Allele frequency of a genetic risk variant for necrotizing meningoencephalitis in pug dogs from Europe and association with the clinical phenotype

Introduction

Necrotizing meningoencephalitis (NME) in pugs is a potentially fatal disease, which needs lifelong treatment with immunosuppressive or immunomodulatory drugs and shares parallels with acute fulminating multiple sclerosis. Genetic variants of the DLA class II gene are associated with an increased risk for NME. Genetic testing is recommended prior to breeding. The aim of this study was to describe the current allele frequency of a previously identified NME risk variant in the European pug population. A secondary aim was to investigate the association of the NME risk variant with the clinical phenotype in pugs.

Methods

Results of genetic testing for the CFA12:2605517delC variant in European pugs between 2012 and 2020 were retrieved (n = 5,974). A validated questionnaire was mailed to all submitters of samples for further information on neurological signs, diagnostic tests, and disease course.

Results

The allele frequency of the CFA12 NME risk variant was 25.7% in the European pug population dogs; 7.4% of the dogs were homozygous and 36.7% were heterozygous for the NME risk variant on CFA12. Completed questionnaires were available in 203 dogs including 25 dogs with epileptic seizures or other neurological signs. The clinical phenotype was consistent with NME in 3.9% with a median age of onset of 1.0 years, and indicative of idiopathic epilepsy in 2.9% with a median onset of 2.5 years. Eleven dogs remained unclassified. Pugs with the NME phenotype were significantly more frequently homozygous for the NME risk variant on CFA12 compared to pugs ≥6 years without neurological signs or seizures (p = 0.008).

Discussion

The CFA12:2605517delC genetic risk variant is widely distributed in the European pug population and frequently homozygous in pugs with a NME phenotype. The data support the clinical relevance of the CFA12:2605517delC genetic risk variant.

Immunohistochemical evaluation of fibrin/fibrinogen, d-dimers, and intravascular thrombosis in brains of dogs with meningoencephalitis of unknown origin

Granulomatous meningoencephalitis (GME) and necrotizing encephalitides (NE) are the most common immune-mediated inflammatory diseases of the central nervous system in dogs. Activation of the fibrinolytic system in multiple sclerosis, a similar immune-mediated disease affecting the central nervous system in humans, seems to be related to disease progression. The aim of this study was to identify fibrin/fibrinogen and D-dimer deposition, as well as presence of intravascular thrombosis (IVT) in brains of dogs with a diagnosis of GME or NE. Immunohistochemical studies using antibodies against fibrin/fibrinogen and D-dimers were performed. Statistical analyses were performed to determine whether there were differences in the presence and location of fibrin/fibrinogen, D-dimers deposits, and IVT between GME and NE. Samples from sixty-four dogs were included in the study: 32 with a diagnosis of GME and 32 with a diagnosis of NE. Fibrin/fibrinogen depositions were detected in all samples and d-dimers were detected in 43/64 samples. IVT was present in 29/64 samples, with a significantly higher score in samples from dogs with NE than in samples from dogs with GME (P = 0.001). These data support hemostatic system activation in both diseases, especially NE. This finding might be related to the origin of the necrotic lesions seen in NE, which could represent chronic ischemic lesions. Further studies are needed to investigate the association between vascular lesions and the histopathological differences between GME and NE and the hemostatic system as a potential therapeutic target.

A shortened whole brain radiation therapy protocol for meningoencephalitis of unknown origin in dogs

Introduction

A variety of treatment options have been described for canine meningoencephalitis of unknown origin (MUO). Few studies focused on radiation therapy as a second line immunomodulating treatment, implicating its effective use. However, a standard radiation therapy protocol is lacking, and further research will help to evaluate the effect of different dose regimens.

Methods

Ten dogs diagnosed with MUO based on MRI and CSF findings were prospectively enrolled. The dogs were treated with a shortened whole brain radiation therapy protocol (5 × 4 Gy) in combination with prednisolone. Neurologic changes were quantified using an established scoring scheme. Follow-up MRI and CSF examination was scheduled three months after radiation therapy. Overall survival and time to progression were calculated. Histopathology of the brain was performed in case of death.

Results

Seven dogs were diagnosed de novo and three had a history of relapsing MUO. Neurological status improved in all 10 dogs during radiation therapy, with 4/10 returning to normal shortly after radiation therapy. Three dogs died within the first three months after radiation therapy. At follow-up MRI lesions completely resolved in two dogs, partially resolved in five dogs, and progressed in one dog. After follow-up MRI, dogs were further treated with prednisolone monotherapy (two dogs) and additional immunosuppressant drugs (five dogs). Overall, four dogs showed disease progression, with a mean time to progression of 691 days (95%CI: 396-987) and mean overall survival for all dogs was 723 days (95%CI: 436-1011) (both medians not reached). Histopathology confirmed MUO in three dogs but was suggestive for oligodendroglioma in one dog. Radiation induced side effects were not seen.

