The Equine Movement Disorder "Shivers" Is Associated With Selective Cerebellar Purkinje Cell Axonal Degeneration.

"Shivers" is a progressive equine movement disorder of unknown etiology. Clinically, horses with shivers show difficulty walking backward, assume hyperflexed limb postures, and have hind limb tremors during backward movement that resembles shivering. At least initially, forward movements are normal. Given that neither the neurophysiologic nor the pathologic mechanisms of the disease is known, nor has a neuroanatomic locus been identified, we undertook a detailed neuroanatomic and neuropathologic analysis of the complete sensorimotor system in horses with shivers and clinically normal control horses. No abnormalities were identified in the examined hind limb and forelimb skeletal muscles nor the associated peripheral nerves. Eosinophilic segmented axonal spheroids were a common lesion. Calretinin-positive axonal spheroids were present in many regions of the central nervous system, particularly the nucleus cuneatus lateralis; however, their numbers did not differ significantly from those of control horses. When compared to controls, calretinin-negative, calbindin-positive, and glutamic acid decarboxylase-positive spheroids were increased 80-fold in Purkinje cell axons within the deep cerebellar nuclei of horses with shivers. Unusual lamellar or membranous structures resembling marked myelin decompaction were present between myelin sheaths of presumed Purkinje cell axons in the deep cerebellar nuclei of shivers but not control horses. The immunohistochemical and ultrastructural characteristics of the lesions combined with their functional neuroanatomic distribution indicate, for the first time, that shivers is characterized by end-terminal neuroaxonal degeneration in the deep cerebellar nuclei, which results in context-specific hypermetria and myoclonus.

Porcine reproductive and respiratory syndrome virus infection in neonatal pigs characterised by marked neurovirulence.

Neonatal pigs from three herds of pigs were somnolent and inappetent and had microscopic lesions characterised by severe meningoencephalitis, necrotic interstitial pneumonia and gastric muscular inflammation. Porcine reproductive and respiratory syndrome virus (PRRSV) infection was diagnosed and confirmed by virus isolation, fluorescent antibody examination of frozen lung sections, serology, immunohistochemistry and in situ hybridisation. Each herd had a history of PRRSV infection and was using or had used a modified-live vaccine. The isolates from the affected pigs were genetically distinct from the modified-live vaccine strain of the virus when compared by restriction enzyme analysis and nucleotide sequencing of PRRSV open reading frames 5 and 6. The virus was identified in macrophages or microglia of brain lesions by immunohistochemical staining of brain sections with an anti-PRRSV monoclonal antibody and an anti-macrophage antibody. The replication of the virus in the brain was verified by in situ hybridisation. The meningoencephalitis induced by the virus in pigs from each of the herds was unusually severe and the brain lesions were atypical when compared with other descriptions of encephalitis induced by the virus, which should therefore be considered as a possible diagnosis for neonatal pigs with severe meningoencephalitis. In addition, field isolates of the virus which are capable of causing disease can emerge and coexist with modified-live vaccine virus in some pig herds.

Identification of porcine reproductive and respiratory syndrome virus in semen and tissues from vasectomized and nonvasectomized boars.

Previous studies have indicated that porcine reproductive and respiratory syndrome virus (PRRSV) can be identified in and transmitted through boar semen. However, the site(s) of replication indicating the origin of PRRSV in semen has not been identified. To determine how PRRSV enters boar semen, five vasectomized and two nonvasectomized PRRSV-seronegative boars were intranasally inoculated with PRRSV isolate VR-2332. Semen was collected three times weekly from each boar and separated into cellular and cell-free (seminal plasma) fractions. Both fractions were evaluated by reverse transcriptase nested polymerase chain reaction (RT-nPCR) for the presence of PRRSV RNA. Viremia and serostatus were evaluated once weekly, and boars were euthanatized 21 days postinoculation (DPI). Tissues were collected and evaluated by RT-nPCR, virus isolation (VI), and immunohistochemistry to identify PRRSV RNA, infectious virus, or viral antigen, respectively. PRRSV RNA was identified in semen from all vasectomized and nonvasectomized boars and was most consistently found in the cell fraction, within cells identified with a macrophage marker. Viral replication as determined by VI was predominately found within lymphoid tissue. However, PRRSV RNA was widely disseminated throughout many tissues, including the reproductive tract at 21 DPI. These results indicate that PRRSV can enter semen independent of testicular or epididymal tissues, and the source of PRRSV in semen is virus-infected monocytes/macrophages or non-cell-associated virus in serum. PRRSV-infected macrophages in semen may result from infection of local tissue macrophages or may originate from PRRSV-infected circulating monocytes or macrophages.

