Clinicopathological findings in dogs with distemper encephalomyelitis presented without characteristic signs of the disease

Multiple Receptors Involved in Invasion and Neuropathogenicity of Canine Distemper Virus: A Review

The canine distemper virus (CDV) is a morbillivirus that infects a broad range of terrestrial carnivores, predominantly canines, and is associated with high mortality. Similar to another morbillivirus, measles virus, which infects humans and nonhuman primates, CDV transmission from an infected host to a naïve host depends on two cellular receptors, namely, the signaling lymphocyte activation molecule (SLAM or CD150) and the adherens junction protein nectin-4 (also known as PVRL4). CDV can also invade the central nervous system by anterograde spread through olfactory nerves or in infected lymphocytes through the circulation, thus causing chronic progressive or relapsing demyelination of the brain. However, the absence of the two receptors in the white matter, primary cultured astrocytes, and neurons in the brain was recently demonstrated. Furthermore, a SLAM/nectin-4-blind recombinant CDV exhibits full cell-to-cell transmission in primary astrocytes. This strongly suggests the existence of a third CDV receptor expressed in neural cells, possibly glial cells. In this review, we summarize the recent progress in the study of CDV receptors, highlighting the unidentified glial receptor and its contribution to pathogenicity in the host nervous system. The reviewed studies focus on CDV neuropathogenesis, and neural receptors may provide promising directions for the treatment of neurological diseases caused by CDV. We also present an overview of other neurotropic viruses to promote further research and identification of CDV neural receptors.

Apoptotic investigation of brain tissue cells in dogs naturally infected by canine distemper virus

Background

Canine distemper caused by canine distemper virus that belongs to the Morbillivirus genus of the Paramyxoviridae family is still a global epidemic significant infectious disease, especially in pet dogs in China and serious harm to the development of the dog industry. It has been known that apoptosis caused by the canine distemper virus can show in culture cells, lymphoid tissues, and the cerebellum. However, its occurrence in brain tissue cells remains unclear. To investigate the relationship among canine distemper infecting brain tissues, apoptosis in brain tissue cells, and demyelinating pathogenesis was investigated.

Methods

16 naturally infected dogs that exhibited clinical signs of CD and tested positive for the anti-CDV monoclonal antibody and six healthy dogs that served as the control, were used in the research. Brain specimens were divided into the cerebrum, brain stem, and cerebellum embedded in paraffin and made the sections respectively. Approximately 5 µm-thick sections were stained by hematoxylin–eosin, methyl green pyronin, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling technique, and immunohistochemistry. CDV nucleocapsid protein was detected by immune streptavidin-biotinylated peroxidase complex.

Results

Alterations in the brain tissues of CDV-infected dogs involved both various cells and nerve fibers. CDV had varying degrees of cytotropism to all brain tissue cells; apoptosis also occurred in all brain cells, especially in the endothelia of cerebral vessels, astrocytes, oligodendrocytes, and ependymal cells, the more serious infection, the more obvious apoptosis. Serious infections also involved the pyramidal and Purkinje cells. The nervous fibers exhibited demyelinating lesions (showed small multifocal vacuole), and some axonal neuron atrophy gradually disappeared (formed large vacuole).

Conclusions

Apoptosis in brain tissue cells was mainly related to the propagation path and cytotropism of CDV. The apoptosis of astrocytes, oligodendrocytes, and some neurons may play a significant role in the demyelinating pathogenesis in dogs with acute canine distemper. A lot of diverse nervous signs shown in the clinic may be related to different neuron apoptosis.