Conclusion

Shortened whole-brain radiation therapy could be an additional treatment option for MUO in conjunction to prednisolone, specifically for cases that require rapid relief of symptoms and with relapsing history.

Concomitant necrotizing encephalitis and granulomatous meningoencephalitis in four toy breed dogs

The term “meningoencephalitis of unknown origin” (MUO) describes a group of different encephalitides in dogs in which no infectious agent can be identified and a multifactorial etiology is suspected. Among others, genetic factors and unknown triggers seem to be involved. Included are necrotizing leukoencephalitis (NLE), necrotizing meningoencephalitis (NME), and granulomatous meningoencephalitis (GME). In this case series, we describe the histopathological findings of four toy breed dogs with focal or multifocal necrotizing encephalitis and mainly lymphocytic perivascular infiltrates on histopathological examination. At the same time, however, in all dogs, focal or multifocal high-grade angiocentric granulomatous inflammatory lesions were evident with focal histiocytic perivascular infiltrates in the brain. The former changes are typical for NLE and NME. In contrast, the latter changes are indicative of GME. This case series shows that the boundaries between the necrotizing and granulomatous variants of MUO might be smooth and suggests that NLE, NME, and GME are not as distinct as previously described. This finding could be a crucial piece of the puzzle in the study of the pathogenesis of MUO as individual susceptibility and specific triggers could be responsible for the manifestation of the different MUO subtypes.

Case report: Lympho-histiocytic meningoencephalitis with central nervous system vasculitis of unknown origin in three dogs

Meningoencephalitis of unknown origin (MUO) is an umbrella term for a variety of subtypes of meningoencephalitis of dogs and cats with no identifiable infectious agent. In dogs, granulomatous meningoencephalitis (GME), necrotizing meningoencephalitis (NME), and necrotizing leukoencephalitis (NLE) are the most commonly reported subtypes. However, sporadically there are reports about other subtypes such as greyhound encephalitis or eosinophilic meningoencephalitis. The following case series presents three dogs with peracute to acute progressive signs of encephalopathy. The magnetic resonance imaging (MRI) of two dogs (post mortem n = 1/2) showed severe, diffuse swelling of the cortical gray matter with increased signal intensity in T2weighted (w) and fluid-attenuated inversion recovery (FLAIR) and decreased signal intensity in T1w. Additionally, focal to multifocal areas with signal void in both dogs and caudal transforaminal herniation of the cerebellum in one dog was observed. Post mortem histopathological examination revealed lympho-histiocytic encephalitis and central nervous system (CNS) vasculitis in all dogs. No infectious agents were detectable by histopathology (hematoxylin and eosin stain), periodic acid-Schiff reaction (PAS), Ziehl-Neelsen stain and immunohistochemistry for Canine adenovirus-1, Parvovirus, Listeria monocytogenes, Parainfluenzavirus, Toxoplasma gondii, Herpes-suis virus, Pan-Morbillivirus, Tick born encephalitis virus, Severe acute respiratory syndrome coronavirus (SARS-CoV) 2. Furthermore, two dogs were tested negative for rabies virus. To the best of the authors' knowledge, this is the first report of a lympho-histiocytic encephalitis with CNS vasculitis with no identifiable infectious agent. It is suggested to consider this as an additional subtype of MUO with severe clinical signs.

Leukocyte and cytokine variables in asymptomatic Pugs at genetic risk of necrotizing meningoencephalitis

BACKGROUND

Necrotizing meningoencephalitis (NME, aka Pug dog encephalitis) is an inflammatory brain condition associated with advanced disease at initial presentation, rapid progression, and poor response to conventional immunomodulatory therapy.

HYPOTHESIS/OBJECTIVES

That genetic risk for NME, defined by a common germline DNA haplotype located on chromosome 12, is associated with altered blood cytokine concentrations and leukocyte subsets in asymptomatic Pugs.

ANIMALS

Forty Pug dogs asymptomatic for NME from a hospital sample.

METHODS

Prospective observational cohort study, including germline genome-wide genotyping, plasma cytokine determination by multiplexed profiling, and leukocyte subset characterization by flow cytometric analysis.

RESULTS

Seven (18%) dogs were high risk, 10 (25%) medium risk, and 23 (58%) low risk for NME, giving a risk haplotype frequency of 30%. High and medium risk Pugs had significantly lower proportion of CD4+ T cells (median 22% [range, 7.3%-38%] vs 29% [range, 16%-41%], P = .03) and higher plasma IL-10 concentrations than low-risk Pugs (median 14.11 pg/mL [range, 9.66-344.19 pg/mL] vs 12.21 pg/mL [range, 2.59-18.53 pg/mL], P = .001). No other variables were significantly associated with the NME haplotype-based risk.

