Canine Distemper Virus Infection Research Articles

Dominating interleukin-10 mRNA expression induction in cerebrospinal fluid cells of dogs with natural canine distemper virus induced demyelinating and non-demyelinating CNS lesions

Canine distemper virus (CDV) infection in dogs is commonly associated with demyelinating leukoencephalitis (DL). Although the mechanism of primary demyelination in distemper remains undetermined recent studies showed a direct virus-induced cytolysis in early non-inflammatory and immune-mediated mechanisms in inflammatory lesions. To further investigate the pathogenesis of this morbillivirus-induced demyelination the expression of a variety of cytokine mRNA species (interleukin (IL)-1β, IL-2, IL-6, IL-10, IL-12, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β1, and interferon (IFN)-γ in cerebrospinal fluid cells of 12 dogs with CDV encephalitis was investigated employing reverse transcription-polymerase chain reaction (RT-PCR) and these findings were correlated to the type of CNS lesions. Neuropathology revealed the whole spectrum of distemper DL lesions from acute to chronic alterations, however, most plaques lacked active demyelination. Three control animals were devoid of any cytokine expression, whereas in distemper animals IL-10 transcripts were found in nine dogs with acute and chronic lesions. IL-6, TNF, and TGF mRNA was found in six, four, and three animals, respectively. IL-12 and IFN-γ, suggestive of a TH 1-like dominated immune response, were detected only in one animal with chronic lesions. Summarized, TNF and IL-6, associated with disease exacerbation, and IL-10 and TGF, indicative of remission, were often observed simultaneously in distemper DL and could not be assigned to a specific disease stage. However IL-10 mRNA remained the most frequently detected cytokine indicating a stage of inactivity in most animals investigated.

Oligodendroglial degeneration in distemper: apoptosis or necrosis?

Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. It was previously shown that the initial demyelinating lesions are directly virus induced since a correlation between the occurrence of demyelination and CDV replication in white matter cells was observed. During the course of infection oligodendrocytes undergo distinct morphological alterations, partly due to a restricted CDV infection of these cells, and eventually disappear from the lesions. This phenomenon has been described in vivo as well as in vitro. However, the reason for the morphological alterations and the following oligodendroglial depletion remained unclear. Since virus infection can induce cell death, it was investigated whether apoptosis or necrosis plays a role in the pathogenesis of demyelination in canine distemper. In brain tissue sections from dogs with acute distemper apoptotic cells were not detected within the demyelinating lesions using morphological and biochemical cell death criteria. In chronic distemper, apoptotic cells - presumably inflammatory cells - were seen within the perivascular cuffs. These in vivo findings were correlated to the in vitro situation using CDV-infected primary dog brain cell cultures as well as Vero cells. Infection with culture-adapted CDV lead to massive necrosis but not to apoptosis. After infection with virulent CDV neither apoptosis nor necrosis was a predominant feature in either culture system. These findings suggest that virus-induced demyelination in canine distemper is not the direct consequence of apoptosis or necrosis. It is speculated that another mechanism must be responsible for the observed morphological alterations of oligodendrocytes, ultimately leading to demyelination.

Detection of IgM antibodies against a recombinant nucleocapsid protein of canine distemper virus in dog sera using a dot-blot assay.

A dot-blot assay for the detection of IgM antibodies (ABs) against canine distemper virus (CDV) in canine serum is described. The diagnostic potential of this technique was evaluated by analysing sera from three test groups: (i) specific pathogen-free (SPF) beagle dogs experimentally infected with virulent CDV; (ii) SPF dogs immunized with a combined vaccine containing CDV, and (iii) SPF dogs immunized with a CDV-free vaccine. As antigen for the dot-blot assay we used the recombinant nucleocapsid protein (N protein) of the virulent A75/17 CDV strain. All 12 dogs of group 1, infected with virulent CDV, showed detectable CDV-specific IgM levels in their serum. All dogs of group 2 were also positive for anti-CDV IgM after the first immunization with the CDV-containing vaccine. The four dogs immunized with a CDV-free vaccine (group iii) remained negative throughout the course of the experiment. From these results, we conclude that the IgM detection test, which requires only a single serum sample, is a useful method for diagnosing current or recent CDV infection in CDV-infected or CDV-immunized dogs under experimental conditions.

