Detection of a Nonoccluded Baculovirus in the Freshwater Crayfish Cherax quadricarinatus in North America

Abstract

A nonoccluded baculovirus was detected during a routine health examination of the tropical freshwater blue crayfish Cherax quadricarinatus reared in a farm in California, USA. The crayfish were progeny of captive-reared adults imported from Australia. There were no external or internal signs of disease in infected crayfish, but histological examination revealed eosinophilic to amphophilic intranuclear inclusions within the tubular epithelial cells of the hepatopancreas. The infected cells occurred throughout the hepatopancreas but never exceeded 10% of the cells constituting the tubule epithelium. Electron microscopy revealed numerous loosely enveloped, rod-shaped baculoviruses. The enveloped virions had a length of 292 ± 15 nm and a diameter of 102 ± 7 nm (mean ± SD). The cylindrical nucleocapsids often possessed squared ends and were 216 ± 13 nm in length by 47 ± 3 nm in width. There was no evidence of occlusion body formation similar to that known for certain other crustacean baculoviruses. The origin of the virus is uncertain, although a similar or identical agent has recently been detected among C. quadricarinatus in Australia.     

Histopathology of Hybrid Tilapias Infected witha Biotype of Streptococcus iniae

Abstract

A systemic streptococcal disease caused by a biotype of Streptococcus iniae affecting hybrids of Nile tilapia Tilapia nilotica × blue tilapia T. aurea at a commercial aquaculture facility in central Texas was investigated. Histological analysis revealed a general septicemia with the occurrence of cellular infiltration and numerous cocci in most organ systems. Observations included cellular infiltration of the eye, meningitis, meningeal granuloma, numerous foci of infection, and massive cellular infiltration in the kidneys. Bacteria were seen in the subcapsular capillaries of the liver, and some liver tissue was granulomatous. Splenic sinuses contained numerous cocci, and both epicarditis and myocarditis was observed in the heart tissue of some specimens. Cocci were free in the plasma of infected fish and often phagocytized by macrophages.     

Identification of Genes Involved in Taura Syndrome Virus Resistance in Litopenaeus Vannamei

Abstract

The goal of the present research was to identify the genes that are differentially expressed between two lineages of Pacific white shrimp Litopenaeus vannamei displaying different susceptibilities to Taura syndrome virus (TSV) and to understand the molecular pathways involved in resistance to the disease. An oligonucleotide microarray was constructed and used to identify several genes that were differentially expressed in the two L. vannamei lineages following infection with TSV. Individual L. vannamei from either resistant or susceptible lineages were exposed via injection to TSV. Individuals were removed at 6 and 24 h postinfection, and gene expression was assessed with the in-house microarray. The microarray data resulted in the selection of a set of 397 genes that were altered by TSV exposure between the different lineages. Significantly differentially expressed genes were subjected to hierarchical clustering and revealed a lineage-dependent clustering at 24 h postinoculation, but not at 6 h postinoculation. Discriminant analysis resulted in the identification of a set of 11 genes that were able to correctly classify Pacific white shrimp as resistant or susceptible based on gene expression data.

Received June 21, 2013; accepted October 24, 2013     

Isolation and Identification of Mycobacterium peregrinum from the Pacific White Shrimp Penaeus vannamei

Abstract

Mycobacterium peregrinum was isolated from multifocal, melanized nodular lesions in the carapace of the cultured marine shrimp Penaeus vannamei. This is the first identification of this species of Mycobacterium in shrimp. The lesions appeared to be the result of opportunistic infections in otherwise healthy animals. The presence of M. peregrinum in cultured shrimp has a direct negative impact on the marketability of shrimp because it causes obvious black lesions. The potential for accidental infections of shrimp farm or packing plant workers from handling infected shrimp is of concern since nodular skin lesions induced by the bacterium are difficult to treat.     