CONCLUSIONS AND CLINICAL IMPORTANCE

These data suggest an immunological underpinning to NME and a biologic rationale for future clinical trials that investigate novel diagnostic, preventative, and therapeutic strategies for this disease.

Evaluation of treatment with a combination of mycophenolate mofetil and prednisolone in dogs with meningoencephalomyelitis of unknown etiology: a retrospective study of 86 cases (2009-2017)

BACKGROUND

Combination therapy with glucocorticoids and adjunctive immunomodulating drugs has been generally accepted as a standard treatment regimen for meningoencephalomyelitis of unknown etiology (MUE). We hypothesized that treatment with MMF as an adjunctive agent along with glucocorticoids would be effective and well-tolerated protocol in dogs with MUE. Eighty-six dogs with MUE between May 2009 and June 2017 were included (59 females and 27 males; mean age of 5.93 years; mean body weight of 3.83 kg). The medical records of dogs with MUE treated with prednisolone and MMF were retrospectively evaluated to determine the therapeutic response, survival time, and treatment-related adverse effects.

RESULTS

A partial or complete response (CR) was recorded for 75 dogs. The overall median survival time from the initiation of treatment was 558 days. Dogs that showed CR with no relapse over the treatment period (from diagnosis to death) had significantly longer median survival times. A significantly higher mortality hazard ratio of 4.546 was recorded in dogs that failed to achieve CR. The interval between the onset of clinical signs and the clinical presentation was not significantly associated with CR, relapse rate, and survival time. Adverse effects included gastrointestinal upsets in 26 dogs (30.23%), sporadic infections in 17 dogs (19.77%), and pancreatitis in seven dogs (8.14%).

CONCLUSIONS

The results suggest that adjunctive MMF treatment for MUE is safe and comparable to other immunosuppressive protocols. The treatment should focus on the achievement of CR and preventing relapse for successful management.

Prognostic Factors for Recovery of Vision in Canine Optic Neuritis of Unknown Etiology: 26 Dogs (2003-2018)

Optic neuritis (ON) is a recognized condition, yet factors influencing recovery of vision are currently unknown. The purpose of this study was to identify prognostic factors for recovery of vision in canine ON of unknown etiology. Clinical databases of three referral hospitals were searched for dogs with presumptive ON based on clinicopathologic, MRI/CT, and fundoscopic findings. Twenty-six dogs diagnosed with presumptive ON of unknown etiology, isolated (I-ON) and MUE-associated (MUE-ON), were included in the study. Their medical records were reviewed retrospectively, and the association of complete recovery of vision with signalment, clinicopathologic findings, and treatment was investigated. Datasets were tested for normality using the D'Agostino and Shapiro-Wilk tests. Individual datasets were compared using the Chi-squared test, Fisher's exact test, and the Mann-Whitney U-test. For multiple comparisons with parametric datasets, the one-way analysis of variance (ANOVA) was performed, and for non-parametric datasets, the Kruskal-Wallis test was performed to test for independence. For all data, averages are expressed as median with interquartile range and significance set at p < 0.05. Twenty-six dogs met the inclusion criteria. Median follow-up was 230 days (range 21–1901 days, mean 496 days). Six dogs (23%) achieved complete recovery and 20 dogs (77%) incomplete or no recovery of vision. The presence of a reactive pupillary light reflex (p = 0.013), the absence of fundoscopic lesions (p = 0.0006), a younger age (p = 0.038), and a lower cerebrospinal fluid (CSF) total nucleated cell count (TNCC) (p = 0.022) were statistically associated with complete recovery of vision. Dogs with I-ON were significantly younger (p = 0.046) and had lower CSF TNCC (p = 0.030) compared to the MUE-ON group. This study identified prognostic factors that may influence complete recovery of vision in dogs with ON. A larger cohort of dogs is required to determine whether these findings are robust and whether additional parameters aid accurate prognosis for recovery of vision in canine ON.

Clinical presentation, diagnostic findings, prognostic factors, treatment and outcome in dogs with meningoencephalomyelitis of unknown origin: A review

Meningoencephalomyelitis of unknown origin (MUO) encompasses a group of idiopathic, most likely immune mediated, inflammatory central nervous system diseases that cause clinical, diagnostic and treatment challenges to veterinary neurologists. Clinical criteria for obtaining this presumptive diagnosis are currently available, and multiple treatment protocols have previously been investigated in small (prospective or retrospective) case series. As this group of diseases is considered fatal if left untreated, the identification of clinically usable prognostic indices could be of great value. This review provides an overview of recent developments in the clinical presentation, diagnostic findings, possible prognostic factors, treatment and outcome in dogs diagnosed with MUO.

Seizure occurrence in dogs under primary veterinary care in the UK: prevalence and risk factors

Background

Primary‐care veterinary clinical records can offer data to determine generalizable epidemiological data on seizures occurrence in the dog population.

