Tetra disseminated microsporidiosis: a novel disease in ornamental fish caused by Fusasporis stethaprioni n. gen. n. sp.

A novel microsporidial disease was documented in two ornamental fish species, black tetra Gymnocorymbus ternetzi Boulenger 1895 and cardinal tetra Paracheirodon axelrodi Schultz 1956. The non-xenoma-forming microsporidium occurred diffusely in most internal organs and the gill, thus referring to the condition as tetra disseminated microsporidiosis (TDM). The occurrence of TDM in black tetra was associated with chronic mortality in a domestic farmed population, while the case in cardinal tetra occurred in moribund fish while in quarantine at a public aquarium. Histology showed that coelomic visceral organs were frequently necrotic and severely disrupted by extensive infiltrates of macrophages. Infected macrophages were presumed responsible for the dissemination of spores throughout the body. Ultrastructural characteristics of the parasite developmental cycle included uninucleate meronts directly in the host cell cytoplasm. Sporonts were bi-nucleated as a result of karyokinesis and a parasite-produced sporophorous vesicle (SPV) became apparent at this stage. Cytokinesis resulted in two spores forming within each SPV. Spores were uniform in size, measuring about 3.9 ± 0.33 long by 2.0 ± 0.2 µm wide. Ultrastructure demonstrated two spore types, one with 9-12 polar filament coils and a double-layered exospore and a second type with 4-7 polar filament coils and a homogenously electron-dense exospore, with differences perhaps related to parasite transmission mechanisms. The 16S rDNA sequences showed closest identity to the genus Glugea (≈ 92%), though the developmental cycle, specifically being a non-xenoma-forming species and having two spores forming within a SPV, did not fit within the genus. Based on combined phylogenetic and ultrastructural characteristics, a new genus (Fusasporis) is proposed, with F. stethaprioni n. gen. n. sp. as the type species.

Characterization of spaC-type Erysipelothrix sp. isolates causing systemic disease in ornamental fish.

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.

Pathologic features of mycobacteriosis in naturally infected Syngnathidae and novel transcriptome assembly in association with disease.

Syngnathidae (seahorses, seadragons and pipefish) suffer significant losses from non-tuberculous mycobacteria. However, they produce markedly different lesions in response to the disease compared to other teleost species, notably infrequent granuloma formation. This study evaluated 270 syngnathid fish, from which 92 were diagnosed with mycobacteriosis by histopathology, culture or both. Microscopic lesions variably consisted of random foci of coagulative necrosis in multiple organs, containing high numbers of free bacteria and large aggregates or sheets of macrophages with cytoplasm laden with acid-fast bacilli. Mycobacterial associated granulomas were identified in only six seahorses. Five fish had positive cultures with no observed microscopic changes. RNA-seq of the head kidney was performed to investigate the transcriptome of two infected and six non-infected lined seahorses Hippocampus erectus. Assembled and annotated putative transcripts serve to enrich the database for this species, as well as provide baseline data for understanding the pathogenesis of mycobacteriosis in seahorses. Putative components of the innate immune system (IL-1ß, IL-6, TNF, NOS, Toll-like receptor 1, MHC Class I, NF-κß, transforming growth factor beta, MyD88) were identified in the RNA-seq data set. However, a homolog for a key component in the TH1 adaptive immune response, interferon-gamma, was not identified and may underlie the unique pathologic presentation.

The teleost acute-phase inflammatory response and caspase activation by a novel alarmin-like ligand.

This study tested the hypothesis that NCAMP-1 has alarmin-like properties and activates the caspase-1-binding site in cells of the teleost bone marrow (equivalent). In mammals, alarmins have been studied extensively; however, in teleosts, little is known about their identity and functions. Similar to alarmins, NCAMP-1 has a broad spectrum of bacteriolytic activity. NCAMP-1 is constitutively present in CF serum, and levels were increased following infection with Edwardsiella ictaluri Binding to AK cells was determined with rNCAMP-1 and an anti-His-tag antibody. In vitro treatment of AK (bone marrow equivalent) or spleen cells with rNCAMP-1 increased the IL-1ß message three- to fivefold at 3 h, 6 h, and 9 h post-treatment. The association of NCAMP-1 with the activities of alarmin ATP and the acute inflammatory response was demonstrated by NCAMP-1-induced P2X7R pore opening and YO-PRO-1 cellular influx. The association of NCAMP-1 binding with inflammasome activation was demonstrated by NCAMP-1 activation of the caspase-1-binding site for tetrapeptide Z-YVAD-FMK. In competition assays, this tetrapeptide competitively inhibited subsequent binding by the pan-caspase substrate tripeptide FAM-VAD-FMK. Lymphocyte-like cells from the spleen were 16%+, and epithelial cells were also positive for NCAMP-1. IHC staining and confocal microscopy confirmed the cytosolic existence of NCAMP-1 in lymphoreticular tissue and IL-1ß in AK cells. CF T cell lines G14D and 28S.3 expressed NCAMP-1 in the cytosol and in storage granules. These studies strongly suggested that NCAMP-1 is an alarmin-like ligand with similar but distinct activities to those of ATP and HMGB-1.