Isolation and Pathogenicity of Streptococcus iniae in Cultured Red Hybrid Tilapia in Malaysia

Abstract

This study describes the isolation and pathogenicity of Streptococcus iniae in cultured red hybrid tilapia (Nile Tilapia Oreochromis niloticus × Mozambique Tilapia O. mossambicus) in Malaysia. The isolated gram-positive S. iniae appeared punctiform, transparently white, catalase and oxidase negative and produced complete β-hemolysis on blood agar, while a PCR assay resulted in the amplification of the 16 S rRNA gene and lactate oxidase encoded genes. The isolate was sensitive to tetracycline, vancomycin, and bacitracin but was resistant to streptomycin, ampicillin, penicillin, and erythromycin. Pathogenicity trials conducted in local red hybrid tilapia (mean ± SE = 20.00 ± 0.45 g) showed 90.0, 96.7, and 100.0% mortality within 14 d postinfection following intraperitoneal exposure to 10⁴, 10⁶, and 10⁸ CFU/mL of the pathogen, respectively. The clinical signs included erratic swimming, lethargy, and inappetance at 6 h postinfection, while mortality was recorded at less than 24 h postinfection in all infected groups. The LD_{50-336 h} of S. iniae against the red hybrid tilapia was 10² CFU/mL. The post mortem examinations revealed congested livers, kidneys, and spleens of the infected fish. This is the first report of S. iniae experimental infection in cultured red hybrid tilapia in Malaysia.

Received January 20, 2017; accepted July 16, 2017 Published online October 11, 2017     

Epizootics of Erythrocytic Inclusion Body Syndrome in Coho Salmon Cultured in Seawater in Japan

Abstract

Epizootics attributable to erythrocyytc inclusion body syndrome (EIBS) occurred among populations of coho salmon Oncorhynchus kisutch cultured in seawater in Japan. Onset of the disease was correlated with water temperatures declining to below 10°C. Symptoms of EIBS were severe anemia with hematocrits of less than 20% and corresponding changes in erythrocyte counts, hemoglobin concentration, and mean corpuscular hemoglobin concentration. Erythrocytes had characteristic inclusion bodies that contained enveloped viral particles with a diameter of approximately 77 nm. The disease was reproduced in artificially induced infections.     

Iridovirus Infections among Missouri River Sturgeon: Initial Characterization,Transmission, and Evidence for Establishment of a Carrier State

Abstract

Iridovirus infections of the integument were associated with disease and mortality among hatchery-reared populations of juvenile pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus from the Missouri River. Virus-infected cells in the integument of fins and body were greatly enlarged, possessed pleomorphic and eccentric nuclei, and exhibited an amphophilic to eosinophilic staining of the cytoplasm in hematoxylin-and-eosin-stained sections. Virus particles found in the host cell cytoplasm were composed of an outer hexagonal capsid measuring 254 nm in diameter and surrounding a dense nucleoid. Despite numerous attempts, the virus could not be propagated on routine cell lines used in fish viral diagnostics or from established cell lines from white sturgeon Acipenser transmontanus, pallid sturgeon, or shovelnose sturgeon. Bath exposures of healthy juvenile pallid sturgeon to a crude extract or a 0.45-μm-filtered extract from the fins of infected fish resulted in transmission of the virus and mortality. At water temperatures of 15°C, the first deaths occurred at approximately 1 month; mortality peaked between 50 and 60 d postexposure, after which surviving fish recovered. Presence of the virus was confirmed among dead and moribund pallid sturgeon by both histology and detection of viral DNA by polymerase chain reaction methods. Feeding of infected tissues and cohabitation with virus-infected shovelnose sturgeon also resulted in successful virus transmission to juvenile pallid sturgeon. Virus infections among experimentally exposed pallid sturgeon that recovered from clinical episodes persisted for at least 8.5 months, and these apparently healthy fish transmitted the virus and disease to juvenile pallid sturgeon by cohabitation. The newly described Missouri River sturgeon iridovirus (MRSIV) as found in pallid sturgeon and shovelnose sturgeon shares many properties with a group of iridoviruses associated with serious skin and gill infections in several species of sturgeon.