Objectives

To identify and examine epidemiologic characteristics of seizure occurrence in dogs under primary veterinary care in the UK participating in the VetCompass™ Programme.

Animals

455,553 dogs in VetCompass™’.

Methods

A cross‐sectional analysis estimated the 1‐year period prevalence and risk factors for dogs with seizures during 2013.

Results

The overall 1‐year period prevalence for dogs having at least one seizure during 2013 was 0.82% (95% CI 0.79‐0.84). Multivariable modelling identified breeds with elevated odd ratios [OR] compared with the Labrador Retriever (e.g. Pug OR: 3.41 95% CI 2.71‐4.28, P < 0.001). Males had higher risk for seizures (Male/Entire OR: 1.47 95% CI 1.30–1.66; Male/Neutered OR: 1.34 95% CI 1.19–1.51) compared to entire females. Age (3.00 ‐ ≤ 6.00 OR: 2.13 95% CI 1.90‐2.39, P < 0.001, compared to animals aged 0.50–≤ 3.00 years), and bodyweight (≥ 40.00kg, OR: 1.24 95% CI 1.08–1.41, P = 0.002, compared to animals weighing < 10.0 kg) were identified as risk factors for seizures.

Conclusion and clinical Importance

Seizures are a relatively common clinical finding in dogs. The results for breed, age, sex and bodyweight as risk factors can assist veterinarians in refining differential diagnosis lists for dogs reported with behaviors that may have been seizures. In addition, the prevalence values reported here can support pharmacovigilance with baseline data from the overall population.

Breed-Specific Magnetic Resonance Imaging Characteristics of Necrotizing Encephalitis in Dogs

Diagnosing necrotizing encephalitis, with its subcategories of necrotizing leukoencephalitis and necrotizing meningoencephalitis, based on magnetic resonance imaging alone can be challenging. However, there are breed-specific imaging characteristics in both subcategories that allow establishing a clinical diagnosis with a relatively high degree of certainty. Typical breed specific imaging features, such as lesion distribution, signal intensity, contrast enhancement, and gross changes of brain structure (midline shift, ventriculomegaly, and brain herniation) are summarized here, using current literature, for the most commonly affected canine breeds: Yorkshire Terrier, French Bulldog, Pug, and Chihuahua.

Clinical presentation, diagnostic findings and long-term survival in large breed dogs with meningoencephalitis of unknown aetiology

Although several studies indicate that meningoencephalitis of unknown aetiology (MUA) might affect every dog breed at every age, little is known about clinical presentation, diagnostic findings and long-term survival in large breed dogs. The aim of this study was therefore to compare the clinical presentation, diagnostic findings and long-term survival between large and small/medium breed dogs diagnosed with MUA. One hundred and eleven dogs met the inclusion criteria. 28 (25 per cent) dogs were considered large breed dogs compared with 83 (75 per cent) small/medium breed dogs. Large breed dogs presented significantly more often with a decreased mentation. Age, gender, duration of clinical signs prior to diagnosis, presence of seizures or cluster seizures, variables on complete blood count and cerebrospinal fluid analysis, and all variables on MRI were not significantly different between small/medium and large breed dogs. Median survival time was 281 and 106 days for the large and small/medium breed dogs, respectively, with no significant difference in survival curves for both groups. Although considered not typically affected by MUA, 25 per cent of dogs included in this study were considered large breed dogs. Therefore, MUA should be included in the differential diagnosis for large breed dogs presenting with intracranial neurological signs. If diagnosed with MUA, large breed dogs also carried a guarded prognosis.

Necrotizing meningoencephalitis in a large mixed-breed dog

CASE DESCRIPTION

A 4-year-old 26-kg (57.2-lb) spayed female Staffordshire Bull Terrier mix was evaluated because of a 24-hour history of cluster seizures.

CLINICAL FINDINGS

Neurologic examination revealed altered mentation and multifocal intracranial signs; MRI was performed. The MRI findings included multifocal, asymmetric forebrain lesions affecting both the gray and white matter, an area suggestive of focal necrosis, and loss of corticomedullary distinction. A midline shift and caudal transtentorial herniation were noted, suggestive of greater than normal intracranial pressure.

TREATMENT AND OUTCOME

Because the dog's clinical signs worsened despite medical treatment and additional evidence of increased intracranial pressure, bilateral craniectomy and durectomy were performed. Histologic evaluation of a brain biopsy specimen revealed bilateral and asymmetric areas of necrosis in the subcortical white matter and adjacent gray matter. At the periphery of the necrotic areas, there was increased expression of glial fibrillary acidic protein and Virchow-Robin spaces were expanded by CD3+ lymphocytes. Results of immunohistochemical analysis of brain tissue were negative for canine distemper virus, Neospora canis, and Toxoplasma gondii. These clinical, imaging, and histopathologic findings were compatible with necrotizing meningoencephalitis. The dog's neurologic status continued to worsen following surgery. Repeated MRI revealed ongoing signs of increased intracranial pressure, despite the bilateral craniectomy. The owners elected euthanasia.

