Comparison of serum creatine kinase and aspartate aminotransferase activity in dogs with Neospora meningoencephalitis and noninfectious meningoencephalitis

Successful Management of Presumed Reactivation of Neospora caninum Following Immunosuppression for Immune Thrombocytopenia in an Adult Doberman

A 5-year old, vaccinated, untravelled and neutered female Doberman with occasional exposure to raw food presented for investigation of severe thrombocytopenia and anaemia. Extensive investigations led to a diagnosis of non-associative immune thrombocytopenia, with secondary bleeds resulting in anaemia. Management with repeated packed red blood cell transfusions, vincristine (0.02 mg/kg single intravenous injection), prednisolone (50 mg/m2/day) and mycophenolate (10 mg/kg twice daily) allowed normalisation of haematology parameters. Scheduled reassessment 10 days after discharge revealed lethargy, ataxia, wide-based stance and marked generalised muscle wastage. Platelet count remained normal, but biochemistry was supportive of muscle damage. Neospora caninum antibodies were elevated (indirect fluorescence antibodies > 1600). Rapid tapering of prednisolone alongside clindamycin (20 mg/kg twice daily) allowed a complete recovery. Mycophenolate was slowly tapered and discontinued after 12 weeks, as was antibiotic therapy. This case describes the successful management of a dog with presumed neuromuscular neosporosis, suspected secondary to reactivation of the parasite from immunosuppression, and absence of long-term complications.

Masticatory muscle changes on magnetic resonance imaging of dogs with Neospora caninum compared to meningoencephalitis of unknown origin

Infectious meningoencephalitides represent an important differential diagnosis for meningoencephalitis of unknown origin (MUO) in dogs. Treatment of the latter requires immunosuppression, but laboratory test results for infectious agents may take several days to return. This study investigated whether the presence of masticatory muscle changes on magnetic resonance imaging (MRI) of the head can be used to distinguish dogs with neosporosis from those with MUO at the time of diagnosis. Cases diagnosed with neosporosis or MUO at two referral centers in the United Kingdom (UK) were retrospectively collected. Clinical data were reviewed, and each MRI study was blindly assessed by a radiologist, a neurologist, and a neurology resident for the presence of masticatory muscle changes by consensus opinion. Statistical analysis was performed on obtained data. Twenty-two neosporosis cases and 23 MUO cases were enrolled. In the neosporosis group, six dogs (27%) had masticatory muscle changes, compared to one dog (4%) in the MUO group (p = 0.047). All six neosporosis cases had bilateral, multifocal, T2W and FLAIR hyperintense, contrast enhancing muscular changes, with three having concurrent masticatory muscle atrophy. The only MUO case with muscle changes had a mild, focal, unilateral temporal muscle lesion which was only visible in the T1W post-contrast images. Within the neosporosis group, dogs with masticatory muscle lesions had significantly higher cerebrospinal fluid WBC counts (p = 0.017) and protein concentrations (p = 0.025) compared to those without muscle changes. In conclusion, characteristic bilateral, multifocal masticatory muscle changes should raise the index of suspicion for neosporosis in dogs with an imaging diagnosis of meningoencephalitis and starting early antimicrobial treatment is recommended. However, the absence of masticatory muscle abnormalities does not exclude active Neospora caninum infection. In these cases, whether immunosuppressive or antimicrobial treatments are started prior to receiving further test results should still be based on the clinical status of the animal and index of suspicion using a combination of all available clinical information at that time.

Magnetic resonance imaging findings in dogs with steroid-responsive meningitis-arteritis in the UK and their clinical significance: 53 cases (2013-2021)

OBJECTIVES

To describe the MRI findings in a UK referral population of dogs with steroid-responsive meningitis-arteritis and to determine if they were associated with any specific clinical features or outcomes.

MATERIALS AND METHODS

We performed a multi-centre retrospective case series of dogs diagnosed with steroid-responsive meningitis-arteritis in the UK that underwent MRI. Blinded consensus review of the MRI studies was performed and the findings described. The presence or absence of specific MRI abnormalities were analysed for significant associations with presenting signs, results of investigations or case outcomes.

RESULTS

Fifty-three dogs were included. The most common MRI findings were paravertebral muscle changes (30/53; 56.6%), meningeal contrast enhancement (13/41; 31.7%) and spinal cord parenchymal T2-W hyperintensity (15/53; 28.3%). Haemorrhage was observed in five of 53 (9.4%) cases - three intradural-extramedullary, one intramedullary and one extradural. Following binary logistic regressions, T2-W spinal cord parenchymal hyperintensity had a significant positive association with paresis/paralysis (odds ratio 14.86, 95% confidence interval 1.42 to 154.99) as did haemorrhage (odds ratio 16.12, confidence interval 2.05 to 126.73). Fifty-two (98.1%) dogs survived to discharge. Relapse occurred in nine of 29 (31.0%) dogs with sufficient follow-up, and no MRI finding had a significant relationship with its occurrence.