Mucosal vaccination with recombinant poxvirus vaccines protects ferrets against symptomatic CDV infection

Canine distemper virus (CDV) infection of ferrets causes a disease characterized by fever, erythema, conjunctivitis and leukocytopenia, similar clinically to measles except for the fatal neurologic sequelae of CDV. We vaccinated juvenile ferrets twice at 4-week intervals by the intranasal or intraduodenal route with attenuated vaccinia (NYVAC) or canarypox virus (ALVAC) constructs containing the CDV hemagglutinin and fusion genes. Controls were vaccinated with the same vectors expressing rabies glycoprotein. Animals were challenged intranasally 4 weeks after the second vaccination with virulent CDV. Body weights, white blood cell (WBC) counts and temperatures were monitored and ferrets were observed daily for clinical signs of infection. WBCs were assayed for the presence of viral RNA by RT-PCR. Intranasally vaccinated animals survived challenge with no virologic or clinical evidence of infection. Vaccination by the intraduodenal route did not provide complete protection. All control animals developed typical distemper. Ferrets can be effectively protected against distemper by mucosal vaccination with poxvirus vaccines.

Early T cell response in the central nervous system in canine distemper virus infection.

The initial demyelinating lesions in canine distemper virus (CDV) infection develop during a period of severe immunosuppression in the absence of inflammation. In vitro and in vivo studies suggest that early demyelination is due to directly virus-induced oligodendroglial changes. In the present spatiotemporal study in experimentally CDV-infected dogs we observed diffuse up-regulation of T cells throughout the central nervous system (CNS) and T cell invasion in early demyelinating lesions. Invasion of T cells in the CNS occurred despite severe immunosuppression and without any perivascular cuffing. However, the major fraction of invading T cells correlated with sites of viral replication and coincided with the demonstration of an early immune response against the nucleocapsid protein of CDV. Activation of microglial cells was thought to have elicited the migration of T cells to the CNS by secretion of chemokines: marked IL-8 activity was found in the CSF of dogs with acute lesions. In areas of early demyelination, large numbers of CD3+ cells accumulated in the tissue in the absence of any morphological sign of inflammation. Whether the T cells at lesion sites contribute to the development of acute demyelination remains uncertain at this stage. Antiviral cytotoxicity was not apparent since viral clearance in demyelinating lesions is only effective when B cells and concurring antiviral antibody production appeared in the subacute and chronic inflammatory stage of the disease. CD3+ cells appear to persist for several weeks after infection since they were also found in recovered dogs that did not develop demyelination. Accumulation of immune cells, including a significant proportion of resting T cells (CD45RA+) in the CNS in the early stages of the disease may facilitate the later development of the intrathecal immune response and associated immunopathological complications.

Disease as a threat to endangered species: Ethiopian wolves, domestic dogs and canine pathogens

With increasing awareness of disease as an endangering process, an assessment of which pathogens might pose a problem and their patterns of infection in natural hosts is necessary. This paper examines the exposure of sympatric Ethiopian wolves (Canis simensis) and domestic dogs to canine distemper virus (CDV), canine adenovirus (CAV) and canine parvovirus (CPV) in the Bale region, Ethiopia and then relates these data to population trends of wolves. Wolves (n= 30) sampled between 1989 and 1992 had been exposed to CDV, CAV and CPV, but only CAV might be able to persist in this wolf population. Anecdotal and serological evidence suggested that an epidemic of CDV occurred in the dog population of the Bale Mountains National Park (BMNP) in 1992–93. All park dogs born since this time were seronegative to CDV, although some young dogs in the nearby urban population were seropositive. Despite evidence of CAV infection in wolves, none of the dogs sampled in the park were CAV seropositive, although this virus appeared highly seroprevalent and endemic in urban dogs. All dogs tested for CPV antibodies were seropositive. The BMNP wolf population declined in the late 1980s and early 1990s, with rabies responsible for a dramatic population reduction between 1990 and 1992. Although the population declined further up until 1995, it is not possible to assess whether the concurrent canine distemper epidemic in park dogs also affected wolves. Nevertheless, with evidence of rabies, CDV, CAV and CPV infections in sympatric domestic dogs and Ethiopian wolves, canid diseases clearly pose a significant threat to the future persistence of this Ethiopian wolf population.

