isolates recovered from diseased SSOs. Methods presented here can facilitate case recognition, aid characterization of Erysipelothrix isolates, and illustrate assessment of virulence using fish models.

Veronaea botryosa is a melanized mold and cause of systemic fungal infections in cultured sturgeon (Acipenser spp.). Mortality in adult female sturgeon caused by this emergent pathogen results in significant economic losses for the caviar industry. Little is known regarding environmental conditions conducive to V. botryosa infection. This study evaluated the effect of temperature on V. botryosa infectivity and dissemination following intramuscular injection challenge of white sturgeon maintained at 13 or 18 °C for 40 days. Daily mortality was recorded and persistence of the fungus in the livers of moribund and surviving fish was investigated using culture and histopathological analysis. Fish maintained at 18 °C developed systemic phaeohyphomycosis and had significantly greater mortality than controls and fish maintained at 13 °C (p

Historically, piscine francisellosis in various warm-, temperate-, and cold-water fish hosts has been attributed to Francisella noatunensis From 2015 to 2016, an undescribed Francisella sp. was recovered during mortality events in cultured spotted rose snapper (Lutjanus guttatus) off the Pacific coast of Central America. Despite high mortality and emaciation, limited gross findings were observed in affected fish. Histological examination revealed multifocal granulomatous lesions, with the presence of numerous small, pleomorphic coccobacilli, predominantly in the peritoneum, spleen, kidneys, liver, pancreas, heart, and intestine. Sequencing of an ∼1,400-bp fragment of the 16S rRNA gene demonstrated these isolates to be most similar (99.9% identity) to Francisella sp. isolate TX077308 cultured from seawater in the Gulf of Mexico, while sharing

Members of the genus Erysipelothrix are emergent pathogens of cultured eels, as well as several characid and cyprinid species. Since 2013, E. rhusiopathiae has been reported from diseased barramundi (Lates calcarifer) cultured in North America; we recovered 8 E. rhusiopathiae isolates from diseased fish during different outbreaks from the same farm. The E. rhusiopathiae isolates from barramundi were compared phenotypically and genetically to E. piscisicarius isolates characterized from ornamental fish and E. rhusiopathiae recovered from aquatic and terrestrial animals. All barramundi isolates were PCR-positive for the surface protective antigen type B (spaB) gene, and shared ≥ 99.7% sequence similarity among concatenated multilocus sequence analysis gene sequences, indicating a high degree of genetic homogeneity. These isolates were > 99% similar to other spaB- positive isolates from marine invertebrates and marine mammals, consistent with findings for other spa types. The spaA and spaB isolates shared < 98% similarity, as well as < 90% similarity with spaC- positive E. piscisicarius. Similar clonality among the spaB isolates was observed using repetitive element palindromic PCR. In experimental intracoelomic injection challenges conducted to fulfill Koch postulates, 67% of exposed tiger barbs (Puntigrus tetrazona) died within 14 d of challenge. Our study supports previous work citing the genetic variability of Erysipelothrix spp. spa types and the emergence of members of the genus Erysipelothrix as nascent fish pathogens. [ABSTRACT FROM AUTHOR]

This article provides a detailed analysis of gonadal neoplasia in Chinese gold barbs kept in home aquariums. The study examines the clinical, pathologic, and immunohistochemical characteristics of multiple gonadal neoplasms found in male and female gold barbs. The neoplasms identified include seminomas in males and fibrosarcoma in a female, as well as various other types of tumors in both sexes. The article also discusses the potential genetic and environmental factors that may contribute to the development of these neoplasms. This research emphasizes the need for further investigation into fish pathology and aquatic animal health in relation to neoplastic diseases. [Extracted from the article]

The myxozoan Henneguya ictaluri is cited as the cause of proliferative gill disease (PGD) in Channel Catfish Ictalurus punctatus and Channel × Blue Catfish I. furcatus hybrids. Differences in host susceptibility result in decreased transmission rates, reduced sporogenesis, and lesser incidence of PGD in hybrid catfish. In experimental pond trials, continuous monoculture of hybrid catfish suppressed H. ictaluri abundance in pond systems compared to Channel Catfish monoculture. The present study examined differences in myxozoan community structure in catfish ponds stocked with Channel Catfish or hybrid catfish. Experimental ponds (0.4 ha) dedicated to Channel Catfish or hybrid catfish monoculture were maintained over three production cycles. Pond water collected during the spring of each year was subjected to metagenomic analysis by targeted amplicon sequencing of a diagnostic hypervariable region (DVR3) of the myxozoan 18S ribosomal RNA gene. Relative abundance of H. ictaluri was significantly greater in Channel Catfish ponds than in hybrid catfish ponds during years 2 and 3. In hybrid catfish ponds, H. ictaluri never exceeded 20% average relative abundance. Hybrid catfish ponds also revealed decreased myxozoan diversity and species evenness compared to Channel Catfish ponds, suggesting that myxozoan taxa associated with Channel Catfish may not be well adapted to the hybridized host. Results corroborate previous research indicating that hybrid catfish monoculture can suppress H. ictaluri compared to ponds that are devoted to Channel Catfish. These data imply that alternating catfish culture species in ponds (crop rotation) has the potential to mitigate PGD by precluding H. ictaluri from accumulating within ponds to levels associated with disease and catastrophic loss. Further, this work identified numerous previously unidentified taxa present within these systems that clustered phylogenetically with both catfish and noncatfish hosts. The impacts that these other myxozoans have on catfish health and production are unknown, but their presence indicates that myxozoan diversity within catfish aquaculture ponds has been greatly underestimated and is significantly influenced by stocking choice. [ABSTRACT FROM AUTHOR]