CLINICAL SIGNIFICANCE

Magnetic resonance imaging findings for steroid-responsive meningitis-arteritis can be severe and extensive, as can the clinical presentation. The presence of paresis/paralysis should raise concern for haemorrhage, though most dogs still have a good prognosis.

Disseminated Neospora caninum Encephalomyelitis and Myositis in a 3-Month-Old Cane Corso Puppy

We present a case of fatal disseminated neosporosis in a 3-month-old Cane Corso puppy. The puppy presented to the Purdue Veterinary Hospital emergency service with a 1-week history of progressive left hindlimb lameness. On presentation, the puppy was nonambulatory paraparetic. Signs progressed over two days to nonambulatory tetraparesis, and decreased to absent limb reflexes, cranial nerve deficits, and dull mentation. Blood work showed eosinophilia, elevated ALT, and extremely elevated creatine kinase at 36,000 IU/L (reference interval 22-491 IU/L). Two days after diagnostics were performed, the puppy experienced acute cardiac arrest, and the body was submitted for necropsy. At necropsy, skeletal muscle in all four limbs was diffusely pale tan. Tan streaks were disseminated through the diaphragm, abdominal wall, and myocardium. Histologically, Skeletal myocytes and cardiomyocytes were frequently degenerative, with abundant lymphohistiocytic inflammation and fibrosis. White matter within the brain and spinal cord was inflamed and contained frequent dilated myelin sheaths and spheroids. A few protozoal cysts were within the brain and skeletal myocytes. Antemortem antibody titers were positive for IgG against Neospora caninum (dilution titer of 1:4096, baseline 1:32), confirming protozoal cysts as Neospora caninum. Disseminated neosporosis is an uncommon but important clinical differential for ascending paresis in young dogs.

Neosporosis in 21 adult dogs, 2010-2023

BACKGROUND

Limited information is available regarding the clinical features, treatment, and prognosis of neosporosis in adult dogs.

OBJECTIVE

Describe the clinical signs, laboratory findings, magnetic resonance imaging (MRI) findings, treatment and outcome in adult dogs (>6 months) diagnosed with neosporosis based on consistent clinical signs and positive serology (titer ≥1 : 800) at a referral hospital in Sydney, Australia.

ANIMALS

Twenty-one client-owned dogs.

METHODS

Retrospective case series of affected dogs between 2010 and 2023. Survival times were determined from onset of clinical signs to date of death or censoring.

RESULTS

Clinical signs varied, and were indicative of generalized myopathy (6 dogs), multifocal intracranial disease (7 dogs), myelopathy (4 dogs), polyneuropathy (2 dogs) and single cases of focal myopathy and cerebellar disease. Serum creatine kinase activity was markedly increased (median, 3369 U/L) in most dogs. The most common MRI abnormalities were multifocal intracranial abnormalities (7/13 dogs) and muscle changes (5/13 dogs) whereas T2-weighted cerebellar abnormalities (2/13 dogs) and cerebellar atrophy (1/13) were less common. Treatment response was complete (resolution to normal) in 8 dogs, incomplete (persistent neurological deficits) in 6 dogs, but there was minimal response in 7 dogs. Thirteen dogs (62%) were alive after 6 months and 12 dogs (57%) alive after 1 year. Relapse was common, with 4 dogs experiencing at least 1 relapse event during the follow-up period.

CONCLUSION AND CLINICAL IMPORTANCE

Adult-onset neosporosis is uncommon and has variable clinical presentations. Treatment response also is variable, and relapse can occur, even among patients that respond completely to initial treatment.

A 20-year serological survey of Toxoplasma gondii and Neospora caninum infection in dogs with neuromuscular disorders from urban areas in Argentina