Disease as a threat to endangered species: Ethiopian wolves, domestic dogs and canine pathogens

AbstractWith increasing awareness of disease as an endangering process, an assessment of which pathogens might pose a problem and their patterns of infection in natural hosts is necessary. This paper examines the exposure of sympatric Ethiopian wolves (Canis simensis) and domestic dogs to canine distemper virus (CDV), canine adenovirus (CAV) and canine parvovirus (CPV) in the Bale region, Ethiopia and then relates these data to population trends of wolves. Wolves (n= 30) sampled between 1989 and 1992 had been exposed to CDV, CAV and CPV, but only CAV might be able to persist in this wolf population. Anecdotal and serological evidence suggested that an epidemic of CDV occurred in the dog population of the Bale Mountains National Park (BMNP) in 1992–93. All park dogs born since this time were seronegative to CDV, although some young dogs in the nearby urban population were seropositive. Despite evidence of CAV infection in wolves, none of the dogs sampled in the park were CAV seropositive, although this virus appeared highly seroprevalent and endemic in urban dogs. All dogs tested for CPV antibodies were seropositive. The BMNP wolf population declined in the late 1980s and early 1990s, with rabies responsible for a dramatic population reduction between 1990 and 1992. Although the population declined further up until 1995, it is not possible to assess whether the concurrent canine distemper epidemic in park dogs also affected wolves. Nevertheless, with evidence of rabies, CDV, CAV and CPV infections in sympatric domestic dogs and Ethiopian wolves, canid diseases clearly pose a significant threat to the future persistence of this Ethiopian wolf population.

Cytokine mRNA expression in whole blood samples from dogs with natural canine distemper virus infection

Cytokines are soluble polypeptides with many physiological functions and a special role during infection and inflammation. Little is known about cytokine regulation in naturally occurring viral diseases of animals. Especially the role of cytokines in the development and progression of lesions in canine distemper virus (CDV) infection in dogs is largely unknown. Whole blood samples from 14 dogs with CDV infection and three dogs suffering from non-distemper diseases were examined for mRNA of pro-inflammatory cytokines such as interleukin-Iβ (IL-1), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-12 (IL-12), tumor necrosis factor-α (TNF), interferon-γ (IFN), and the anti-inflammatory transforming growth factor-β1 (TGF) using reverse transcription polymerase chain reaction (RT-PCR). Blood samples from the three dogs that showed no clinical abnormalities during a pre-vaccination physical examination served as control. CDV infection was confirmed by post-mortem immunohistochemistry for CDV nucleoprotein. The degree of immunoreactivity and the number of virus antigen positive organs were expressed as antigen index. IFN transcripts were not identified in any dog and IL-8 transcripts were present in RNA isolates from all 20 dogs. None of the other cytokines was detected in control animals. IL-1 and IL-6 were each found in one non-distemper dog and TGF transcripts were amplified in two dogs with non-distemper disease. The following transcripts were found in variable numbers in distemper dogs: IL-1 (7/14 dogs), IL-6 (3/14 dogs), IL-12 (3/14 dogs), TNF (8/14 dogs), and TGF (10/14 dogs) with multiple cytokines in ten dogs. No cytokine transcripts were detected in three distemper dogs. There was no obvious correlation between cytokine mRNA expression and respiratory and gastrointestinal tract diseases. In the CNS, demyelination was frequently associated with IL-1, IL-12, TNF and TGF mRNA expression in the blood. IL-6 transcripts were found only in animals with early CNS lesions and TGF was the only detectable cytokine in an animal with chronic demyelination. Lack of detectable cytokine transcripts in whole blood samples was associated with a high antigen index and viremia, indicating that an overwhelming virus infection may suppress cytokine production, possibly due to paralysis of the immune system. Simultaneous occurrence of pro- and anti-inflammatory cytokines in whole blood preparation from most of the dogs with distemper, indicated a complex most likely disease stage dependent orchestrated cytokine expression.