Immunohistochemical detection of lymphocyte subpopulations in the tarsal joints of chickens with experimental viral arthritis.

We characterized the lymphocytes in the tarsal joint synovium of chickens inoculated with an arthrotropic strain of avian reovirus. Cryostat sections of whole joints taken from 2 days to 35 days postinoculation were analyzed using monoclonal antibodies directed against B lymphocytes, T lymphocytes, and chicken Ia antigen. Plasma cells were morphologically identified using stained sections of whole joints. Time-dependent changes were found in the type and number of positively staining cells. Synoviocytes and cells with a dendritic morphology stained positive for Ia in normal joint sections. T cells, mostly CD8 positive, were present in low numbers in acute phase arthritis (2-6 days postinfection) in the perivascular and superficial regions of the synovium. Subacute arthritis (8-14 days postinfection) was characterized by increased numbers of CD4 and Cd8 T cells in the perivascular and superficial regions. The perivascular T cells began to organize into aggregates, with IgM-positive B cells and plasma cells on the periphery of these aggregates. Some CD8-positive cells were detected on the surface of the articular cartilage. Cells staining positively for Ia were not lymphocytes. Chronic arthritis ( > 14 days postinfection) was characterized by large numbers of T cells in the perivascular and superficial regions, with the CD4-positive T cells found primarily in the lymphoid aggregates of the perivascular regions. IgM-positive B cells were fewer, but more plasma cells, few of which stained positive for IgM, were present. Lymphocytes in chronic arthritis stained positively for Ia. These data suggest that the types, numbers, and activation level of lymphocytes present in the tarsal joints are similar but not identical to those seen in rheumatoid arthritis.

Evaluation of serum and seminal plasma markers in the diagnosis of canine prostatic disorders.

Serum and seminal plasma concentrations or activities of acid phosphatase (AP), prostate specific antigen (PSA), and canine prostate specific esterase (CPSE) were measured in normal dogs, dogs with benign prostatic hyperplasia (BPH), dogs with bacterial prostatitis, and dogs with prostatic carcinoma to determine if these assays would be of value in differentiating dogs with prostatic carcinoma from normal dogs, and dogs with other prostatic disorders. In addition, tissue sections of prostatic adenocarcinomas were stained with antiprostatic AP, anti-CPSE, and anti-PSA antibodies to determine if these would be suitable immunohistochemical markers of prostatic carcinoma. Prostate-specific antigen was not detected in canine serum or seminal plasma. Serum and seminal AP activities did not differ significantly between normal dogs and those with prostatic diseases, or among dogs with different prostatic disorders. Serum CPSE activities were significantly higher in dogs with BPH than in normal dogs. Mean serum CPSE activities in dogs with BPH, bacterial prostatitis, and prostatic carcinoma were not significantly different from each other. Slight to moderate immunohistochemical staining of canine prostatic adenocarcinomas was noted for prostatic AP and PSA; most tumors did not stain for CPSE. These results show that proteins of prostatic origin appear in the serum of dogs as a result of prostatic pathology, especially BPH. Canine prostatic adenocarcinoma does not appear to be associated with significant increases in CPSE or AP activities, possibly because of down-regulation of these enzymes by prostatic carcinoma cells. It is also possible that failure to detect significant differences resulted from limited statistical power for some groups and pairwise analyses because of the small number of dogs evaluated.

Acid phosphatase activity of chondroclasts from Fusarium-induced tibial dyschondroplastic cartilage.

Tibial dyschondroplasia was induced in broiler chickens by oral administration of fusarochromanone, the toxic component of Fusarium equiseti. In two experiments, the activity of acid phosphatase in chondroclasts was assessed histochemically. Chicks were examined at 7, 14, 21, and 28 days of treatment in Expt. 1 and at 2, 4, and 6 days of treatment in Expt. 2. The staining for acid phosphatase was consistently lower in fusarochromanone-treated chicks after 2 days of treatment than in age-matched controls, and the onset of this difference corresponded to the onset of lesions. However, the decrease in acid phosphatase staining intensity was significant only at day 21 in Expt. 1 and at day 6 in Expt. 2. The deficiency of acid phosphatase in chondroclasts was judged to be of insufficient magnitude to account for the accumulation of growth plate cartilage that characterizes tibial dyschondroplasia.