Histopathological, ultrastructural and molecular phylogenetic analysis of a novel microsporidium in a loggerhead sea turtle Caretta caretta

Microsporidial spores were identified in the musculature of a loggerhead sea turtle Caretta caretta found dead on the shore in New Brunswick, Canada. Gastroenteritis was diagnosed on gross postmortem examination, with no gross abnormalities detected in the skeletal muscle. Histologically, the microsporidial spores were associated with inflammation and muscular necrosis and measured 1.1-1.7 × 2.2-3.4 µm. Spores were typically identified within sporophorous vesicles and, less often, in sporophorocysts and were weakly Gram positive, had punctate PAS staining, and were occasionally strongly acid-fast. Ultrastructural characteristics included 7-10 polar filament coils and other standard features of microsporidial spores. PCR for the microsporidial small subunit rRNA gene sequence was performed on DNA extracted from the muscle and small intestine, and the resulting amplicon was sequenced and queried against published microsporidial genomes. DNA sequences shared 98.2-99.8% sequence identity to Clade III of the Marinosporidia. This is the first report of a microsporidial infection contributing to the mortality of a sea turtle.

Isolation and identification of infectious salmon anaemia virus (ISAV) from Coho salmon in Chile

The isolation of infectious salmon anaemia virus (ISAV) from asymptomatic wild fish species including wild salmon, sea trout and eel established that wild fish can be a reservoir of ISAV for farmed Atlantic salmon. This report characterizes the biological properties of ISAV isolated from a disease outbreak in farmed Coho salmon in Chile and compares it with ISAV isolated from farmed Atlantic salmon in Canada and Europe. The virus that was isolated from Coho salmon tissues was initially detected with ISAV-specific RT-PCR (reverse transcription-polymerase chain reaction). The ability of the virus to grow in cell culture was poor, as cytopathology was not always conspicuous and isolation required passage in the presence of trypsin. Virus replication in cell culture was detected by RT-PCR and IFAT (indirect fluorescent antibody test), and the virus morphology was confirmed by positive staining electron microscopy. Further analysis of the Chilean virus revealed similarities to Canadian ISAV isolates in their ability to grow in the CHSE-214 cell line and in viral protein profile. Sequence analysis of genome segment 2, which encodes the viral RNA polymerase PB1, and segment 8, which encodes the nonstructural proteins NS1 and NS2, showed the Chilean virus to be very similar to Canadian strains of ISAV. This high sequence similarity of ISAV strains of geographically distinct origins illustrates the highly conserved nature of ISAV proteins PB1, NS1 and NS2 of ISAV. It is noteworthy that ISAV was associated with disease outbreaks in farmed Coho salmon in Chile without corresponding clinical disease in farmed Atlantic salmon. This outbreak, which produced high mortality in Coho salmon due to ISAV, is unique and may represent the introduction of the virus to a native wild fish population or a new strain of ISAV.

Pathology associated with an aquareovirus in captive juvenile Atlantic halibut Hippoglossus hippoglossus and an experimental treatment strategy for a concurrent bacterial infection

A large-scale mortality of larval and juvenile halibut Hippoglossus hippoglossus occurred at a semi-commercial halibut farm in Atlantic Canada. Investigation of the cause revealed aquareovirus particles in necrotic liver tissue of affected fish. Cytopathic effect on CHSE-214 cell lines occurred from all fish cultured for viruses, and the viral morphology of the particles in culture was consistent with that observed in necrotic host tissue. The virus was placed in the family of Reoviridae, genus Aquareovirus based on morphology and RT-PCR results. Multifocal hepatocellular necrosis was a consistent finding in all fish as well as acute necrosis of proximal renal tubules. Concurrent bacterial infections were present in some specimens. Fish experimentally treated with oxytetracycline or a combination of oxytetracycline and chloramine-T had a significantly lower mortality rate than untreated fish. Fish treated with chloramine-T alone had a significantly elevated mortality rate compared to controls. Despite supportive medical therapy, mortality levels in treated and untreated groups remained elevated, supporting the hypothesis that the primary pathogen was of viral origin. This is the first report of elevated mortalities in Atlantic halibut associated with an aquareovirus.

Proliferative pododermatitis associated with virus-like particles in a northern gannet

Small multifocal lesions of proliferative pododermatitis were observed in an emaciated adult male northern gannet (Morus bassanus). Ultrastructurally, these lesions were associated with numerous virus-like particles with a size and morphology suggestive of Papovaviridae. DNA in situ hybridization with probes for avian polyomaviral and papillomaviral nucleic acid and an immunohistochemical test for the presence of papillomaviral antigen failed to identify this virus further. To our knowledge, papovavirus-like particles have not been recognized previously in this avian species.