Serum distemper virus and parvovirus antibody titers among dogs brought to a veterinary hospital for revaccination

Objective To determine serum canine distemper virus (CDV) and canine parvovirus (CPV) antibody titers in healthy dogs brought to a veterinary hospital for revaccination. Design Case series. Animals 122 dogs. Procedure Serum antibody titers were measured by means of hemagglutination inhibition (CPV titers) or serum neutralization (CDV titers) at the time dogs were brought to the hospital for revaccination. All dogs had been vaccinated between 271 and 1,665 days previously. Dogs were grouped by age, breed (purebred vs mixed breed), sex, and weight to determine whether these factors were associated with antibody titers. Serum CPV titers ≥ 1:80 and serum CDV titers ≥ 1:96 were considered protective. Results Breed, sex, and weight were not significantly associated with serum CPV and CDV titers. Age was significantly associated with CPV titer, with younger dogs having higher titers, but was not associated with CDV titer. Thirty-three of 122 (27%; 95% confidence interval, 19.0 to 34.9%) dogs had a less-than-protective CPV titer. Twenty-five of 117 (21%; 95% confidence interval, 13.6 to 28.4%) dogs had a less-than-protective CDV titer. Clinical Implications Results suggest that, on the basis of serum antibody titers, the current practice of annual revaccination of dogs against CPV and CDV infection should be maintained. Measurement of antibody titers to determine whether revaccination is truly needed would seem justifiable in those dogs that have previously had an adverse reaction to vaccination. (J Am Vet Med Assoc 1998;213:72-75)

Bone-marrow changes in infectious diseases and lymphohaemopoietic neoplasias in dogs and cats—a retrospective study

Bone-marrow changes in infectious diseases due to feline infectious peritonitis virus (FIPV), feline immunodeficiency virus (FIV), parvovirus (PV, canine and feline) and canine distemper virus (CDV), and in the lymphohaemopoietic neoplasias (LHNs) usually associated with feline leukaemia virus infection were studied in samples obtained from 204 cats and 82 dogs at necropsy. The study demonstrated (1) no changes, (2) non-specific reactive changes, and (3) disease-specific changes (similar to those occurring in extramedullary sites) in: 51.2, 48.8 and 9.7% of 41 cases of FIPV infection, respectively; 0, 100 and 0% of nine cases of FIV infection, respectively; 1.3, 0 and 92% of 75 cases of canine PV infection, respectively; 5.3, 3.9 and 84% of 76 cases of feline PV infection, respectively; 71.4, 28.6 and 0% of seven cases of CDV infection, respectively; and 35.9, 52.6 and 11.5% of 78 cases of LHN, respectively. The distribution of the disease-specific bone-marrow changes was either diffuse or focal; diffuse changes were frequently found in cases of feline and canine PV infection, and focal changes were found inconsistently in FIPV infections and feline LHN. To the extent that the bone marrow showed any changes in FIV and CDV infections, they were mostly reactive and not pathognomonic.

Comparison of Risk Factors for Hypertrophic Osteodystrophy, Craniomandibular Osteopathy and Canine Distemper Virus Infection

SummaryAn analysis of hypertrophic osteodystrophy (HOD), craniomandibular osteopathy (CMO) and canine distemper virus (CDV) infection was undertaken. Risk factors (age, breed, sex, neuter status, weight, geographical and seasonal distribution) of the three diseases were determined and compared. Patient records were searched using the Veterinary Medical Database (VMDB) during the period of 1980 through 1989. This search identified 131 cases of HOD, 68 cases of CMO and 1,757 of CDV infection. Dogs less than six months of age were identified to be at greatest risk for HOD, CMO and CDV. The Great Dane, Cairn Terrier and the Greyhound were identified to be at highest risk for HOD, CMO and CDV infection, respectively. Males puppies were twice as likely to develop HOD. We concluded, from the risk factors analyzed, that risk factors for HOD, CMO or CDV infection were not similar.Patient information was obtained from clinical cases of 16 veterinary teaching hospitals to examine a possible relationship between Hypertrophic Osteodystrophy (HOD), Craniomandibular Osteopathy (CMO), and Canine Distemper Virus (CDV) infections. Risk factors for each disease were determined. Subjective comparison of risk factors for HOD and CMO did not support the notion of a relationship between HOD and CMO. In addition, no evidence for a possible relationship between CDV and HOD or CMO was found.

Oligodendroglial pathology in canine distemper.

Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. The mechanism of acute demyelination in distemper is still poorly understood. The initial demyelinating lesion in distemper is directly virus induced, since there is a clear correlation between the occurrence of demyelination and CDV replication in the cells of the white matter. Yet, there is little evidence for oligodendroglial infection. Changes of these cells have been reported in vitro and in vivo. The in vitro studies showed that – in contrast to other cells such as astrocytes and macrophages – oligodendrocytes hardly express CDV protein. However, we could show that these cells underwent a restricted infection with transcription of CDV RNA and that this phenomenon correlated with down-regulation of myelin gene transcription. The extension of these in vitro findings in vivo was obscured by the lack of reliable oligodendrocyte labelling techniques in canine brain tissue sections. In this study we combined immunohistochemistry with in situ hybridization to examine oligodendrocytes in demyelinating lesions and to investigate the question of oligodendrocyte infection in vivo. We could demonstrate that CDV infection leads to massive down-regulation of myelin gene expression in demyelinating lesions and that this effect correlates in part with a restricted infection of oligodendrocytes.

Inhibition of Tyrosine Hydroxylase Expression within the Substantia Nigra of Mice Infected with Canine Distemper Virus

Experimental infection of mouse brain with a neuroadapted strain of canine distemper virus (CDV) leads to early acute encephalitis, followed by late neurological diseases such as motor pathologies (paralysis and turning behavior) or obesity syndrome. We have previously shown that, during the early stage of infection, CDV replicates transiently in selective structures of the brain including the substantia nigra, a structure known to play a critical role in motor control. In this study we demonstrate that CDV replication in the substantia nigra induces an early decrease in transcript level of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis. The CDV infection of neuroblastoma cell culture, constitutively expressing TH, results in downregulation of TH transcription in the absence of cell death. In the few surviving mice with motor deficiencies, a pronounced decrease in TH expression is associated with a loss of dopaminergic cell bodies in the absence of any viral transcripts and proteins, suggesting that the initial CDV infection was sufficient to trigger irreversible neurodegenerative processes.

Protective vaccination of ferrets against canine distemper with recombinant pox virus vaccines expressing the H or F genes of rinderpest virus

Abstract Objective To investigate the ability of rinderpest virus (RPV) antigens, expressed in pox virus vectors, to protect against canine distemper virus (CDV) infection in ferrets. Animals Ferrets (Mustela putorius; n = 27) with no previous exposure to CDV. Procedure Ferrets were inoculated intradermally with recombinant vaccinia viruses expressing the H gene of RPV, the F gene of RPV, the H and F genes of RPV, or a fowlpox virus recombinant expressing both genes. Two ferrets were vaccinated SC with CDV vaccine as positive controls, and 1 group was left unvaccinated as a negative control. Blood was obtained from ferrets biweekly; antibody titer to RPV was detected by ELISA, and CDV antibody titer was measured by serum neutralization testing and ELISA. Results Partial protection was seen in all groups, with vRVFH vaccination being the most protective (60%). Conclusions and Clinical Relevance A single inoculation with a vaccinia virus expressing the H and F genes of RPV was able to protect 60% of the vaccinated ferrets challenge exposed with a high dose of CDV. These results indicate the ability of RPV antigens expressed by vaccinia virus to protect ferrets against a related morbillivirus. Further, they document the safety and efficacy of a recombinant vaccinia virus vaccine for ferrets. Such vaccines may be useful given the susceptibility of ferrets to CDV and the problem of maternal antibody interfering with vaccination of young animals. (Am J Vet Res 1997;58:590–593)

