Porcine Astrovirus Type 3 in Central Nervous System of Swine with Polioencephalomyelitis.

Using next-generation sequencing, we identified and genetically characterized a porcine astrovirus type 3 strain found in tissues from the central nervous system of 1 piglet and 3 sows with neurologic signs and nonsuppurative polioencephalomyelitis. Further studies are needed to understand the potential for cross-species transmission and clinical impact.

Experimental teschovirus encephalomyelitis in gnotobiotic pigs.

A central nervous system (CNS) disorder characterized by non-suppurative encephalomyelitis with neurological signs was induced experimentally in gnotobiotic pigs by intravenous and oral or intranasal inoculation of the porcine teschovirus (PTV) Toyama 2002 strain isolated from breeding pigs in Japan. Lesions consisting of perivascular cuffing of mononuclear cells, focal gliosis, neuronal necrosis and neuronophagia were observed in the brainstem, cerebellum and spinal cord. Non-suppurative ganglionitis in the spinal ganglion and neuritis in the spinal root were also observed. Regardless of the route of inoculation, all pigs infected experimentally with PTV showed a similar distribution of CNS lesions. Histological lesions in the CNS caused by oral or intranasal inoculation of the virus were mild compared with those induced by intravenous infection. Immunohistochemically, the distribution of PTV antigens corresponded closely with the distribution of brain lesions. PTV particles were detected via electron microscopy in the cytoplasm of nerve cells and the endothelial cells of blood vessels in the spinal cord of inoculated pigs. Polymerase chain reaction analysis demonstrated the presence of PTV RNA in the CNS, tonsils and large intestines of 21 of the 22 pigs inoculated. Direct CNS invasion via the blood vessels appears to be a major route of infection for PTV. The gnotobiotic pig provides a useful model for further study of PTV pathogenesis.

Porcine teschovirus polioencephalomyelitis in western Canada.

Beginning in 2002, a small number of pig farms in western Canada began reporting 4-7-week-old pigs with bilateral hind-end paresis or paralysis. Low numbers of pigs were affected, some died, most had to be euthanized, and those that survived had reduced weight gains and neurological deficits. Necropsies revealed no gross lesions, but microscopic lesions consisted of a nonsuppurative polioencephalomyelitis, most severe in the brain stem and spinal cord. The lesions were most consistent with a viral infection. Tests for circovirus, Porcine reproductive and respiratory syndrome virus, coronavirus, Rabies virus, and Pseudorabies virus were negative. Using immunohistochemistry, virus neutralization, fluorescent antibody test, and nested reverse transcription polymerase chain reaction, Porcine teschovirus was identified in tissues from affected individuals. To the authors' knowledge, this is the first report of teschovirus encephalitis in western Canada and the first reported case of polioencephalomyelitis in pigs in Canada, where teschovirus was confirmed as the cause.

A wild-type porcine encephalomyocarditis virus containing a short poly(C) tract is pathogenic to mice, pigs, and cynomolgus macaques.

Previous studies using wild-type Encephalomyocarditis virus (EMCV) and Mengo virus, which have long poly(C) tracts (61 to 146 C's) at the 5' nontranslated region of the genome, and variants of these viruses genetically engineered to truncate or substitute the poly(C) tracts have produced conflicting data on the role of the poly(C) tract in the virulence of these viruses. Analysis of the nucleotide sequence of an EMCV strain isolated from an aborted swine fetus (EMCV 30/87) revealed that the virus had a poly(C) tract that was 7- to 10-fold shorter than the poly(C) tracts of other EMCV strains and 4-fold shorter than that of Mengo virus. Subsequently, we investigated the virulence and pathogenesis of this naturally occurring short-poly(C)-tract-containing virus in rodents, pigs, and nonhuman primates. Infection of C57BL/6 mice, pigs, and cynomolgus macaques resulted in similar EMCV 30/87 pathogenesis, with the heart and brain as the primary sites of infections in all three animals, but with different disease phenotypes. Sixteen percent of EMCV 30/87-infected pigs developed acute fatal cardiac failure, whereas the rest of the pigs were overtly asymptomatic for as long as 90 days postinfection (p.i.), despite extensive myocardial and central nervous system (CNS) pathological changes. In contrast, mice infected with >/==" BORDER="0">4 PFU of EMCV 30/87 developed acute encephalitis that resulted in the death of all animals (n = 25) between days 2 and 7 p.i. EMCV 30/87-infected macaques remained overtly asymptomatic for 45 days, despite extensive myocardial and CNS pathological changes and viral persistence in more than 50% of the animals. The short poly(C) tract in EMCV 30/87 (CUC(5)UC(8)) was comparable to that of strain 2887A/91 (C(10)UCUC(3)UC(10)), another recent porcine isolate.

[Method of preparation of the specimens for combined immunocytological examinations by light and electron microscopy]. / Sposob prigotovleniia praparatov dlia sovmeshchennogo immunotsitologicheskogo issledovaniia v svetovom i elektronnom mikroskopakh.

A method for making preparations for combined immunocytological examinations in light and electron microscopes is described. An infected cell culture grown on slides (a piglet kidney cell culture infected with Teschen virus) was fixed with 2.5% glutaraldehyde in phosphate buffer, pH 7.2-7.4 for 10-15 min and incubated with a conjugate (peroxidase-labeled immune serum to the causative agent of the infection under study). After postfixation, cytochemical reaction for peroxidase was performed, then the material was fixed with 2% OsO4 solution in phosphate buffer, pH 7,2-7,4, dehydrated in an ascending series of alcohols and gradually impregnated with polymerising resins (epon, araldit, etc.). The cells were embedded in foil baths, and after polymerization and separation of the slide and foil preparations with good light microscopy properties. In the light microscope, the desired parts of cells or a cell were selected, removed, cut in an ultratome and examined in electron microscope.

Atypical porcine enterovirus encephalomyelitis: possible interraction between enteroviruses and arsenicals.

Porcine enteroviruses were isolated from weaner pigs that had nervous signs and mild non-suppurative meningoencephalomyelitis and ganglioneuritis. The clinical signs and lesions were not typical of enterovirus infection and it is believed that an organic arsenical present in feed enhanced pathogenicity of enteroviruses. Severe non-suppurative polioencephalomyelitis and ganglioneuritis were produced in gnotobiotic pigs by oral inoculation of the viruses.