Formation of virus-like particles when the polyprotein gene (segment A) of infectious bursal disease virus is expressed in insect cells

The baculovirus expression vector system was used to examine the expression of the full-length infectious bursal disease virus (IBDV) segment A cDNA, which encodes the structural proteins in a polyprotein precursor that is autocatalytically cleaved to VPX, VP3, and VP4. No VP2 was observed in lysates of recombinant baculovirus infected cells indicating the lack of processing of VPX to VP2 in this system. Virus-like particles (VLP) were purified from the infected insect cells, and on negative staining electron microscopy, looked very similar to authentic IBDV particles in shape and size, suggesting that processing of VPX to VP2 is not necessary for capsid assembly.

Multicentric undifferentiated spindle-cell sarcoma with virus-like particles in an aged dairy cow

A 10-year-old Holstein dairy cow was slaughtered because of weight loss and ataxia. In addition to a neoplastic mass in the animal's forehead, there was extensive neoplastic infiltration of the skeleton and liver. Other viscera were spared. Tumours were composed of sheets and interlacing fascicles of poorly differentiated, vimentin-positive cells in a fibrillar matrix. Intracytoplasmic virus-like particles, 80 nm in diameter, with a central electron-dense core were found in many neoplastic cells. This neoplasm had an unusual predilection for bone. The significance of the virus-like particles requires further investigation.

Establishment of conditions for the detection of bovine herpesvirus-1 by polymerase chain reaction using primers in the thymidine kinase region

Polymerase chain reaction (PCR) for detection of bovine herpesvirus-1 (BHV-1) was developed and optimized using 22 bp sense and 20 bp antisense primers in the thymidine kinase (TK) coding region. The amplification product is 183 bp long. The PCR optimization was done using BHV-1 tissue culture supernate (BHV-1TCS), concentrated BHV-1 tissue culture supernate (cBHV-1TCS) and sucrose gradient purified BHV-1 (pBHV-1). The sensitivity of four methods of sample preparation which are standard DNA extraction, modified proteinase K (PK) digestion, GeneReleaserTM + 34 cycles or + 44 cycles, and boiling were compared with virus isolation (VI) using BHV-1TCS. The incorporation of 10% glycerol in the reaction mixture, the incubation in PK for 18 hours and predenaturation of samples and cooling in ice prior to PCR were essential for the amplification of BHV-1 DNA for samples prepared by standard DNA extraction and modified PK digestion. The preparation of samples by Gene-ReleaserTM, a proprietary nucleic acid releasing cocktail, showed 10 to 1,000-fold increase in sensitivity compared to standard DNA extraction and modified PK digestion. No amplification was observed in samples prepared by boiling. The sample preparation of BHV-1 LA strain by GeneReleaserTM showed sensitivity equivalent to virus isolation. The BHV-1 TK PCR using GeneReleaserTM has a detection limit of 1 picogram and 10 fentograms of purified BHV-1 DNA using ethidium bromide stained gel and Southern blot hybridization, respectively. It could detect viral DNA in 1,000 infected cells in a total suspension of 10,000 cells using either ethidium bromide stained gel or Southern blot hybridization.

Amplification of strains of bovine herpesvirus 1 by use of polymerase chain reaction with primers in the thymidine kinase region

A primer pair was designed from the published nucleotide sequence of the coding region of the bovine herpesvirus 1 (BHV-1) thymidine kinase (tk) gene for use in detection of the virus by use of polymerase chain reaction (PCR) amplification of 12 BHV-1 strains (3 ATCC and 9 local isolates). A tk deletion mutant BHV-1, and 2 BHV-4 strains from ATCC were used as negative controls. One strain each of feline herpes-virus, equine herpesvirus, and bovine adenovirus, and 2 noninoculated bovine cultured cells--bovine fetal testis and Madin-Darby bovine kidney--also were examined to verify specificity of the primers. A PCR product, 183 bp long, was detected by ethidium bromide staining after agarose gel electrophoresis, when purified DNA from cell cultures infected with BHV-1 strain LA was used as template. Specificity of the PCR product was confirmed by restriction digestion with Sac II enzyme and Southern blot hybridization. Amplification was detected by ethidium bromide staining of agarose gels and/or Southern blot hybridization with the radiolabeled PCR product of the LA strain in similarly prepared DNA templates of 5 other BHV-1 strains, 2 obtained from ATCC and 3 of the 9 local isolates. In a modified PCR protocol, using virus suspensions treated with a nucleic acid-releasing cocktail, substantial amplification was obtained for the 3 BHV-1 strains from ATCC and for all 9 local bovine herpesvirus field isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

Interstitial pneumonia in piglets on Prince Edward Island

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