Determinants of persistence in canine distemper viruses

Viral persistence in the central nervous system is the driving force behind the chronic progressive disease caused by natural canine distemper virus (CDV) infection in dogs. Persistence of CDV is associated with non-cytolytic spread and impaired viral budding. Since budding is to a large extend dependent on the nucleocapsid- (N) and matrixproteins (M) of the virus, we analyzed the nucleotide- and deduced amino acid sequences of the corresponding genes of a spectrum of CDV strains, that differ with respect to virulence and persistence in vivo and in vitro. The wild type CDV ( A75 17 ), which is capable of causing a persistent infection in vivo was compared to two tissue culture adapted CDV strains (passaged A75 17-CDV and Rockborn-CDV), which retain a residual virulence and the capacity to spontaneously persist in vitro. A modified distemper virus (Snyder Hill-CDV), which is neurovirulent but not capable of causing a persistent infection in vivo, and an avianized virus (Onderstepoort-CDV) which is completely apathogenic and spreads by budding in cell cultures were also examined. Differences were found in the C-terminal of the nucleocapsid protein, which — comparing the two extremes of the spectrum (wild A75 17-CDV and OP-CDV) — lead to changes of the predicted protein structure. Such changes could affect the budding process and thus play a role in persistence. Marked changes in the M-gene were found in its non-coding region: the nucleotide sequences of the SH-CDV and OP-CDV differed considerably from the other three strains. Moreover, an additional second open reading frame was detected in the ‘non-coding’ region of the M gene in the wild A75-CDV, the two tissue culture adapted CDV strains and SH-CDV, but not in OP-CDV. The presence of this additional open reading frame correlated with the ability to cause a spontaneous persistent infection in vitro. Our findings support the notion that both N- and M-genes of CDV harbor determinants of viral persistence.

Phosphorylation of Canine Distemper Virus P Protein by Protein Kinase C-ζ and Casein Kinase II

Transcription by nonsegmented negative-strand RNA viruses is mediated by the viral RNA-dependent RNA polymerase and transcriptional cofactor P. The P protein is activated by phosphorylation, an event initiated by cellular kinases. The kinase used differs among this group of RNA viruses; vesicular stomatitis virus and respiratory syncytial virus utilize casein kinase II (CKII), whereas human parainfluenza virus type 3 utilizes PKC isoform zeta (PKC-ζ) for activation of its P protein. To identify the cellular kinase(s) involved in the phosphorylation of the canine distemper virus (CDV) P protein, we used recombinant CDV P in phosphorylation assays with native kinase activities present in CV1 cell extracts or purified CKII and PKC isoforms. Here, we demonstrate that the CDV P protein is phosphorylated by two cellular kinases, where PKC-ζ has the major and CKII the minor activities. In contrast, the P protein of another member of the morbillivirus genus, measles virus, is phosphorylated predominantly by CKII, whereas PKC-ζ has only minor activity. Selective inhibition of PKC-ζ activity within CV1 cells eliminated permissiveness to CDV replication, indicating anin vivorole for PKC-ζ in the virus replication cycle. The broad tissue expression of PKC-ζ parallels the pantropic nature of CDV infections, suggesting that PKC-ζ activity is a determinant of cellular permissiveness to CDV replication.

Abundant expression of viral nucleoprotein mRNA and restricted translation of the corresponding viral protein in inclusion body polioencephalitis of canine distemper

Brain and other tissues of three dogs aged 4-21 months with inclusion body polioencephalitis caused by canine distemper virus (CDV) were examined for CDV nucleoprotein (N) antigen and mRNA distribution. Two animals (nos 3 and 1) had suddenly shown central nervous system (CNS) signs 4 days and 5 months, respectively, after vaccination with a modified live CDV vaccine; animal no. 2 had shown similar signs 4 weeks after vaccination with an unknown product. Lesions in the CNS, which were restricted to the grey matter, occurred most frequently in the diencephalon, mesencephalon, medulla oblongata and, in one animal, in the cerebral cortex. Changes were characterized by mild to moderate perivascular lymphohistiocytic cuffs, loss of neurons, neuronal necrosis, glial nodules, and oedema. Intranuclear and cytoplasmic inclusion bodies, especially prominent in neurons, were observed. By in-situ hybridization, CDV N mRNA expression was confirmed with a non-radioactively labelled N-specific mRNA probe. The corresponding RNA translation product was detected immunohistochemically with a proteinspecific monoclonal antibody. Viral antigen and mRNA were observed in the same cell types and brain compartments. However, the number of cells expressing N mRNA exceeded the number of cells containing viral antigen greatly in two animals and slightly in one. Some areas with abundant viral mRNA expression were almost completely devoid of viral antigen. mRNA and the corresponding translation product were demonstrated in neurons and less frequently in astrocytes, but not in perivascular inflammatory cells. It would appear that distemper inclusion-body polioencephalitis may be due to a non-productive CDV infection of neurons, characterized by abundant expression of CDV N mRNA and reduced translation of the corresponding viral protein. These findings suggest that in distemper the pathogenesis of grey-matter lesions differs substantially from that of white-matter lesions, which constitute the most common manifestation of distemper encephalitis.

