Introduction: This retrospective study was designed to evaluate the possible effects of age on the neurological patterns of canine distemper virus-induced encephalitis.

Materials and Methods: Only cerebellar sections originated from 181 cases of canine distemper encephalitis (CDE) that were diagnosed by histopathology during 1985-1997 were utilized. Four histopathological patterns were determined: 1) acute distemper encephalopathy, 74 cases; 2) acute distemper encephalitis with necrotic areas, 15 cases; 3) subacute distemper encephalitis, 78 cases; and 4) chronic distemper encephalitis, 14 cases. All animals were divided into four age groups: 0-1.5 years (109 dogs); 1.6-3 years (32 dogs); 3.1-6 years (29 dogs); and 6.1-12 years (11 dogs). A non-parametric statistical analysis using the Chi-square test was used to evaluate the possible relationship between age and the occurrence of the different types of CDE.

Conclusions: Acute distemper encephalopathy and subacute distemper encephalitis were not significantly different (P > 0.0005) within the four age groups examined and were the predominant alterations observed in all age groups. However, these alterations were significantly different (P < 0.0005) from animals that demonstrated acute distemper encephalitis with necrotic zones and in dogs with chronic distemper encephalitis. Significant differences (P < 0.0005) were observed within the four age groups of dogs that demonstrated acute distemper lesions with necrosis and in those with chronic CDE. Age seems to increase progressively with the number of dogs with chronic distemper encephalitis; acute distemper encephalitis with necrotic zones apparently decreased as age increased; acute and subacute distemper encephalitis were not affected by age and occurred in dogs from all age groups.