CLINICAL RELEVANCE

To the author's knowledge, this is the first report of necrotizing meningoencephalitis in a large mixed-breed dog. Necrotizing meningoencephalitis should be considered as a differential diagnosis in dogs other than small or toy breeds that have signs suggestive of inflammatory disease.

Adult autologous mesenchymal stem cells for the treatment of suspected non-infectious inflammatory diseases of the canine central nervous system: safety, feasibility and preliminary clinical findings

Background

Non-infectious inflammatory diseases of the canine central nervous system (CNS) are common idiopathic disorders grouped under the term meningoencephalomyelitis of unknown origin (MUO). Ante mortem diagnosis is achieved via assessment of clinical signs, magnetic resonance imaging (MRI), and cerebrospinal fluid (CSF) analysis, but the definitive diagnosis needs histopathological examination. MUO are mostly considered as autoimmune CNS disorders, so that suppressing the immune reaction is the best management method for patients. Mesenchymal stem cells (MSCs) are under investigation to treat autoimmune and degenerative disorders due to their immunomodulatory and regenerative properties. This study aims to verify the safety, feasibility, and efficacy of MSCs treatment in canine idiopathic autoimmune inflammatory disorders of the CNS.

Methods

Eight dogs presented with acute onset and rapid progression of multifocal neurological signs were selected to the study. In all patients’ physical and neurological examinations, MRI and CSF analyses were performed. Clinical diagnosis in all cases was MUO. All selected dogs responded initially to immunosuppressive drugs (prednisone and a combination of prednisolone and cytosine arabinoside) but developed undesirable side effects. For all eight dogs, the owners considered euthanasia but accepted cell therapy as a last possibility. Autologous bone marrow MSCs (BMMSCs), isolated, cultured, and expanded, were administered by intrathecal (IT) injection in the cisterna magna intravenously (IV) and by intra-arterial (IA) injection in the right carotid artery. Adverse effects and clinical response were monitored for 6 months up to 2-year follow-up.

Results

The use of autologous BMMSCs in dogs with MUO was safe for IT, IV, and IA injections. No major short- or long-term adverse effects were registered. All the dogs presented early improvement in their general and neurological conditions, with particular effect on cervical pain. The group of dogs treated by IT+IA administration showed a shorter time of reaction to therapy compared to the group treated by IT+IV administration.

Conclusions

MSCs treatment in dogs affected by MOU is safe and feasible. A larger group of dogs is needed to confirm these results as well as CNS histology in order to better understand the underlying mechanisms.

A newly designed radiation therapy protocol in combination with prednisolone as treatment for meningoencephalitis of unknown origin in dogs: a prospective pilot study introducing magnetic resonance spectroscopy as monitor tool

Background

A plethora of treatment options have been described for canine meningoencephalitis of unknown origin (MUO), yet a gold standard has not been established. The aim of this prospective pilot study was to document the effect of a newly designed 30 Gray (Gy) radiation therapy (RT) protocol plus corticosteroids as treatment for focal and multifocal MUO, to monitor clinical and imaging changes during the course of the disease with conventional magnetic resonance imaging (MRI) and proton MR Spectroscopy (H-1 MRS) and to detect the occurrence of radiation related side effects.

Results

Six dogs (3 with focal and 3 with multifocal lesions) were included in the study. The RT protocol used consisted of 30 Gy in 10 fractions. The neurological status of all six dogs improved during RT, with 3 of 6 cases returning to a normal condition. One dog was euthanized early during follow-up (<3 weeks after end of RT). Three month follow up MRI was normal in one dog and improved in 3 dogs and H-1 MRS normalized in 4. In the dog without improvement of the MRI lesions, the N-acetyl aspartate continued to decrease, while choline and creatine concentrations remained stable during that time. This dog was euthanized 18 month after the end of RT due to relapse. One dog was lost to follow up 12 month after completion of RT. The other 3 dogs are still alive at the time of writing.

Conclusions

RT with 30 Gy in 10 fractions can provide an additional option for anti-inflammatory treatment of focal and multifocal MUO. The protocol used for treatment monitoring was feasible while no side effects of RT could be observed during the follow up period. Moreover, H-1 MRS could represent a new and non-invasive tool to control the progression of the disease during the treatment course.