Immunohistochemical evidence of canine morbillivirus (canine distemper) infection in coatis (Nasua nasua) from Southern Brazil

The pathological and immunohistochemical (IHC) findings associated with infection due to canine morbilivírus (canine distemper virus, CDV) are described in coatis (Nasua nasua). Tissue fragments of coatis (n = 13) that died at the Bela Vista Sanctuary, Paraná, Southern Brazil, were routinely processed for histopathology to identify the main histopathologic patterns as compared to that of the domestic dog. Selected formalin-fixed paraffin-embedded (FFPE) tissue fragments of the lungs, liver, urinary bladder and small intestine were used in IHC assays designed to identify the antigens of CDV, canine adenovirus (CAdV-1 and CAdV-2) and canine parvovirus type 2 (CPV-2). The main histopathologic patterns identified were interstitial pneumonia (n = 9), interstitial nephritis (n = 6), atrophic enteritis (n = 4) and ballooning degeneration of the uroepithelium (n = 3). Positive immunolabelling for intralesional antigens of CDV was identified in the lung with interstitial pneumonia (n = 3), in the intestine (n = 2) and in the degenerated epithelium of the urinary bladder (n = 2). Antigens of CPV-2, CAdV-1 and CAdV-2 were not identified in any FFPE tissue sections evaluated. These findings indicate that these wild carnivores were infected by a viral disease pathogen common to the domestic dog and develop similar histopathologic findings. Collectively, these findings suggest that these coatis were infected by CDV and can serve as a potential host for this infectious disease pathogen.

Distemper Encephalomyelitis Presenting with Lower Motor Neuron Signs in a Young Dog

A 4 mo old spayed female mixed-breed dog was presented for focal lower motor neuron signs of the right forelimb and marked hyperesthesia on axillary palpation. Her signs progressed rapidly over the following days to diffuse lower motor neuron signs in all limbs and a seizure. MRI demonstrated a focal, slightly right-sided, 2.5 cm region of noncontrast-enhancing T2 hyperintensity and T1 isointensity at C4-C5 spinal cord segments. Imaging of the brain was unremarkable. The dog was euthanized as a result of poor prognosis. Polymerase chain reaction on cerebrospinal fluid and immunohistochemistry of brain tissue were both positive for canine distemper virus. This report documents an atypical presentation of canine distemper encephalomyelitis causing lower motor neuron signs and hyperesthesia.

Molecular and serological surveys of canine distemper virus: A meta-analysis of cross-sectional studies

BACKGROUND

Canine morbillivirus (canine distemper virus, CDV) persists as a serious threat to the health of domestic dogs and wildlife. Although studies have been conducted on the frequency and risk factors associated with CDV infection, there are no comprehensive data on the current epidemiological magnitude in the domestic dog population at regional and national levels. Therefore, we conducted a cross-sectional study and included our results in a meta-analysis to summarize and combine available data on the frequency and potential risk factors associated with CDV infection.

METHODS

For the cross-sectional study, biological samples from dogs suspected to have canine distemper (CD) were collected and screened for viral RNA. Briefly, the PRISMA protocol was used for the meta-analysis, and data analyses were performed using STATA IC 13.1 software.

RESULTS

CDV RNA was detected in 34% (48/141) of dogs suspected to have CD. Following our meta-analysis, 53 studies were selected for a total of 11,527 dogs. Overall, the pooled frequency of CDV positivity based on molecular and serological results were 33% (95% CI: 23-43) and 46% (95% CI: 36-57), respectively. The pooled subgroup analyses of clinical signs, types of biological samples, diagnostic methods and dog lifestyle had a wide range of CDV positivity (range 8-75%). Free-ranging dogs (OR: 1.44, 95% CI: 1.05-1.97), dogs >24 months old (OR: 1.83, 95% CI: 1.1-3) and unvaccinated dogs (OR: 2.92, 95% CI: 1.26-6.77) were found to be positively associated with CDV infection. In contrast, dogs <12 months old (OR: 0.36, 95% CI: 0.20-0.64) and dogs with a complete anti-CDV vaccination (OR: 0.18, 95% CI: 0.05-0.59) had a negative association.

CONCLUSION

Considering the high frequency of CDV positivity associated with almost all the variables analyzed in dogs, it is necessary to immediately and continuously plan mitigation strategies to reduce the CDV prevalence, especially in determined endemic localities.

Tropism and molecular pathogenesis of canine distemper virus

Background

Canine distemper virus (CDV), currently termed Canine morbillivirus, is an extremely contagious disease that affects dogs. It is identified as a multiple cell tropism pathogen, and its host range includes a vast array of species. As a member of Mononegavirales, CDV has a negative, single-stranded RNA genome, which encodes eight proteins.