Distemper: not a new disease in lions and tigers

In light of recent canine distemper virus (CDV) epidemics, we set out to determine the historical significance of CDV infection in captive lions and tigers in Switzerland. The retrospective case material consisted of 42 lion and tiger necropsy cases from 1972 to 1992. Necropsy reports for all lions and tigers were reviewed. All existing paraffin tissues were immunohistochemically examined with a polyclonal antibody raised against CDV. The results for 19 of the 42 lions and tigers were classified as positive by immunohistochemistry; 23 results were negative or questionable. The results for four animals (three positive and one negative ) were further tested by in situ hybridization, and the results concurred with the immunohistochemistry findings. CDV infection of large cats is older and more widespread than previously thought. All large cats in captivity should be immunized even if canine distemper is not believed to be a problem for large cats in the area.

Canine distemper virus (CDV) infection of ferrets as a model for testing Morbillivirus vaccine strategies: NYVAC- and ALVAC-based CDV recombinants protect against symptomatic infection.

Canine distemper virus (CDV) infection of ferrets causes an acute systemic disease involving multiple organ systems, including the respiratory tract, lymphoid system, and central nervous system (CNS). We have tested candidate CDV vaccines incorporating the fusion (F) and hemagglutinin (HA) proteins in the highly attenuated NYVAC strain of vaccinia virus and in the ALVAC strain of canarypox virus, which does not productively replicate in mammalian hosts. Juvenile ferrets were vaccinated twice with these constructs, or with an attenuated live-virus vaccine, while controls received saline or the NYVAC and ALVAC vectors expressing rabies virus glycoprotein. Control animals did not develop neutralizing antibody and succumbed to distemper after developing fever, weight loss, leukocytopenia, decreased activity, conjunctivitis, an erythematous rash typical of distemper, CNS signs, and viremia in peripheral blood mononuclear cells (as measured by reverse transcription-PCR). All three CDV vaccines elicited neutralizing titers of at least 1:96. All vaccinated ferrets survived, and none developed viremia. Both recombinant vaccines also protected against the development of symptomatic distemper. However, ferrets receiving the live-virus vaccine lost weight, became lymphocytopenic, and developed the erythematous rash typical of CDV. These data show that ferrets are an excellent model for evaluating the ability of CDV vaccines to protect against symptomatic infection. Because the pathogenesis and clinical course of CDV infection of ferrets is quite similar to that of other Morbillivirus infections, including measles, this model will be useful in testing new candidate Morbillivirus vaccines.

In vivoandin vitroDetection of Canine Distemper Virus Nucleoprotein Gene with Digoxigenin‐Labelled RNA, Double‐Stranded DNA Probes and Oligonucleotides byin situHybridization

A single-stranded RNA, two double-stranded (ds) DNA probes and 10 oligonucleotides labelled with digoxigenin were comparatively evaluated for their usefulness to detect canine distemper virus (CDV) nucleoprotein RNA in in vitro infected Vero cells and in tissues of dogs with spontaneous CDV infection by in situ hybridization (ISH). In addition, results were compared to CDV nucleoprotein antigen distribution as demonstrated by immunohistochemistry. The RNA probe was derived from the virulent A75/17 strain, the DNA and oligonucleotide probes from the avirulent Onderstepoort strain of CDV. The two DNA probes were 287 and 126 base pairs long. For ISH, various factors including fixatives, proteolytic digestion, probe concentration, hybridization conditions and detection systems were compared. All probes were suitable for demonstration of CDV RNA in in vitro infected cells, regardless of the CDV strain employed. In vivo CDV nucleic acid was detected by RNA and the dsDNA probes. However, the probes varied substantially with respect to sensitivity and specificity. The CDV RNA probe was far superior in sensitivity when compared to the DNA probes. Furthermore, the shorter DNA probe displayed a higher sensitivity, indicating that length of the probe is an important parameter when selecting probes. Oligonucleotides displayed only rarely a positive signal and caused frequently hybridization signals in the nucleus, which where considered not specific for CDV. Summarized, the present study reveals that RNA probes are currently the most sensitive tool for detection of CDV RNA in tissues.