Identification of novel genetic risk loci in Maltese dogs with necrotizing meningoencephalitis and evidence of a shared genetic risk across toy dog breeds

Necrotizing meningoencephalitis (NME) affects toy and small breed dogs causing progressive, often fatal, inflammation and necrosis in the brain. Genetic risk loci for NME previously were identified in pug dogs, particularly associated with the dog leukocyte antigen (DLA) class II complex on chromosome 12, but have not been investigated in other susceptible breeds. We sought to evaluate Maltese and Chihuahua dogs, in addition to pug dogs, to identify novel or shared genetic risk factors for NME development. Genome-wide association testing of single nucleotide polymorphisms (SNPs) in Maltese dogs with NME identified 2 regions of genome-wide significance on chromosomes 4 (chr4:74522353T>A, p = 8.1×10⁻⁷) and 15 (chr15:53338796A>G, p = 1.5×10⁻⁷). Haplotype analysis and fine-mapping suggests that ILR7 and FBXW7, respectively, both important for regulation of immune system function, could be the underlying associated genes. Further evaluation of these regions and the previously identified DLA II locus across all three breeds, revealed an enrichment of nominal significant SNPs associated with chromosome 15 in pug dogs and DLA II in Maltese and Chihuahua dogs. Meta-analysis confirmed effect sizes the same direction in all three breeds for both the chromosome 15 and DLA II loci (p = 8.6×10^–11 and p = 2.5×10⁻⁷, respectively). This suggests a shared genetic background exists between all breeds and confers susceptibility to NME, but effect sizes might be different among breeds. In conclusion, we identified the first genetic risk factors for NME development in the Maltese, chromosome 4 and chromosome 15, and provide evidence for a shared genetic risk between breeds associated with chromosome 15 and DLA II. Last, DLA II and IL7R both have been implicated in human inflammatory diseases of the central nervous system such as multiple sclerosis, suggesting that similar pharmacotherapeutic targets across species should be investigated.

Establishment of a rat model for canine necrotizing meningoencephalitis (NME)

The pathogenesis of necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalomyelitis (GME) is still uncertain, although they are considered immune-mediated diseases. The purpose of the present study is to generate a rodent model(s) of these diseases. Rats were injected with rat cerebral or cerebellar homogenate. Rats injected with cerebral homogenate (Cbr) exhibited vacuolar or malacic changes mainly in the cerebral cortex. CD3-positive T cells and Iba-1-positive and CD163-negative microglia infiltrated and activated around the lesions. IgG deposited in the glial fibrillary acid protein (GFAP)-positive glia limitans from the early phase, and CD3-positive T cells attached to GFAP-positive astrocytes. Autoantibodies against GFAP were detected in the sera. These pathological features of Cbr rats were consistent with those of canine NME. In contrast, rats injected with cerebral homogenate (Cbe) exhibited demyelinating lesions with inflammatory reactions in the cerebellum, brainstem, and spinal cord. The presence of demyelination and autoantibodies against myelin proteins in Cbe rats was similar to murine experimental autoimmune encephalitis and differed from NME, NLE, and GME. All the present findings indicate that autoantibodies together with microglia and T cells may play a major role in the pathogenesis of idiopathic canine meningoencephalomyelitis.

Necrotizing meningoencephalitis in atypical dog breeds: a case series and literature review

Background

Canine necrotizing meningoencephalitis (NME) is a fatal, noninfectious inflammatory disease of unknown etiology. NME has been reported only in a small number of dog breeds, which has led to the presumption that it is a breed‐restricted disorder.

Hypothesis/Objectives

Our objective was to describe histopathologically confirmed NME in dog breeds in which the condition has not been reported previously and to provide preliminary evidence that NME affects a wider spectrum of dog breeds than previously reported.

Animals

Four dogs with NME.

Methods

Archives from 3 institutions and from 1 author's (BS) collection were reviewed to identify histopathologically confirmed cases of NME in breeds in which the disease has not been reported previously. Age, sex, breed, survival from onset of clinical signs, and histopathologic findings were evaluated.

Results

Necrotizing meningoencephalitis was identified in 4 small dog breeds (Papillon, Shih Tzu, Coton de Tulear, and Brussels Griffon). Median age at clinical evaluation was 2.5 years. Histopathologic abnormalities included 2 or more of the following: lymphoplasmacytic or histiocytic meningoencephalitis or encephalitis, moderate‐to‐severe cerebrocortical necrosis, variable involvement of other anatomic locations within the brain (cerebellum, brainstem), and absence of detectable infectious agents.

Conclusions and Clinical Importance

Until now, NME has only been described in 5 small dog breeds. We document an additional 4 small breeds previously not shown to develop NME. Our cases further illustrate that NME is not a breed‐restricted disorder and should be considered in the differential diagnosis for dogs with signalment and clinical signs consistent with inflammatory brain disease.