Main body

Regarding the molecular pathogenesis, the hemagglutinin protein (H) plays a crucial role both in the antigenic recognition and the viral interaction with SLAM and nectin-4, the host cells’ receptors. These cellular receptors have been studied widely as CDV receptors in vitro in different cellular models. The SLAM receptor is located in lymphoid cells; therefore, the infection of these cells by CDV leads to immunosuppression, the severity of which can lead to variability in the clinical disease with the potential of secondary bacterial infection, up to and including the development of neurological signs in its later stage.

Conclusion

Improving the understanding of the CDV molecules implicated in the determination of infection, especially the H protein, can help to enhance the biochemical comprehension of the difference between a wide range of CDV variants, their tropism, and different steps in viral infection. The regions of interaction between the viral proteins and the identified host cell receptors have been elucidated to facilitate this understanding. Hence, this review describes the significant molecular and cellular characteristics of CDV that contribute to viral pathogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12985-019-1136-6) contains supplementary material, which is available to authorized users.

Molecular analysis of the full-length F gene of Brazilian strains of canine distemper virus shows lineage co-circulation and variability between field and vaccine strains

Canine distemper is a highly contagious systemic viral disease, with worldwide distribution that affects a wide variety of terrestrial carnivores. This study characterized full-length fusion (F) genes from 15 Brazilian wild-type canine distemper virus (CDV) strains collected between 2003-2004 (n = 6) and 2013-2016 (n = 9). Using deduced amino acid (aa) sequence analysis, 14 strains were classified into Europe 1/South America 1 (EU1/SA1) lineage, with a temporal clustering into past (2003-2004) and contemporary (2013-2016) strains. One strain clustered to Rockborn-like lineage, showing high similarity (98.5%) with the Rockborn vaccine strain. In analyzed strains, the fusion protein signal-peptide (Fsp) coding region was highly variable at the aa level (67.4%-96.2%). The Brazilian strains were more Fsp-divergent from the North America 1 (NA1) strains (24.5%-36.3%) than from the Rockborn (11.2%-14.9%) vaccine strain. Seventeen cysteine residues in the full-length F gene and four non-conserved glycosylation sites in the Fsp region were detected. The results reveal that past and contemporary CDV strains are currently co-circulating. This first analysis of full-length F genes from Brazilian wild-type CDV strains contributes to knowledge of molecular epidemiology of CDV viral infection and evolution.

Epidemiology and clinical presentation of canine distemper disease in dogs and ferrets in Australia, 2006-2014

OBJECTIVE

To determine the status and distribution of distemper in Australian dogs and ferrets.

DESIGN

Retrospective case series.

METHODS

Cases were identified via a national voluntary disease reporting system, veterinarian groups and a national laboratory database. The geographic distribution, seasonal distribution, signalment and clinical presentation of cases were described using maps and frequency distributions.

RESULTS

A total of 48 individually affected dogs and ferrets in 27 case groups were identified, including eight confirmed case groups (> one individual). Confirmed cases were more common in summer and on the central coast of New South Wales and southern Victoria, and occurred exclusively in young, unvaccinated dogs. For dogs there was no obvious sex predilection. A mortality rate of 100% in ferrets and up to 77% in dogs was estimated. Neurological, gastrointestinal and respiratory were the most commonly reported systems affected in dogs and ferrets. There was no evidence that any large, unreported outbreaks occurred during the study period.

CONCLUSIONS

Continuation of vaccination against canine distemper virus is justified within Australia, particularly for younger dogs. Veterinarians should continue to consider distemper in their differential diagnosis of cases with neurological, gastrointestinal and respiratory presentation.