Focal duodenal necrosis (FDN) is a common intestinal disease of table egg layers. In this research we aimed to identify the bacteria commonly found in FDN lesions as seen with histopathological analysis. Fifty-nine ethanol-fixed duodenum samples were collected from egg layers on eight FDN-affected farms, and 42 samples had typical FDN lesions. Excision of bacteria-containing lesions using laser capture microdissection was performed, followed by 16S rRNA gene sequencing of extracted DNA for bacterial identification. Bacterial sequencing analysis revealed no consistent bacterial species identified from samples with FDN. However, analysis of the relative phylum abundance revealed differences in the duodenal microbiota between layers with FDN and healthy birds. There were differences in the abundance of Proteobacteria, Firmicutes, and Actinobacteria between FDN-positive and FDN-negative control samples compatible with intestinal dysbiosis. In addition, 10 duodenal samples with FDN lesions were collected for bacteriological analysis, yielding 47 colonies on tryptone soy agar, MacConkey agar, and blood agar plates. Using 16S rRNA gene PCR, 39/47 (53.8%) colonies were identified as Escherichia coli. PCR for E. coli virulence genes identified 21/39 (53.8%) E. coli isolates as avian pathogenic E. coli–like. PCR analysis for 19 E. coli virulence genes associated with intestinal disease strains including inflammatory bowel disease found 11/39 (28.2%) isolates containing more than 10 of these virulence genes. In conclusion, FDN appears to be a multifactorial inflammatory intestinal disease associated with intestinal dysbiosis, and Gram-negative bacteria including E. coli may contribute to the pathogenesis of this disease. Microdisección por captura láser, análisis de cultivos y secuenciación bacteriana para evaluar la microbiota de la necrosis duodenal focal en aves de postura de huevo comercial. La necrosis duodenal focal (FDN) es una enfermedad intestinal común en las gallinas de postura de huevo comercial. En esta investigación, el objetivo fue identificar las bacterias que se encuentran comúnmente en las lesiones provocadas por la necrosis duodenal focal tal como se aprecian con el análisis histopatológico. Se recolectaron 59 muestras de duodeno fijadas con etanol de gallinas de postura de ocho granjas afectadas por necrosis duodenal focal, y 42 muestras tenían lesiones típicas de dicha enfermedad. Se realizó la escisión de las lesiones que contenían bacterias mediante microdisección por captura láser, seguida de la secuenciación del gene 16S rRNA del ADN extraído para la identificación bacteriana. El análisis de secuenciación bacteriana no reveló especies bacterianas consistentes identificadas a partir de muestras con necrosis duodenal focal. Sin embargo, el análisis de la abundancia relativa del phylum reveló diferencias en el microbiota duodenal entre gallinas de postura con necrosis duodenal focal y aves sanas. Hubo diferencias en la abundancia de Proteobacteria, Firmicutes y Actinobacteria entre las muestras controles positivas y negativas para la necrosis duodenal focal compatibles con disbiosis intestinal. Además, se recolectaron 10 muestras duodenales con lesiones de la necrosis duodenal focal para análisis bacteriológico, lo que produjo 47 colonias en placas de agar triptona soya, agar MacConkey y agar sangre. Utilizando un método de PCR para el gene 16S rRNA, 39/47 (53.8 %) colonias se identificaron como Escherichia coli. El método de PCR para genes de virulencia de E. coli identificó 21/39 (53.8 %) aislados de E. coli como similares a E. coli patogénica aviar. El análisis de PCR para 19 genes de virulencia de E. coli asociados con cepas que provocan enfermedades intestinales, incluida la enfermedad inflamatoria intestinal, detectó 11/39 (28.2 %) aislados que contenían más de 10 de estos genes de virulencia. En conclusión, la necrosis duodenal focal parece ser una enfermedad intestinal inflamatoria multifactorial asociada con disbiosis intestinal, y las bacterias Gramnegativas, incluida E. coli, pueden contribuir a la patogenia de esta enfermedad. [ABSTRACT FROM AUTHOR]

Advances in aquatic animal medicine and continued growth of the fish hobbyist and aquaculture communities have led to a developing interest in antemortem diagnostic imaging of aquatic species. The aims of this prospective, pilot study were to determine whether advanced neuroimaging can be safely achieved in live fish using clinically available equipment, to optimize imaging parameters, and to develop a comparative MRI atlas of a few fish species of economic or research value. Two each of channel catfish (Ictalurus punctatus), koi (Cyprinus rubrofuscus), and grass carp (Ctenopharyngodon idella) of at least 30 cm in length were individually anesthetized for 3 Tesla (3T) magnetic resonance imaging (MRI) of the brain. All fish achieved an adequate anesthetic level for prolonged immobilization during imaging. Diagnostic quality images were obtained for all subjects; however, the spatial resolution was maximized with larger fish. Imaging protocols were optimized for standard neuroimaging sequences. Additionally, inversion times for fluid‐attenuation inversion recovery (FLAIR) sequences were adapted to the naturally high protein content of fish pericerebral fluid. Following imaging, the fish successfully recovered from anesthesia, were humanely euthanized, and were immediately processed to assess brain histopathology. Necropsy confirmed the sex and health status of each fish. A limited comparative MRI atlas was created of the brains of these species for clinical reference. Findings from the current study supported the use of 3T MRI as an adjunct diagnostic test for fish with suspected neurologic disease and provided a limited anatomic atlas of the teleost brain for use as a reference. [ABSTRACT FROM AUTHOR]