Unique topographic distribution of greyhound nonsuppurative meningoencephalitis

Greyhound nonsuppurative meningoencephalitis is an idiopathic breed-associated fatal meningoencephalitis with lesions usually occurring within the rostral cerebrum. This disorder can only be confirmed by postmortem examination, with a diagnosis based upon the unique topography of inflammatory lesions. Our purpose was to describe the magnetic resonance (MR) imaging features of this disease. Four Greyhounds with confirmed Greyhound nonsuppurative meningoencephalitis were evaluated by MR imaging. Lesions predominantly affected the olfactory lobes and bulbs, frontal, and frontotemporal cortical gray matter, and caudate nuclei bilaterally. Fluid attenuation inversion recovery (FLAIR) and T2 weighted spin-echo (T2W) sequences were most useful to assess the nature, severity, extension, and topographic pattern of lesions. Lesions were predominantly T2-hyperintense and T1-isointense with minimal or absent contrast enhancement.

Comprehensive Immunohistochemical Studies on Canine Necrotizing Meningoencephalitis (NME), Necrotizing Leukoencephalitis (NLE), and Granulomatous Meningoencephalomyelitis (GME)

In dogs, there are several idiopathic meningoencephalitides, such as necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalomyelitis (GME). Although they are often assumed to be immune mediated, the etiology of these diseases remains elusive. In this study, the histopathology of the lesions caused by these conditions and the inflammatory cell populations produced in response to them were examined among dogs affected with GME, NME, or NLE to understand their pathogeneses. The brain tissues of dogs with NME (n = 25), NLE (n = 5), or GME (n = 9) were used. The inflammatory cells were identified by immunohistochemistry using antibodies against CD3, IgG, CD20, CD79acy, and CD163. In NME and NLE, malacic changes were located in the cerebral cortex, as well as the cerebral white matter and thalamus, respectively. The distribution of the brain lesions in NME and NLE was breed specific. In GME, granulomatous lesions that were mostly composed of epithelioid macrophages were observed in the cerebral white matter, cerebellum, and brainstem. Although the proportions of IgG-, CD20-, and CD79acy-positive cells (B cells) were not significantly different among the GME, NME, and NLE lesions, that of CD3-positive cells (T cells) was increased in GME. In NME and NLE, CD163-positive cells (macrophages) had diffusely infiltrated the cerebral cortex and white matter, respectively. However, in GME, CD163-positive cells accumulated around the blood vessels in the cerebral and cerebellar white matter. The distributions of these lesions were quite different among GME, NME, and NLE, whereas there were no marked differences in the proportions of inflammatory cells.

Identification of risk loci for necrotizing meningoencephalitis in Pug dogs

Due to their unique population structure, purebred dogs have emerged as a key model for the study of complex genetic disorders. To evaluate the utility of a newly available high-density canine whole-genome array with >170,000 single nucleotide polymorphisms (SNPs), genome-wide association was performed on a small number of case and control dogs to determine disease susceptibility loci in canine necrotizing meningoencephalitis (NME), a disorder with known non-Mendelian inheritance that shares clinical similarities with atypical variants of multiple sclerosis in humans. Genotyping of 30 NME-affected Pug dogs and 68 healthy control Pugs identified 2 loci associated with NME, including a region within dog leukocyte antigen class II on chromosome 12 that remained significant after Bonferroni correction. Our results support the utility of this high-density SNP array, confirm that dogs are a powerful model for mapping complex genetic disorders and provide important preliminary data to support in depth genetic analysis of NME in numerous affected breeds.

Clinical and clinicopathological features of non-suppurative meningoencephalitis in young greyhounds in Ireland

The clinical and clinicopathological features of non-suppurative meningoencephalitis in 30 greyhounds were reviewed. The dogs were from 21 separate litters, comprised both sexes (16 males and 14 females) and ranged in age from five to 18 months. In 14 (66.7 per cent) litters, more than one case was suspected or confirmed, and the number of siblings affected within individual litters ranged from one to seven. Clinical signs were progressive and varied from five days to 12 months in duration; 12 dogs had signs of two weeks' duration or less. The rate of progression of signs was variable. Common features included dullness or lethargy (22), altered behaviour (21), proprioceptive and postural reaction deficits (18), circling (17), ataxia (17), decreased appetite (15) and weight loss (13). No consistent haematological or biochemical abnormalities were identified and serology failed to implicate Toxoplasma gondii or Neospora caninum. Cerebrospinal fluid analysis revealed mild or moderate mononuclear pleocytosis in 12 (70.6 per cent) of 17 dogs. No definitive antemortem diagnosis could be made in any affected dog.

Clinical findings and treatment of non-infectious meningoencephalomyelitis in dogs: a systematic review of 457 published cases from 1962 to 2008

Non-infectious meningoencephalomyelitis (NIME) presents clinicians with diagnostic problems because specific diagnosis requires histopathological examination of central nervous system (CNS) tissue. In the absence of a precise diagnosis, clinicians refer instead to 'meningoencephalomyelitis of unknown origin' (MUO). This article compares published data on histopathologically diagnosed disease (granulomatous meningoencephalomyelitis and necrotising encephalitis) with information available on the clinically-defined category of MUO. Small, middle-aged female dogs are most commonly affected by all types of NIME, but there is considerable overlap in diagnostic parameters of these diseases. Future clinical trials must aim to compare prospectively two or more randomly allocated treatments and to include pre-trial power calculations. This article provides the necessary background information to permit rational patient selection on clinical presentation alone, rather than requiring CNS biopsy, thus maximising patient recruitment whilst minimising heterogeneity.

