Immunohistochemical investigation of cerebellum in dogs infected with canine distemper virus

Pathological Study of Demyelination with Cellular Reactions in the Cerebellum of Dogs Infected with Canine Distemper Virus

The purpose of this study was to examine the relationship between demyelination and cellular reactions in the cerebellum of Canine Distemper Virus (CDV)-infected dogs. We subdivided the disease staging by adding the degree of demyelination determined by Luxol Fast Blue staining to the previously reported disease staging from the acute stage to the chronic stage, and investigated the relationship between demyelination in the cerebellum and the number and histological changes in astroglia, microglia, and Purkinje cells in each stage. Reactions of astrocytes and microglia were observed at an early stage when demyelination was not evident. Changes progressed with demyelination. Demyelination initially began in the medulla adjoining the fourth ventricle and gradually spread to the entire cerebellum, including the lobes. CDV immune-positive granules were seen from the early stage, and inclusion bodies also appeared at the same time. CDV immune-positive reaction and inclusion bodies were observed in astrocytes, microglia, neurons, ependymal cells, and even leptomeningeal mononuclear cells. On the other hand, infiltration of CDV-immunoreactive particles from the pia mater to the gray matter and further into the white matter through the granular layer was observed from an early stage. Purkinje cells decreased from the intermediate stage, and a decrease in cells in the granular layer was also observed. There was no clear association between age and each stage, and the stages did not progress with age.

Controversial results of the genetic analysis of a canine distemper vaccine strain

Canine distemper (CD) is a highly contagious, often fatal, multisystemic viral disease of receptive carnivores. The presence of a PsiI cleavage site on a specific location of the hemagglutinin (H) gene was found to be a hallmark of vaccine strains, thus, a previously published restriction fragment length polymorphism (RFLP) test using PsiI theoretically allows the distinction between all currently used vaccine strains and virulent field strains. The RFLP test was carried out on all brands of CD vaccines available in Hungary. The present work describes the extensive sequencing and phylogenetic study of the strain present in Vanguard (Pfizer Animal Health) vaccines, which following the PsiI based RFLP test reacted as a wild-type strain. Based on the product description provided by the manufacturer, all batches should have contained a virus strain (Snyder Hill) belonging to the group of vaccine strains (America-1). Extensive genetic analysis involving the full nucleic acid sequence of four other genes (N, M, P and F) of the CDV genome revealed that the incriminated virus strain showed a higher level of genetic identity to wild-type strains from the America-2 group than to any of the strains belonging to America-1 group, therefore the vaccine does not contain the virus strain stated by the manufacturer in its product description and has not been containing it since at least 1992.

Immunohistochemical distribution of alpha B-crystallin in the cerebellum of dogs infected with canine distemper virus

The cerebella of 12 dogs infected with canine distemper virus (CDV) and those of three normal dogs were examined. The avidin-biotin-peroxidase complex technique was used to detect alphaB-crystallin (alphaB-c) immunoreactivity and immunolocalisation of the CDV antigen. CDV antigens, immunopositive astrocytes, oligodendrocytes and granular neurons were seen in both the white and grey matter of the infected dogs. In the controls, alphaB-c immunopositive glial cells were seen in the white matter and around the Purkinje cells. In dogs with distemper, alphaB-c immunoreactivity was not observed in some of the glial cells around the Purkinje cells. A significant negative correlation of P < 0.01 level was found between areas of severe demyelination and the number of alphaB-c immunopositive cells in dogs infected with CDV. Such correlation was not observed between mild and moderate demyelinating areas and alphaB-c immunostaining. The alphaB-crystallin/ total number of cells ratio was found to be significant in severely affected demyelinating areas (P < 0.05). These data indicate that there was a relationship between the degrees of CDV associated with demyelination and the level of alphaB-c expression in the glial cells.

Genetic diversity of Hungarian canine distemper virus strains

To achieve proper diagnosis of dogs based on acute clinical symptoms and poorly preserved field samples taken from animals that died due to canine distemper (CD), a new differential diagnostic test has been developed based on polymerase chain reaction (PCR). In this study, more than 150 samples collected from dogs showing respiratory, gastrointestinal and neurological signs suggesting canine distemper virus (CDV) infection were examined. The samples consisted of urine, blood and nasal swabs collected from clinically ill patients, sent to our laboratory by clinicians from various veterinary clinics throughout Hungary. Various organs collected during the necropsy of dogs with pathological changes that suggested CDV infection were also included. Three distinct PCRs were designed. For diagnostic purposes, a primer pair specific to a 409 bases-long segment within the conservative part of the large polymerase region (L) of the CDV genome was designed. Using this test, out of the 150 analyzed samples, 46 (30.66%) proved to be positive for CDV, indicating that CDV still represents a high risk to the canine population in Hungary. For the phylogenetical analysis, a primer pair that completely encompasses the hemagglutinin (H) gene of the CDV genome was designed. The amplicons of this region were sequenced in both directions using the appropriate primers. Our results indicate that several different CDV genotypes are currently present in Hungary. Nine of the analyzed Hungarian strains turned out to belong to the so-called Arctic group of CDVs, and were most closely related to non-European strains from North America, China and Greenland, as well as to the phocine distemper virus 2 (PDV-2) isolated from Baikal seals (Phoca sibirica). One of the Hungarian strains showed high similarity to other European isolates from Denmark, Germany, Italy and Turkey, as well as to other isolates from geographically more distant regions, such as the USA. Three Hungarian strains seem to join a new cluster that is formed by only a couple of strains, one isolated from a mink in Denmark, and another from a dog in North America. Using a third set of primers, a restriction fragment length polymorphism (RFLP) assay has also been designed for the fast and reliable differentiation of the wild-type CDVs from the vaccine strains.

Cerebellum progesterone concentration decreased in canine distemper virus infection

Progesterone has neuroprotective effects including augmentation of myelination in the central and peripheral nervous system. This study was designed to determine if demyelinating lesions in the cerebellum resulting from canine distemper virus (CDV) infection are associated with progesterone levels. Progesterone was measured using radioimmunoassay in samples of the cerebellum, corpus callosum, medulla oblongata, parietal, frontal, temporal, and occipital cortices as well as cerebrospinal fluid (CSF) and plasma collected from ten CDV infected and six non-infected dogs. The cerebellum progesterone level was significantly different between CDV infected (0.66+/-0.09 ng/g) and control dogs (1.14+/-0.09 ng/g) (p<0.001); however, no difference was observed for the other CNS regions, plasma and CSF (p>0.05). The cerebellum progesterone level was also significantly different between acute (0.71+/-0.0 5 ng/g) and chronic cases (0.61+/-0.09 ng/g) (p<0.05). The CDV infected cerebella were also categorized histopathologically according to the severity of demyelinating lesions as mild (n=5), moderate (n=2), or severe (n=3) among which the cerebellum progesterone level was significantly different (p<0.05). Progesterone concentration was 0.71+/-0.05 ng/g in mild, 0.65+/-0.10 ng/g in moderate, and 0.56+/-0.07 ng/g in severe cases. In conclusion, progesterone concentration decreases in the cerebellum in CDV infection and the severity of demyelinating lesions is the greatest in cerebella with the lowest progesterone concentrations. The results suggest that local impairment of progesterone metabolism may be associated with the initiation and progression of cerebellar lesions in CDV infection.