Canine distemper virus (CDV) is a highly contagious disease with high morbidity and mortality rates in veterinary medicine. This retrospective study aimed to identify epidemiological characteristics and potential risk factors associated with CDV infection in dogs exhibiting neurological manifestations. The diagnosis was confirmed through immunochromatographic antigen testing, RT-PCR, or Lentz corpuscles identification. Dogs diagnosed with central nervous system (CNS) disorders unrelated to CDV served as the control group. Age, breed, weight, sex, and neuter status were compared between groups using logistic regression (p < 0.05), the log-likelihood method, and log odds ratio (LOR) calculations. Clinical signs, seasonality, and vaccination protocols were documented. Prevalence, mortality, lethality, and survival rates were determined. Younger dogs (p = 0.00690; LOR = −0.01438) and Shih Tzu (p = 0.00007; LOR = 1.53774) and Lhasa Apso (p = 0.000264; LOR = 1.76084) showed a significantly increased likelihood of developing neurological signs due to CDV infection. Most CDV-infected dogs exhibited multifocal CNS involvement and accompanying extra-neural signs. The highest occurrence of CDV-related neurological signs was recorded in autumn. Many infected dogs had an updated vaccination protocol. The prevalence of dogs with CDV was 4.72%. Mortality and lethality rates were 1.94% and 47.06%, respectively. The median survival time was 754 days. The identified epidemiological characteristics and risk factors provide essential insights for improving preventive strategies against CDV infection.

Canine distemper virus (CDV) is a critical disease in veterinary neurology, marked by high morbidity, mortality, and frequent neurological sequelae. This study aimed to identify epidemiological patterns and risk factors associated with neurological manifestations of CDV infection. CDV-naturally infected dogs with neurological signs were retrospectively analyzed and compared to a control group of dogs with other CNS diseases. Infection was confirmed using antigen tests, RT-PCR, and/or Lentz corpuscle observation. Clinical signs, seasonality, and vaccination protocols were documented. Prevalence, mortality, lethality, and survival rates were also determined. Younger dogs (p=0.0069; OR=-0.01438), Shih-Tzu (p=0.00007; OR=1.53774), and Lhasa Apso (p=0.000264; OR=1.76084) were more likely to develop neurological CDV signs. Most CDV-infected dogs exhibited multifocal CNS involvement (10/17) and accompanying extra-neural signs (16/17). Motor deficits represented the most frequent neurological manifestation (13/17), while myoclonus was observed in only one-third (6/17) of the cases. Cases were more frequent in autumn (8/17), and many dogs had updated vaccination protocols (6/17). The prevalence, mortality and lethality of dogs with CDV were estimated at 4.72%, 1.94% and 47.06%, respectively. The median survival time was 754 days. Young adult dogs, particularly Shih-Tzu and Lhasa Apso, are more susceptible to neurological CDV manifestations, with the highest incidence in autumn.

Sarcocystis sp.-induced disease is known especially in horses, in which S. neurona is the primary causative agent of Equine Protozoal Myeloencephalitis in the Americas. While horses are aberrant hosts, the range of susceptible species includes marine mammals, raccoons, and cats. Reports of clinical disease in dogs are rare, remaining unreported in South America. This study describes the clinical, pathological, and immunohistochemical findings of a naturally occurring, fatal case of meningoencephalomyelitis and myositis caused by Sarcocystis sp. in a dog in Brazil. A 5-year-old mixed-breed bitch presented with acute non-ambulatory tetraparesis, generalized muscle atrophy, and blindness. Despite supportive therapy, the patient deteriorated and was euthanized. Gross findings included enlarged lymph nodes, moderate splenomegaly and hepatomegaly, with multifocal mild fibrin deposition on the liver capsule, accompanied by multifocal mild hemorrhages in the pancreas. Histopathology demonstrated severe, multifocal necrotizing meningoencephalomyelitis, myositis, splenitis, lymphadenitis and interstitial pneumonia, associated with intralesional protozoal schizonts. Immunohistochemistry supported immunolabelling consistent with Sarcocystis sp. while excluding Toxoplasma gondii and Neospora caninum . To the authors’ knowledge, this represents the first report of clinical canine sarcocystosis with this severity in South America supported by histopathological and immunohistochemical findings. These findings support that Sarcocystis sp. should be considered a differential diagnosis for canine progressive neurological disease, highlighting the potential role of wildlife reservoirs in the disease’s epidemiology.