Estudo epidemiológico e avaliação de fatores de risco da infecção por Toxoplasma gondii e achados clinico-patológicos da infecção aguda em cães admitidos em um Hospital Escola Veterinário

RESUMO: Esse trabalho teve como objetivo estudar a prevalência e respectivos fatores de risco para infecção do Toxoplasma gondii em cães provenientes de uma população hospitalar. Além disso, avaliou-se as taxas de ocorrência e as repercussões clínico-patológicas da infecção aguda pelo T. gondii nesses animais. Anticorpos foram detectados em 7% (26/386) da população estudada, composta de 386 cães de ambos os sexos e diferentes raças e idades. Somente as variáveis, ingestão de vísceras, origem rural e contato com bovinos apresentaram valores significativos com p<0.05. Adicionalmente os cães de origem rural apresentaram maiores risco (OD=7.00) de infecção do que aqueles de origem urbana. Em 6,5% (25/386) foram detectados títulos de contato (entre 16 e 256); esses títulos não significam necessariamente infecção aguda e sim apenas exposição prévia. É de fundamental importância o reconhecimento da infecção prévia por T. gondii nesses pacientes hospitalares. Dependendo da causa da admissão, mesmo não sendo a toxoplasmose a responsável, o paciente deve receber o tratamento anti-protozoário profilaticamente ou ser monitorado para posterior tratamento em caso de reagudização da enfermidade por recrudescência dos bradizoítos encistados. Apenas um animal (3.44%, 1/386) foi admitido com titulação elevada, o qual pode ser sugestivo de infecção aguda (titulo de 4096). Embora o animal com infecção aguda tenha sido apresentado com sinais neurológicos, cautela é necessária para não extrapolar uma falsa interpretação que a toxoplasmose é a grande responsável por quadros neurológico, uma vez que inúmeros outros casos incluídos nesse estudo tinham manifestações neurológicas e não tinham títulos de infecção aguda, nem mesmo título de contato prévio. A toxoplasmose aguda não foi uma afecção clínica expressiva nessa ambiência hospitalar, no entanto diagnóstico diferencial deve ser feito nos pacientes enfermos, principalmente os da área rural, e diagnostico definitivo deve ser alcançado para a correta conduta terapêutica.

Detection of respiratory viruses in shelter dogs maintained under varying environmental conditions

Three dog shelters in Rio Grande do Sul were investigated for associations between the occurrence of respiratory viruses and shelter environmental conditions. Nasal secretions randomly collected during the cold season were tested via PCR, and this data collection was followed by nucleotide sequencing of the amplicons. In shelter #1 (poor sanitary and nutritional conditions, high animal density and constant contact between dogs), 78% (58/74) of the nasal samples were positive, 35% (26/74) of which were in single infections and 44% (32/74) of which were in coinfections. Shelters #2 and #3 had satisfactory sanitary and nutritional conditions, outdoors exercise areas (#2) and animal clustering by groups (#3). In shelter #2, 9% (3/35) of the samples were positive for Canine parainfluenza virus (CPIV), and 6% (2/35) were positive for Canid herpesvirus 1 (CaHV-1). In shelter #3, 9% (7/77) of the samples were positive for Canine adenovirus type 2 (CAdV-2), and 1% (1/77) were positive for Canine distemper virus (CDV). The amplicon sequences (CPIV and CDV nucleoprotein gene; CAdV-2 E3 gene; CaHV-1 glycoprotein B gene) showed 94-100% nucleotide identity with GenBank sequences. Our results demonstrate that CPIV, CAdV-2 and CDV are common in dog shelters and that their frequencies appear to be related with environmental and nutritional conditions. These results indicate the need for control/prevention measures, including vaccination and environmental management, to minimize these infections and improve dog health.

Molecular detection and phylogenetic relationship of wild-type strains of canine distemper virus in symptomatic dogs from Uberlândia, Minas Gerais

This study investigated the occurrence of canine distemper virus (CDV) by evaluating the presence of viral RNA within urine samples of dogs from Uberlândia, MG, with clinical manifestations suggestive of infection by CDV by targeting the CDV N gene. Of the clinical samples collected ( n =33), CDV viruria was detected in 45.5%. Five dogs died spontaneously; all had characteristic CDV-associated histopathological alterations and demonstrated CDV viruria. Statistical analyses revealed that the age, gender, breed, or the organ system of the dog affected had no influence on the occurrence of canine distemper. Myoclonus and motor incoordination were the most significant neurological manifestations observed. A direct association was observed between keratoconjunctivitis and dogs with CDV viruria. These findings suggest that CDV viruria in symptomatic dogs might not be age related, and that symptomatic dogs can demonstrate clinical manifestations attributed to CDV without viruria identified by RT-PCR. Additionally, the results of the sequence identities analysed have suggested that all Brazilian wild-type strains of CDV currently identified are closely related and probably originated from the same lineage of CDV. Nevertheless, phylogenetic analyses suggest that there are different clusters of wild-type strains of CDV circulating within urban canine populations in Brazil.