A novel Henneguya species from channel catfish described by morphological, histological, and molecular characterization.

Channel catfish Ictalurus punctatus from a commercial farming operation in the Mississippi Delta were submitted for examination for the presence of infection by the trematode Bolbophorus damnificus. The fish were instead found to possess skin nodules suggestive of Henneguya pellis, a species previously described in the blue catfish I. furcatus. Despite the dermal location and distribution of lesions, morphological characteristics of the myxospores were inconsistent with H. pellis. Spores possessed a lanceolate spore body 15.4 +/- 1.5 microm (mean +/- SD; range = 12.2-19.3 microm) in length and 5.5 +/- 0.6 microm (range = 4.5-6.8 microm) in width in valvular view, and 4.7 +/- 0.2 microm (range = 4.2-5.0 microm) in width in sutural view. Polar capsules were pyriform and unequal in both length and width and contained polar filaments with six coils. Polar capsules measured 6.1 +/- 0.8 microm (range = 4.0-7.9 microm) long and 1.7 +/- 0.3 microm (range = 1.0-2.2 microm) wide. The caudal appendages were 50.5 +/- 8.3 microm (range = 34.8-71.4 micorm) long and the total length of the spore was 65.9 +/- 8.6 microm (range = 48.2-90.0 microm). The "blister like" plasmodia were round or ovoid, up to 2 mm in diameter, and randomly distributed throughout the epidermis of the fish. Histologically, plasmodia were confined to the dermis and elicited no inflammatory reaction from the fish. A blast search of the 18S small subunit rDNA sequence obtained by polymerase chain reaction amplification resulted in no identical sequence matches but indicated a close relationship to H. gurlei, H. ictaluri, and H. exilis. The unique host record, spore morphology, and novel genetic sequence derived from this isolate lead us to propose this isolate as a novel species, H. sutherlandi.

Extensive venous thrombosis and hind-limb edema associated with adrenocortical carcinoma in a dog.

A 10-year-old, spayed female, mixed-breed dog was referred for evaluation of bilateral hindlimb edema and weakness. Abdominal ultrasonography showed increased echogenicity of the lumen of the caudal vena cava from the level of the urinary bladder to the level of the cranial pole of the right kidney. Bilateral saphenous venograms displayed numerous filling defects in the caudal vena cava, right external iliac vein, right femoral vein, and the right common iliac vein. Extensive venous thrombosis was diagnosed, and the animal was euthanized. Necropsy confirmed the presence of venous thrombosis and revealed a right adrenocortical carcinoma that had invaded the caudal vena cava.

Intraosseous epidermoid cyst in a horse.

A 21-year-old female American Saddle Horse with a prominent swelling on the ventral aspect of the right hemimandible and radiographic evidence of a bone cyst was examined. The cyst cavity was surgically explored and was found to contain mucinous fluid and sheets of keratin. Microscopically, the cyst was lined by well-differentiated squamous epithelium characterized by various degrees of hyperkeratosis and parakeratosis. The stromal component varied from scant areas in which epithelium was closely apposed to bone to wide regions of dense connective tissue that contained fragments of keratin surrounded by foreign-body giant cells. Histologic features were consistent with a diagnosis of intraosseous epidermoid cyst. After curettage of the cyst and repulsion of the second premolar tooth, drainage was established and iodine flushes were begun. Nine months after surgery, drainage was not detectable and size of the hemimandible had decreased by approximately a fourth.

Neurologic disease attributable to infection with Parelaphostrongylus tenuis in blackbuck antelope.

Substantial mortality attributable to infection with Parelaphostrongylus tenuis was reported in 2 herds of blackbuck antelope (Antelope cervicapra) in southwestern Louisiana. Both herds had outbreaks in which all affected antelope had neurologic disease and subsequently died. Affected antelope were anorectic and weak. They staggered, trembled, isolated themselves from the herd, became recumbent, and, possibly, were blind. In 1 herd, 6 of 27 antelope were affected, and in the second herd, 7 antelope were affected. Both herds were on farms that raised various native and imported ruminants, including white-tailed deer. None of the remaining ruminants was affected during these outbreaks, and subsequent outbreaks have not been reported. Four antelope and the brain of a fifth antelope were submitted for postmortem examination. Meningeal worms were identified grossly in only 1 antelope. Metastrongyloid nematodes were detected histologically in 3 antelope. The amount and extent of inflammation varied greatly among affected antelope.

Chlamydiosis in commercial rheas (Rhea americana).

Mild to marked splenomegaly was observed in three of four rheas that died acutely in three unrelated commercial ratite facilities in Southeastern Louisiana. Mortalities occurred within a 5-week period in birds ranging from 2 months to 3 years of age. Multifocal hepatic and splenic necrosis with mononuclear cell infiltrates, typical of chlamydiosis in other avian species, was present on histopathologic sections. The diagnoses were confirmed by demonstration of inclusion bodies in splenic impression smears and fluorescent-antibody testing performed on Vero cell cultures.