Received October 5, 2010; accepted October 26, 2010     

Diseases of Cultured Brown-Spotted Grouper Epinephelus tauvina and Silvery Black Porgy Acanthopagrus cuvieri in Kuwait

Abstract

Several diseases have been encountered in cultured brown-spotted grouper and silvery black porgy in the mariculture facilities of the Kuwait Institute for Scientific Research. More than 50% of juvenile brown-spotted grouper cultured in concrete tanks died during an initial outbreak of the protozoan parasite Cryptocaryon irritans. Formalin treatment (35–50 mg/L, 5 h/d, twice a week) was used to control and prevent the disease. Formalin-treated fish experienced several reinfestations by this parasite, but no further deaths occurred. Brown-spotted grouper also suffered from severe eye lesions, including exophthalmia and opaqueness of the cornea. Only 35% of these fish cultured in fiberglass tanks did not have idiopathic lesions. Silvery black porgy cultured in floating cages in the open sea did not show any lesions from July to November 1985 apart from eroded fins, which increased in frequency with increasing stocking densities. However, a disease occurred during the winter of 1986, when the water temperature averaged 14.8°C, and 65% mortality resulted. Vibrio anguillarum, V. ordain, V. carchariae, V. damsela, and three other Vibrio spp. were isolated from diseased silvery black porgy. Deaths associated with broken isthmuses occurred among silvery black porgy cultured in floating cages in August 1987. There was no further incidence of this condition after the addition of vitamin C (500 mg/kg) of feed to the diet.     

Rapid diagnosis of vibriosis and white spot syndrome (WSS) in the culture of shrimp, <Emphasis Type="Italic">Penaeus monodon</Emphasis> in Philippines

Viral and bacterial pathogens have raised serious concerns in the sustainability of the shrimp culture industry in the Philippines. Heavy mortality associated with luminous vibriosis and white spot syndrome virus (WSSV) infection has been the major problem besetting the industry. Using published PCR protocols for the diagnosis of vibriosis and white spot syndrome virus (WSSV) disease in shrimp, we optimized these assays that could be suited to the shrimp aquaculture setting in the Philippines. Genomic DNAs of Vibrio spp. that exhibited luminescence as well as those that grew on thiosulfate citrate bile salt sucrose agar (TCBS) were used for the PCR amplification of the ribonuclease P (RNase P) gene. There was differential amplification of the RNase P gene based on the phenotypic characters of the Vibrio spp. Similar results were also obtained using direct colony PCR of the bacterial colonies. White spot syndrome virus was also detected in the infected shrimp and there were differences in the detection frequency in relation to the tissues used for PCR amplification. Duplex PCR was also optimized that could be used for simultaneous detection of these pathogens in shrimp.     

Evaluation of Difloxacin for Shrimp Aquaculture: In Vitro Minimum Inhibitory Concentrations,Medicated Feed Palatability,and Toxicity to the Shrimp Penaeus vannamei

Abstract

Standard in vitro minimum inhibitory concentrations (MICs) were determined for difloxacin and compared with the MICs of several other antimicrobials, against a standardized battery of 13 gram-negative bacterial isolates associated with shrimp disease. The palatability and safety (toxicity) of difloxacin to the shrimp Penaeus vannamei were also evaluated during 15 d of medicated feeding at 1× (100 mg/kg of feed), 2×, and 4× treatment levels to give doses of approximately 5, 10, and 20 mg difloxacin/kg body weight. A significant reduction (P ≤ 0.05) in difloxacin-medicated feed palatability was noted in the 2× and 4× trials. However, differences were still acceptable, because more than 80% of the feeds were consumed in both treatments relative to the control diet. Shrimp mortality rates increased with difloxacin level from 7% for the control treatment to 20% for the 4× treatment. Differences in percent survival were not significant (P > 0.05) by the Williams test; however, analysis of mean survival time indicated that difloxacin significantly (P ≤ 0.05) reduced survival time at the highest dose. Signs of animal stress, characterized by extreme lethargy, were noted in the 4× treatment. An actual therapeutic dose for difloxacin in penaeid shrimp is unknown; however, the 1× treatment (100-mg/kg) was acceptable with respect to both palatability and toxicity, whereas 400 mg/kg of feed or more may be unpalatable and toxic to shrimp.     

Amyloodiniosis in Cultured Hybrid Striped Bass (Morone saxatilis × M. chrysops) in North Carolina

Abstract

An outbreak of amyloodiniosis in pondcultured hybrid striped bass × white bass (female Morone saxatilis × male M. chrysops) is the northernmost documented outbreak caused by an endemic source in fish of the western Atlantic. Dinospores produced by this isolate of Amyloodinium ocellatum were anteroposteriorly flattened, as contrasted with the gymnodinoid dinospores of the A. ocellatum-type species, suggesting that more than one strain or species of A. ocellatum may exist.     