Virological and serological findings in dogs with naturally occurring distemper

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The collection of suitable samples are crucial for Canine Distemper (CD) diagnosis.

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Urine proved to be the most suitable sample for CD diagnosis.

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The global epidemiology of CD reinforces the importance of an accurate diagnostic.

Canine distemper virus (CDV) is the cause of a severe and highly contagious disease in dogs. The unpredictable and variable course of CDV-related disease may hamper correct diagnosis of infection and makes it crucial the collection of samples suitable for laboratory confirmation. In the present study we were able to follow the disease in two dogs infected naturally, collecting different biological matrices during the entire period of infection. By real time RT-PCR, viral RNA was detected and quantified, suggesting that urine and rectal swabs would be useful for ante-mortem diagnosis of distemper in dogs, regardless of the clinical stage and form of the illness.

Detection and differentiation of field and vaccine strains of canine distemper virus using reverse transcription followed by nested real time PCR (RT-nqPCR) and RFLP analysis

Canine distemper virus (CDV) is the cause of a severe and highly contagious disease in dogs. Practical diagnosis of canine distemper based on clinical signs and laboratory tests are required to confirm CDV infection. The present study aimed to develop a molecular assay to detect and differentiate field and vaccine CDV strains. Reverse transcription followed by nested real time polymerase chain reaction (RT-nqPCR) was developed, which exhibited analytical specificity (all the samples from healthy dogs and other canine infectious agents were not incorrectly detected) and sensitivity (all replicates of a vaccine strain were positive up to the 3125-fold dilution - 10(0.7) TCID50). RT-nqPCR was validated for CDV detection on different clinical samples (blood, urine, rectal and conjunctival swabs) of 103 animals suspected to have distemper. A total of 53 animals were found to be positive based on RT-nqPCR in at least one clinical sample. Blood resulted in more positive samples (50 out of 53, 94.3%), followed by urine (44/53, 83.0%), rectal (38/53, 71%) and conjunctival (27/53, 50.9%) swabs. A commercial immunochromatography (IC) assay had detected CDV in only 30 conjunctival samples of these positive dogs. Nucleoprotein (NC) gene sequencing of 25 samples demonstrated that 23 of them were closer to other Brazilian field strains and the remaining two to vaccine strains. A single nucleotide sequences difference, which creates an Msp I restriction enzyme digestion, was used to differentiate between field and vaccine CDV strains by restriction fragment length polymorphism (RFLP) analysis. The complete assay was more sensitive than was IC for the detection of CDV. Blood was the more frequently positive specimen and the addition of a restriction enzyme step allowed the differentiation of vaccine and Brazilian field strains.

Atypical necrotizing encephalitis associated with systemic canine distemper virus infection in pups

This report describes the naturally occurring atypical neuropathological manifestation of systemic canine distemper virus (CDV) infection in two 16-day-old Pit Bull pups. CDV-induced changes affected the gray and white matter of the forebrain while sparing the hindbrain. Histologically, there was necrosis with destruction of the nervous parenchyma due to an influx of inflammatory and reactive cells associated with eosinophilic intranuclear inclusion bodies within glial cells. Positive immunoreactivity against CDV antigens was predominantly observed within astrocytes and neurons. RT-PCR was used to amplify CDV-specific amplicons from brain fragments. These findings suggest the participation of CDV in the etiopathogenesis of these lesions.