Toxoplasma gondii and Neospora caninum infections may be associated with neuromuscular disorders in dogs. The aim of this study was to assess the seroprevalence to these protozoan parasites in dogs with neuromuscular disease from urban areas of Buenos Aires province, Argentina, over a period of 20 years, and to evaluate the association of seropositivity and antibody titres with different variables such as sex, breed and age. For this, a total of 7238 serum samples from urban owned dogs were analysed by the indirect fluorescence antibody test (IFAT) for specific IgG antibodies. The observed seropositivity rates were 35.7 % for T. gondii and 25.7 % for N. caninum. Crossbred dogs had a significantly higher seroprevalence for T. gondii than purebred dogs (41 % vs. 29.3 %), while a trend towards significance was observed for N. caninum, which was slightly higher in purebred dogs (26 % vs. 23.6 %). Seroprevalence for both parasites increased with age and was higher in older animals. Regarding the distribution of specific antibody titres, the most frequent IFAT T. gondii titre found was 100 and for N. caninum it was ≥800. For toxoplasmosis, there was no association with age group, and low titres (50, 100 and 200) predominated in all groups. However, for neosporosis, age and titres were significantly associated for one age group, with dogs under 12 months of age having a higher proportion of high titres (400 and 800). The trend in the seroprevalence for T. gondii is increasing over the years and lower antibody titres predominate in the dogs studied, which may be more related to the presence of chronic infections and not necessarily to the clinical signs of the animals. Despite the generally low titres observed for toxoplasmosis in this study, it is important to highlight the high seroprevalence found in our region, as dogs can act as sentinels of environmental contamination and as indicators of possible human infection. In the case of neosporosis, although the trend in seroprevalence in dogs with signs appears to be decreasing over the years, our work shows that higher antibody titres predominate, and are probably related to the clinical signs presented by the dogs. This study provides the most recent epidemiological data and serological profiles of T. gondii and N. caninum infections in a large number of canine sera from urban areas in Argentina, providing relevant information for clinical veterinarians and epidemiologists in order to understand the circulation of the parasites.

Insights into the clinical presentation, diagnostics and outcome in dogs presenting with neurological signs secondary to infection with Neospora caninum: 41 cases (2014-2023)

OBJECTIVES

To describe the clinical signs and outcome of a large cohort of dogs presenting with neurological signs secondary to Neospora caninum infection.

MATERIALS AND METHODS

Retrospective review of cases presenting to two UK referral centres with neurological signs secondary to N. caninum infection between 2014 and 2023. Presenting signs, diagnostic test results, treatment, short- and long-term outcome analysed.

RESULTS

A total of 1690 cases were assessed for eligibility. Forty-four cases with a diagnosis of neosporosis were obtained. Three cases were then excluded due to non-neurological presentations (two hepatitis and one myocarditis). A total of 41 cases were included in the study. Cerebello-vestibular signs predominated; however, presenting clinical signs were varied and the neurolocalisation was often multifocal in nature (46.3%), making neosporosis an important differential diagnosis for meningoencephalitis of unknown origin. Complete clinical improvement was rare (5.6%), and relapses were common (27.8% cases with follow-up).

CLINICAL SIGNIFICANCE

Neosporosis remains an important differential diagnosis for dogs at any age presenting with multifocal neurological signs. The outcome is considered poor and relapse rate is high.

Corticosteroid monotherapy versus combined cytarabine continuous rate infusion and corticosteroid therapy in dogs with meningoencephalitis of unknown origin: A blinded, randomized, controlled trial

BACKGROUND

Treatment options available for meningoencephalitis of unknown origin (MUO) in dogs are suboptimal, and currently, no single treatment protocol appears to be superior.

OBJECTIVES

Compare neurological deterioration rates at 7 days between dogs with MUO treated with corticosteroids alone or combined with cytosine arabinoside (CA) continuous rate infusion (CRI) and compare clinical deterioration and survival at 30 and 100 days.

ANIMALS

Sixty-nine dogs with magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) features or both compatible with MUO.

METHODS

Parallel, blinded, randomized controlled trial. Simple randomization into 2 treatment groups: 4 mg/kg/day prednisolone (or dexamethasone equivalent) for 2 days or 200 mg/m2 CA CRI over 8 hours plus 2 mg/kg/day prednisolone. Blinding of the treatment protocol was carried out using reversible redaction of clinical records, and treatment failure was defined as deterioration of neurological assessment or death. Using intention-to-treat analysis, proportions failing treatment at 7, 30, and 100 days were compared using Fisher's exact test. All-cause mortality at 100 days was compared using Kaplan-Meier survival curves.

RESULTS

Thirty-five dogs were allocated to corticosteroid only, and 34 dogs were allocated to combined CA CRI and corticosteroid. Proportions failing treatment at 7, 30, and 100 days were 7/35 (20%), 9/35 (26%), and 15/35 (43%) in the corticosteroid-only group and 8/34 (24%), 11/34 (32%), and 23/34 (68%) in the corticosteroid and CA CRI group. All-cause mortality at 100 days was not significantly different between groups (P = .62). Clinically relevant treatment-related adverse effects were not observed.

CONCLUSIONS AND CLINICAL IMPORTANCE

We found no difference in outcome between corticosteroid monotherapy and combined cytarabine CRI and corticosteroid therapy at 7, 30, and 100 days after diagnosis in dogs with MUO.