Three Myxosporeans Found in the Cranial and Branchial Tissues of Rainbow Trout in California

Abstract

Three myxosporeans were encountered in the cranial tissues of a California population of rainbow trout Oncorhynchus mykiss examined for the presence of Myxobolus cerebralis, the causative agent of whirling disease. Typical spores of M. cerebralis and a previously undescribed species of Myxobolus were found in the cranial tissues prepared by the pepsin HCl-trypsin digestion method. Henneguya zschokkei was also detected in digest preparations of cranial tissues, but was more numerous when branchial cartilage was included in the preparations. Microscopic examinations of tissues of individual rainbow trout showed occasional infections with both myxobolid species. Myxobolus cerebralis trophozoites and spores were found in the cranial and gill cartilage, and Myxobolus sp. was found in the brain and spinal cord. Henneguya zschokkei was also found within granulomas in the connective tissues below the gill arch. Both M. cerebralis and H. zschokkei were associated with a chronic inflammatory response in their respective tissues. In contrast, the Myxobolus sp. spores were found in pockets within the nervous tissues with no detectable host response. The spore measurements, calculated from fresh digests of infected tissues for the three myxosporeans (N = 20), for length × width × thickness in micrometers (SD) were 11.7 (0.6) without tails and 42.6 (5.2) with tails × 7.7 (0.8) × 7.0 (0.1) for H. zschokkei, 9.9 (0.4) × 8.4 (0.1) × 6.5 (0.3) for M. cerebralis, and 12.7 (0.7) × 10.5 (1.0) × 9.5 (0.8) for Myxobolus sp. Examined under scanning electron microscopy, the latter two species were morphologically similar although distinctive in size.     

Communications: Detection of Anti-Amyloodinium ocellatum Antibody from Cultured Hybrid Striped Bass (Morone saxatilis × M. chrysops) during an Epizootic of Amyloodiniosis

Abstract

After an epizootic of amyloodiniosis (caused by the protozoan Amyloodinium ocellatum) in a commercial aquaculture facility for hybrid striped bass (female striped bass Morone saxatilis × male white bass M. chrysops), sera from these fish, as well as from others that had been experimentally immunized with the parasite, were evaluated by an enzyme-linked immunosorbent assay for antibody specific for the parasite. Titers were similar between the fish infested in culture and the experimentally immunized fish, and were significantly higher in both the cultured and artificially exposed fish than in unexposed fish. These results suggest that an infestation of A. ocellatum can stimulate the production of humoral antibodies to the parasite, providing further evidence that natural infestations of the parasite may confer protective resistance in fish that survive the initial parasitic infestation.     

Experimental transmission of malignant catarrhal fever to red deer (Cervus elaphus)

Abstract

Malignant catarrhal fever was transmitted from affected to recipient red deer (Cervus eluphus) using bloodor lymphoid suspension as inoculum. Incubation periods ranged from 11 to 26 days. The disease was also transmitted using lymphoid suspension stored overnight at 4°C or at ?70°C for 8 months.

The experimental disease was characterised by fever, depression, anorexia, diarrhoea and dysentry. The course of the disease was approximately 96 hours.

Major lesions consisted of acute mesenteric lymphadenitis and acute haemorrhagic typhlitis and colitis. Lesions in the caecum and colon started as multifocal mucosal haemorrhages and progressed rapidly to massive mucosal haemorrhage.     

Infectious Salmon Anemia (ISA) Virus: Infectivity in Seawater under Different Physical Conditions

Abstract

Infectious salmon anemia (ISA) virus (genus Isavirus, family Orthomyxoviridae), present in all major salmon producing countries, is the causative agent for a serious and commercially important disease affecting Atlantic Salmon Salmo salar. Nearly all ISA outbreaks occur in the marine production phase and knowledge about survival time for ISA virions in seawater is crucial for an adequate strategy to combat the disease. To acquire knowledge about this important factor, a study of ISA virus exposed to four different physical conditions was carried out. The virions’ survival was tested in sterile seawater, sterile seawater with normal ultraviolet light radiation (UVR), natural seawater, and natural seawater with UVR. During the 72-h experiment both presence of ISA virus RNA and the infectivity of ISA virions were monitored. The result of this study showed that the infectivity of ISA virions is lost within 3 h of exposure to natural seawater or sterile seawater with UVR. However, it was possible to detect ISA virus RNA throughout the experimental period. This indicates that the effect of both UVR and biological activity of natural seawater limits the survival time of ISA virions under normal conditions. The survival time of ISA virions in sterile seawater was less than 24 h. Based on the available literature and the present study it is not very likely that passive horizontal transmission in seawater over long distances can occur. This is due to the following factors: (1) the effect of UVR and biological activity on ISA virions infectivity found in the present study, (2) the speed and dilution effect in seawater currents in salmon farming areas, (3) the temperature during the major outbreak periods, and (4) the need for an infective dose of ISA virions to reach naive Atlantic Salmon.