Neuropatologia da cinomose canina: 70 casos (2005-2008)

Este estudo teve como objetivo realizar uma investigação anátomo-patológica detalhada das lesões e sua distribuição no sistema nervoso central (SNC) de cães com cinomose. Foram avaliadas secções padronizadas do encéfalo e da medula espinhal de 70 cães. Os casos foram agrupados de acordo com a idade dos cães e classificados conforme a evolução das lesões. Os resultados permitem concluir que: (1) encefalomielite induzida pelo vírus da cinomose canina é mais prevalente em filhotes e adultos; (2) lesões macroscópicas no SNC ocorrem com baixa freqüência; (3) o encéfalo é mais acometido do que a medula espinhal; (4) as cinco regiões anatômicas mais afetadas do encéfalo são, em ordem decrescente de freqüência, o cerebelo, o diencéfalo, o lobo frontal, a ponte e o mesencéfalo; (5) a região anatômica mais afetada da medula espinhal é o segmento cervical cranial (C1-C5); (6) lesões subagudas e crônicas são mais comuns do que lesões agudas; (7) desmielinização é a lesão mais prevalente e ocorre principalmente no cerebelo, na ponte e no diencéfalo, quase sempre acompanhada de astrogliose e inflamação não-supurativa; (8) na maior parte dos casos em que há astrogliose, observam-se astrócitos gemistocíticos, freqüentemente com formação de sincícios; (9) leptomeningite não-supurativa, malacia e necrose cortical laminar são lesões relativamente freqüentes no encéfalo, mas não na medula espinhal; (10) corpúsculos de inclusão no encéfalo são muito comuns, ocorrem principalmente em astrócitos e com freqüência menor em neurônios; no entanto, independentemente da célula afetada, são vistos predominantemente no núcleo; (11) uma classificação da encefalite na cinomose com base em síndromes clínicas relacionadas com a idade do cão é imprecisa.

Pathogenesis and immunopathology of systemic and nervous canine distemper

Canine distemper is a worldwide occurring infectious disease of dogs, caused by a morbillivirus, closely related to measles and rinderpest virus. The natural host range comprises predominantly carnivores. Canine distemper virus (CDV), an enveloped, negative-sense RNA virus, infects different cell types, including epithelial, mesenchymal, neuroendocrine and hematopoietic cells of various organs and tissues. CDV infection of dogs is characterized by a systemic and/or nervous clinical course and viral persistence in selected organs including the central nervous system (CNS) and lymphoid tissue. Main manifestations include respiratory and gastrointestinal signs, immunosuppression and demyelinating leukoencephalomyelitis (DL). Impaired immune function, associated with depletion of lymphoid organs, consists of a viremia-associated loss of lymphocytes, especially of CD4+ T cells, due to lymphoid cell apoptosis in the early phase. After clearance of the virus from the peripheral blood an assumed diminished antigen presentation and altered lymphocyte maturation cause an ongoing immunosuppression despite repopulation of lymphoid organs. The early phase of DL is a sequel of a direct virus-mediated damage and infiltrating CD8+ cytotoxic T cells associated with an up-regulation of pro-inflammatory cytokines such as interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-alpha and IL-12 and a lacking response of immunomodulatory cytokines such as IL-10 and transforming growth factor (TGF)-beta. A CD4+-mediated delayed type hypersensitivity and cytotoxic CD8+ T cells contribute to myelin loss in the chronic phase. Additionally, up-regulation of interferon-gamma and IL-1 may occur in advanced lesions. Moreover, an altered balance between matrix metalloproteinases and their inhibitors seems to play a pivotal role for the pathogenesis of DL. Summarized, DL represents a biphasic disease process consisting of an initial direct virus-mediated process and immune-mediated plaque progression. Immunosuppression is due to early virus-mediated lymphocytolysis followed by still poorly understood mechanisms affecting antigen presentation and lymphocyte maturation.

Diagnostic investigation of emerging viruses of companion animals

In this article, the authors are specifically concerned with the timely and accurate detection of emerging diseases of small animals that are viral in origin. Veterinarians are bound to encounter emerging viruses in their practice. The problem is unavoidable, because viruses are highly mutagenic. Even the immune response dictates the nature of virus that evolves in a host. If the clinical signs and diagnostic methods fail to correlate, the veterinarian should work with the diagnostic laboratory to solve the diagnostic puzzle.