Necrotizing meningoencephalitis of Pug dogs associates with dog leukocyte antigen class II and resembles acute variant forms of multiple sclerosis

Necrotizing meningoencephalitis (NME) is a disorder of Pug Dogs that appears to have an immune etiology and high heritability based on population studies. The present study was undertaken to identify a genetic basis for the disease. A genome-wide association scan with single tandem repeat (STR) markers showed a single strong association near the dog leukocyte antigen (DLA) complex on CFA12. Fine resolution mapping with 27 STR markers on CFA12 further narrowed association to the region containing DLA-DRB1, -DQA1 and, -DQB1 genes. Sequencing confirmed that affected dogs were more likely to be homozygous for specific alleles at each locus and that these alleles were linked, forming a single high risk haplotype. The strong DLA class II association of NME in Pug Dogs resembles that of human multiple sclerosis (MS). Like MS, NME appears to have an autoimmune basis, involves genetic and nongenetic factors, has a relatively low incidence, is more frequent in females than males, and is associated with a vascularly orientated nonsuppurative inflammation. However, NME of Pug Dogs is more aggressive in disease course than classical human MS, appears to be relatively earlier in onset, and involves necrosis rather than demyelination as the central pathobiologic feature. Thus, Pug Dog encephalitis (PDE) shares clinical features with the less common acute variant forms of MS. Accordingly, NME of Pug Dogs may represent a naturally occurring canine model of certain idiopathic inflammatory disorders of the human central nervous system.

Magnetic resonance imaging characteristics of necrotizing meningoencephalitis in Pug dogs

BACKGROUND

The magnetic resonance imaging (MRI) characteristics of necrotizing meningoencephalitis (NME) are not well documented.

OBJECTIVES

To describe common MRI features of NME, to compare the MRI features to histopathologic findings, and to determine whether or not MRI lesions are predictive of survival time.

ANIMALS

Eighteen Pugs with NME.

METHODS

Retrospective MRI case study of Pugs identified by a search of medical records at 6 veterinary institutions. Eighteen dogs met inclusion criteria of histopathologically confirmed NME and antemortem MRI exam. MRI lesions were characterized and compared with histopathology with the kappa statistic. Survival times were compared with MRI findings by use of Mann-Whitney U-tests and Spearman's rho.

RESULTS

Twelve of 18 lesions were indistinctly marginated with mild parenchymal contrast enhancement. Prosencephalic (17/18) lesion distribution included the parietal (16/18), temporal (16/18), and occipital (16/18) lobes. There were cerebellar (4/18) and brainstem (3/18) lesions. Asymmetric lesions were present in both gray and white matter in all dogs. Falx cerebri shift was common (11/18), and 6 dogs had brain herniation. Leptomeningeal enhancement was present in 9/18 dogs. A moderate positive association was found between parenchymal contrast enhancement and both necrosis (kappa= 0.45; P= .045) and monocytic inflammation (kappa= 0.48; P= .025). Higher MRI lesion burden was correlated with longer time from disease onset to MRI (P= .045). MRI lesion burden did not correlate to survival time.

CONCLUSIONS AND CLINICAL IMPORTANCE

Asymmetric prosencephalic grey and white matter lesions with variable contrast enhancement were consistent MRI changes in Pugs with confirmed NME. While not pathognomonic for NME, these MRI characteristics should increase confidence in a presumptive diagnosis of NME in young Pugs with acute signs of neurologic disease.

Immunohistochemical characterization of inflammatory and glial responses in a case of necrotizing leucoencephalitis in a French bulldog

A 3-year-old male French bulldog was presented with blindness, staggering and ataxia and was humanely destroyed due to worsening of the neurological signs. At post-mortem examination a non-suppurative leucoencephalitis with extensive malacia within the forebrain was found. In addition, a bilateral necrotizing optic neuritis and focal retinitis was detected. Immunohistochemistry revealed a CD3(+) T-cell dominated inflammatory response with intralesional reactive astrocytes expressing glial fibrillary acidic protein. Astroglia-like cells expressing vimentin, which is characteristic of immature astrocytes, were found within the malacic lesions. The pathological findings are similar to those described in idiopathic necrotizing leucoencephalitis (NLE) of Yorkshire terriers and substantiate the hypothesis that NLE is not a breed-specific disorder that exclusively affects Yorkshire terriers, but also the French bulldog.