Received August 22, 2013; accepted November 7, 2013     

Shrimp Antimicrobial Testing. I. In Vitro Susceptibility of Thirteen Gram-Negative Bacteria to Twelve Antimicrobials

Abstract

Standard minimum inhibitory concentration (MIC) studies were conducted in vitro on eleven prospective antimicrobials and one reference antimicrobial. The compounds were tested against a standardized battery of 13 gram-negative bacterial isolates associated with shrimp disease. Two additional bacterial organisms not associated with shrimp, Escherichia coli and Pseudomonas aeruginosa, were also tested as system controls. The compounds tested were chloramphenicol (reference), enrofloxacin, erythromycin, florfenicol, oxytetracycline, paromomycin, four experimental fluoroquinolines (PD124816, PD127391, PD131628, PD132133), Romet-30®, and Sarafin®. All compounds, with the possible exception of paromomycin, had significantly better overall MIC ranges than did chloramphenicol.     

Evaluation of injection volumes for the transversus abdominis plane block in dog cadavers: a preliminary trial

ObjectiveTo evaluate staining of nerve branches after the injection of different volumes during ultrasound-guided transversus abdominis plane (TAP) block in dog cadavers.Study designProspective randomized study.AnimalsA total of 15 frozen/thawed adult dog cadavers.MethodsHemiabdomens were randomly allocated to one of four groups. In groups G0.3, G0.6 and G1.0, ropivacaine–methylene blue solution (0.3, 0.6 and 1.0 mL kg^–1 in seven, eight and eight hemiabdomens, respectively) was injected at the midpoint between the iliac crest and the last rib at the height of the shoulder. In group G0.3×2 (seven hemiabdomens), two injections (0.3 mL kg^–1) were performed, caudal to the last rib and cranial to the iliac crest at the same height. Total time for injection was recorded; after 30 minutes, cadavers were dissected and spread of dye was evaluated.ResultsAccuracy of injection site was 80% and injection time was 71 (48–120) seconds for all groups together. Craniocaudal spread was 6.4 ± 1.6, 9.1 ± 2.6, 11.4 ± 2.3 and 11.2 ± 3.8 cm for G0.3, G0.6, G1.0 and G0.3×2, respectively [G0.3 to G0.3×2 (p = 0.044) and G1.0 (p = 0.034)]. There was no difference in dorsoventral spread among groups. Number of ventral nerve branches stained was 3 (2–4), 3 (2–4), 3 (3–4) and 3 (2–4) for G0.3, G0.6, G1.0 and G0.3×2, respectively, including nerve branches from twelfth thoracic to third lumbar (L3) in different proportions among groups.Conclusions and clinical relevanceResults suggest that a single-injection TAP block, using 0.3 mL kg^–1, stains comparable number of nerve branches as higher volumes or two-point injection. Despite the volume or technique, consistent staining of the innervation of the caudal abdomen (L1–L3) was observed. Additional cadaveric studies are necessary to identify the optimal technique for complete abdominal wall staining.     

Intranuclear Inclusions in Cells Infected with Newcastle Disease Virus

Cells infected by Newcastle Disease Virus were observed to contain both intracytoplasmic and intranuclear inclusion bodies. Ultrastructurally, they consisted of twisted strands of about 18–20 nm diameter resembling nucleocapsids. The presence of these inclusions was detected irrespective of host cell or pathogenicity of the virus. In immunofluorescence and immunogold labelling experiments, these structures were tagged by an anti-P protein monoclonal antibody. In summary, we show that intracytoplasmic and intranuclear inclusion bodies, hitherto used as a taxonomic characteristic for the genus Morbillivirus of the Paramyxoviridae, also occur in a member of the genus Rubulavirus.